# AC 120-29A: Criteria for Approval of Category I and Category II Weather Minima for Approach - Type: Advisory circular (guidance, not mandatory unless a rule or AD requires it) - Status: Historical - Approved: August 12, 2002 - Last reviewed: August 7, 2024 - Family: AC 120-29 - Cancels: [AC 120-29 CHG 3](https://openairdocs.org/ac/120-29-CHG-3) - Cancelled by: [AC 20-191](https://openairdocs.org/ac/20-191) - 14 CFR parts: 91, 121, 125, 129, 135, 25 - Pages: 273 - PDF: https://openairdocs.org/files/sha256/e0/f8/e0f846402d195473acc1b277b27f2e818769a50507aad34d81886fd03f228e05 - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/A05FA73B0896E36B86256C14006A665B.0001 - DRS record last changed: July 1, 2026 - Page: https://openairdocs.org/ac/120-29 ## Versions - [AC 120-29A](https://openairdocs.org/ac/120-29) (Historical), approved Aug 12, 2002, 273 pages - [AC 120-29 CHG 3](https://openairdocs.org/ac/120-29-CHG-3) (Historical), approved Sep 25, 1970, 48 pages. Change 3 of AC 120-29. ## ADs that cite it (1) - [AD 90-23-13](https://openairdocs.org/ad/90-23-13): AFM Changes - Operation · F.28 Mark 0100. Effective Nov 26, 1990 ## Text Each page's text from the PDF; open the PDF at a page with #page=N. Some pages are OCR from the scanned FAA advisory circular. OCR can misread letters and numbers. Those pages are marked (OCR). ### Page 1 AC 120-29A August 12, 2002 **CRITERIA FOR APPROVAL OF** **CATEGORY I AND CATEGORY II** **WEATHER MINIMA FOR APPROACH** ### Page 3 Forward. This advisory circular (AC) provides an acceptable means, but not the only means, for obtaining and maintaining approval of operations in Category I and II Landing Weather Minima including the installation and approval of associated aircraft systems. It includes additional Category I and II criteria or revised Category I and II criteria for use in conjunction with RNAV, Required Navigation Performance (RNP), VNAV, xLS, satellite navigation systems (GLS), Head up Displays (HUD), and Category II during certain engine inoperative operations. This revision also updates and incorporates provisions of the former AC 120-29 through Change 3 into the revised AC 120-29A. This revision incorporates changes resulting from the first steps toward international all weather operations (AWO) criteria harmonization taken by the Federal Aviation Administration (FAA), European Joint Aviation Authorities (JAA), and several other regulatory authorities. Subsequent revisions of this AC are planned as additional all weather operations harmonization items (AHI) are agreed and completed by FAA JAA, and other regulatory authorities. /s/ Nicholas A. Sabatini Associate Administrator for Regulation and Certification ### Page 4 TABLE OF CONTENTS Par Paragraph Titles 1 PURPOSE 2 RELATED REFERENCES AND DEFINITIONS 2.1 Related References 2.2 Definitions 3 BACKGROUND 3.1 Major Changes Addressed in this Revision 3.2 Relationship of Operational Authorizations for Category I or Category II and Airborne System Demonstrations 3.3 Applicable Criteria 3.4 Category I, II, and III Terminology. 3.5 Requirement for Evaluation Prior to Operations 4 OPERATIONAL CONCEPTS 4.1 Classification and Applicability of Minima 4.2 Takeoff 4.3 Landing 4.3.1 Approach and Landing Concepts and Objectives 4.3.1.1 Operational Safety Evaluation 4.3.1.2 Primary and Supplementary Means of Navigation and Required Navigation Performance (RNP) 4.3.1.3 Use of ICAO Standard NAVAIDs 4.3.1.4 Standard Instrument Approach Procedures (SIAPS) 4.3.1.5 “Steep Approaches” and Approach Path Descent Angle Constraints 4.3.1.6 “Normal Maneuvering” Considerations 4.3.1.7 Non-Normal Events or Configurations 4.3.1.8 Go-Around Safety 4.3.2 ILS, GLS, or MLS (xLS) Instrument Approach Operations 4.3.3 Instrument Approaches other than ILS, GLS, or MLS (xLS) 4.3.4 Applicability of a DA(H), MDA(H) or RA 4.3.4.1 Application of a DA(H) for Category I 4.3.4.2 Application of an MDA(H) for Category I 4.3.4.3 Application of a DA(H), or equivalent (i.e., Inner Marker), for Category II 4.3.4.4. “Specified Visual Reference” Requirements for Category I or Category II. 4.3.5 Visibility and RVR minima 4.3.6 Visibility Assessment and RVR Equivalence for Landing 4.3.7 General Requirements for Category I Operations and Minima 4.3.7.1 Category I Definition, Background, Classification, and General Criteria 4.3.7.2 “xLS” Procedures - Minima not less than 200 feet DA(H) 4.3.7.3 “3D” RNAV Procedures - Minima not less than 200 feet DA(H) 4.3.7.4 “3D” RNAV Procedures - Minima not less than 250 feet DA(H) 4.3.7.5 “2D” RNAV Procedures (e.g., VOR/DME-based RNAV, or GPS-based RNAV) - Minima not less than 250 ft. MDA(H) 4.3.7.6 Procedures other than xLS or RNAV (e.g., VOR, NDB, LOC, Back Course LOC, or ASR Procedures) - Minima not less than 250 ft. DA(H) 4.3.7.7 Other Special Procedures or Authorizations 4.3.7.8 Previously Approved Category I Operations or Use of Previous or New Category I Criteria 4.3.8 Requirements for Category II 4.3.8.1 General Category II Requirements 4.3.8.2 Specification of a Category II DA(H) 4.3.8.3 Eligibility for Category II minima not less than 100 ft. DA(H) ### Page 5 4.3.8.4 Use of Inner Marker 4.3.8.5 Barometric Altimeter DAs not currently used for 14 CFR parts 121 or 135 Category II 4.3.8.6 Category II on U.S. Type I ILS 4.3.8.7 Category II using RVR 300 “Meter” Minima 4.3.8.8 Precision Approach Radar (PAR) 4.3.8.9 Previously Approved Category II Operations or Use of Previous or New Category II Criteria 4.3.9 Runway Field Length Requirements and Runway Clutter 4.3.10 NAVAIDs or Landing System Sensors and Aircraft Position Determination 4.3.10.1 Instrument Landing System (ILS) 4.3.10.2 Microwave Landing System (MLS) 4.3.10.3 Global Navigation Satellite System (GNSS) Landing System (GLS) 4.3.10.4 Satellite Systems 4.3.10.4.1 GPS/GLONASS and Reference Datum Information 4.3.10.4.2 Local Area Systems 4.3.10.4.3 Wide Area Systems 4.3.10.5 LOC/LDA/SDF/Back Course 4.3.10.6 VOR Authorized Procedures **4.3.10.7 DME** 4.3.10.8 NDB Authorized Procedures 4.3.10.9 Radar Systems (e.g., PAR, ASR) 4.3.10.10 Other Systems, Procedures, and Special Systems. 4.3.10.11 Circling Approaches 4.4 RNAV/Flight Management Systems (FMS) 4.4.1 FMS Use for xLS Procedures 4.4.2 FMS Use for Procedures other Than xLS or RNAV 4.4.3 FMS Use for RNAV 4.4.3.1 Use of a Single RNAV Airborne System 4.4.4 FMS Use for RNAV with RNP 4.4.4.1 Standard RNP Qualification 4.4.4.2 “Fleet Qualification” For Use of RNP 4.4.4.3 Assessment Credit for RNP-qualified aircraft flying “non-RNP” based RNAV Procedures 4.4.4.4 Assessment of Expected Levels of ANP for RNP-qualified aircraft flying “RNP” Procedures. **4.4.5 FMS VNAV** 4.4.6 FMS Use for International Procedures 4.4.7 FMS RNAV Use for Substitution for VOR, DME, NDB, or Marker Beacon NAVAIDs or Fixes 4.4.8 Inhibiting RNAV System Use of Inoperative or Unsuitable VOR, DME, VORTAC, TACAN, or NDB NAVAIDs 4.5 Required Navigation Performance (RNP) 4.5.1 RNP Levels or Types 4.5.2 Other RNP Levels or Types 4.6 Flight Path Definition 4.6.1 Landing and Rollout Flight Path 4.6.2 Runway Datum Point (RDP) 4.6.3 Flight Path Alignment Point (FPAP) 4.6.4 Flight Path Control Point (FPCP) 4.6.5 Datum Crossing Height (DCH) 4.6.6 Glide Path Angle (GPA) 4.6.7 Glide Path Intercept Reference Point (GIRP) 4.6.8 Approach and Missed Approach Segments 4.6.9 Procedure Design Related Waypoint Definitions and Use 5 AIRBORNE SYSTEM REQUIREMENTS 5.1 General 5.1.1 Airborne Systems 5.1.2 Non-Airborne Systems (e.g., NAVAIDS or equivalent GNSS Capability) ### Page 6 5.1.3 Flight Path Specification 5.1.3.1 Lateral 5.1.3.2 Vertical 5.1.3.3 Longitudinal 5.1.3.4 Typical Wind and Wind Gradient Disturbance Environment 5.2 Airborne Equipment for Category I 5.3 Airborne Equipment for Category II 5.3.1 Standard Category II Minima 5.3.2 Special Category II Authorizations 5.4 Automatic Flight Control Systems and Automatic Landing Systems 5.5 Flight Director Systems 5.6 Head up Display Systems 5.7 Enhanced/Synthetic Vision Systems 5.8 Hybrid Systems 5.9 Instruments, Systems, and Displays 5.9.1 Instruments, Systems, and Displays for Category I. 5.9.2 Instruments, Systems, and Displays for Category II. 5.10 Annunciations 5.11 Auto Aural Alerts 5.12 Navigation Sensors 5.12.1 Navigation Sensors for (xLS) - ILS, GLS, or MLS. 5.12.2 Navigation Sensors for Approaches other than ILS, GLS, or MLS. 5.12.3 Aircraft Navigation Reference Points, Wheel to Eye Height, and Wheel to Navigation Reference Point Height 5.12.4 Threshold Crossing Height (TCH) 5.13 Supporting Systems and Capabilities 5.13.1 Flightdeck Visibility 5.13.2 Rain and Ice Removal 5.13.3 Miscellaneous Systems 5.14 Go-Around Capability 5.15 Excessive Deviation Alerting 5.16 Rollout Deceleration Systems or Procedures for Category I or II 5.16.1 Stopping Means 5.16.2 Antiskid Systems 5.17 Engine Inoperative Category II Capability 5.18 Special Airports with Irregular Pre-Threshold Terrain 5.19 Airborne System Evaluation and Approval 5.19.1 “Operator Use Suitability” Demonstrations-Applicability 5.19.2 Airborne Equipment Operational Validation 5.19.2.1 Category II Assessments 5.19.2.2 Flight Technical Error (FTE) Assessments 5.19.3 Data Collection and Analysis for an Airborne System Evaluation 5.19.3.1 FTE Data Collection and Analysis 5.19.3.2 Data Collection for a Category II Demonstration 5.19.3.3 Definition of a Successful Approach for a Category II Demonstration 5.20 Ground Proximity Warning System (GPWS) or Terrain Awareness Warning System (TAWS) Interface 5.21 Flight Data Recorder (FDR) Interface 5.22 Takeoff, or Dispatch, with Inoperative Navigation Receivers, Instruments, or Displays for Category I or II. 5.22.1 Inoperative System Departure or Dispatch For Category I. 5.22.2 Inoperative System Departure or Dispatch For Category II. 5.22.3 Inoperative System Departure or Dispatch For Either Category I or Category II. 5.23. Continuation of Flight After Navigation System Failure Enroute, or During Approach, for Category I or II. 5.23.1 Continuation of a Flight After Failures For Category I. 5.23.2 Continuation of a Flight After Failures For Category II. 5.23.3 Continuation of a Flight After Failures For either Category I or Category II. ### Page 7 **6 PROCEDURES** 6.1 Operational Procedures 6.1.1 AFM Provisions 6.1.2 Crew Coordination 6.1.3 Monitoring 6.1.4 Use of the DA(H) and MDA(H) 6.1.5 Call Outs 6.1.6 Configurations 6.1.7 Compatibility between Category I, Category II, and Category III Procedures 6.1.8 Procedure Considerations During Non-Normal Operations 6.2 Category I or Category II Instrument Approach Procedures 6.2.1 Acceptable Procedures for Category I 6.2.2 Acceptable Procedures for Category II 6.2.3 Standard Obstacle Clearance for Approach and Missed Approach 6.2.4 Special Obstacle Criteria 6.2.5 Irregular Pre-threshold Terrain Airports 6.2.6 Airport Surface Depiction for Category I or II Operations 6.2.7 Continuing Category I or Category II Approaches in Deteriorating Weather Conditions 6.2.8 “Approach Ban” Applicability 6.2.9 Approach Operations at Non-US Airports when Weather is Reported “Below Minima” 6.2.10 IFR Approaches or Low Visibility Takeoffs in Class G Airspace 6.2.11 Wind Constraint Applicability 6.2.12 Crosswind Component Determination at Airports with Significant Magnetic Variation (Polar Regions) 6.2.13 Unusual or Extreme Temperatures or Pressures 6.2.13.1 General Cold Temperature Considerations 6.2.13.2 Temperatures below those used in Procedure Design 6.2.13.3 Segments which may need to be Corrected for Temperature 6.2.13.4 Uncorrected Procedures 6.2.13.5 VNAV Path and Visual Guidance (VGSI) Temperature Considerations 6.2.13.6 Unusual Cold Temperature Operations within the United States 6.2.13.7 Unusual Cold Temperature Operations outside the United States 6.2.13.8 Use of Standard Cold Temperature Table (Table 6.2.13-1) 6.2.13.9 Use of other Cold Temperature Correction Tables 6.2.13.10 Altimeter Settings 6.2.13.11 Altimeter Settings (Not Recent) 6.2.13.12 Precautions for Unusually High or Low Temperatures or High or Low Pressures 6.2.14 Metric Altitudes 6.2.15 International “Approach Procedure Title” Requirements for or Limitations on NAVAID Use 6.2.16 “U.S. TERPS” or “ICAO PANS-OPS” Obstacle Clearance Procedural Protection Limitations 6.2.17 Navigation Reference Datum Compatibility (e.g.,WGS-84/Other Datum) 6.2.18 Alternative Use Of FAA/JAA Harmonized Minima 6.2.19 Assessment of Threshold Crossing Height (TCH), Approach Descent Gradient, and Runway Slope. **7 TRAINING AND CREW QUALIFICATION** 7.1 General Knowledge (Ground) Training for All Weather Operations (AWO) 7.1.1 Ground Systems and NAVAIDs for Category I or Category II 7.1.2 The Airborne System 7.1.3 Flight Procedures, Operations Specifications, and Other Information 7.2 Maneuver or Procedure (Flight) Training for All Weather Operations (AWO) 7.2.1 Initial Qualification 7.2.2 Recurrent Qualification 7.2.3 Qualification in Conjunction with Advanced Qualification Programs (AQP) 7.2.4 Re-qualification ### Page 8 7.2.5 Upgrade Qualification 7.2.6 Differences Qualification - Addressing Cockpit or Aircraft System Differences 7.2.7 Recency of Experience 7.3 Checking or Evaluations 7.3.1 Checking For Category I Qualification 7.3.2 Checking For Category II Qualification 7.3.3 Combined Checking For Simultaneous Category I/II or I/II/III Qualification 7.3.4 Checking For Low Visibility Takeoff Qualification 7.4 Experience with Line Landings 7.5 Crew Records 7.6 Multiple Aircraft Type or Variant Qualification 7.7 Aircraft Interchange 7.8 Training Regarding Use of Foreign Airports for Category I or Category II Operations 7.9 Initial Operating Experience (IOE)/Supervised Line Flying (SLF) 7.10 Line Checks, Route Checks, LOE, LOS, or LOFT 7.11 Special Qualification Requirements for Particular Category I or Category II Operations 7.11.1 HUD or Autoland 7.11.2 Use of Lowest Category I Minima at Certain Obstacle Limited or Restricted ILS Facilities 7.11.3 Simultaneous Operations Using PRM Radar 7.11.4 Simultaneous Operations with Converging Approaches and Coordinated Missed Approaches 7.11.5 Simultaneous Runway Operations 7.11.6 Special Qualification Airports 7.11.7 Special Qualification Instrument Procedures or Types of Instrument Procedures 7.12 Special Qualification Requirements for Category II Operations at Certain U.S. Type I ILS Facilities 7.13 Simultaneous Training and Qualification for Category I and II 7.14 Simultaneous Training and Qualification for Category I, II, and III 7.15 Credit for “High Limit Captains” (Reference Sections 121.652, 125.379, 135.225) 7.16 Particular Approach System/Procedure Qualification 7.16.1 Autoland Qualification 7.16.2 Head Up Display Qualification 7.16.3 RNAV Approach Qualification 7.16.4 Category I or II Operations with an Engine Inoperative 7.16.5 Enhanced Vision Systems (EVS), or Synthetic Vision Systems (SVS), or Independent Landing Monitor (ILM) 8 AIRPORTS, NAVIGATION FACILITIES, AND METEROLOGICAL CRITERIA 8.1 Use of Standard Navigation Facilities 8.2 Use of Other Navigation Facilities or Methods 8.3 Lighting Systems 8.4 Marking and Signs 8.5 Low Visibility Surface Movement Guidance and Control System (SMGCS) Plans 8.6 Meteorological Services and RVR 8.6.1 Meteorological Services 8.6.2 RVR Availability and Use Requirements 8.6.2.1 RVR Availability. 8.6.2.2 RVR Use. 8.6.2.3 Alternate RVR Requirements For Short Field Length Operations. 8.6.2.4 International RVR Reporting and Use Equivalence Considerations. 8.6.3 Pilot Assessment of Takeoff Visibility Equivalent to RVR 8.7 Critical Area Protection 8.8 Operational Facilities, Outages, Airport Construction, and NOTAMs 8.9 Use of Military Facilities 8.10 Special Provisions for Facilities Used for ETOPS Alternates or EROPS Alternates 8.11 Alternate Minima 8.12 Dispatch or Release to Airports That are Below Landing Minima ### Page 9 8.13 Temperatures and Temperature Extremes 8.14 Pressures and Unusually High or Low Pressures 9 CONTINUING AIRWORTHINESS / MAINTENANCE 9.1 Maintenance Program General Provisions 9.2 Maintenance Program Requirements 9.3 Initial and Recurrent Maintenance Training 9.4 Test Equipment/Calibration Standards 9.5 Return to Service Procedures 9.6 Periodic Aircraft System Evaluations 9.7 Reliability Reporting and Quality Control 9.7.1 Reliability Reporting - Category I 9.7.2 Reliability Reporting - Category II 9.8 Configuration Control/System Modifications 9.9 Records 9.10 Part 129 Foreign Operator Maintenance Programs 9.10.1 Maintenance of Part 129 Foreign Registered Aircraft 9.10.2 Maintenance of Part 129 Foreign Operated U.S. “N” Registered Aircraft 10 APPROVAL OF U.S. OPERATORS 10.1 Operations Manuals and Procedures 10.2 Training Programs and Crew Qualification 10.3 Dispatch Planning (e.g., MEL, Alternate Airports, ETOPS) 10.4 Formulation of Operations Specification Requirements (e.g., RVR limits, DA(H) or MDA(H), equipment requirements, field leng ths) 10.5 Operational/Airworthiness Demonstrations 10.5.1 Aircraft System Suitability Demonstration 10.5.2 “Operator Use Suitability” Demonstration 10.5.2.1 Data Collection For Airborne System Demonstrations 10.5.2.2 Data Analysis 10.5.3 Use of Autoland or Head up Guidance at US Type I Facilities or Equivalent (e.g., Type I ILS). 10.6 Eligible Airports and Runways 10.7 Irregular Pre-Threshold Terrain and Other Restricted Runways 10.8. Category II Engine-Inoperative Operations and ETOPS or EROPS Alternates based on Category II. 10.8.1 General Criteria for Engine Inoperative Category II Authorization 10.8.2. Category II Engine Inoperative “Flight Planning” 10.8.3 Category II Engine Inoperative En Route 10.8.4 Category II Engine Failure During Approach, Prior to Decision Altitude (Height) (DA(H)) 10.8.5 Category II Engine Failure After Passing Decision Altitude (Height) (DA(H)) 10.8.6 Operators using Combined Category II and Category III Engine-Inoperative Approach Provisions. 10.9 New Category II Operators 10.10 Experienced Category II or Category III Operators for New Category II Authorizations 10.10.1 Category I or II at New Airports/Runways 10.10.2 Category II with New Aircraft Systems 10.10.3 Adding a New Category II Aircraft Type 10.11 Category II Program Status Following Operator Acquisitions/Mergers 10.12 Initiating Combined Category I and II, or Category I, II, and III Programs for New Equipment Types 10.13 U.S. Carrier Category I and II Operations at Foreign Airports 10.14 Category I and II Operations on Off-Route Charters 10.15 Approval of Category I and II Minima 10.16 Operations Specification Amendments 10.17 Use of Special Obstacle Clearance Criteria (e.g., MASPS, or non-standard RNP Criteria) 10.18 Proof-of-Concept Requirements for New Systems/Methods 10.19 RNP Qualification and Authorization ### Page 10 11 FOREIGN AIR CARRIER CATEGORY I WITH SYSTEMS OTHER THAN ILS OR CATEGORY II AT U.S. AIRPORTS (PART 129 OPERATIONS SPECIFICATIONS) 11.1 Use of ICAO or FAA Criteria 11.1.1 Acceptable Criteria 11.1.2 Foreign Operator AFM Provisions 11.1.3 Foreign Operator Category II Demonstrations 11.2 Issuance of Part 129 Operations Specifications 11.3 Use of Certain Restricted U.S. Facilities 12 OPERATOR REPORTING, AND TAKING CORRECTIVE ACTIONS 12.1 Operator Reporting 12.2 Operator Corrective Actions APPENDIX 1 DEFINITIONS AND ACRONYMS APPENDIX 2 AIRBORNE SYSTEMS FOR CATEGORY I 1 APPENDIX 2 PURPOSE 2 APPENDIX 2 GENERAL 3 APPENDIX 2 INTRODUCTION 4 APPENDIX 2 TYPES OF APPROACH OPERATIONS 4.1 APPENDIX 2 Operations based on a Standard Landing Aid 4.2 APPENDIX 2 Operations based on Required Navigation Performance (RNP) 4.2.1 APPENDIX 2 Standard RNP Types 4.2.2 APPENDIX 2 Non-standard RNP Types 4.3 APPENDIX 2 Operations based on Area Navigation System(s) 5 APPENDIX 2 TYPES OF APPROACH NAVIGATION SERVICE 5.1 APPENDIX 2 Instrument Landing System (ILS) 5.1.1 APPENDIX 2 ILS Flight Path Definition 5.1.2 APPENDIX 2 ILS Airplane Position Determination 5.2 APPENDIX 2 Microwave Landing System (MLS) 5.2.1 APPENDIX 2 MLS Flight Path Definition 5.2.2 APPENDIX 2 MLS Airplane Position Determination 5.3 APPENDIX 2 GNSS with Ground Based Augmentation (GLS) [PoC] 5.3.1 APPENDIX 2 GLS Flight Path Definition 5.3.2 APPENDIX 2 GLS Airplane Position Determination 5.3.3 APPENDIX 2 Data link [PoC] 6 APPENDIX 2 BASIC AIRWORTHINESS REQUIREMENTS 6.1 APPENDIX 2 General Requirements 6.2 APPENDIX 2 Approach System Accuracy Requirement **6.2.1 APPENDIX 2 ILS** **6.2.2 APPENDIX 2 MLS** 6.2.3 APPENDIX 2 GLS [PoC] **6.2.4 APPENDIX 2 RNP** 6.2.5 APPENDIX 2 Flight Path Definition 6.2.6 APPENDIX 2 Area Navigation Systems 6.3 APPENDIX 2 Approach System Integrity Requirements **6.3.1 APPENDIX 2 ILS** **6.3.2 APPENDIX 2 MLS** **6.3.3 APPENDIX 2 GLS** **6.3.4 APPENDIX 2 RNP** 6.3.5 APPENDIX 2 Area Navigation Systems 6.4 APPENDIX 2 Approach System Availability Requirements 6.5 APPENDIX 2 Go-around Requirements 6.6 APPENDIX 2 Flightdeck Information, Annunciation, and Alerting Requirements ### Page 11 6.6.1 APPENDIX 2 Flightdeck Display Information Requirements 6.6.2 APPENDIX 2 Annunciation Requirements 6.6.3 APPENDIX 2 Alerting 6.6.3.1 APPENDIX 2 Warnings 6.6.3.2 APPENDIX 2 Cautions 6.6.3.3 APPENDIX 2 System Status 6.7 APPENDIX 2 Multiple Landing Systems and Multi-mode Receivers (MMR) for Category I 6.7.1 APPENDIX 2 General Requirements 6.7.2 APPENDIX 2 Indications 6.7.3 APPENDIX 2 Annunciations 6.7.4 APPENDIX 2 Alerting 6.7.5 APPENDIX 2 Multi-mode Receivers (MMR) 6.7.5.1 APPENDIX 2 “ILS Look-alike” Definition Applicable to MMR 6.7.5.2 APPENDIX 2 General Certification Considerations 6.7.5.2.1 APPENDIX 2 Certification Process 6.7.5.2.2 APPENDIX 2 Equipment Approval 6.7.5.2.3 APPENDIX 2 Aircraft Installation Approval (14 CFR Part 25) 6.7.5.2.4 APPENDIX 2 Alternative Means of Compliance using JAR-AWO 6.7.5.2.5 APPENDIX 2 Recertification of an ILS function following the Introduction of a New or Modified ILS Navigation Receiver Installation 6.7.5.2.5.1 APPENDIX 2 New or Modified ILS Impact Assessment 6.7.5.2.5.2 APPENDIX 2 New or Modified ILS Failure Analysis 6.7.5.2.5.3 APPENDIX 2 New or Modified ILS Autoland or HUD Guidance Landing Function Flight Testing (if necessary) 6.7.5.2.5.4 APPENDIX 2 New or Modified ILS Documentation 6.7.5.2.6 APPENDIX 2 Recertification following the Introduction of an MLS or GLS Navigation Receiver Installation 6.7.5.2.6.1 APPENDIX 2 MLS or GLS Introduction Impact Assessment 6.7.5.2.6.2 APPENDIX 2 MLS or GLS Failure Analysis 6.7.5.2.6.3 APPENDIX 2 MLS or GLS Statistical Performance Assessment 6.7.5.2.6.4 APPENDIX 2 MLS or GLS Antenna or Navigation Reference Point Location 6.7.5.2.6.5 APPENDIX 2 MLS or GLS Introduction Flight Testing (as necessary) 6.7.5.2.6.6 APPENDIX 2 MLS or GLS Introduction Documentation 6.8 APPENDIX 2 Steep Angle Approaches 7 APPENDIX 2 APPROACH SYSTEM EVALUATION 7.1 APPENDIX 2 Performance Evaluation 7.2 APPENDIX 2 Safety Assessment 8 APPENDIX 2 AIRBORNE SYSTEM REQUIREMENTS 8.1 APPENDIX 2 General 8.2 APPENDIX 2 Autopilot 8.3 APPENDIX 2 Head Down Guidance 8.4 APPENDIX 2 Head Up Guidance 8.5 APPENDIX 2 Hybrid HUD/Autoland System [PoC] 8.6 APPENDIX 2 Satellite Based Approach System 8.7 APPENDIX 2 Aircraft Navigation Systems 8.8 APPENDIX 2 Autothrottle 8.9 APPENDIX 2 Data link [PoC] 9 APPENDIX 2 AIRPLANE FLIGHT MANUAL (AFM) APPENDIX 3 AIRBORNE SYSTEMS FOR CATEGORY II 1 APPENDIX 3 PURPOSE 2 APPENDIX 3 GENERAL 3 APPENDIX 3 INTRODUCTION 4 APPENDIX 3 TYPES OF APPROACH OPERATIONS 4.1 APPENDIX 3 Operations based on a Standard Landing Aid 4.2 APPENDIX 3 Operations based on Required Navigation Performance (RNP) ### Page 12 4.2.1 APPENDIX 3 Standard RNP Types 4.2.2 APPENDIX 3 Non-standard RNP Types 5 APPENDIX 3 TYPES OF APPROACH NAVIGATION SERVICE **5.1 APPENDIX 3 ILS** 5.1.1 APPENDIX 3 ILS Flight Path Definition 5.1.2 APPENDIX 3 ILS Airplane Position Determination **5.2 APPENDIX 3 MLS** 5.2.1 APPENDIX 3 MLS Flight Path Definition 5.2.2 APPENDIX 3 MLS Airplane Position Determination 5.3 APPENDIX 3 GNSS with Ground Based Augmentation (GLS) [PoC] 5.3.1 APPENDIX 3 GLS Flight Path Definition [PoC] 5.3.2 APPENDIX 3 GLS Airplane Position Determination [PoC] 5.3.3 APPENDIX 3 Data link [PoC] 6 APPENDIX 3 BASIC AIRWORTHINESS REQUIREMENTS 6.1 APPENDIX 3 General Requirements 6.2 APPENDIX 3 Approach System Accuracy Requirements **6.2.1 APPENDIX 3 ILS** **6.2.2 APPENDIX 3 MLS** 6.2.3 APPENDIX 3 GLS [PoC] **6.2.4 APPENDIX 3 RNP** 6.2.5 APPENDIX 3 Flight Path Definition 6.3 APPENDIX 3 Approach System Integrity Requirements **6.3.1 APPENDIX 3 ILS** **6.3.2 APPENDIX 3 MLS** **6.3.3 APPENDIX 3 GLS** **6.3.4 APPENDIX 3 RNP** 6.4 APPENDIX 3 Approach System Availability Requirements 6.5 APPENDIX 3 Go-around Requirements 6.6 APPENDIX 3 Flightdeck Information, Annunciation, and Alerting Requirements 6.6.1 APPENDIX 3 Flightdeck Display Requirements 6.6.2 APPENDIX 3 Annunciation Requirements 6.6.3 APPENDIX 3 Alerting 6.6.3.1 APPENDIX 3 Warnings 6.6.3.2 APPENDIX 3 Cautions 6.6.3.3 APPENDIX 3 System Status 6.7 APPENDIX 3 Multiple Landing Systems and Multi-mode Receivers (MMR) for Category II 6.7.1 APPENDIX 3 General Requirements 6.7.2 APPENDIX 3 Indications 6.7.3 APPENDIX 3 Annunciations 6.7.4 APPENDIX 3 Alerting 6.7.5 APPENDIX 3 Multi-mode Receiver(s) (MMR) 6.7.5.1 APPENDIX 3 “ILS Look-alike” Definition applicable to MMR 6.7.5.2 APPENDIX 3 General Certification Considerations 6.7.5.2.1 APPENDIX 3 Certification Process 6.7.5.2.2 APPENDIX 3 Equipment Approval 6.7.5.2.3 APPENDIX 3 Aircraft Installation Approval (14 CFR Part 25) 6.7.5.2.4 APPENDIX 3 Alternate Means of Compliance using JAR-AWO 6.7.5.2.5 APPENDIX 3 Recertification of an ILS function following the introduction of a New or Modified ILS Navigation Receiver Installation 6.7.5.2.5.1 APPENDIX 3 New or Modified ILS Impact Assessment 6.7.5.2.5.2 APPENDIX 3 New or Modified ILS Failure Analysis 6.7.5.2.5.3 APPENDIX 3 New or Modified ILS Autoland or HUD Guidance Landing Function Flight Testing (if necessary) 6.7.5.2.5.4 APPENDIX 3 New or Modified ILS Documentation 6.7.5.2.6 APPENDIX 3 Recertification Following the Introduction of an MLS or GLS Navigation Receiver Installation ### Page 13 6.7.5.2.6.1 APPENDIX 3 MLS or GLS Introduction Impact Assessment 6.7.5.2.6.2 APPENDIX 3 MLS or GLS Failure Analysis 6.7.5.2.6.3 APPENDIX 3 MLS or GLS Statistical Performance Assessment 6.7.5.2.6.4 APPENDIX 3 MLS or GLS Antenna or Navigation Reference Point Location 6.7.5.2.6.5 APPENDIX 3 MLS or GLS Introduction Flight Testing (as necessary) 6.7.5.2.6.6 APPENDIX 3 MLS or GLS Introduction Documentation 7 APPENDIX 3 APPROACH SYSTEM EVALUATION 7.1 APPENDIX 3 Performance Evaluation 7.2 APPENDIX 3 Safety Assessment 8 APPENDIX 3 AIRBORNE SYSTEM REQUIREMENTS 8.1 APPENDIX 3 General 8.2 APPENDIX 3 Autopilot 8.3 APPENDIX 3 Head Down Guidance 8.4 APPENDIX 3 Head Up Guidance 8.5 APPENDIX 3 Hybrid HUD/Autoland Systems [PoC] 8.6 APPENDIX 3 Satellite Based Approach System 8.7 APPENDIX 3 Reserved 8.8 APPENDIX 3 Autothrottle 8.9 APPENDIX 3 Data link 9 APPENDIX 3 AIRPLANE FLIGHT MANUAL (AFM) APPENDIX 4 WIND MODEL FOR APPROACH SIMULATION APPENDIX 5 OBSTACLE ASSESSMENT FOR RNP FOR CATEGORY I OR CATEGORY II 1 APPENDIX 5 Obstacle Assessment for Standard Required Performance (RNP) Types (e.g., Linear Values of RNP) 1.1 APPENDIX 5 Obstacle Assessment for RNP Approaches and Missed Approaches 1.1.1 APPENDIX 5 General 1.1.2 APPENDIX 5 Final Approach (FAS), Missed Approach (MAS) and other Related Segments 1.1.3 APPENDIX 5 Approach and Missed Approach Conditions To Be Assessed 1.1.4 APPENDIX 5 Touchdown Zone 1.2 APPENDIX 5 Obstacle Criteria 1.2.1 APPENDIX 5 Obstacle Identification Surface Between Point Of Lowest DA(H) and the Runway 1.2.2 APPENDIX 5 Obstacle Identification Surface Between the Point of Lowest DA(H) and a Missed Approach 1.2.3 APPENDIX 5 Obstacle Identification Surface Between the End of the TDZ and a Missed Approach Waypoint 1.2.4 APPENDIX 5 FAS Turn Construction 1.2.4.1 APPENDIX 5 FAS Turn Construction for Fly-by Waypoints 1.2.4.2 APPENDIX 5 FAS Turn Construction for Fly-over Waypoints 1.2.5 APPENDIX 5 MAS Turn Construction 1.2.5.1 APPENDIX 5 MAS Turn Construction for Fly-by Waypoints 1.2.5.2 APPENDIX 5 MAS Turn Construction For Fly-over Waypoints 1.2.6 APPENDIX 5 RNP Reductions 1.2.7 APPENDIX 5 Coordinate Systems 1.2.8 APPENDIX 5 Obstruction and Terrain Charts 1.2.8.1 APPENDIX 5 Recommended Use of USGS Charts 1.2.8.2 APPENDIX 5 Vertical Clearance Adjustments for Certain Topographical Charts 1.2.8.3 APPENDIX 5 Tree Heights 1.2.8.4 APPENDIX 5 Assumptions for Terrain Elevations 1.2.9 APPENDIX 5 Man-Made Obstacle Data 1.2.10 APPENDIX 5 Wheel to Navigation Reference Point or Longitudinal Navigation Reference Points 1.3 APPENDIX 5 Examples of completed RNP Forms 2 APPENDIX 5 FINAL APPROACH OBSTACLE ASSESSMENT - NON-STANDARD LEVELS OF RNP 2.1 APPENDIX 5 Obstacle Assessment For Non-Standard Levels of RNP **2.2 APPENDIX 5 OBSTACLE CRITERIA** ### Page 14 2.3 APPENDIX 5 USE OF THESE CRITERIA FOR AIRBORNE SYSTEM AIRWORTHINESS DEMONSTRATIONS WITH **NON-STANDARD LEVELS OF RNP** **2.3.1 APPENDIX 5 LATERAL PERFORMANCE** **2.3.2 APPENDIX 5 VERTICAL PERFORMANCE** 2.4 APPENDIX 5 OTHER CONSIDERTIONS APPENDIX 6 GROUND SYSTEMS AND OBSTACLE CLEARANCE CRITERIA FOR CATEGORY II AND CATEGORY III OPERATIONS 1 APPENDIX 6 PURPOSE 2 APPENDIX 6 GENERAL 3 APPENDIX 6 SUPPORTING NAVIGATION AIDS OR SENSORS FOR CATEGORY II PROCEDURES 4 APPENDIX 6 OBSTACLE CLEARANCE CRITERIA APPENDIX 7 OPERATIONS SPECIFICATIONS 1 APPENDIX 7 General 2 APPENDIX 7 14 CFR Part 121 Operations Specifications - PART A 3 APPENDIX 7 14 CFR Part 121 Operations Specifications - PART C C051 APPENDIX 7 OpSpec C051, Terminal Instrument Procedures C052 APPENDIX 7 OpSpec C052, Basic Instrument Approach Procedure Authorization - All Airports C053 APPENDIX 7 OpSpec C053, Straight-in Category I Approach Procedures other than ILS, MLS, or GPS and IFR Landing Minimums - All Airports C054 APPENDIX 7 OpSpec C054, Limitations and Provisions for Instrument Approach Procedures and IFR Landing Minimums C055 APPENDIX 7 OpSpec C055, Alternate Airport IFR Weather Minimums C056 APPENDIX 7 OpSpec C056, IFR Takeoff Minimums, Part 121 Airplane Operations - All Airports C059 APPENDIX 7 OpSpec C059, Category II Instrument Approach and Landing Operations C061 APPENDIX 7 OpSpec C061, Flight Control Guidance Systems for Automatic Landing Operations Other Than Categories II and III C062 APPENDIX 7 OpSpec C062, Manually Flown Flight Control Guidance System Certified for Landing Operations Other Than Categories II and III C074 APPENDIX 7 OpSpec C074, Straight-in Category I, ILS, MLS, or GLS Approach Procedures and IFR Landing Minimums - All Airports C075 APPENDIX 7 OpSpec C075, Category I IFR Landing Minimums - Circling Maneuvers C076 APPENDIX 7 OpSpec C076, Category I IFR Landing Minimums - Contact Approaches C078 APPENDIX 7 OpSpec C078, IFR Lower Than Standard Takeoff Minimums, 14 CFR Part 121 Airplane Operations - All Airports C090 APPENDIX 7 OpSpec C090, Required Navigation Performance (RNP) APPENDIX 8 USE OF ALTERNATIVE OPERATING MINIMA 1 APPENDIX 8 General 2 APPENDIX 8 Terminology 3 APPENDIX 8 “Go-Around” Transition To A Missed Approach When Using a DA(H) or MDA(H) 4 APPENDIX 8 Alternative RVR/Visibility Value Table 5 APPENDIX 8 Approach and Runway Lighting Systems Definition, Classification, and Equivalence 6 APPENDIX 8 Applicability to Various Classes of Instrument Approach Procedures 7 APPENDIX 8 Transition Provisions 8 APPENDIX 8 Authorized RVR Minima Conversions between “Feet and Meters” 9 APPENDIX 8 Acceptable Meteorological Visibility or RVR Equivalence or Conversion ### Page 15 Par 1 Page 1 1. PURPOSE. This advisory circular (AC) provides an acceptable means, but not the only means, for obtaining and maintaining approval of Category I and II Weather Minima including the installation and approval of associated aircraft systems. This AC is applicable to Title 14 of the Code of Federal Regulations (14 CFR) parts 121, 135, and those part 125 operators not exempted under section 125.1 or not having received an applicable deviation authorization under section 125.3. Certain aspects of this AC are applicable to 14 CFR part 129 operators. Many of the principles, concepts, and procedures described also may apply to 14 CFR part 91 operations and are recommended for use by those operators when applicable. a. This AC provides some guidance that may be applicable to operations conducted by civil helicopters and powered-lift aircraft. Supplementary guidance for those aircraft may be provided by other FAA or industry documents. b. Mandatory terms used in this AC such as “shall” or “must” are used only in the sense of insuring applicability of these particular methods of compliance when the acceptable means of compliance described herein is used. This AC does not change, add, or delete regulatory requirements or authorize deviations from regulatory requirements. c. Major changes introduced in this revision include new provisions for Required Navigation Performance (RNP), Vertical Navigation (VNAV), Flight Management System (FMS), Global Navigation Satellite System (GNSS), Head Up Display (HUD), Global Positioning System (GPS) or GNSS Landing System (GLS), revised obstacle assessment criteria related to RNP, and revised airborne equipment requirements for Category I and II. d. With issuance of AC120-29A, the former AC 120-29, Criteria for Approving Category I and Category II Landing Minima for FAR 121 Operators, dated December 3, 1974, is canceled. **2. RELATED REFERENCES AND DEFINITIONS.** 2.1. Related References. a. Regulations. 14 CFR part 91, sections 91.175, and 91.189; 14 CFR part 121, sections 121.579, and 121.651; 14 CFR part 125, sections 125.379, and 125.381; 14 CFR part 129, section 129.11; and 14 CFR part 135, section 135.225; 14 CFR part 25, sections 25.1309, and 25.1329. b. ACs. Current editions of: AC 120-28, Criteria for Approval of Category III Landing Weather Minimal; AC 20-129, Airworthiness Approval of Vertical Navigation (VNAV) Systems for Use In the U.S. NAS and Alaska; AC 20-130, Airworthiness Approval of Navigation or Flight Management Systems Integrating Multiple Navigation Sensors; AC20-138, Airworthiness Approval of GPS Navigation Equipment for use as a Supplemental Navigation System; and AC 25-15, Approval of Flight Management Systems in Transport Category Airplanes. c. Orders. FAA Orders 8400.8, Procedures for Approval of Facilities for FAR Part 121 and Part 135 CAT III Operations; 8400.10, Air Transportation Operations Inspector’s Handbook; 8400.13, Procedures for the Approval of Category II Operations and Lower Than Standard Category I Operations on Type I Facilities; and 6750.24, Instrument Landing System (ILS) and Ancillary Electronic Component Configuration and Performance Requirements. d. OpSpecs. Standard Operations Specifications Part A and C. e. Foreign. Joint Aviation Authority (JAA) ACJ AWO 231, Flight Demonstration (Acceptable Means of Compliance) dated August, 1996. 2.2. Definitions. A comprehensive set of definitions pertinent to Category I and II is included in Appendix I. ### Page 16 Page 2 Par 3 **3. BACKGROUND.** 3.1. Major Changes Addressed in this Revision. This advisory circular includes additional Category I and Category II criteria or revised Category II criteria for use of Head up Displays, use of Required Navigation Performance (RNP), satellite based navigation, and “engine inoperative” Category II approach procedures. This revision expands information regarding Category I approach procedures, and now includes material pertinent to types of approach procedures other than ILS, MLS, or GLS (e.g., also addresses approaches previously considered as non-precision approaches). a. This AC also clarifies existing criteria to address frequently asked questions. b. This revision incorporates changes resulting from the first steps toward international all weather operations (AWO) criteria harmonization taken by the FAA, European JAA, and several other regulatory authorities. Subsequent revisions of this AC are planned as additional all weather operations harmonization items (AHI(s)) are agreed and completed by FAA and JAA, or internationally. 3.2. Relationship of Operational Authorizations for Category I or Category II and Airborne System Demonstrations. Approach weather minima are approved through applicable operating rules, use of approved instrument procedures and issuance of Operations Specifications (Op-Specs)*. Airworthiness demonstration of aircraft equipment is usually accomplished in support of operational authorizations on a one-time basis at the time of Type Certification (TC) or Supplemental Type Certification (STC). This demonstration is based upon the airworthiness criteria in place at that time. Since operating rules continuously apply over time and may change after airworthiness demonstrations are conducted, or may be updated consistent with safety experience, additional Category I or Category II credit or constraints may apply to Operators or aircraft as necessary for safe operations. In general, criteria related to operational approval is contained in the main body of this AC and criteria related primarily to the airworthiness demonstration of systems or equipment is included in the appendices to this AC. *NOTE: Operations Specifications are unique Federal Aviation Regulations applicable to a particular operator. OpSpecs are based on the regulations. However, they are specifically applicable to and tailored to a particular operator’s aircraft, routes, and operating circumstances. Standard Operations Specifications are developed by FAA and provided to FAA field offices to aid in development and issuance of the particular and unique OpSpecs issued to each operator. 3.3. Applicable Criteria. Except as described below, new airworthiness demonstrations or operational authorizations should use the criteria of AC 120-29A. Airworthiness demonstrations may use equivalent JAA criteria where agreed by FAA through the FAA/JAA criteria harmonization process. Operators electing to comply with these revised criteria may receive additional credit when using the revised criteria. Aircraft manufacturers or modifiers may elect to demonstrate their aircraft using the revised criteria to seek credit for additional operations. Aircraft demonstrated using earlier criteria may continue to be approved for Category I or Category II operations in accordance with (IAW) that earlier criteria. Operators seeking additional credit provided for in this AC must, however, use the criteria of this AC for that credit. 3.4. Category I, II, and III Terminology. a. Since 1985, the FAA has referred to all approaches other than Category II or Category III as Category I, for purposes of regulatory authorization for part 121, 125, 135, and 129 operators (e.g., Operations Specifications). Thus for consistency and continuity, all Category I approach procedures and operational authorizations are now addressed in this AC. In addition to typical Category I Instrument Landing System (ILS), Microwave Landing System (MLS) and Global Navigation Satellite System (GNSS) Landing System (GLS) procedures (e.g., procedures historically considered as precision approach), information about approaches other than ILS, MLS, and GLS are now included (e.g., procedures historically considered as non-precision approach). The use of the term “non-precision” has been dropped within this AC to reduce confusion which exists with use of this term with current and future ### Page 17 Par 3 Page 3 systems and authorizations, particularly with Vertical Navigation (VNAV) and Area Navigation (RNAV), and with other approaches that may incorporate the use of barometric VNAV to provide a stabilized descent path to a runway. b. Accordingly, Category I, II, and III terminology used in this AC is based on and is consistent with current U.S. Standard Operations Specifications for part 121, 125, 135, and 129 Operators. Definition usage is also consistent with other ACs (e.g., AC120-28D). Definitions of instrument approach Categories in current use in the U.S. are listed in Appendix 1 of this AC (i.e., Category I, Category II, Category IIIa, IIIb, and IIIc). While there are slight variations of these definitions as used within ICAO and various countries internationally, the broad objectives and practical operational applications are similar. It is significant to note that for U.S. applications to part 121, 125, 135, and 129 operators, Category I is considered to include any instrument approach procedure having minima not less than 200 ft. Height Above Touchdown (HAT) and RVR not less than 1800ft. Accordingly, approaches such as Localizer (LOC); LOC BCRS; Localizer-Type Directional Aid (LDA); Simplified Directional Facility (SDF); Very High Frequency (VHF) Omni-directional Radio Range (VOR); Non-Directional Beacon (NDB); and RNAV are each considered to be Category I approaches. In other states, Category I may only apply to straight-in ILS or MLS instrument procedures. Also, in certain states, lowest authorized minima may be slightly different than as promulgated by the U.S. or ICAO criteria. In a few states, these approach categories relate more closely to aircraft configuration or ILS facilities used, rather than directly landing minima (e.g., Decision Altitude (Height) (DA(H)) and visibility or RVR). 3.5. Requirement for Evaluation Prior to Operations. Instrument approach procedures in the United States and its territories must be validated by an authorized FAA process. Special procedure requests should be made through the CMO to AFS-400. **4. OPERATIONAL CONCEPTS.** 4.1. Classification and Applicability of Minima. Landing minima are generally classified by Category I, Category II, and Category III. Definitions for Category I, II, and III are as specified by ICAO and individual states. For the U.S. these definitions are as included in Appendix 1. Certificate Holding District Offices (CHDO) and Operators should be aware that slight differences exist in definition and use of Category I, II, and III terminology in international operations. Operators should ensure that any differences in definitions do not adversely affect intended operations (see Paragraph 3.4 above). a. This AC addresses criteria for Category I and Category II instrument approach operations. AC 120-28 addresses takeoff in low visibility conditions and Category III landing operations. b. Landing minima are generally addressed by parts 91.175, 121.649, 121.651, 121.652 and standard or special OpSpecs Part C. Application of these definitions of Category I, II, and III to landing is discussed in paragraph 4.3.1 below. c. Although a wide variety of normal and non-normal situations are considered in the design and approval of systems and procedures for Category I and Category II, landing weather minima are primarily intended to apply to normal operations. For non-normal operations, flightcrews are expected to take the safest course of action appropriate for the situation, notwithstanding landing weather minima. When aircraft systems have been demonstrated to account for certain non-normal configurations and a procedure is specified (e.g., an approach with an engine inoperative non-normal procedure), the flightcrew may take account of this information in assessing the safest course of action. In addition, when inoperative aircraft systems have been accounted for in the Airplane Flight Manual (AFM) as an alternate configuration using criteria of this AC (e.g., an approach with an engine inoperative is specified as a demonstrated configuration) operational credit for that configuration (alternate minima credit) may be authorized. d. Takeoff minimums are generally addressed by parts 91, 121, 135, and standard or special OpSpecs. Application of takeoff minima is discussed in paragraph 4.2 below. 4.2. Takeoff. ### Page 18 Page 4 Par 4 a. Takeoff Minima. (1) Takeoff minima are addressed by sections 91.175(f), 121.649, 121.651, 135.225, and standard or special OpSpecs Part C. The authority for lower than standard takeoff minima is contained in sections 135.225(h)(3) and 121.651(a)(1). (2) OpSpecs are applicable to part 121 and 135 Operators and certain other Operators (e.g., part 125 and part 129). Where minima lower than that provided in standard OpSpecs are necessary, applicable criteria for use of those minima are specified in AC 120-28D. When appropriate, principal operations inspectors (POI(s)) issue OpSpecs specifying the lower minima through paragraph C056 for part 121 Operators and OpSpecs paragraph C057 for part 135 Operators. OpSpecs contain specific guidance regarding pilots, aircraft, and airports when lower than standard takeoff minimums are used. b. Takeoff RVR Equivalence and Assessment (See also 8.6.3). For takeoff procedures where minima are published only in terms of RVR, but visibility is being reported as a meteorological visibility, tables referenced in Standard OpSpecs may be used to establish equivalent RVR (see Appendix 7, OpSpec Paragraph). This table does not apply to minima published as meteorological visibility being reported as RVR c. Pilot Assessment of equivalent RVR. For takeoff circumstances where Touchdown Zone RVR is inoperative or is determined by the pilot to be significantly in error (e.g., patchy fog obscuring a transmissometer but not the runway, snow on transmissometer causing erroneous readings), a pilot assessment may be made in lieu of RVR (see Appendix 7, OpSpec Paragraph C078). (1) To be eligible to use this provision the operator must ensure that each pilot authorized to make this determination has completed approved training addressing pilot procedures to be used for visibility assessment in lieu of RVR, and the pilot can determine the necessary runway markings or runway lighting that must be available to provide an equivalent RVR to that specified to ensure adequate visual reference for the takeoff. (2) When any pilot assessment of equivalent RVR is made, the pilot must be able to positively determine position on the airport and correct runway, and positively establish that the aircraft is at the correct position for initiation of takeoff. Typically this equivalent RVR assessment is applicable only at a runway threshold where runway identifying markings and number(s) are visible from the takeoff position (e.g., not applicable to intersection takeoffs). (3) When such a pilot RVR assessment is made, the result of the assessment should typically be provided to any pertinent air traffic facility when practical, and may also be provided to the operator (e.g., dispatch) to facilitate other operations. 4.3. Landing. 4.3.1. Approach and Landing Concepts and Objectives. Landing minima are classified as Category I, Category II, and Category III. Definitions of these categories are provided in Standard OpSpecs Part A paragraph A002, and in Appendix 1. While generally consistent with ICAO definitions, the definitions used in Standard OpSpecs, where different from ICAO, apply and take precedence for U.S. operators, or for international operators conducting operations within the United States, or at U.S. facilities. a. For U.S. Operators, any instrument approach with a DA(H) or Minimum Descent Altitude (Height) (MDA(H)) and visibility above that specified in OpSpecs for Category I, (see Appendix 7) is considered to be a Category I operation (e.g., an approach with either a DA(H) or an MDA(H) which is not lower than 200 ft. HAT and visibility not less than 1800 RVR is considered to be Category I, even though it may be based on a Navigational Aid (NAVAID) other than ILS). ### Page 19 Par 4 Page 5 b. Any instrument approach with a DA(H) or visibility less than that specified for Category I, but above that specified for Category II, is considered to be a Category II operation. c. Any instrument approach with a DA(H) less than that specified for Category II (or with no DA(H) or with an Alert Height), or with a visibility less than that specified for Category II, IAW applicable OpSpecs is considered to be a Category III operation. d. Category I operations may be conducted manually using raw data information, by reference to flight guidance displays (flight directors), or automatically using approved autopilot or autoland systems. However, air carrier operations, particularly with turbine powered aircraft, typically have minima restricted by OpSpecs if a flight director or autopilot is not used. e. For Category I, basic airworthiness certification for IFR under provisions of 14 CFR part 25 typically is considered an acceptable means of demonstration of capability for operational acceptance of an aircraft and its associated systems. Specific criteria for airworthiness demonstration of certain specific systems or capabilities for Category I are included in Appendix 2 (e.g., FMS or RNP). f. For Category I minima, it is expected that for non-normal operations (e.g., engine(s) inoperative, hydraulic or electrical system(s) failure) the pilot or operator should consider any necessary adjustment of operating minima, wind limit constraints, or other factors to ensure safe operation with the non-normal condition. g. Category II operations may be conducted manually using flight guidance (e.g., flight director) displays. However, most Category II operations are conducted using an autopilot or autoland system, or with combinations of systems using both automatic and flight guidance (e.g., flight director) elements. Additional demonstration or operational assessment beyond that required for basic IFR flight under provisions of basic aircraft 14 CFR part 25 type certification typically is necessary for operational authorization of an aircraft for Category II (see Paragraph 5 and Appendix 3). Specific criteria for airworthiness demonstration of systems or capabilities for Category II are included in Appendix 3 (e.g., for flight director(s), autopilot(s), or HUD) for cases where an applicant seeks prior credit for such a prior airworthiness demonstration documented in the AFM). h. For Category II minima, certain non-normal conditions are typically considered in the assessment and authorization process. Response to those non-normal conditions may be explicitly defined in the Category II authorization (e.g., engine failure, electrical component failure, or engine inoperative Category II). For failures other than those addressed by the Category II authorization, the pilot or operator may need to adjust the operating minima used, introduce wind limit constraints, or address other factors to ensure safe operation for the particular non-normal condition. 4.3.1.1. Operational Safety Evaluation. For any instrument approach using either Category I or Category II minima, the operator must adequately consider and provide for safe operations considering at least the following: a. The possibility of a failure of any one of the pertinent navigation systems, flight guidance system, flight instrument system, or annunciation system elements used for the approach or missed approach (e.g., ILS receiver failure, Autopilot disconnect, etc.). b. The possibility of a failure of a key aircraft component or related supporting system during the approach or missed approach (e.g., engine failure, electrical generator failure, single hydraulic component failure). Even though a particular failure may in itself be considered too remote based on exposure time (e.g., engine failure), it is nonetheless important to address these considerations since, in practical circumstances, a “go-around” may be due to a factor which relates to or leads to the failure, and thus is not an independent event (e.g., flocking bird ingestion). This is consistent with the long standing principle of safety of operation of multi-engine aircraft in air carrier operations which notes that after passing V1 on takeoff, until touchdown, the aircraft should typically be able to sustain a failure such as engine failure and still safely be able to continue flight and land. c. The possibility of a balked landing or rejected landing at or below DA(H), or MDA(H), as applicable. ### Page 20 Page 6 Par 4 d. The possibility of loss or significant reduction of visual reference, that may result in or require a go-around. e. Suitable obstacle clearance following a missed approach, considering applicable aircraft configuration during approach and any configuration changes associated with a go-around (e.g., engine failure, flap retraction). f. For special airports identified IAW section 121.445 (e.g., mountainous terrain), or other airports with critical obstacles that have not otherwise been accounted for, the ability to ensure suitable obstacle clearance following a rejected landing; applicable aircraft configuration(s) during approach and any configuration changes associated with a go-around and missed approach should be considered. g. Unusual atmospheric or environmental conditions that could adversely affect the safety of the operation (e.g., extreme cold temperatures, known local atmospheric or weather phenomena that introduce undue risk, etc.). When conducting a safety assessment of issues listed above, and uncertainty exists as to aircraft failure condition effects, procedural design intent or margins, aircraft characteristics or capabilities following failure, or other such issues, the operator should consult with an appropriate organization source able to provide reliable and comprehensive information. Typically this includes consultation with one or more of the following as applicable, and as necessary: • Aircraft manufacturer, • Avionics manufacturer; • Procedure designer; • Air Traffic Service provider, or regulatory authority. NOTE: For definitions and discussion of differences among the terms “balked landing,” “rejected landing,” “go-around,” and “missed approach,” see Appendix 1. 4.3.1.2. Primary and Supplementary Means of Navigation and Required Navigation Performance (RNP). For the purpose of this AC, “Primary” and “Supplementary” means of navigation and Required Navigation Performance (RNP) are defined in Appendix 1. Application of these terms to instrument approach or takeoff is described below. In addition, it should be noted that the term “Primary Means of Navigation” may apply to either instrument approach initial, intermediate final approach, or missed approach courses of procedures flown to Category I or Category II minima. The term Supplemental Means of Navigation can typically apply to initial or intermediate segments or Missed approach segments, but typically does not apply to flying a final approach course of an instrument procedure. For definitions of Category I or Category II as used by the U.S. and ICAO, see Appendix 1. a. Primary Means of Navigation. A “Primary Means” of navigation is a means of navigation that satisfies each of the necessary levels of accuracy and integrity for a particular area, route, procedure or operation. The failure of a “Primary Means” of navigation may result in, or require reversion to a “non-normal” means of navigation or alternate level of RNP. (1) “Availability” as relates to a primary means of navigation is typically addressed in conjunction with the applicable operating rules for use of the system, in the context of the area, airspace, route, procedures, or operations for which system use is intended (e.g., use of multiple versus single sensors or systems, or NAVAID signal access, reliability, or continuity of service as might apply to a particular approach path). (2) As applicable to instrument approach operations for an air carrier, particularly for a final approach segment or a missed approach segment, the following may be considered to satisfy requirements for a primary means of navigation. (3) For sensor specific approaches (e.g., VOR, or NDB, or ILS) each particular airborne system using its respective associated NAVAID (e.g., ILS) may be considered as the “primary means of navigation” for completion of that respective specified approach procedure (e.g., ILS RWY 16R). ### Page 21 Par 4 Page 7 (4) When multiple components are required (e.g., ILS, with use of an NDB for the missed approach), the collective set of specified navigation components are considered to be the primary means of navigation for that procedure. Failure of any one of the required components may preclude use of the procedure, or may require reversion to a non-normal means of navigation for completion of the procedure (e.g., failure of the NDB missed approach NAVAID associated with an ILS approach). (5) For RNAV based procedures where the only method of flying the procedure is by an RNAV or RNAV/RNP system (e.g., FMS), RNAV is considered to be the primary means of navigation for that approach procedure. Any associated NAVAID, or combinations of NAVAIDs, or airborne sensors necessary to achieve the necessary level of FMS performance may be considered as an input sensor(s) to the FMS, but the sensors or NAVAIDs taken alone are not necessarily considered to be the primary means of navigation. (6) Where RNAV systems are used to overfly other types of instrument approach procedures (e.g., FMS RNAV systems over-flying VOR or NDB procedures), the RNAV system may be considered as a supplemental system if the aircraft can revert to use of the underlying procedure flown with “raw data,” in the event of failure of the RNAV system (see b. below). b. Supplementary Means of Navigation. A “Supplementary Means” of navigation is a means of navigation which satisfies one or more, but not necessarily all of the necessary levels of accuracy, integrity, and availability for a particular area, route, procedure, or operation. The failure of a “Supplementary Means” of navigation may result in, or require reversion to another alternate “normal” means of navigation for the intended route, procedure, or operation. (1) As applicable to instrument approach operations for an air carrier, particularly for a final approach segment or a missed approach segment, the following may be considered to satisfy requirements as a supplementary means of navigation. (2) When procedures have multiple methods to achieve compliance (e.g., a multi-sensor FMS over-flying a VOR approach, or an ILS approach with the choice of either an NDB or a VOR-based missed approach), those airborne systems which have another alternate normal means to accomplish the procedure, or a portion of the procedure, for one or more applicable segments, may be considered as supplementary for those applicable segments (e.g., if the FMS should fail, and the crew is monitoring the underlying VOR information, and the crew can transition to use of VOR-based navigation) the FMS may be considered as supplementary. (3) Or, if, after an ILS approach, FMS RNAV capability is used to overfly a VOR/DME-based missed approach (with VOR/ DME NAVAID facilities operating), the FMS RNAV capability may be considered supplementary. Note, however, that if the specified approach/missed approach VOR/DME NAVAIDs are not operative, and the FMS RNAV operation is based on use of multi-sensor NAVAID capability, then the FMS use for that approach/missed approach would typically be considered a primary means of navigation. c. Required Navigation Performance (RNP). Required Navigation Performance is a statement of the navigation performance necessary for operation within a defined airspace (Adapted from ICAO - IS&RP Annex 6). Required Navigation Performance is specified in terms of accuracy, integrity, and availability of navigation signals and equipment for a particular airspace, route, procedure, or operation. 4.3.1.3. Use of ICAO Standard NAVAIDs. U.S. Category I or Category II Operations are based on use of ICAO standard NAVAIDs, equivalent NAVAIDs, or other NAVAIDs acceptable to FAA and approved in OpSpecs. Authorization for use of NAVAIDs other than ICAO Standard NAVAIDs must be coordinated with AFS-400. In the context of this AC, a Standard Landing Aid (SLA) is considered to be any navigation service or navigation aid provided by a State which meets internationally accepted performance standards (e.g., ICAO Standards and Recommended Practices (SARPs), or equivalent U.S. or other State standards - see Appendix 1). ### Page 22 Page 8 Par 4 4.3.1.4. Standard Instrument Approach Procedures (SIAPS). a. Acceptable Instrument Approach Procedure Basis. Instrument approach procedures used by Operators IAW with this AC should be based on: (1) U.S. Standard Instrument Approach Procedures; (2) For non-U.S. airports, foreign instrument approach procedures acceptable to FAA promulgated by the state of the airport of landing (i.e., ICAO - State of the Aerodrome). The operator may propose use of such procedures for Principal Operations Inspector (POI), Aircrew Program Manager (APM), or Certificate Management Office (CMO) acceptance; (3) Military instrument procedures acceptable to FAA for operations at military facilities. The operator may propose use of such procedures for POI, APM, or CMO acceptance; (4) Special instrument approach procedures approved by the FAA; (5) Special instrument approach procedures developed by the operator which are acceptable to FAA, or procedures developed by the operator using methods acceptable to FAA; or (6) Special instrument approach procedures, acceptable to FAA, developed by other U.S. or non-U.S. Operators, or by the State of the Aerodrome (for foreign airports). b. Considerations for use of procedures other than U.S. Standard procedures. For procedures other than those developed IAW FAA Order 8260.3, United States Standards for Terminal Instrument Procedures (TERPS), the operator must ensure consideration of at least the following factors related to use of those instrument procedures: (1) Availability of suitable weather reporting and forecasts; (2) Identification of any necessary alternate airports or alternate minima; (3) Ability to discontinue an approach, if necessary, from any point to touchdown; (4) Suitability of the airborne equipment to use the procedure (e.g., compatibility of the airborne equipment with the type/characteristics of the ILS, VOR, DME, NDB ground facilities used); (5) Suitability of Ground Systems/Equipment (e.g., lighting, transmissometers, pilot control of lighting); (6) Suitability of NAVAIDs (e.g., maintenance, monitoring); (7) Suitability of Airport/Runway (e.g., obstructions, clear zones, markings); (8) Availability of Aeronautical Information (e.g., timely NOTAM availability); (9) Identification of any special Training or qualification related to the procedure; and (10) Resolution of any issues identified from adverse “service experience” with the procedure. c. Special Instrument Approach Procedures. Special instrument approach procedures should be coordinated with the Flight Standards Division of the FAA region having responsibility for the airport of the procedure. Special procedures should address any provisions associated with application of section 121.445 for special airport qualification. Special procedures are approved by AFS-400 and issued by the POI after coordination with pertinent FAA organizations. ### Page 23 Par 4 Page 9 d. Use of FAA/JAA Harmonized Instrument Approach Minima Tables. Information from FAA/JAA harmonized instrument approach minima tables are provided in Appendix 8. Unless otherwise authorized by AFS-400, procedures incorporating these minima are issued as special instrument procedures through OpSpecs, or through a Letter of Authorization (LOA). Minima based on values provided in Appendix 8 should not be below the lowest minima authorized through a Category I Standard OpSpec authorization, or below any applicable published foreign aerodrome minima when operating outside the United States (see Paragraph 6.2.18 and Appendix 8). 4.3.1.5. “Steep Approaches” and Approach Path Descent Angle Constraints. Approach path angles between 2.75 degrees and 3.77 degrees are considered standard for air carrier operations. Approach angles above 3.77 degrees are considered “steep angle” and, if authorized, may require additional assessment. Air carrier use of approach angles over 3.77 degrees requires coordination with AFS-400. Use of approach angles over 4.5 degrees should normally be based on an associated aircraft type AFM provision for “steep angle approaches,” IAW AC 25-7A, Flight Test Guide for Certification of Transport Category Airplanes, or equivalent, and paragraph 6.8 of Appendix 2. 4.3.1.6. “Normal Maneuvering” Considerations. Part 91, section 91.175 requires that approach procedures should be based on use of “normal maneuvers” before and after passing DA(H) or MDA(H). Normal maneuvers typically do not involve use of bank angles greater than 30 degrees, pitch attitudes in excess of 25 degrees nose up or 10 degrees nose down, or sink rates in excess of 1100 ft. per minute below 500 ft. HAT while maneuvering to land within the touchdown zone, during go-around, or during a rejected landing. During a missed approach, pitch attitudes in excess of +30 degrees or bank angles greater than 30 degrees would typically be considered excessive. 4.3.1.7. Non-Normal Events or Configurations. Takeoff and landing weather minimums are intended for normal operations. When non-normal events occur, flightcrews are expected to take the safest course of action to ensure safe completion of the flight. Using emergency authority, crews may deviate from rules or polices, to the extent necessary for the circumstances, to minimize risk during landing. Paragraph 6.1.8 addresses guidelines and procedures to be considered in conducting an instrument approach during a non-normal event. 4.3.1.8. Go-Around Safety. a. General. A multiengine aircraft conducting a Category I or Category II instrument approach should be capable of safely executing a “one-engine-inoperative” go-around from any point in an approach prior to touchdown with the aircraft in a normal configuration, or specified non-normal configurations (e.g., engine out, if applicable). This is necessary to provide for go-around safety due to missed approaches or rejected landings due to a variety of circumstances such as: • Unexpected environmental conditions (e.g., cross winds, turbulence) • Aircraft related failures (e.g., gear unsafe) • Air Traffic Service contingencies (e.g., RTO on a crossing runway) • Loss of visual reference • When a pilot finds the runway surface unsuitable (e.g., clutter, flocking birds) • When the runway is blocked (airport vehicles or exiting aircraft ahead not clear), or due to a go-around or missed approach due to any other reason (1) This objective may be achieved by the operator providing information to flightcrews on an appropriate lateral flight path to follow to enable the aircraft to safely operate to the runway, and out from the runway following a rejected landing. In the rare event that operation out of a runway may not be possible following a rejected landing, then provision of suitable information on a “commit point,” or equivalent condition (e.g., limit weight, minimum speed, or suitable configuration) may instead be provided. The intent of providing information on safe go-around capability is to identify the best option or options for a safe lateral ground track and flight path to follow in the event that a missed approach, balked landing, rejected landing or go-around is necessary. It is not the intention of this provision to require or indicate the need for an analysis of each flight, or a dispatch assessment, or an individual ### Page 24 Page 10 Par 4 flight landing weight assessment or limitation. Operators may make the judgment as to whether a review on a “perflight” or specific condition basis may or may not be needed. (2) While coping with the go-around contingency situation is appropriate for any operation, it is particularly important for low visibility operations in which the pilot has minimum time to respond, and may have limited visual reference available to safely cope with the adverse condition (e.g., night and poor visibility). Further, “go-around” safety should be addressed regardless of when an engine failure may occur prior to landing. However, operators may elect to distinguish between procedures or expected crew response for engine failures occurring at various times during a flight as follows: (a) Engine failure occurring enroute or prior to passing a final approach fix or point, (b) Engine failure during a final approach segment, or (c) Engine failure after passing DA(H) or after descending below MDA(H) but prior to touchdown, or during a go-around or missed approach. (3) For an engine failure occurring prior to final approach, flight diversion planning should allow for the potential need for a missed approach or balked landing, and for the need to maintain subsequent suitable obstacle clearance (e.g., when making suitable diversion choices - sections 121.161, 121.191, or 121.193. The pilot should consider any adjustment to minima, procedures or missed approach path that may be appropriate to facilitate safe obstacle clearance (e.g., following a suitable operator-developed takeoff procedure, published takeoff procedure, or IFR Departure Procedure (DP)). This is particularly appropriate if U.S. TERPS or ICAO PANS-Ops-specified instrument procedural gradients cannot be met during any portion of a go-around or missed approach, or if following a suitable lateral path cannot be ensured (e.g., crosswinds with no course guidance available, cannot maintain VMC, or at night). (4) For engine failure during approach, if there is any doubt of the ability to safely complete the landing or ensure a safe balked landing and missed approach capability, the pilot should consider the advisability of discontinuing the approach and diverting to a different airport or runway, to better ensure safe missed approach or balked landing obstacle clearance. (5) For engine failure after passing DA(H) or descending below MDA(H), the pilot should be prepared to expeditiously follow or join any pre-established and applicable “T-procedure” or “IFR Departure Procedure,” or equivalent, until becoming established on a published segment of the missed approach procedure, at or above a safe altitude. (6) Accordingly, an operator should have reviewed the missed approach and rejected landing flight path to ensure that in the event of a go-around the aircraft is able to ensure safe obstacle clearance following a missed approach or go-around. This can be particularly important in mountainous areas where the landing runway may be in a direction not typically used for takeoff (e.g., an airport that is one way in, and the opposite direction out). b. Go-Around Assessment Considerations. (1) Operators may accomplish such assessments generically for a particular runway, procedure, aircraft type, and expected performance, and need not perform this assessment for each specific flight. Operators may use simplifying assumptions to account for the transition, reconfiguration, and acceleration distances following goaround (e.g., use expected landing weights, assume anticipated landing flap settings). (2) The operational considerations should include: (a) Go-around configuration transitions from approach to missed approach configuration including expected flap settings and flap retraction procedures. ### Page 25 Par 4 Page 11 (b) Expected speed changes. (c) Appropriate engine failure and shutdown (feathering if applicable) provisions, if the approach was assumed to be initiated with all engines operative. (d) Any lateral differences of the missed approach flight path from the corresponding takeoff flight path, and (e) Suitable balked landing obstacle clearance, until reaching instrument approach missed approach or enroute procedurally protected airspace. (f) Any performance or gradient loss during turning flight, if necessary to follow a flight path that is not over the runway or is not aligned with the runway after the balked landing transition. (g) Any relevant related situations such as if the aircraft cannot dump fuel and may need to make an emergency return landing above maximum landing weight immediately after takeoff. (h) Methods used for takeoff analysis, such as “Overspeed V2”, “engine-out maximum angle climb,” or other such techniques may be used if determined to be appropriate by the operator or aircraft manufacturer. (i) Applicable flight guidance system operational procedures used. Information about any techniques required to achieve the specified performance should be available to the flightcrew (e.g., appropriate mode selection). (j) Operators may make obstacle clearance assumptions similar to those applied to corresponding takeoff flight paths (e.g., Section 121.189) in the determination of net vertical flight path clearance or lateral track definition or lateral track obstacle clearance within an airport boundary or beyond an airport boundary, until the point at which cruise or other obstacle clearance requirements apply. c. Go-Around Assessment Conditions. (1) Assessments may assume the following initial conditions: (a) A “balked landing” starts at the end of the Touchdown Zone (TDZ). (b) An engine failure occurs at the initiation of the balked landing, from an all-engine configuration. (c) Balked landing initiation speed > VREF or VGA (as applicable). (d) Balked Landing initiation height is equal to the specified elevation of the TDZ. (e) Balked landing initiation configuration is normal landing flaps, gear down. (f) At the initiation of the maneuver, all engines are at least in a spooled configuration. (2) A TDZ typically is considered to be the first 3000 ft. of a designated landing runway. When appropriate for the purposes of this provision, Operators may propose to use a different designation for a touchdown zone. For example, alternate consideration of a TDZ may be appropriate for runways that: (a) Are less than 6000 ft. in length and which do not have standard TDZ markings; (b) Short runways requiring special aircraft performance information or procedures for landing; (c) Runways for STOL aircraft; or (d) Runway where markings or lighting dictate that a different TDZ designation would be more appropriate. ### Page 26 Page 12 Par 4 d. “One Way” Airports, “Commit Point,” or Other Special Situations. (1) Where obstacle clearance is determined by the operator to be critical such as for: (a) “One-way in,” “opposite way out” airports in mountainous terrain, or (b) Runways at which a landing is to be planned or attempted, but at a weight which is significantly greater than that which would otherwise be allowed for a takeoff, or (c) Where rejected landing obstacle clearance may not be readily ensured, a review should be completed by the operator to determine whether a contingency go-around path can be appropriately defined or whether a “commit point” or equivalent condition is necessary (e.g., limit weight, speed, or configuration). (2) A “commit point” or equivalent condition however, should only be used where it is not otherwise possible to identify a safe go-around path. For a “commit point,” the operator should either provide a representative weight, configuration or condition at which obstacle clearance can be ensured after initiation of a balked landing at the TDZ, or identify a path related waypoint, location, altitude, height, or fix, beyond which a go-around should not be attempted. For such determinations, the operator should consider at least the runway elevation, temperature, and appropriate aircraft configurations or configuration changes. If a “commit point” is used, the operator should provide any necessary advisory information to flightcrews to address any events which, while unlikely, could nonetheless occur beyond the designated “commit” point or condition (e.g., unforeseen significant wind shear, unacceptable winds, turbulence, or runway clutter, loss of visual reference, flare extending beyond the touchdown zone, or an obstruction on the runway). e. TERPS/ICAO PANS-Ops Criteria Not Applicable to “Non-Normal” Operations. TERPS or ICAO PANS-Ops- based criteria do not typically address “special” instrument approach procedures, and they do not and are not intended to address non-normal operations (engine inoperative) or operations below published segments of instrument procedures (e.g., operations below DA(H) or MDA(H)). TERPS or ICAO PANS-Ops based criteria are intended only to address “standard procedures”, normal operations (e.g., all-engine), and published segments of the resulting procedures. Thus, operator assessments of missed approach safety related to operations below published segments of instrument procedures, or operations with non-normal configurations or situations, need not apply provisions of TERPS or ICAO PANS-Ops. Compliance with TERPS or ICAO PANS-Ops based instrument procedure requirements alone may not necessarily ensure missed approach or rejected landing go-around safety. For example, it is recognized that certain types of aircraft (e.g., two-engine aircraft) may operate at weights that achieve gradients with an engine inoperative that may be less than TERPS or PANS-Ops gradients. Go-around from below DA(H) or MDA(H) (e.g., following loss of visual reference, or runway not suitable or available) does not necessarily provide for and does not need to apply TERPS or PANS-Ops criteria or provide for TERPS or PANS-Ops specified levels of obstacle clearance vertically or laterally. Methods related to TERPS or PANS-Ops criteria such as “Collision risk model (CRM)” also are not applicable to assessments other than for TERPS and PANS-Ops related procedure elements. f. Flight Guidance System (FGS) Use. If not already assessed for the aircraft type during basic type certification, or STC, flight guidance systems (FGS) suitability for the intended procedure(s) should be considered. The operator may need to assess FGS mode use to ensure compatibility with intended flight path, mode transitions, and gradient determinations. This may be achieved by demonstrating (in simulation or flight) a safe go-around from 100 ft. above the TDZ (HAT) operationally for the specific procedure or, if applicable, for the most critical runway for that operator. For aircraft that have airworthiness demonstrations conducted IAW Appendix 2 or 3 or with AC 120-28D this provision is considered to be addressed. g. Performance and Obstacle Data Availability and Use. (1) Information or methods used by the operator for this assessment may be the best available information or methods from applicable aircraft manuals, terrain or obstruction charts, or supplementary information from aircraft or engine manufacturers. In the event that performance, obstacle, or flight path data are not otherwise available to support the necessary analysis from the above sources, the operator may develop, compute, demonstrate, ### Page 27 Par 4 Page 13 or determine such information to the extent necessary to provide for safe obstacle clearance during an engine-out missed approach or an engine-failure following a rejected landing. Data or methods used need not necessarily be from the applicable AFM or from the original aircraft manufacturer. Data or methods may be developed by the operator based on equivalence to other data or methods (e.g., takeoff data) or may be derived by using standard practices applicable to aircraft performance assessment or procedure construction, or may be derived by appropriate aircraft performance or engineering analysis, techniques, or methods. (2) Information on terrain or obstructions for these assessments may be based on the best available information to the operator or to the agency or entity supporting the operator at the time the information is supplied (e.g., data available to a performance information contractor, or chart supplier). Best available information may be used, notwithstanding that certain information or data may not necessarily be “approved” by an authority, or may be data that is not necessarily recent (e.g., certain types of charting or obstruction information is not frequently updated). FAA Order 8260.19, paragraph 271 describes how the accuracy of the source data should be considered when constructing the procedure. h. Related Information. Other paragraphs of this AC contain information related to this paragraph. Paragraph 5.14 describes typical factors to be considered when assessing go-around capability for a particular aircraft and flight guidance system. Paragraph 6 addresses procedures including those used for go-around or rejected landing, and Paragraph 7 addresses Training and Crew Qualification including relevant aspects of missed approach, go-around, or rejected landing. 4.3.2. ILS, GLS, or MLS (xLS) Instrument Approach Operations. ILS, GLS, or MLS (i.e., xLS) operations may be authorized to the lowest applicable DA(H) for the procedure used, and to the lowest visibility minima specified in the OpSpecs for the NAVAID, facilities, and lighting systems used (see Appendix 7, Standard OpSpecs Part C Paragraph C053 for Category I, and Standard OpSpecs Part C paragraph C059 for Category II). a. ILS, GLS, or MLS (e.g., xLS) operations are typically authorized based on use of two or more navigation receivers or multi-mode receivers (MMRs) of a pertinent type (see 14 CFR, part 121, section 121.349, and part 125 section 125.203), each providing independent information to the appropriate flight guidance system elements and pilot displays. b. Provisions of sections 121.349, and 125.203 applicable to ILS may also be considered as applicable to GLS or MLS. c. Provisions of section 121.349 for use of a single navigation (e.g., ILS) receiver are typically limited to operations using minima at or above RVR4000, or for Minimum Equipment List (MEL) authorization for dispatch with a NAVAID receiver inoperative. d. Precision Approach Radar (PAR) procedures are not considered xLS procedures( see paragraph 4.3.3). 4.3.3. Instrument Approaches other than ILS, GLS, or MLS (xLS). Instrument approach procedures other than ILS, GLS, or MLS (xLS) that may be authorized for air carriers include the procedure types shown in the following paragraphs. a. Standard Instrument Procedures Other Than xLS. The following NAVAID specific instrument procedures are considered to be standard procedures for the purpose of air carrier operation specification approval. Typically these procedures do not inherently specify use of vertical guidance (i.e., most were traditionally considered as non-precision approaches). (1) Some of these approach types may provide vertical guidance (e.g., a glideslope), however, the procedure may be offset from the runway, may not otherwise permit a straight in landing in the touchdown zone when flying the specified path, or may not have flight deck display of path information. Hence the approach is not considered to be an xLS approach. ### Page 28 Page 14 Par 4 (2) Approvable standard approach types other than xLS are considered to include: • Localizer (LOC) • Localizer Back Course (BC) • SDF • LDA • VOR • VOR/DME • NDB • Dual NDB • NDB/DME • TACAN, and • RNAV (2D)* based on a procedurally specified NAVAID (e.g., typically when a particular VOR/DME is specified as a “Procedure tuned” facility to serve as a basis for a particular RNAV procedure - These RNAV procedures usually are those which meet U.S. TERPS Chapter 15 criteria for RNAV). b. Standard Procedures Flown Using Vertical Navigation Path Guidance (VNAV). The procedures specified in paragraph a. above may also be flown in conjunction with use of FMS derived vertical guidance (e.g., FMS VNAV capability). In this instance, VNAV capability is considered to be based on a pre-specified and defined vertical path. c. Standard Procedures Flown Using “Constant Vertical Descent Rate” Techniques. NAVAID specific procedures other than xLS may be flown using “Constant Vertical Descent Rate” Techniques as a “pilot procedural technique” to maintain a pre-determined vertical speed to achieve a corresponding assumed descent path (e.g., “open-loop” vertical speed descent profile). Operators may use these techniques, particularly when xLS or VNAV path guidance is not available or cannot otherwise be used. However, such “Constant Vertical Descent Rate” techniques are not considered to be “VNAV vertical guidance”. This is true regardless of whether such a procedure or technique is based on an altitude/distance cross check or not. While use of such techniques may be desirable for aircraft that are not using xLS or VNAV, they are not considered to be eligible for DA(H) use or credit. d. “RNAV” Procedures (3D or 2D)* Based On RNP. Operators may use RNAV procedures based on RNP criteria that are found to be acceptable to FAA. Those RNAV procedures may use minima based on RNP criteria, or may use RNP for definition of some or all procedure segments (e.g., initial, intermediate, final, or missed approach segments). e. Other “RNAV” Procedures (3D or 2D)*. (1) When determined acceptable to FAA, Operators may also use RNAV Procedures (3D or 2D)* other than those based on criteria specified in U.S. TERPS Chapter 15 for RNAV (e.g., RNAV procedures as listed in paragraph a. above), or other than procedures based on RNP (RNAV procedures as listed in paragraph d. above), as follows: • RNAV procedures identified as “GPS” instrument approach procedures, if those procedures are determined to be suitable for the aircraft and navigation system to be used (e.g., use of FMS with GNSS sensor inputs). • International RNAV procedures, when appropriate for use at non-U.S. airports. ### Page 29 Par 4 Page 15 • RNAV procedures based on multi-sensor FMS using inertial systems and NAVAIDs other than specific “procedure-tuned” VOR or DME facilities. For example, RNAV Procedures (3D or 2D)* may be based on multi-sensor FMS systems which use DME-DME updating, or scanning DME updating, or VOR/DME updating, or VOR/VOR updating, from suitable and available NAVAIDs. • RNAV procedures based on multi-sensor FMS using inertial systems and GNSS, or GNSS with Ground Based Augmentation System (GBAS), or Space Based Augmentation System (SBAS)). (2) RNAV procedures may also be based on combinations of sensors if equivalent performance, availability, and integrity are established compared with any of the above methods. *NOTE: For the purpose of this AC a “3D” approach procedure (3D) is considered to be one having both lateral and vertical path guidance (e.g., three dimensions - with x, y, and z path coordinates). These procedures may be identified as LNAV/VNAV. A “2D” procedure (2D) is considered to be one having only lateral path guidance (two dimensions - x and y path coordinates). These procedures may be identified as LNAV. f. Airport Surveillance Radar (ASR) Procedures. ASR or international equivalent procedures may be used. g. Precision Approach Radar (PAR) Procedures. PAR or international equivalent procedures may be used. h. Other Limited Use Special Procedures. Other special instrument approach procedures (e.g., LORAN, Transponder Landing System (TLS), airborne radar approach, Eastern European KRM). Special procedures include use of LORAN C, airborne radar, or any other landing system or non-ICAO NAVAID. Special procedures typically require unique approval of an operator’s operational procedures, flightcrew qualification, and maintenance programs as well as proof of concept demonstration prior to operational authorization. Special Category I operations, by definition, require the use of airborne and/or ground based or satellite-based equipment over and above the minimum equipment necessary to operate in the U.S. national airspace. Special Category I operations usually also require special knowledge, skills, proficiency, and procedures. As a result, changes and amendments to the operator’s overall Category I operations program are usually necessary to ensure safe conduct of these operations. There is additional criteria which must be incorporated into an operator’s program for special Category I operations. 4.3.4. Applicability of a DA(H), MDA(H), or RA. Instrument approach and landing operations have limitations related to the minimum altitude (height) to which descent can be made without establishing visual reference (e.g., 14 CFR part 91, section 91.175). Minimum altitude or height to which descent can be made is typically related to assurance of clearance over terrain or obstacles, airborne instrumentation and equipment, NAVAIDs, and visual aids. Such a minimum altitude or height is usually specified as a DA(H), or MDA(H). A DA(H) may be intended for use as either a Decision Altitude (DA), or as a Decision Height (DH). A DH may be used directly, or it may be specified as a corresponding radio altitude (RA) value above underlying approach terrain. The type of instrument approach procedure determines whether a DA or DH is used, and whether a DH is specified directly, or is defined in terms of a corresponding radio altitude (RA) value above terrain. For a Category I procedure, a DA is typically used. For a Category II procedure, a DH with a corresponding radio altimeter (RA) height above approach terrain is usually used. When a RA value above approach terrain is specified, it typically corresponds to a particular desired DH value for the intended height above the TDZ (HAT). Uses of DA(H), MDA(H), and RA are further described in paragraphs 4.3.4.1 through a. DA, DH, RA, OCA, OCH, OCL. For xLS approaches (e.g., precision approaches), and certain RNAV approaches with VNAV, the minimum altitude or height for flight without having established the necessary visual reference during an approach is specified as a DA(H). For Category I within the U.S., the DA element of a DA(H) usually defines the applicable minima. For Category II, applicable minima are usually based on a DH, expressed in the published procedure as an RA value. In other countries, for Category I, either a DA or a DH may be used. For Category II outside the U.S., minima may be based either on a direct specification of DH, or on a corresponding RA value, as is done within the U.S. Other expressions of minima equivalent to a decision altitude (DA) or decision ### Page 30 Page 16 Par 4 height (DH) may also be encountered outside of the U.S., such as when an obstacle clearance altitude (OCA), obstacle clearance height (OCH), or obstacle clearance limit (OCL) is specified, and is to be treated as a corresponding DA or DH. (1) In the United States and other countries that use U.S. TERPS criteria, the minimum instrument flight altitude for xLS approaches is considered to be the DA element of the DA(H) if minima are based on a barometric altimeter, or the (H) value of the DA(H) expressed as an RA minima, if minima are based on use of a radio altimeter. When a DH applies, it is usually specified as an RA value above the pertinent underlying approach terrain, considering a nominal approach vertical path. When a barometric altimeter specified DA is used to establish minima, the associated height value (H) is typically considered to be advisory. When a DH specified in terms of a radio altitude (RA) value is used, the corresponding published RA value is considered to be controlling, and any associated barometric altitude value shown in a procedure is typically considered to be advisory. (2) For procedures with minima based on a DA, the DA is specified as a decision altitude referenced to mean sea level (MSL) using QNH altimeter settings. While the (H) element of the DA(H) is typically advisory for such procedures, in certain circumstances the (H) value may be the basis for minima, such as when a QFE referenced barometric altimeter setting is used. (3) Obstacle Clearance Height (OCH) and Obstacle Clearance Limit (OCL) are used in some countries IAW various versions or revision levels of ICAO PANS-OPS. OCA, where used, is referenced to a barometric altitude (MSL). OCH and OCL are referenced to height above either the elevation of the airport, the elevation of the touchdown zone, or the elevation of the landing threshold. b. Minimum Descent Altitude (MDA), Minimum Descent Height (MDH), HAT, Height Above Airport (HAA), Obstacle Clearance Altitude (OCA), OCH, OCL. (1) For approaches other than xLS, the minimum height or altitude may be specified as a decision altitude DA or a DA(H) if suitable vertical guidance is authorized and provided (e.g., VNAV path), or specified as a minimum descent altitude MDA of an MDA(H) if vertical guidance is not provided. Minima may also be specified height above touchdown (HAT), height above airport (HAA), minimum descent height (MDH), obstacle clearance altitude (OCA), obstacle clearance height (OCH), or obstacle clearance limit (OCL). MDA, HAT, and HAA are typically used by certain countries that use various earlier versions of U.S. TERPS criteria. OCA, OCH, and OCL are used in countries having procedures established IAW ICAO PANS-OPS. Although ICAO PANS-OPS now does not use OCL, some procedures still use OCL criteria from previous versions of PANS-OPS. Some countries, in addition to OCA and OCH, provide MDA and MDH. MDA and OCA are barometric flight altitudes referenced to mean sea level (MSL). HAT, HAA, MDH, OCH, and OCL are radio or radar altitudes referenced to either the elevation of the airport, the elevation of the touchdown zone, or the elevation of the landing threshold. (2) Accordingly, for international operations, the following equivalent minima formulations should be used by U.S. Operators: (a) Use the altitude value of the MDA(H) where OCA may be specified for procedures other than xLS. (b) Use the equivalent altitude value of the MDA(H) where HAT, OCH, or OCL are specified for “straight-in” approach procedures. (c) Use the equivalent altitude value of the MDA(H) where HAA, OCH, or OCL may be specified circling approach maneuvers. c. Lowest Permissible DA(H) or MDA(H). The lowest permissible DA(H) or MDA(H) for instrument flight (IMC) for any approach should not be lower than the most restrictive of the following, as applicable: • Minimum height or altitude published or otherwise established for the instrument approach ### Page 31 Par 4 Page 17 • Minimum height or altitude authorized in OpSpecs for the approach • Minimum height or altitude authorized for the flightcrew • Minimum height or altitude authorized for the operator, aircraft, and airborne equipment • Minimum height or altitude permitted by operative airborne equipment and NAVAIDs • Minimum height or altitude for which required NAVAIDs can be relied upon* • Minimum height or altitude which provides adequate obstacle clearance*, and • Minimum altitude which provides compensation for extremely cold temperatures, if applicable** * Note: Item normally addressed by the published instrument approach procedure. ** Note: Applicable only when an operator has a procedure to correct altimeter errors for extremely cold temperatures (Typically T less than -22F/-30C). 4.3.4.1. Application of a DA(H) for Category I. Procedures established based on use of NAVAID electronic vertical guidance (e.g., ILS, MLS, or GLS) use the barometrically based DA (of the specified DA(H)) for minima determination. Radio altitude above the approach terrain or touchdown zone, if provided, is advisory. Procedures established based on use of other acceptable electronic vertical guidance (e.g., Baro VNAV meeting provisions of this AC, GNSS based geometric path VNAV) may use a barometrically based DA (of the specified DA(H)) for minima determination if an appropriate obstacle assessment has been completed for the region between the earliest point along the approach path at which the DA may be reached, to the runway threshold. Radio altitude, if provided, is advisory. For Category I a decision height (DH) is not used. DA(H) is applied to Category I instrument approach procedures as follows: a. Category I ILS, MLS, or GLS (xLS) Approaches. (1) For Category I approaches based on ILS, MLS, or GLS (e.g., xLS, or precision approaches), a DA(H) is typically specified. The DA(H) represents the minimum altitude in an approach to which descent may continue, or by which a missed approach must be initiated, if the required visual reference to continue the approach has not been established. The DA(H) “altitude” value is typically measured by a barometric altimeter, and is the determining factor for descent minima for an xLS approach procedure. The “height” value specified in parenthesis is typically a radio or radar altitude equivalent height above the TDZ (HAT) used only for advisory reference, and does not necessarily reflect actual height above underlying terrain. Where a Middle Marker (MM) beacon is installed, it may be used as advisory information, confirming a barometrically determined DA(H) that is coincident with the glide slope altitude at that point. (2) For approaches which normally provide vertical guidance (e.g., xLS), but when vertical guidance capability cannot be used, such as due to an airborne system failure, see paragraph 4.3.4.2 below. b. Category I Approaches with VNAV. For Category I approaches other than ILS, MLS, or GLS which use a published VNAV descent path to the runway threshold, a DA(H) may be specified instead of an MDA(H). See (a) above for DA(H) applicability. c. Precision Approach Radar (PAR) procedures. For Category I minima, a DA(H) may be specified for PAR. See paragraph a. above for DA(H) applicability. Category II is not typically applicable to civil aircraft use of PAR (see 4.3.8.g). ### Page 32 Page 18 Par 4 4.3.4.2. Application of an MDA(H) for Category I. Procedures that are not based on use of vertical guidance (e.g., VOR, NDB, Back Course ILS) use the barometrically based MDA (of the specified MDA(H)) for minima determination. Radio altitude, if provided, is advisory. a. Category I Approaches other than ILS, MLS, or GLS. For Category I approach other than ILS, MLS, or GLS (e.g., non-precision approaches), an MDA(H) is typically specified. The MDA(H) represents the minimum altitude in an approach to which descent may continue, until either the required visual reference is established and the aircraft is in a position to continue the descent to land using normal maneuvering, or until reaching the specified missed approach point. The MDA(H) “Altitude” value is typically measured by a barometric altimeter, and is the determining factor for descent minima for approaches other than ILS, MLS, or GLS (other than xLS) Category I instrument approach procedures. The “Height” value specified in parenthesis is typically a radio or radar altitude equivalent height above the touchdown zone (HAT), and is used only for advisory reference. This height value does not necessarily reflect actual height above underlying terrain. Where a VHF marker beacon (e.g., FM) is used, it may indicate a longitudinal position for a step-down fix, if identified in the procedure. b. Circling Approaches. Many instrument procedures provide for circling approach minima. U.S. criteria require SIAP publication of circling maneuver minima if the inbound course does not meet straight-in alignment criteria, or when a specified descent gradient for a straight-in approach is steeper than a maximum value allowed by instrument procedure design criteria. Sufficient visual references for manually maneuvering the aircraft to a landing must be maintained throughout a circling maneuver. The pilot must keep the aircraft’s position within the established maneuvering area while performing the circling maneuver. The circling MDA(H) or equivalent must be maintained until an aircraft is in a position from which a normal descent can be made to touchdown within the touchdown zone, using normal maneuvers and a safe descent path. 4.3.4.3. Application of a DA(H), or equivalent (i.e., Inner Marker), for Category II. Procedures using Category II minima typically use a radio altimeter and the associated DH (of the specified DA(H)) for minima determination. Barometric altitude is advisory. a. Procedures that have “Radio Altitude Not Authorized (RA NA)” (for example, due to irregular underlying terrain) typically use the first indication of arrival at the “inner marker” as a means to establish DA(H). However, an operator may elect to use first indication of arrival at either the “inner marker” or the barometric altitude DA, which ever comes first, as the means for minima determination. In the first instance, both radio altitude and barometric altitude are advisory. In the second instance barometric altitude may be an acceptable means to establish DA(H), but only if it occurs before arriving at the “inner marker.” When a procedure specifies “RA NA,” a DA(H) greater than 100 ft. HAT is typically not used, since a marker beacon is not located in a position along the approach path corresponding to that minima. b. While for Category II the use of barometric decision altitude (DA) is advisory, this does not preclude an operator or flightcrew from initiating a missed approach if the altitude equivalent to the barometric altitude minima (DA) is reached prior to arrival at the specified DH. A barometrically specified “DA” is not currently used for air carrier Category II minima. This applies regardless of whether radio altimeter or inner marker determines the DH. c. For Category II a Decision Height of a published DA(H) (or an equivalent Inner Marker (IM) for irregular pre-threshold terrain) is used as the applicable descent minima. Any “altitude” value specified is considered to be advisory. The altitude value is available for cross-reference and backup. Use of the barometrically referenced DA element of a published DA(H) is not currently authorized for parts 121, 129, or 135 operations at U.S. facilities. If an operator elects to base discontinuance of an approach on the DA, if the DA is reached prior to the applicable DH, the DA element of a DA(H) may be considered applicable to Category II in other than an advisory capacity. 4.3.4.4. “Specified Visual Reference” Requirements for Category I or Category II. a. Section 91.175 and Standard OpSpecs specify that for operation below the DA(H) or MDA(H) on an instrument approach, the required visual reference to continue the approach must be established. Unless otherwise ### Page 33 Par 4 Page 19 authorized by the CMO (e.g., POI or APM for a particular type) the required visual reference may be considered to be those provisions as listed in section 91.175 items (c) and (d). b. Circumstances in which the operator may request and the CMO may authorize use of alternative visual reference provisions might be situations such as certain Category I and II minima are based on use of autoland or HUD (see paragraph 10.5.3). In this instance provisions such as those shown in section 91.175 (c) (3) (i) for “red terminating bars” or “red side row bars” may not be necessary or appropriate. This is because these particular approach lighting visual references or configurations may not always be needed when operations are predicated on HUD or autoland use. They may not even be installed or applicable as a part of the approach lighting system for the runway or runways to be specially authorized. Conversely, for operations such as the ones noted above for autoland or HUD, it may be determined by the operator and CMO that continued descent below the DA(H) based solely on visual contact with a VGSI (which may in instances be otherwise permitted by 14 CFR), but without having sight of either the runway, runway lights, touchdown zone lights, centerline lights, or runway markings would not be appropriate. In this instance, the CMO may authorize the operator to define and use alternate visual references or visual reference combinations for Category I and II operations, rather than relying solely on the sighting of a VGSI as a basis for continued descent below a DA(H). c. Refer to FAA Order 8400.13 for lower Category I operations. Changing the required visual reference requires the use of a Special Procedure and additional authorization. 4.3.5. Visibility and RVR Minima. Visibility minima are as specified in Standard or Special Instrument Approach Procedures approved for use by the operator, or as otherwise listed in standard OpSpecs applicable to that operator for Category I or II landing. Operating minimums may be expressed as meteorological visibility (VIS), runway visual range (RVR), or runway visibility values (RVV). a. Meteorological Visibility (VIS). Meteorological visibility may be used as reported by the NWS, a source approved by the NWS, by FAA, or a source approved by the FAA. (1) Outside of the U.S., the FAA may accept meteorological reporting sources for use by a particular operator. Outside the U.S. meteorological visibility determination may vary, and the operator should ensure that the meaning, definition, and significance of any meteorological visibility reported for use in determining minima is understood by that operator’s pilots. (2) For approval of use of weather sources other than the NWS (e.g., international), Operators should consult their respective CMO, CMU, or POI. FAA FSDOs, CMOs, or CMUs that need assistance in responding to operator inquiries regarding approval of weather sources that are not otherwise already addressed by current directives (e.g., FAA Order 8400.10) should consult AFS-400. b. Runway Visual Range (RVR). RVR is considered to be an instrumentally derived value measured by transmissometers. RVR is calibrated by reference to runway lights and/or the contrast of objects. (1) Controlling RVR means the reported values of one or more RVR reporting locations (TDZ, Mid, Rollout, or equivalent international locations) used to determine whether operating minima are or are not met, for the purpose of approach initiation, or in some cases, approach continuation. (2) All U.S. Category I operating minimums below 1/2 statute mile (RVR2400) and all Category II and III operating minimums are based on RVR. (3) Where RVR is used, the controlling RVR for Category I minima is touchdown RVR. All other readings are advisory. (4) For Category II minima, controlling RVR is as specified by OpSpecs. ### Page 34 Page 20 Par 4 (5) RVR use has practical limitations that should be familiar to both the operator and pilot. For example, RVR is a value which typically only has meaning for the portions of the runway associated with the RVR report (TDZ, MID, or Rollout). RVR is a value that may vary with runway light step settings (1 through 5). Operators should ensure that pilots are familiar with runway light setting effects on reported RVR. RVR may not be representative of actual visibility along portions of the runway due to the location of the transmissometer baseline and limited length of the baseline, or due to variable conditions of fog, blowing snow, or other obscurations along the runway, or due to obscurations varying rapidly in time (e.g., patchy fog). Additionally, newer RVR systems may have localized performance sensitivity since they do not use a baseline along the runway (e.g., a scatter array may be used for visibility assessment). Thus, pilots and Operators should note that RVR is an instrumentally derived value that has operationally significant limitations and can be greater than or less than the actual visibility available to a pilot at typical flight deck eye height (ground level) at the runway. This is particularly true at night, if runway lights are not at settings standard for the prevailing conditions, or if unusual daylight conditions are experienced such as when a runway is aligned with a sunrise or sunset condition, in shallow or patchy fog. (6) Outside of the U.S. some RVR reports may not necessarily be instrumentally derived by transmissometers or scatter meters, and may alternately be made by pilots or other weather observers. Accordingly, Operators should ensure that the meaning, definition, significance, and variability of any non-instrumentally derived value of RVR reported to the pilot for use in determining minima is understood by that operator, and that operator’s pilots. c. Runway Visibility Values (RVV). RVV minima are now used infrequently, are being phased out, and should be used only where minima cannot otherwise be specified as a meteorological visibility (VIS) or runway visual range (RVR). 4.3.6. Visibility Assessment and RVR Equivalence for Landing. a. For instrument procedures where minima are expressed in terms of meteorological visibility, but reported visibility available to the flightcrew is specified as an RVR, the tables referenced in standard OpSpecs may be used to establish equivalent meteorological visibility minima. (see Appendix 7, OpSpecs paragraph C051). b. Conversely, for instrument procedures outside of the United States where minima available to the flightcrew on instrument procedures are expressed only in terms of RVR, but reported visibility available to the flightcrew by ATS or other approved source is specified only as a meteorological visibility and RVR is not reported, the “Visibility-RVR Equivalence” table referenced in standard OpSpecs may be used to establish an equivalent RVR value (see Appendix 7, OpSpec paragraph C051). Use of this provision, however, specifically requires FAA authorization in addition to issuance of paragraph C051, and should be limited by the POI or CMO to only those Operators and locations outside of the U.S. that have a need to use the “visibility-RVR” equivalence table for this type of determination. 4.3.7. General Requirements for Category I Operations and Minima. 4.3.7.1. Category I Definition, Background, Classification, and General Criteria. a. Category I Definition. Within the United States, a Category I instrument approach is considered to be any instrument approach or approach and landing with a decision altitude (height) not lower than 60m (200 ft) and with either a visibility not less than 1/2 statute mile (800m), or a runway visual range not less than 550m (1800 ft). b. Background. Originally the term Category I applied only to the difference between basic turbojet ILS minima and use of a 200 foot DH with a commensurate low RVR. Subsequently, the definition and common use of the Category I classification evolved several additional times, and variations in its use developed internationally. For U.S. air carriers, the current Category I definition has been in use since FAA’s standard OpSpecs were revised in the 1980s. Air carriers since that time have been issued these revised OpSpecs, in both domestic and international operations. ### Page 35 Par 4 Page 21 (1) This latest adjusted U.S. Category I definition was necessary because previous criteria for instrument approaches relating to “precision” and “non-precision” approach classification was inadequate to address modern air carrier operations. Provisions were not made for numerous levels of navigation system performance capability that are possible and needed by operators. Systems or methods such as FMS, RNAV, VNAV, electronic map displays, multi-sensor filtering, GPS, inertial systems, RNP, and various GPS augmentation schemes such as GBAS or SBAS now make possible significant improvements in instrument approach capability and cannot be suitably addressed by former criteria or classifications. Combinations of the above approach capability also cannot be adequately classified, represented, or used. Former classifications and criteria failed to appropriately consider the linear nature of modern RNAV systems, certain rare-normal and non-normal conditions, and often did not properly relate to necessary supporting airport systems (e.g., lighting, markings) or meteorological reporting capabilities (e.g., RVR). Previous criteria did not recognize that some procedures or systems formerly considered as “non-precision” (RNAV) may actually have superior performance to systems considered as “precision” systems (e.g., FMS can have better performance than ILS at and beyond distances several miles from the runway). With former criteria and classifications, it was not easy to appropriately classify these systems or derive appropriate benefits. (2) An important consequence of the U.S. definition for Category I is that, for an air carrier, any instrument approach with minima not less than a DA(H) or MDA(H) of 200 HAT, and visibility not less than RVR 1800, is considered to be Category I. This means that VOR, NDB, RNAV, LOC, Back Course LOC and other such approaches, other than ILS or MLS, are also treated as Category I. This is true even though those approach types may have been considered “non-precision.” (3) This use of Category I is important to consistently apply to certification and authorization criteria for modern systems and procedures. It is also necessary to ensure that Operators or authorities can implement safety and efficiency advances in a timely and effective way, provide effective and uniform training, and provide necessary facilities, meteorological services, and air traffic services. c. Instrument Approach Classification. (1) Accordingly, this AC is based on and uses the definition of Category I as provided in 4.3.7.1. a. The AC treats classification of instrument approach procedures as being grouped into any one of three broad classes: (a) “xLS,” (b) “RNAV,” and (c) “Instrument procedures other that xLS, or RNAV” (e.g., traditional or classic procedures such as VOR, NDB, LOC, and ASR). (2) Procedures identified as “xLS” may apply to ILS, MLS or GLS. (3) Procedures identified as RNAV include procedures based on use of • FMS • RNAV systems using traditional VOR/DME sensors systems, or • GNSS (GPS) or augmented GNSS systems (e.g., includes SBAS/WAAS) (4) RNAV procedures are addressed as either three-dimensional (3-D) if suitable LNAV and VNAV is used, or two-dimensional (2-D) if only lateral navigation is used. It is recognized that various levels of performance are possible either laterally or vertically. Hence, provision is made to address Required Navigation Performance (RNP). RNAV procedures are also considered to include those which may use RNAV methods, techniques or systems to fly traditional sensor specific VOR, NDB, or Localizer based approaches (e.g., use of FMS to fly a VOR, NDB or Back Course Localizer approach in LNAV and VNAV, based on an electronic map display rather than using a “raw data” readout of course deviation). The remaining instrument procedure group titled “Instrument approaches other than xLS, or RNAV” address traditional or classic procedures such as VOR, VOR/DME, NDB, LOC, BC ### Page 36 Page 22 Par 4 LOC, and ASR. This group is considered to include any other remaining types of instrument approach procedures that are not already covered by or addressed by the groups xLS or RNAV. (5) The AC and associated classification schema do not use former terminology of “precision” or “non-precision” as applies to xLS or RNAV instrument approaches. However, it does not preclude continued use of the term by Operators as apply to classic procedures, particularly when training materials or manuals may take a very long time to eventually be amended in the normal course of longer term revision. Since the terms “precision” and “non-precision” are not necessary to implement or conduct operations and can be confusing and ambiguous, their use is discouraged in favor of use of the common generic term “instrument approach” or use of “xLS”, “RNAV”, or “approaches other than xLS or RNAV” for many important applications (e.g., Inappropriately classifying as “non-precision” operations of aircraft using RNAV systems to fly multi-sensor based and highly accurate levels of RNP and accurate VNAV paths, to a low DA(H)). d. General Criteria For Category I. The following general requirements apply to the operational authorization of Category I instrument approach procedures: (1) The airborne system(s) should meet the requirements of the applicable paragraphs of 5.2 for the type of Category I procedures to be flown; (2) Appropriate NAVAIDs and airport/lighting facilities for the procedures to be flown should be available, consistent with paragraph 8; (3) Flightcrew qualification consistent with provisions of paragraph 7 for Category I has been completed; (4) An acceptable airworthiness (maintenance) program for the airborne system is provided IAW paragraph 9; and (5) An operational authorization has been completed IAW paragraph 10 for a U.S. operator or paragraph 11 for a Non-U.S. operator. e. Minimum authorized DA(H). For simplicity of description, where a minimum authorized DA(H) is cited in this paragraph as applicable to Category I minima, it is stated in terms of a height above touchdown zone elevation (e.g., HAT value), even though operational minima for Category I are specified as a DA, based on MSL altitudes. 4.3.7.2. “xLS” Procedures - Minima not less than 200 feet DA(H). Instrument approach operations that may be authorized Category I minima not less than 200 ft. DA(H) include at least the following: a. ILS. b. GLS (GBAS/LAAS). c. MLS. d. Special Procedures - Special procedures having individual FAA approval for each operator or location that are capable of supporting a DA(H) down to at least 200 ft. HAT may be authorized (e.g., PAR, GLS SCAT I). Such special procedures typically require associated conditions or limitations for special flightcrew training, for navigation facility use coordination, site-specific suitability review, or operator or other agency monitoring (e.g., as for DOD provision of PAR capability). 4.3.7.3. “3D” RNAV Procedures - Minima not less than 200 feet DA(H). Instrument approach operations that may be authorized Category I minima not less than 200 ft. DA(H) include: a. 3D RNAV procedures based on suitable levels of RNP and VNAV capability (e.g., RNP.15/125 ft. or lower) ### Page 37 Par 4 Page 23 b. 3D RNAV procedures based on acceptable full capability GNSS/SBAS(WAAS) augmentation 4.3.7.4. “3D” RNAV Procedures - Minima not less than 250 feet DA(H). Instrument approach operations that may be authorized Category I minima not less than 250 ft. DA(H) include: a. NAVAID specific procedures flown using RNAV lateral and vertical guidance (e.g., “VOR Rwy 16R” flown using acceptable FMS LNAV and VNAV) such as a VOR, VOR/DME, NDB, Localizer, or Localizer Back Course approach flown using RNAV, when the procedural identified NAVAID(s) are referenced in the FMS position determination, or when the procedure is flown with the crew monitoring the specified facility(s) by instrument display cross reference (e.g., RDMI raw data display, or equivalent); b. RNAV (FMS LNAV/VNAV) Procedures overlaying a NAVAID-specific procedure, when FMS position updating is referenced to “data base procedural tuning” of the specified facility(s) (e.g., “RNAV or VOR Rwy 16R” flown using acceptable LNAV and VNAV, with FMS using the appropriate procedurally identified NAVAID(s) along with any other applicable sensors for position determination); c. RNAV (FMS LNAV/VNAV) Procedures overlaying a NAVAID-specific procedure, when FMS position updating is not based on the “data base procedural tuning” of the specified facility(s), but instead is based on the FMS’s selection of optimum NAVAIDs or sensors (e.g., “RNAV or VOR Rwy 16R” flown using an FMS which is using optimally identified sensors or NAVAID(s) combinations for position determination); These procedures may be flown with or without the underlying NAVAID operational; d. RNAV (FMS LNAV/VNAV) Procedures not based on a specific ground based NAVAID, when suitable FMS position updating is used (e.g., a “GPS Approach” flown using a suitably capable FMS and appropriate updating capability); or e. RNAV RNP based procedures with levels of RNP or vertical navigation capability other than as qualify paragraph under 4.3.7.2. 4.3.7.5. “2D” RNAV Procedures (e.g., VOR/DME-based RNAV, or GPS-based RNAV) - Minima not less than 250 ft. MDA(H). Instrument approach operations in this group may be authorized Category I minima of not less than 250 ft. MDA(H). a. This group includes at least the following: • 2D RNAV based on sensor inputs from GPS • 2D RNAV based on sensor inputs from DME/DME • 2D RNAV based on sensor inputs from VOR/DME • 2D RNAV based on sensor inputs from combinations of LOC and VOR or DME b. RNAV (2D - LNAV only) Procedures overlaying a NAVAID-specific procedure (e.g., FMS/RNAV, used to fly an underlying VOR or NDB approach, but flown as a 2D RNAV procedure - without procedural tuning of the specified NAVAID facility); c. RNAV (FMS LNAV/VNAV) Procedures not based on a specific ground based NAVAID, when suitable FMS position updating is used (e.g., a “GPS Approach” flown using a suitably capable FMS and appropriate updating capability); or d. Other FAA authorized RNAV-based approach procedures (e.g., Loran, Airborne radar). ### Page 38 Page 24 Par 4 4.3.7.6. Procedures Other than xLS or RNAV (e.g., VOR, NDB, LOC, Back Course LOC, or ASR Procedures) - Minima not less than 250 ft. MDA(H). Instrument approach operations in this group may be authorized Category I minima of not less than 250 ft. MDA(H). a. This group includes ICAO or U.S. NAVAID-specific procedures other than those based on xLS or RNAV, including at least the following: • VOR • VOR/DME • NDB • NDB/DME • LOC • LOC Back Course • LDA, and • SDF b. NAVAID-specific procedures as listed in item (1) above, but when flown with vertical guidance (e.g., using VNAV) c. NAVAID-specific procedures as listed in item (1) above, but when flown with an “open loop” vertical speed based descent profile, and d. Radar Surveillance Approach Procedures including ASR. 4.3.7.7. Other Special Procedures or Authorizations. Other special procedures or authorizations may be issued as follows: a. Lower than Standard Category I minima authorizations may be issued, as addressed in FAA Order 8400.13 (e.g., Authorization for HUD or Autoland RVR 1800 minima, when using limited facilities for approach lighting and runway lighting). b. Special Obstacle Assessment Procedures may be issued for a particular runway, operator, or a group of Operators (e.g., KDTW RW21R). Special Authorization to use a 200 ft. HAT DA(H) based on an obstacle assessment of the runway touchdown zone region and operator use of flight director or autoflight guidance systems. c. Airborne Radar Approach authorizations may be issued to qualified applicants, for use with qualified airborne systems. d. Special Limited Use (Non-ICAO) Procedures (e.g., TLS, KRM). 4.3.7.8. Previously Approved Category I Operations or Use of Previous or New Category I Criteria. Operators approved IAW criteria of earlier versions of AC 120-29 (e.g., AC 120-29 Change 3) for Category I, or operating IAW approved OpSpecs for instrument approaches other than ILS, MLS, or GLS may continue to operate IAW their previously approved program, consistent with current standard operations specifications or any special provisions approved for that operator in that Operator’s approved operations specifications. a. Approval criteria used for a particular aircraft are typically listed in an AFM. If not shown in an AFM, the applicable FAA Aircraft Evaluation Group (AEG) may be consulted through the POI or CMO, to determine eligibility. ### Page 39 Par 4 Page 25 b. Aircraft qualified using other than FAA criteria will be as designated in approved OpSpecs or as designated by the applicable AEG (e.g., through the FAA Flight Standardization Board Report for the aircraft type) or AFS-400. c. Aircraft demonstrated to meet airworthiness provisions of previous versions of AC 120-29 through Change 3, or criteria previous to AC 120-29, may remain eligible for previously approved operational authorizations. Additional airworthiness demonstration under provisions of this AC are not necessary for these aircraft unless additional credit based on meeting the criteria in the appendices of this AC is specifically sought. d. Operators seeking credit provided for only by this version of AC 120-29A and which were not available in previous versions of AC 120-29 must meet operational criteria as described in the main body of this AC. e. New airworthiness approvals addressing Category I, intended for use by an air carrier, may use criteria earlier than this AC only on a case by case basis as determined by FAA. Examples of cases where criteria prior to this AC may be acceptable include providing information from a service bulletin based on a previous version of AC 120-29 to ensure compliance status of an “in-service” aircraft. Another situation would be for continuing the production and delivery of an aircraft or autoflight system type which had a type certification basis using a preceding version of this AC, or when seeking certification of a new derivative aircraft which has an autoflight system the same as or very similar to one previously approved based on an earlier version of AC 120-29. 4.3.8. Requirements for Category II. 4.3.8.1. General Category II Requirements. The following requirements apply to the operational authorization of Category II instrument approach procedures: a. The airborne system should meet the requirements of the applicable paragraph of 5.2 for the type of Category II procedures to be flown, b. Appropriate NAVAIDs and airport/lighting facilities for the procedures to be flown, consistent with Paragraph 8, should be available, c. Flightcrew qualification consistent with provisions of Paragraph 7 for Category II has been completed, d. An acceptable airworthiness program for the airborne system is provided IAW Paragraph 9, and e. An operational authorization has been completed per Paragraph 10 for a U.S. operator or Paragraph 11 for a Non-U.S. operator. 4.3.8.2. Specification of a Category II DA(H). To simplify description of Category II operations and minima, the lowest authorized DA(H) for Category II is cited in this paragraph as an equivalent DH related to wheel height above touchdown zone elevation (e.g., HAT value of 100 ft.). This is done even though operational minima for Category II are typically specified as an equivalent DH value based on radio altitude height above the underlying approach terrain. a. DH for a Category II procedure may be set and procedurally identified by the following nominal conditions: (1) The aircraft’s navigation reference point tracks the center line of the glide path and FAS, (2) Standard wheel to navigation reference point height and distance assumptions are used, (3) A 100 foot or 150 foot wheel height HAT is assumed for the landing aircraft at DH, depending on minima to be specified, and (4) A determination is made of the actual radio altitude above underlying terrain that occurs when an aircraft with nominal wheel to navigation reference height reaches the point on approach where its wheel height first reaches 100 ft. HAT. ### Page 40 Page 26 Par 4 b. Alternately a Category II DH may be set based on specifying use of a 100 foot DH above underlying terrain, regardless of circumstance in which the 100 foot above terrain point is reached. In this instance, the first point or time in which any aircraft, with any arbitrary wheel to navigation reference height, pitch attitude, configuration, lateral displacement, or speed, first reaches the point at which 100 ft. radio altitude is indicated above underlying terrain, the aircraft is considered to have reached DH. c. While a DA is conceptually not precluded for use with Category II, DAs are not currently operationally used for Category II, except as a backup for inner marker-based minima when irregular terrain precludes reliable radio altimeter use to determine minima. 4.3.8.3. Eligibility for Category II Minima not less than 100 ft. DA(H). Instrument approach operations that may be authorized Category II minima not less than 100 ft. DA(H) include: a. ILS, b. GLS (GBAS/LAAS), and c. MLS. 4.3.8.4. Use of Inner Marker. Use of Inner Marker may be authorized in lieu of a DA(H). An Inner Marker is typically used at runways designated by the applicable procedure, such as where radar altimeter use is limited due to irregular underlying terrain (e.g., RA NA). 4.3.8.5. Barometric Altimeter DAs not currently used for 14 CFR Parts 121 or 135 Category II. Barometric altimeter-specified DAs are not currently used as a basis for minima for air carrier Category II, except for those Operators electing to discontinue an approach upon reaching either the DA or DH, which ever is reached first, when visual reference is not established, or upon reaching either the DA or IM, which ever is reached first, when using an IM as the basis for Category II minima. 4.3.8.6. Category II on U.S. Type I ILS. Category II on FAA Type I ILS (limited to FAA-specified locations) for certain qualified flight guidance systems. Instrument approach operations may be authorized Category II minima not less than 100 ft. DA(H). Criteria for special authorizations for air carriers to conduct Category II operations on certain FAA Type I ILS facilities is contained in FAA Order 8400.13 4.3.8.7. Category II using RVR 300 “Meter” Minima. Category II using RVR300m minima (at designated international locations) may be authorized when meeting special provisions of Standard OpSpecs paragraph C059a Table 1. (see Appendix 7). This provision permits an operator to be authorized use of Non-U.S. State minima of RVR300m with a DA(H) of 100 ft. HAT at certain international runways qualifying for a minima less than that specified by ICAO for Category II. A flight guidance system meeting provisions of Appendix 7, Paragraph C059, paragraph c, is required. Corresponding flightcrew procedures must be used. Following successful operational experience using this provision, FAA may determine that the above authorization may be also acceptable using an auto-coupled approach to 100 ft. HAT or other flight guidance system (e.g., HUD) without necessarily meeting other provisions for Category III. Following successful operational experience using this provision, FAA may determine that the above authorization may also be approved for use at certain U.S. facilities having appropriate Category II procedures with a minimum RVR of 1000 and a DA(H) of 100 ft. HAT. For use of this provision internationally, where such operations are authorized by the State of the Aerodrome (e.g., certain European airports), FAA considers the operation to be the equivalent of a limited U.S. Category III operation (1000RVR), even though the State may locally classify or consider it to be Category II. 4.3.8.8. Precision Approach Radar (PAR). Precision Approach Radar Minima may be authorized to minima of not less than 200 ft. HAT, or the published PAR minima, whichever is higher. PAR authorizations are limited to those Operators and crews specifically qualified to use PAR. Request for PAR operations with minima below 200 ft. HAT are approved only on a case by case basis, considering any special crew qualification required, the aircraft type and its characteristics (e.g., aircraft size, aircraft geometry, and PAR radar signature), and the specific facilities to be used. ### Page 41 Par 4 Page 27 4.3.8.9. Previously Approved Category II Operations or Use of Previous or New Category II Criteria. Operators approved IAW earlier versions of AC 120-29 (e.g., AC 120-29 Change 3) for Category II may continue to operate IAW their previously approved program, consistent with current standard OpSpecs or any special provisions approved for that operator in that Operator’s approved OpSpecs. a. Approval criteria used for a particular aircraft are typically listed in an AFM. If not shown in an AFM, the applicable FAA Aircraft Evaluation Group (AEG) may be consulted through the POI or CMO, to determine eligibility. b. Aircraft qualified using other than FAA criteria will be as designated in approved OpSpecs or as designated by the applicable AEG (e.g., through the FAA Flight Standardization Board Report for the aircraft type) or AFS-400. c. Aircraft demonstrated to meet airworthiness provisions of previous versions of AC 120-29 through Change 3, or criteria previous to AC 120-29, may remain eligible for previously approved operational authorizations. Additional airworthiness demonstration under provisions of this AC are not necessary for these aircraft unless additional credit based on meeting appendices of this AC is specifically sought. d. Operators seeking credit provided for only by this version of AC 120-29A, and that were not available in previous versions of AC 120-29 must meet operational criteria as described in the main body of this AC. e. New airworthiness approvals addressing Category II, intended for use by an air carrier, may use criteria prior to this AC only on a case by case basis as determined by FAA. Examples of cases where criteria prior to this AC may be acceptable include providing information from a service bulletin based on a previous version of AC 120-29 to ensure compliance status of an “in-service” aircraft. Another situation would be for continuing the production and delivery of an aircraft or autoflight system type which had a type certification basis using a preceding version of this AC, or when seeking certification of a new derivative aircraft which has an autoflight system the same as or very similar to one previously approved based on an earlier version of AC 120-29. 4.3.9. Runway Field Length Requirements and Runway Clutter. For Category I or II, landing distance requirements are as specified by 14 CFR 121.185, 121.187, 121.195 or 121.197. a. The following typical means of complying with the above provisions of part 121 are considered to be acceptable. Examples are provided for turbine aircraft. Aircraft other than turbine powered aircraft, or aircraft operating under 14 CFR parts other than part 121, may apply equivalent provisions in a similar manner. b. Part 121 turbine aircraft operations must meet provisions of section 121.195(b). Normally these landing distances (e.g., that already include the specified 60% factor) are factored into the AFM data provided for landing distance. They do not have to be added additionally or separately to the AFM data. c. If it is determined during dispatch, in weather forecasts or reports, that the landing runway may be wet (e.g., may is considered to include “chance,” “occasional,” “temporary,” or a probability equal to or greater than 10%), the effective runway length must be at least 115% (i.e., IAW section 121.195(d)) of the distance determined under section 121.195(b). d. Unless otherwise authorized by FAA, wet is considered to be any condition “not clear and dry” on any part of the useable area of the runway (useable area does not include edges, sides, melting of ice or snow banks at edges or sides, area beyond the advertised plowed and sanded surface, overruns, etc.). NOTE 1: FAA may authorize a wet grooved runway with good braking friction characteristics, or equivalent, to be considered a dry runway for purposes of dispatch determination. A wet runway is considered to be a runway that is other than clear and dry, and has no standing water. ### Page 42 Page 28 Par 4 NOTE 2: Aircraft for which a special demonstration has been made for stopping distance on a wet runway for compliance with section 121.195(d) may use information from this determination for low visibility landing distance assessment (see AC 121.195-1A). e. If any useable part of the expected landing runway or runways are slippery (e.g., wet and not-grooved or porous friction coarse (PFC), snow, slush, ice, or standing water) the provisions of section 121.195(d) apply. In addition, operators should consider the possible need for extra stopping distance beyond that required by section 121.195(d) if braking action is reported or expected to be worse than “good.” The amount of additional stopping distance, if any is determined by the operator to be appropriate, may be related to any estimated reduction in stopping capability for the assumed conditions. f. Information on autobrake distance provided by the manufacturer may be used as the basis for Category I or Category II field length determinations. If AFM autobrake data is used as the basis for determining acceptable landing distance, the operator should ensure that appropriate factors for use of autobrakes are considered, and if appropriate, accounted for (e.g., brake configuration, autobrake setting(s), runway surface friction, and runway slope). If a dispatch process applies, dispatch should consider, and provide any necessary information to the flightcrew regarding any pertinent “autobrake settings” on which dispatch may be based. If autobrakes are to be used, it is not necessary to additionally factor autobrake stopping distance data by the 115% specified in section 121.195(d) beyond the stopping distance otherwise protected by section 121.195(d). However, if expected stopping distance based on using an autobrake system, or any particular setting(s) of an autobrake system, is greater than that protected by section 121.195(d), then the operator should take that fact into consideration and provide appropriate stopping distance information or stopping procedures to the flightcrew. g. When an operator needs to provide for an instrument approach and low visibility landing following an emergency return after takeoff, or when using a takeoff alternate, the operator should consider the expected landing configuration, braking method, and initial braking speeds in assessing landing field length requirements (e.g., consider landing weight, engine out flap settings, engine inoperative speeds as applicable, potential for partial brakes, or partial antiskid, or inoperative reverse thrust). h. When determining alternate airport field length provisions (e.g., section 121.187 or 121.197 as applicable) it is recommended that the operator consider the weights, flap settings and approach speeds that may be applicable to use of that alternate airport with an engine inoperative. For credit for use of an alternate airport based on “Engine Inoperative Category II” capability, the operator must consider such representative speeds, as applicable to the engine inoperative configuration, in assessment of the required landing distance. i. The following field length factors and considerations are considered acceptable: (1) Category I Field Lengths. (a) For minima or conditions expected to be at or above RVR 3000, the runway field-length requirement for Category I is as specified by section 121.195 for either a dry or wet runway. For minima or conditions expected to be below RVR 3000, the field length requirement should be based on conditions for a wet runway (section 121.195(d)). (b) Field length requirements are determined based on applicable weather reports and forecasts considered at the time of dispatch or release (i.e., section 121.195 reference to “takeoff”). Once an aircraft is enroute, it is recommended that field length requirements be reassessed if conditions significantly change from the conditions on which the departure was based. (2) Category II Field Lengths. The Runway Field-Length Requirement for Category II is as specified by section 121.195(d) for a wet runway. (a) When auto brake systems are used for Category II, information must be available to the flightcrew to assist in making the proper selection of a suitable auto brake setting consistent with the field length available for landing and the runway condition, including braking action. ### Page 43 Par 4 Page 29 (b) Category II operations should not normally be conducted with braking action less than “fair” unless the operator has a method to ensure that timely updates of field conditions are provided to the flightcrew, and, if applicable, also provided to the dispatcher, and that the flightcrew considers that sufficient runway length is available for the landing in the conditions reported. (3) Runway Field Length Airborne Considerations. Runway field length requirements are typically considered to be dispatch or release (pre-departure) requirements rather than “in-flight” assessment requirements. In the event of unforecast adverse weather enroute, or if braking system or other failures affecting stopping performance occur enroute, the crew should consider any adverse landing distance consequences that may result from a decision to make a landing on a particular runway (e.g., braking action reports, clutter). 4.3.10. NAVAIDs or Landing System Sensors and Aircraft Position Determination. a. Various landing system sensors (NAVAIDs) or combinations of sensors may be used to provide the necessary position fixing capability to support authorization of Category I or II landing weather minima. While certain navigation sensors (NAVAIDs) are installed and classified primarily based on landing operations, the sensors described in this paragraph may also be used for takeoff, missed approach, or other operations (e.g., RNAV position determination). Regardless of the sensors, NAVAIDs, or combination of NAVAIDs used, the NAVAIDs and sensors must provide coverage for the intended flight path and anticipated displacements from that flight path for normal operations, rare normal operations (e.g., winds and wind gradients), and for specified non-normal operations where applicable (e.g., “VNAV out” flight path, “engine-out go-around” flight path). In addition, Category I or II authorizations should be consistent with the provisions or characteristics for specific sensors listed below in paragraph 4.3.10.1 through paragraph 4.3.10.3 unless otherwise accepted or approved by FAA. b. For NAVAID-specific procedures (e.g., ILS), use of ICAO recognized NAVAIDs are eligible for authorization as either a Standard Instrument Approach Procedure or as a Special Instrument Approach Procedure. NAVAID types that are not recognized by or in ICAO criteria (e.g., in Annex 6, Annex 10, ICAO Doc 9365/AN910 Manual of All Weather Operations) are eligible only for authorization as Special Instrument Approach Procedures. 4.3.10.1. Instrument Landing System (ILS). The ILS provides a reference signal aligned with the runway centerline and deviation signals when the airplane is displaced left or right of the extended runway centerline. The linear coverage area for this signal is approximately 3 degrees either side of the extended runway centerline from a point emanating at the far end of the runway. The ILS also provides a vertical flight path (nominally 3 degree descent angle) to a point in the landing zone of the runway. The vertical coverage is approximately 0.7 degrees on either side of the vertical reference path. ILS characteristics should be considered as defined in ICAO Annex 10, unless otherwise specified by FAA. U.S. ILS systems are classified by Type as defined in FAA Order 6750.24 (II/D/2, etc.). 4.3.10.2. Microwave Landing System (MLS). The MLS provides a reference signal aligned with the runway centerline and deviation signals when the airplane is left or right of the extended centerline. The linear coverage area is approximately 40 degrees either side of the extended runway centerline emanating from a point at the far end of the runway. The MLS provides a vertical flight path to the runway similar to ILS. MLS characteristics should be considered as defined in ICAO Annex 10, unless otherwise specified by FAA. U.S. MLS systems are classified by Type, similar to ILS. 4.3.10.3. Global Navigation Satellite System (GNSS) Landing System (GLS). GLS is a landing systems based upon the Global Navigation Satellite System (GNSS). For lowest Category I minima and Category II operations the landing system typically includes a local area differential augmentation system in the vicinity of the runway for which lowest Category I or Category II procedures are specified. The local area system may serve one or more runways, or nearby airports, depending on its classification for each particular runway. The classification of a GLS service may be different for different runway ends (e.g., III/E/3 for Runways 14L and 14R, but I/D/1 for RW 22L). Desired path, centerline, and deviation signals as applicable, are computed by airborne avionics. The coverage area for GLS is typically within a 30 mile radius of a ground facility, but extended service volumes are possible. GLS ### Page 44 Page 30 Par 4 provides for both vertical and lateral flight path specification to the touchdown zone of the runway(s) served, and a lateral path for rollout or takeoff guidance. GLS characteristics should be considered as defined in ICAO Annex 10, unless otherwise specified by FAA (e.g., FAA-accepted references to RTCA SC-159 MASPS). U.S. GLS systems should typically be classified by “Type” of system for each runway end served, similar to ILS (e.g., GLS II/D/2), or by an equivalent schema. Authorization for use of GLS is for each specific air carrier, aircraft type, and GLS system type until pertinent GLS international standards accepted by FAA are promulgated. 4.3.10.4. Satellite Systems. Navigation Satellite systems currently consist of the U.S. Global Position System (GPS) and the Russian Federation Global Navigation Satellite System (GLONASS). These systems may be considered part of a GNSS. a. Various forms of augmentation exist or are in development including Space Based Augmentation Systems (SBAS), Ground Based Augmentation Systems (GBAS), and Aircraft Based Augmentation Systems (ABAS). b. These augmentation systems may also be classified as wide area (e.g., EGNOS, WAAS, MSAS) or local area augmentation systems (e.g., LAAS). c. GNSS may be combined with certain augmentation systems (e.g., LAAS) to provide a GNSS based Landing System (GLS). 4.3.10.4.1. GPS/GLONASS and Reference Datum Information. Satellite position fixing systems authorized for use by U.S. Operators include GPS and FAA-authorized augmentation systems for use with GPS (e.g., WAAS or LAAS). These systems may be used in the U.S., in U.S. territories, in other States that authorize GPS use, and in international airspace. a. When using GPS or navigation systems that base position fixing on GPS, it is the responsibility of the operator to ensure that in airspace outside of the U.S. that an appropriate Reference Datum (e.g., WGS-84) is used for definition of waypoint or critical path point coordinates. Information on states using WGS-84 or various other databases are typically available from commercial charting sources, and may be available on the worldwide web. b. An example of one worldwide web data source for “Datum” information that is acceptable for use is: http://www.jeppesen.com/qref.html c. GLONASS, or other satellite position fixing systems than GPS, may be used only as approved by the CHDO/POI following coordination with AFS-400. 4.3.10.4.2. Local Area Systems. Ground Based Augmentation Systems (GBAS) are considered to include the FAA's Local Area Augmentation System (LAAS) and non-federally provided systems (e.g., SCAT I). a. Initial GLS augmentation authorizations have been limited to use of a DA(H) not lower than 200 ft. HAT. This value may be reduced as more capable airborne or ground based LAAS equipment is implemented or upgraded, amended criteria are issued, increasing numbers of GLS operational authorizations are issued for a wider variety of operating conditions, and satisfactory operating experience is gained. b. Procedures based on any form of GBAS augmentation with performance that is equivalent to or better than a U.S. Type I ILS may be identified as “GLS” (GPS Landing System) procedures. 4.3.10.4.3. Wide Area Systems. a. Space Based Augmentation Systems (SBAS) include the FAA’s wide area augmentation system (WAAS) and other internationally accepted wide area augmentation systems (e.g., EGNOS, MSAS). ### Page 45 Par 4 Page 31 b. Credit for use of SBAS augmentation alone would currently be limited to use of DA (H) not lower than 200 ft. HAT. Procedures based on any form of SBAS augmentation alone or SBAS augmentation in multi-sensor systems such as FMS should be identified as “RNAV” or “RNAV RNP” procedures, as applicable. 4.3.10.5. LOC/LDA/SDF/Back Course. Localizer, Localizer Type Directional Aid (LDA), Simplified Directional Facility (SDF), and Back Course (BC) ILS procedures are authorized for air carrier use and may be authorized to Category I minima not less than 250 ft. HAT. 4.3.10.6. VOR Authorized Procedures. VOR based procedures, when based on VOR alone, when based on multiple VORs, or when specified in conjunction with use of DME, may be authorized to use Category I minima not less than 250 ft. HAT. a. VOR or VOR/DME based procedures may be flown using any of the following flight instrument displays suitable for the procedure to be accomplished, and for course or intended flight path to be achieved, including: • EHSI or ND Map Display • EHSI or ND Raw data display (e.g., EHSI lateral deviation display or VOR needle(s)) • Electromechanical HSI • RMI, RDMI, or equivalent, or • raw data lateral deviation display (e.g., cross pointer display) b. VOR procedures, when flown as a procedure without vertical guidance (e.g., without VNAV), should use an MDA(H). c. Qualifying VOR procedures, when flown with approved vertical guidance (e.g., with VNAV), may use either an MDA(H) or a DA(H), as determined to be suitable by the operator for the procedure or group of procedures to be flown. d. The aircraft navigation system or flight instrument system display(s) used should be determined to be acceptable by the POI, for the procedures to be flown, considering that operator’s routes, procedures, crew qualification, training, and recency of experience policies or programs. e. Use of a Single VOR Airborne System. (1) Under certain conditions, the use of a Single Airborne VOR system may be acceptable. The objective is for the pilot to have multiple ways of navigating, when operating with a single airborne VOR system such that, in the event of failure of a single element of the airborne navigation or display system, or the NAVAID, the approach can be safely discontinued at any point during the approach to touchdown, or at any time during a missed approach. (2) Additionally, following initiation of the missed approach or rejected landing, a transition can be made to use some other NAVAID or NAVAIDs, other than the failed system or facility, to complete a safe missed approach and subsequent flight and an approach to an alternate. NOTE: A period of dead reckoning may be permissible between the time the failure occurs and the time alternate navigation means are established for continuing the missed approach and flight to alternate. During this period of dead reckoning the aircraft should not be unduly exposed to loss of obstacle clearance due to proximity to terrain or significant obstacles. Suitable navigation performance should be achievable to safely complete the missed approach, fly to the alternate, and complete a subsequent approach using a different navigation system or NAVAID, without loss of knowledge of position, loss of appropriate obstacle clearance, or loss of terrain clearance. ### Page 46 Page 32 Par 4 f. Use of RNAV for VOR, VORTAC, or TACAN Fix Substitution. VOR, NDB and TACAN fixes may be authorized for substitution use with “xLS” procedures. (1) RNAV waypoints or along track fixes may otherwise be substituted for any VOR, TACAN, DME, NDB, Compass Locator, marker beacon, or other fix on any segment of a VOR, VOR/DME, ILS or MLS, LOC, LOC BCRS, or NDB procedure where a corresponding VOR azimuth (radial) or TACAN fix is procedurally specified or can be determined by the FMS to the necessary degree of accuracy and reliability. (2) The substitution of RNAV capability based on FMS or GPS must be determined to be acceptable for that operator by the CMO or POI. g. Inoperative or Unsuitable VOR, VORTAC, TACAN, or DME NAVAID. If VOR, VORTAC, TACAN, or DME updating is used in support of area navigation system (e.g., FMS) position determination, Operators and flightcrews should be aware of when and how to disable use of an unsuitable NAVAID or NAVAID element within the navigation system. This is especially true when the unsuitable NAVAID is likely to cause a significant map shift (e.g., movement of a ground NAVAID to a new geographic location without making a corresponding update to that NAVAID’s recorded position in an aircraft’s navigation system database, thus leading to introduction of a sudden navigation system map display position error). 4.3.10.7. DME. DME based procedures, when used in conjunction with VOR, NDB, LOC, LDA, SDF, or BC are authorized for air carrier use, and may be authorized to Category I minima not less than 250 ft. HAT. a. When used in conjunction with ILS or MLS, DME along track fixes may be authorized for use with Category I, II, or III procedures, as applicable to the specified procedure. b. Except for Category II or Category III procedures that are specifically identified by FAA as requiring use of an Inner Marker, DME along track fixes may otherwise be substituted for any marker beacon, VOR, NDB, or Compass Locator on any segment of an ILS or MLS procedure where the corresponding DME value is procedurally specified or can be determined. c. Use of RNAV for DME Fix Substitution. Suitable RNAV systems including FMS or GPS may be used to substitute for DME when equivalent DME fix information can be established by the flightcrew. For this substitution to be authorized, suitable chart information and flight deck navigation system display information (e.g., electronic navigation map displays) must be available to establish the equivalent DME fix capability required for the areas, airspace, routes, or procedures to be used by the operator. Such substitution may be applicable to normal inflight use, to continuation of flight after failure, or to dispatch with inoperative DME capability if consistent with the applicable MMEL for the aircraft type. The substitution of RNAV capability based on FMS or GPS must be determined to be acceptable for that operator by the CMO or POI. d. Inoperative or Unsuitable DME NAVAID. If DME updating is used in support of area navigation system (FMS) position determination, Operators and flightcrews should be aware of when and how to disable use of an unsuitable NAVAID or NAVAID element within the navigation system. This is especially true when the unsuitable NAVAID is likely to cause a significant map shift (e.g., movement of a ground NAVAID to a new geographic location without making a corresponding update to that NAVAIDs recorded position in an aircraft’s navigation system database, thus leading to introduction of a sudden navigation system map display position error). 4.3.10.8. NDB Authorized Procedures. NDB based procedures, when based on NDB alone, when based on multiple NDBs, or when specified in conjunction with use of DME are authorized for air carrier use, and may be authorized to minima not less than 300 ft. HAT. a. NDB or NDB/DME based procedures may be flown using an appropriate EHSI or ND Map Display, EHSI or ND Raw data display, Electromechanical HSI, RMI, RDMI, or ADF display for course guidance, as determined ### Page 47 Par 4 Page 33 acceptable to the POI considering the crew qualification, training, and recency of experience applicable to that operator. b. NDB procedures, when flown as a procedure without vertical guidance (e.g., without VNAV), use an MDA(H). c. NDB procedures, when flown as a procedure with approved vertical guidance (e.g., with VNAV), may use a DA(H). d. Use of a Single NDB/ADF Airborne System. Other than following an in-flight failure of one of several installed airborne systems NDB/ADF receivers, instrument procedures based on NDB/ADF may be flown using a single airborne NDB/ADF receiver in lieu of two airborne NDB/ADF receivers (reference section 121.349) under the following conditions: (1) The operator is authorized to conduct procedures using a single airborne NDB/ADF receiver; NOTE: Authorization for use of a single NDB/ADF may be for a specific procedure, a group of procedures, for an operator’s particular fleet of aircraft (e.g., B727 fleet), for all of an operator’s aircraft, or for a geographic region (e.g., within the United States and U.S. territories), as applicable to the operator’s route structure, and fleet. (2) Instrument procedures requiring simultaneous use of more than one NDB/ADF NAVAID facility are not authorized, unless approved for that operator and each specific procedure; (3) In the event of failure of the airborne NDB/ADF receiver, or other essential element of the airborne NDB/ADF navigation or display system, or the NDB/ADF NAVAID, the approach can be safely discontinued at any point during the approach to touchdown, or at any time during a missed approach, and (4) Following initiation of the missed approach or rejected landing, a transition can be made to use some other NAVAID or NAVAIDs, other than the failed system or facility, to complete a safe missed approach and subsequent flight to an alternate. NOTE: A period of dead-reckoning may be permissible between the time the NDB/ADF airborne system or NDB/ADF NAVAID failure occurs and the time alternate navigation means are established for continuing the missed approach and flight to alternate. During this period of dead-reckoning the aircraft should not be unduly exposed to loss of obstacle clearance due to proximity to terrain or significant obstacles. Suitable navigation performance should be achievable to safely complete the missed approach, fly to the alternate, and complete a subsequent approach using a different navigation system or NAVAID, without loss of knowledge of position, loss of appropriate obstacle clearance, or loss of terrain clearance. e. Use of RNAV for NDB Fix Substitution. (1) Suitable RNAV systems including FMS and GPS may be used to substitute for NDB or ADF when equivalent NDB fix information can be established by the flightcrew. RNAV (FMS) fixes may be authorized for use as an NDB substitute with Category I, II, or III procedures, as applicable. RNAV fixes based on FMS may also be substituted for bearing or cross track fixes. RNAV waypoint or along track fixes may be substituted for any NDB, Compass Locator or other NDB based fix on any segment of a VOR, ILS or MLS, LOC, LOC BC, or NDB procedure where the corresponding NDB bearing is procedurally specified or can be determined by the FMS to the necessary degree of accuracy and reliability. (2) For substitution to be authorized, suitable chart information and flight deck navigation system display information (e.g., electronic navigation map displays) must be available to establish the equivalent NDB fix ### Page 48 Page 34 Par 4 capability required for the areas, airspace, routes, or procedures to be used by the operator. Such substitution may be applicable to normal inflight use, to continuation of flight after failure, or to dispatch with inoperative ADF capability if consistent with the applicable MMEL for the aircraft type. The substitution of RNAV capability based on FMS or GPS must be determined to be acceptable for that operator by the CMO or POI. f. Inoperative or Unsuitable NDB NAVAID. If NDB updating is used in support of area navigation system (FMS) position determination, Operators and flightcrews should be aware of when and how to disable use of an unsuitable NAVAID or NAVAID element within the navigation system. This is especially true when the unsuitable NAVAID is likely to cause a significant map shift (e.g., movement of a ground NAVAID to a new geographic location without making a corresponding update to that NAVAID’s recorded position in an aircraft’s navigation system database, thus leading to introduction of a sudden navigation system map display position error). 4.3.10.9. Radar Systems (e.g., PAR, ASR). Various other systems are in limited use (e.g., PAR, ASR). These systems are considered for air carrier operations only as described below. a. Air carrier approach operations using ASR or PAR may only be approved if OpSpecs contain authority for their use. b. For use of ASR, dedicated training is not specifically required unless the POI determines that the Operators general training and qualification program is not satisfactory for routine use of ASR procedures, and that specific ASR training is needed. c. For use of PAR, dedicated PAR training is appropriate unless the POI determines that the Operators training and qualification program is otherwise able to ensure adequate crew preparation so that dedicated PAR/ASR training or demonstration is not needed (also see 4.3.8.8). 4.3.10.10. Other Systems, Procedures, and Special Systems. a. Marker Beacons. 75 MHz marker beacons are used in the NAS or internationally as part of ILS, and for other limited or special applications (e.g., step-down fixes, departure turn points for instrument departure heading assignments). Use of marker beacons does not require dedicated crew training or qualification beyond that for conduct of ILS approaches. b. Airborne Radar Approach. Operational authorization of use of any “airborne radar approach” procedure (e.g., use of ground mapping radar or equivalent) for purposes of conducting an instrument approach requires coordination with AFS-400, and may require proof of concept demonstration acceptable to FAA. c. KRM, RMS, SRE or other unique systems or procedures which are not necessarily used IAW ICAO criteria (e.g., as used in certain parts of Europe) may only be approved for use by an air carrier if the aircraft is suitably equipped to receive and use the specified system and the system can meet the performance, integrity, and availability standards equivalent to those established for currently approved types of U.S. operations (e.g., ILS, LDA, ASR, RNAV using FMS). Minima authorized should not be less than any corresponding minima that would be applicable to an equivalent U.S. procedure. If not otherwise an ICAO standard NAVAID, operational authorization of use of such systems should include coordination with the state of the aerodrome and with AFS-400, and may require acceptable review of use or demonstration of use to FAA (e.g., to a POI, APM, or CMO). d. Transponder Landing System. Transponder Landing System or other such “multi-lateration” systems may only be approved for an air carrier if the system can meet the performance, integrity, and availability standards equivalent to those established for currently approved types of operations (ILS, FMS, etc.), to corresponding minima. Operational authorization of use of any of these systems requires successful completion of a proof of concept demonstration acceptable to FAA. e. Enhanced Vision Systems are intended to provide the flightcrew with a visual presentation of a view of the approach to a runway that may otherwise be obscured by weather or darkness. Air carrier approach operations using ### Page 49 Par 4 Page 35 these systems may only be approved if the system can meet the performance, integrity, and availability standards equivalent to those established for currently approved types of operations (e.g., ILS, FMS, etc.), to corresponding minima. Operational authorization for use of enhanced vision systems requires successful completion of a proof of concept demonstration acceptable to FAA. 4.3.10.11. Circling Approaches. When instrument approach design criteria or operational factors do not permit a “straight-in” approach to the landing runway, circling procedures may be used. U.S. criteria require SIAP publication of circling maneuver minima if the inbound course is offset more than 30 degrees from the runway centerline, or when a specified descent gradient for a straight-in approach is steeper than a maximum value allowed by instrument procedure design criteria. a. Use of circling minima, however, does not preclude a pilot making a straight in landing if the requirements of section 91.175 can be continuously met below MDA(H), to touchdown, for adequate visual reference and for normal landing maneuvering. Typically, circling approaches are based only on an MDA(H). Use of a DA(H) for circling is addressed because certain procedures using a DA(H) may apply to “sidestep” maneuvers, or may be used with very high values of DA(H), such as in mountainous areas that otherwise may require a circling maneuver to position to land after reaching minimums. b. The circling maneuver can be initiated from any instrument approach procedure where circling is authorized, and may be continued below MDA(H) or beyond the missed approach point (MAP) only when the specified visual reference exists, and when in a position for a normal descent to landing. Electronic course or glidepath information, or FMS flight path presentations are only considered supplementary information to visually accomplishing the circling maneuver. The pilot must keep the aircraft’s position within the established maneuvering area for the approach speed and category specified for the procedure while performing the circling maneuver. An altitude at or above the circling MDA(H) must be maintained until an aircraft (using normal maneuvers) is in a position from which a normal descent can be made to touchdown within the touchdown zone. A missed approach must be executed when external visual references are lost or sufficient visual cues to manually maneuver the aircraft cannot be maintained. c. It is important to note that the published missed approach procedure may not provide obstacle clearance when below DA(H) or MDA(H), or when past the published missed approach point (MAP). If it is necessary to conduct a missed approach from below the DA(H) or MDA(H) or from past the published MAP (e.g., as a result of a balked landing, rejected landing, loss of visual reference, not in a safe position to land, blocked runway, or other similar reason for a go-around), reference to the associated IFR departure procedure for the applicable runway(s) usually provide help to the pilot in determining a safe course of action to climb back to procedurally protected airspace (adequate obstacle clearance) as specified by the published missed approach procedure. d. When a missed approach from a circling maneuver is executed from below DA(H) or MDA(H) such as when visual reference is lost after passing DA(H) or MDA(H), or when initiating the missed approach from beyond the missed approach point such as when not able to maneuver to be able to accomplish a normal landing in the touchdown zone, the direction of the initial missed approach turn should typically be in a direction toward an appropriate runway, to ensure obstacle clearance. This is to keep the aircraft within the maneuvering area, until climb above the DA(H) or MDA(H), and intercept of a published segment of the missed approach procedure can be accomplished. Pilots should be aware of the applicable radius of protected airspace for the respective approach category used for the circling maneuver, and attempt to maneuver the aircraft within that protected airspace radius from the airport. e. Operators may be authorized to perform circling approaches as published, or may choose not to train flightcrews to accomplish circling maneuvers and accept corresponding high minima limitations regarding circling approaches. If an operator chooses not to train for circling approaches, a 1000 ft HAT DA(H) or MDA(H) and 2 mile visibility limit, or greater, is typically included in OpSpecs to limit use of circling minima for that operator or aircraft type. ### Page 50 Page 36 Par 4 f. It is recommended that unless special circumstances exist, wide body (long wingspan) aircraft or aircraft needing to accomplish circling maneuvers at speeds in excess of 165 KTS ground speed should not typically be authorized circling minima below 1000 ft. HAT and 3 miles meteorological visibility. 4.4. RNAV/Flight Management Systems (FMS). An FMS provides a means to navigate along a flight path based upon earth referenced waypoints. These waypoints can define a flight path that originates or terminates at a runway or at other relevant fixes located in terminal or en route airspace. This type of system may be approved for low visibility approach and missed approach operations IAW criteria in pertinent appendices of this AC and standard OpSpecs. a. FMS systems eligible for use must meet criteria of AC 25-15, AC 20-129 and AC 20-130, or subsequent criteria, or equivalent criteria. Equivalent systems are considered to be those systems previously shown to meet AC 90-45 which predated the above references, but would have otherwise been capable of meeting essential elements of the later criteria (e.g., B757, B767), or other aircraft that have subsequently been determined to be capable of meeting essential elements of the above criteria even though they were not specifically certificated using that criteria (e.g., certain non-U.S. manufactured aircraft such as the A320). b. For RNP operations, additional information is provided below and in paragraph 4.5 and Appendix 5. 4.4.1. FMS Use for xLS Procedures a. ILS, MLS, or GLS approaches or procedures are typically flown with FMS only to the extent that the FMS: • Serves as a means to display the ILS, MLS, or GLS procedure (e.g., as on a navigation map display); • May be used to tune appropriate ILS, MLS, or GLS NAVAIDs or radio frequencies; • May be used to define and display and fly various LNAV or VNAV segments to intercept the final approach path or segment, or glideslope; or • May be used to define, display and fly various LNAV or VNAV segments for a missed approach path. b. Use of FMS to fly ILS, MLS, or GLS approaches when ILS, MLS, or GLS navigation aids are out of service (e.g., localizer or glideslope inoperative, or GNSS GBAS facility inoperative) may be authorized only in conjunction with RNP criteria (See paragraph 4.4.4 below). 4.4.2. FMS Use for Procedures Other Than xLS or RNAV. FMS may be used to conduct VOR, VOR/DME, NDB, NDB/DME, LOC, and LOC Back Course approaches when suitable navigation position updating which provides required accuracy and integrity is used by the FMS (e.g., DME-DME-IRS, or scanning DME, or VOR/DME, or GNSS position updating, or Localizer (LOC) updating, etc.). 4.4.3. FMS Use for RNAV. FMS may be used as a 2D or 3D RNAV system, to conduct RNAV instrument approaches. a. RNAV procedures may be authorized based on one or more “procedure specified” NAVAID(s) (e.g., the FMS data base identifies a specific VOR/DME “Procedure tuned (“P” tuned)” NAVAID, or a combination of specific DME facilities to use as a basis for the procedure). b. GPS approaches are considered to be RVAV approaches when flown by an FMS. GPS approaches may only be flown by those FMS systems which are capable of suitable GPS position updating and have appropriate navigation data base information to properly load and display the procedure to the flightcrew. Not all GPS approaches may necessarily be suitable for use with FMS because of procedure design, vertical path definition, an inability to “call up” or “load” the procedure from a data base, because the FMS may not be able to appropriately recognize “GPS” as a type of approach classification, or because the airplane AFM may not suitably provide for GPS procedure use. Operators intending to fly “GPS approaches” using FMS should treat such procedures as ### Page 51 Par 4 Page 37 RNAV procedures, and ensure that the FMS can properly fly each procedure or each type of procedure to be used (e.g., LNAV/VNAV or LNAV only). c. RNAV procedures may also be authorized based on use of a “NAVAID rich environment” in which specific “procedure identified” NAVAIDs may not be identified, but rather the FMS is permitted to select optimum NAVAID’s from those available. When such RNAV and NAVAID updating procedures are used, the NAVAID service provider, authority, or operator must ensure that the normally selected NAVAID(s) and the alternately selected NAVAID(s) suitably support the procedure to an acceptable level of accuracy and availability (e.g., at ranges, at altitudes, and along the expected flight paths relevant to achieving appropriate system approach performance). For an FMS which uses DME-DME or VOR-DME-based NAVAID sensors in conjunction with IRS, in a NAVAID rich environment, this can typically be accomplished by analysis, or by in-flight assessment (usually during line operations) to show suitable NAVAID reception for normal facilities to be used and for the first alternate facilities anticipated to be used for a particular system and procedure if the normal facility(s) become unavailable. For equivalent RNAV procedure assessments for RNP-qualified aircraft, see paragraph 4.4.3.3 below. d. RNAV procedures that do not use “procedure tuned facilities” may be authorized for use with multi-sensor FMS based on use of “DME-DME” updating, “VOR/DME” updating, “scanning DME” updating, or “GNSS (GPS)” updating. These methods may be used individually, or may be used in combination, or may be used in conjunction with inertial position filtering. NOTE: For purposes of this paragraph, any 14 CFR part 97 procedure with a specified DME limitation must be reviewed and resolved by the POI prior to the operator's use of that procedure. 4.4.3.1. Use of a Single RNAV Airborne System. Other than following an in-flight failure of one of several installed airborne RNAV systems (e.g., failure of one FMS), instrument procedures based on RNAV may be flown using a single airborne RNAV system in lieu of two RNAV systems (reference section 121.349) under the following conditions: a. The operator is authorized to conduct procedures using a single RNAV (FMS) system, NOTE: Authorization for use of a single RNAV may be for a specific procedure, a group of procedures, for an operator’s particular fleet of aircraft (e.g., B737 fleet), for all of an operator’s aircraft, or for a geographic region (e.g., within the United States and U.S. territories), as applicable to the operator’s route structure, and fleet. b. Instrument procedures requiring simultaneous use of more than one RNAV system are not authorized, unless approved for that operator and each specific procedure, c. In the event of failure of the airborne RNAV system, or other essential element of the airborne RNAV navigation or display system, or associated NAVAID(s), the approach can be safely discontinued at any point during the approach to touchdown, or at any time during a missed approach, and d. Following initiation of the missed approach or rejected landing, a transition can be made to use some other NAVAID or NAVAIDs, other than the failed RNAV system or facility(s) used by that system, to complete a safe missed approach and subsequent flight to an alternate. NOTE: A period of dead-reckoning may be permissible between the time the RNAV system is used and reversion to another system, or following NAVAID failure, to the time alternate navigation means are established for continuing the missed approach and flight to alternate. During this period of dead-reckoning the aircraft should not be unduly exposed to loss of obstacle clearance due to proximity to terrain or significant obstacles. Suitable navigation performance should be achievable to safely complete the missed approach, fly to the alternate, and complete a subsequent approach using a different navigation system or ### Page 52 Page 38 Par 4 NAVAID(s), without loss of knowledge of position, loss of appropriate obstacle clearance, or loss of terrain clearance. 4.4.4. FMS Use for RNAV with RNP. RNP operations may be based on capability as specified in a FAA approved AFM. RNP operations may also be based on “Fleet Qualification” of and individual aircraft, a group of aircraft, or an aircraft type using criteria acceptable to FAA (e.g., RTCA DO-236 Appendix D for RNP Fleet Qualification). a. Approach or departure RNP operations for an air carrier typically require dual FMS capability for RNP. b. See paragraph 4.4.2 above for operations and limitations that may apply for a single FMS with RNP capability. In addition, procedures for departure or approach for air traffic separation that are based on use of RNP may require use of dual RNP-capable systems, when so designated. c. FAA may authorize other approach types for use by FMS on a case by case basis for each operator or aircraft type. 4.4.4.1. Standard RNP Qualification. FMS may be used as a 2D or 3D RNAV RNP system, as appropriate, to conduct RNAV instrument approaches based on aircraft qualification for RNP. Operations should be consistent with the approved AFM and apply appropriate RNP obstacle clearance criteria. Appendix 5 provides obstacle clearance criteria for RNP that can be used for RNAV approaches using RNP-based minima. FAA Order 8260.47, or other criteria acceptable to FAA, may be used to specify vertical obstacle clearance criteria for use of VNAV. 4.4.4.2. “Fleet Qualification” For Use of RNP. Some FMSs do not incorporate provisions for RNP as part of their type design approval. Aircraft with such FMSs may be candidates for fleet qualification for one or more RNP levels when certain provisions are met for autoflight systems, displays, annunciations, and FMSs. These aircraft may use corresponding RNP procedures and criteria (e.g., see Appendix 5 for RNP-based obstacle criteria). Criteria of Appendix 5 applicable to RNP-based RNAV approaches may be used for these FMS systems when approved by the FAA. RNP vertical criteria or vertical criteria of FAA Order 8260.47, or other criteria acceptable to FAA, may be used to specify vertical obstacle clearance requirements for use of VNAV. a. Examples of aircraft and systems which may typically “fleet qualify” under this provision would be aircraft having IRS and dual FMS incorporating GPS updating, or dual FMS using DME-DME or scanning DME updating when the aircraft is operated in an area with a significant number of DME facilities. A significant number of DME or other NAVAID facilities are considered to be a number which provide for adequate signal coverage in the event of failure of any single facility, and with more than one facility or facility pair providing acceptable position update geometry and accuracy, considering the updating requirements for the FMS and any other relevant sensors used (e.g., IRS, IRU, ADIRU). Typically, aircraft having FMS and sensor systems such as these are considered to meet either /E or /F flight plan classification. b. The following capabilities for aircraft and systems (e.g., for aircraft systems described, named or described differently but providing equivalent capability) should be considered for fleet qualification for RNP 0.3 or greater. (1) Suitable autopilot or Flight Director use*, (2) Suitable alerting; e.g., an “IRS Only” annunciation message, should suitable NAV updating not be available, and (3) Suitable navigation display; e.g., A 10 mile (or lower) EFIS Map Scale, showing the designated flight path (such as an FMS designated green or magenta flight path line), with a suitable aircraft position symbol allowing a pilot to suitably monitor availability of a correct flight path, and aircraft path displacements (FTE)**, (4) Suitable navigation check procedures; e.g., if not otherwise ensured by system performance or flight deck annunciation, a “reasonableness check” for acceptable position fixing error to be completed not later than passing a Final Approach Fix (FAF), and ### Page 53 Par 4 Page 39 (5) Suitable navigation system status assessment; e.g., a NAVAID or sensor updating capability suitability cross check, performed not later than passing a Final Approach Fix (FAF)***. c. Additional criteria may be necessary depending on the specific fleet, and desired operations, routes, or procedures. Additional information may be found in DO 236, Appendix D. *NOTE: Credit may be limited by Flight Technical Error (FTE) capability that can be achieved. **NOTE: The objective is to assure that the pilot has that information, in a suitable form, necessary to conduct the operation (e.g., appropriate to the airspace/type of operation). Credit for systems other than EFIS “map displays” (e.g., systems using only an HSI or lateral deviation scale display) for RNP may be permitted, but credit is limited to use of “simple procedures.” Procedures considered to be unacceptable (i.e., not simple) are those procedures involving: • multiple short flight path segments, • frequent or large angle turns • critical obstacles adjacent to turns • adjacent aircraft flight paths with turns • adjacent significant or mountainous terrain • use of multiple or complex VNAV gradients • procedures requiring a high level of pilot “situation awareness” to detect and correct the consequence of flight path definition or waypoint difficulties (e.g., an FMS “Legs Page” waypoint “Bypass”) • procedures unduly sensitive to pilot setup errors or mistakes made in programming a navigation system that could readily be detected when using a map display • procedures that require unusual levels of attention, FTE monitoring, or • other criticality that are aided by use of a map display ***NOTE: May be a limiting factor for the level of RNP to be authorized, considering the pilot or operator’s ability to assess position fixing errors as relate to sensors or NAVAIDs intended to be used. 4.4.4.3. Assessment Credit for RNP-qualified aircraft flying “non-RNP” based RNAV Procedures. RNAV procedure assessment credit may be based on an RNP (AFM qualified) aircraft flying non-RNP based RNAV procedures to demonstrate that acceptable system performance is achieved and that a NAVAID rich environment (e.g., DME-DME IRS or RNAV-DME IRS updating) is capable of appropriately supporting an RNAV procedure for that aircraft and system type. For such assessments, it is acceptable for an operator to show that the demonstrated ANP (EPE) remains below an acceptable value throughout an approach, and any applicable parts of a missed approach, for the normal and first alternate FMS NAVAID facility selections expected to be used (see paragraph 4.4.3). 4.4.4.4. Assessment of Expected Levels of ANP for RNP-qualified aircraft flying “RNP” Procedures. When RNP qualified aircraft (“AFM Qualified” or “Fleet Qualified”) fly “RNP” based RNAV procedures, suitable levels of positioning accuracy (e.g., anticipated, projected, or achievable) should be available appropriate to the level(s) of RNP intended and the procedures used. ### Page 54 Page 40 Par 4 a. If the procedure specifies ground-based facilities to be used for the procedure, this assessment may be considered to have already been done. Otherwise, an assessment must be accomplished (e.g., by that operator, by another operator, by a designee, by an authority, or by a service provider). b. An accuracy assessment of navigation services may apply to an airspace, areas, routes, procedures or operations planned or otherwise intended (e.g., contingency alternates). The assessment may be accomplished by any one or more of a variety of technically qualified people or organizations, including the operator, a pilot, a fleet manager or other qualified representative of the operator (e.g., dispatcher), an authority, airspace planners, procedure developers, air traffic services, charting agencies, through ICAO global or regional agreement, by technically qualified supporting contractors to any of the above entities, or by a relevant aircraft or avionics manufacturer. c. When determining the suitability of the airplane/system to achieve the expected level(s) of accuracy, the person or organization accomplishing the assessment should refer to appropriate airplane and system material. The expected levels of accuracy should be applicable to the system or systems to be used (e.g., airborne system as well as supporting NAVAIDs or space-based system elements external to the aircraft), should be suitable to support the level(s) of RNP to be used for the time period(s) to be used, and should be compatible with the airspace or procedures to be used (e.g., consider geographic or geometric effects such as “terrain masking,” if applicable). d. Acceptable source material for determining anticipated, expected, projected, or achievable ANP may include any one or more of the following: • Information from an applicable aircraft AFM • Information from an applicable aircraft operating manual • Applicable operational navigation documents (e.g., Systems Requirements and Objective (SR&O) documents) available from the aircraft or avionics manufacturer that apply to a navigation system • Appropriate authority or air traffic service provider assessments or airspace studies • Appropriate published instrument procedure provisions • Authority, ATS provider, or ICAO-specified NAVAID locations, standard NAVAID characteristics, NAVAID performance and service volume charts or plans • Published GNSS satellite constellation characteristics or GNSS augmentation method characteristics found acceptable to FAA and the State of the Aerodrome or ICAO • NOTAM information • AIP or AIM, or equivalent, information • Appropriate studies or assessments conducted by an operator found acceptable to FAA, or • Any other source material able to help assess projected accuracy that is found acceptable to FAA e. The primary and secondary NAVAIDs identified during this process should be determined to be operating prior to use (e.g., the operator or pilot should ensure that the pertinent NAVAIDs are not “out of service”). 4.4.5. FMS VNAV. FMS procedures typically use vertical navigation capability (VNAV) based on a barometric pressure-based VNAV path (e.g., Barometric (Baro) VNAV). FMS systems may also use a VNAV path based on a geometrically defined VNAV path which is fixed in space by “earth centered earth fixed (ECEF) coordinates” (e.g., fixed relative to earth reference and does not vary with barometric pressure - analogous to an ILS Glide Slope, except does not compensate for earth curvature). In this AC these paths are referred to as “ECEF Geometric VNAV Paths.” a. ECEF Geometric VNAV Paths (if and when used) typically are only used for final approach segment path definition. ECEF Geometric VNAV Paths, if used in either an FMS or instrument procedure, must be clearly distinguished from Baro VNAV paths, and must have clearly defined and compatible transitions from Baro VNAV ### Page 55 Par 4 Page 41 paths to the ECEF Geometric VNAV Path. Baro VNAV paths may be used for all applications including final approach paths. b. Baro VNAV paths may be defined as follows: (1) Baro VNAV paths with constraints for “at,” “at or above,” “at or below,” or the proceeding with corresponding speed constraints. (2) Baro VNAV geometrically-based path defined as an approximate straight line segment from one defined WP pressure altitude to another WP pressure altitude (following earth curvature), or (3) Baro VNAV geometrically-based path defined as two approximate straight line segments from one defined WP pressure altitude to another WP pressure altitude (following earth curvature), but using a reduced gradient for the final part of the path preceding the “to” WP to accommodate a speed constraint at the “to” WP, or (4) Baro VNAV Performance-based climb or descent paths may be used. (5) When used for a final approach segment, Baro VNAV paths may be based on a defined descent path angle rather than a segment between two sequential WP barometric altitudes, and (6) For credit within this AC for use in a final approach segment (e.g., DA(H) credit) a Baro VNAV path should: (a) Meet provisions of AC 20-129, as amended, for VNAV, or equivalent (e.g., equivalent means aircraft such as the B757 or A320 which meet AC 90-45A or other earlier international standard as a certification basis, but have systems which operationally have been determined to meet objectives of AC 20-129. Such aircraft system designs preceded issuance of AC 20-129, and were the basis for its subsequent development), and (b) Be capable of providing vertical tracking performance within + 125 ft vertically (two sigma) (e.g., meeting or meeting the equivalent of RNP 0.3/125 ft. for the vertical performance component), excluding temperature correction for deviation from ISA, (see 4.2.5-1), or, (c) Alternately, FMS systems may provide for additionally more accurate vertical tracking performance within + 45 ft vertically (two sigma) or + 15 ft. vertically (e.g., meeting or meeting the equivalent of RNP x.xx/45 ft. or RNP x.xx/15 ft. for the vertical performance component), excluding temperature correction for deviation from ISA, (see 4.2.5-1), and (d) Provide a VNAV path vertical displacement scale display showing a displacement range within at least + 550 ft. or less (with a scale of + 400 ft. recommended), unless meeting the more stringent requirement of paragraph 5.9.2 Figure 5.9.2-1 for final approach segment displays. c. It is also recommended that the FMS systems have digital readout capability available to the pilot showing vertical displacement (e.g., FMS progress page or equivalent). d. For “Go-Around,” when using a VNAV path for a final approach segment and a corresponding DA(H) is authorized for use, momentary descent below the DA(H) is considered acceptable while the aircraft transitions from the descent approach path to a missed approach. 4.4.6. FMS Use for International Procedures. For international operations (e.g., for instrument procedures outside the United States), equivalent criteria to the criteria specified above (e.g., ICAO PANS-OPS) may be used. In addition, operators may use criteria of this AC, and related U.S. criteria referenced by this AC, internationally when approved by FAA, and when found acceptable by the country in which the Aerodrome is located for the procedure being used. For international operations it may be important to apply provisions of this AC regarding use ### Page 56 Page 42 Par 4 of an appropriate waypoint or NAVAID reference datum (e.g., WGS-84 see paragraph 6.2.17), or provisions for extreme cold temperature correction (see paragraph 8.13). 4.4.7. FMS RNAV Use for Substitution for VOR, DME, NDB, or Marker Beacon NAVAIDs or Fixes. Where suitable NAVAID updating of an FMS or GNSS navigation system is available, FMS or GNSS-based RNAV may be used to substitute for inoperative or unavailable VOR, DME, NDB, or Marker Beacon NAVAIDs or fixes for approach procedures, missed approach procedures, or departure procedures. For such substitution, except as provided in item 4 below where an authority has already specified an acceptable substitution, the operator should ensure that the navigation system used and updating method available, taken with the available remaining NAVAID(s) or sensors are suitable for the route or procedure segment to be flown. a. FMS RNAV substitution for VOR, DME, NDB, or Marker Beacon NAVAIDs or fixes may be applied if: (1) The operator can ensure the necessary accuracy of the aircraft's RNAV system to substitute for the desired fix, NAVAID, or waypoint, and (2) If the aircraft’s navigation system is able to suitably depict the substitute WP, facility, or fix, and (3) The aircraft can suitably fly any applicable leg, route, or procedure segment that otherwise would be based on the inoperative NAVAID or unavailable fix, or (4) If the responsible authority (e.g., FAA or JAA) has otherwise established or provided for, and the operator uses, an acceptable RNAV substitution (e.g., IAW AIM GPS substitution provisions for NDB or DME, or FAA’s enroute NAVAID RNAV substitution policy, or IAW an acceptable RNAV substitution method promulgated via NOTAM). b. Also see provisions for various specific NAVAID types within paragraph 4.3.10, such as 4.3.10.7 for inoperative DME substitution. 4.4.8. Inhibiting RNAV System Use of Inoperative or Unsuitable VOR, DME, VORTAC, TACAN, or NDB NAVAIDs. If VOR, DME, VORTAC, TACAN, or NDB updating is used in support of area navigation system (FMS) position determination, Operators and flightcrews should be aware of when and how to disable RNAV system use of an unsuitable NAVAID or NAVAID element within the navigation system. This is especially true when the unsuitable NAVAID is likely to cause a significant map shift (e.g., movement of a ground NAVAID to a new geographic location without making a corresponding update to that NAVAID’s recorded position in an aircraft’s navigation system database, thus leading to introduction of a sudden navigation system map display position error). 4.5. Required Navigation Performance (RNP). RNP is a navigation performance standard for a particular area, airspace, route, procedure, or operation. A definition of RNP is specified in Appendix 1. a. The specification of RNP has two major aspects, the airspace (e.g., area, route, route segment, leg, procedure, or particular operation) and the airborne system. The airspace requirement is to specify airspace, routes, procedures, or operations within which the aircraft must be located with a high degree of assurance. The airborne systems requirement is to provide a level of performance that is reliable, repeatable, and predictable. The airborne system specification of navigation performance is as defined in RTCA DO-236, or equivalent (e.g., as agreed in an FAA-approved certification plan), except as otherwise found acceptable to FAA. b. Application of an appropriate airborne specification for RNP serves as a basis to ensure that airborne system performance will match or exceed the level necessary for the area, route, route segment, leg, procedure, or operation. RNP criteria have currently been developed and applied for area navigation standards for use with lateral types and levels of RNP (e.g., types such as addressing 95% lateral performance only, or addressing lateral performance using RNP x 2 containment areas, or various levels of RNP such as RNP .3, RNP .5, RNP 1). Extension of the RNP concept to other types or levels of RNP (e.g., levels such as RNP .15/45 ft.) represent more stringent lateral and vertical performance standards that may in the future be applied to approaches or 3D terminal arrival and departure VNAV paths. Other future applications of RNP may provide for along track performance (e.g., “Required Time of Arrival (RTA)”) and are anticipated to evolve as general navigation requirements and operational concepts evolve. ### Page 57 Par 4 Page 43 Hence this AC currently addresses only initial RNP applications, and recognizes that RNP criteria will continuously evolve to address other future operational requirements as necessary to define and manage evolutionary changes in the International Airspace System (INAS). Accordingly, different aircraft may meet RNP requirements in different ways regarding sensors used or criteria met (e.g., FANS 1, FANS A, RTCA DO-236, Fleet qualification). Regardless of RNP application, however, it must be possible to determine that each specific aircraft meets the level of RNP required for the airspace application, and that a suitable identifiable standard has been applied. c. RNP addresses the aircraft and navigation service (non-aircraft) accuracy, integrity, continuity, and availability requirements for normal and rare fault-free performance and for performance with failures. RNP specifies the nominal and limit lateral, and if applicable, vertical flight path displacements permissible for a particular procedure. RNP can be related to obstacle clearance or aircraft separation requirements to ensure a consistent set of operational procedures and design requirements. d. The following elements of RNP, and error components, are thus considered applicable to systems and operations, as defined and described below in Figure 4.5-1. e. A desired flight path is the path that the pilot, or pilot and air traffic service, expect the aircraft to fly. A desired flight path may be identified by the pilot, by ATS, by an airspace planner or by a procedure developer. It is typically specified in the form of a route or procedure, or is as otherwise identified by ATS in a pre-specified flight plan or clearance, or is as defined by an ATS clearance issued in “real time” (e.g., an assigned track, radial, bearing, course, arc, or heading). The desired flight path may be a simple straight segment, may be a path defined by multiple waypoints connected by straight segments, or may be a complex path defined by continuous straight and curved segments. The path may be defined in two dimensions (2D) consisting of lateral and longitudinal elements, three dimensions (3D) including vertical path elements, or may be defined in four dimensions (4D) including a longitudinal position as a function of time elements, or “time of arrival” constraints at waypoints. f. In order for an aircraft to follow the desired flight path it is necessary that the navigation system (airborne or on the ground) generate a defined flight path. The defined flight path is the path as determined by the path definition function of an aircraft’s navigation system (Note: It may also be defined by a system external to the aircraft, and intrinsically provided, or otherwise communicated to the aircraft). While the defined flight path is typically intended to be the same as the desired flight path, the defined flight path is often only a close approximation to the desired flight path due to unavoidable path definition error factors. Factors such as non-spherical earth shape or curvature, determination of geometric altitude versus true altitude or pressure altitude, changing magnetic variation or outdated NAVAID declination, differences in “great circle” route calculations, survey errors, database resolution limitations, or other such factors can result in the defined path being slightly different than the desired path. This difference between the desired path and the defined path is called the path definition error. g. The aircraft elements of the navigation system estimate the aircraft’s position and compare that position with the defined flight path. A deviation indication is produced which represents the calculated displacement of the airplane from the defined flight path. This deviation is typically displayed on a primary flight display, or navigation displays, for flightcrew awareness, and is provided as an input to an autopilot and/or flight director system for command guidance or automatic control. The resulting difference (i.e., non-zero deviation) between the estimated aircraft position from the desired flight path is called the path steering error. This error includes display errors and flight technical error. h. The error in the estimation of the aircraft’s position is referred to as position estimation error, or navigation system error. The navigation system error may result in a displacement from the desired flight path. i. The accuracy with which the aircraft is controlled as measured by the indicated aircraft position with respect to the indicated command or defined flight path position is called flight technical error (FTE). FTE does not include human performance conceptual errors (e.g., entry of an incorrect waypoint or waypoint position, selection of an incorrect procedure, selection of an incorrect NAVAID frequency, or failure to select a proper flight guidance mode). FTE can be influenced by factors such as flightcrew response to guidance (e.g., response to Flight Director information), or external environment conditions such as a wind gradient or turbulence. ### Page 58 Page 44 Par 4 j. The sum of the path definition error, navigation system error, and the path steering error (i.e., flight technical error plus any display error) is the total system error (TSE), which is the difference between the desired flight path and the actual flight path. Figure 4.5-1 below shows the error terms considered in the cross-track dimension of the total system error. Desired Path Actual Position Estimated Position Flight TechnicalError Defined Path Path Definition ErrorNavigation System Error Total System Error Navigation Lateral Error Components Related to RNP Figure 4.5-1. k. Particular levels of RNP can be satisfied using various NAVAIDs such as ILS and MLS, or by the use of a combination of navigation sensors (DME/DME, VOR/DME, IRU/IRS, GNSS, etc.) using a navigation computer (e.g., FMS). When a computed path (e.g., series of waypoints) is used as the basis for an approach operation, the desired flight path must typically be defined by a series of three dimensional earth-based coordinates for the applicable waypoints or path definition points. l. Approach or missed approach operations can be approved by demonstration of the capability to meet the required navigation performance (e.g., accuracy, integrity, availability) for a specific approach procedure, for a set of particular procedure types, or for a set of RNP levels. m. The transition from typical en route or terminal RNP levels to an approach RNP level is accomplished by transitioning to the required RNP level for the approach IAW the approved instrument procedure or by a point no later than the final approach fix, if an aircraft is radar-vectored to final. n. Associated with the RNP level is a containment limit that is specified as “two times the level of RNP (2xRNP).” The system performance integrity provided by this RNP containment limit is intended to support its application as a basic element for either aircraft separation or obstacle or terrain clearance assessment. However, other considerations such as an obstacle rich environment, potential weather factors, high traffic density, limited communication or surveillance environment, or other such factors may also be appropriate to consider in determining if any additional airspace buffers may be appropriate beyond the RNP containment limit. Similarly, operations at less than 2xRNP, may be found to be appropriate, such as if an ATS communication and surveillance environment otherwise safely permits ATS management of the airspace by other means than RNP containment (e.g., where ATS radar monitoring and radar vector separation on adjacent Standard Terminal Arrival Route (STAR) transitions may be used to ensure safe separation, in lieu of use of RNP containment). 4.5.1. RNP Levels or Types. The expression “RNP Level” is used to describe a specific value or level of required navigation performance. The term “RNP Level” may be interchangeably described as “RNP Type” in some industry and FAA references. However in this AC, the term “RNP Level” is meant to apply only to a lateral RNP element (e.g., RNP .5) or to specific paired lateral and vertical elements (e.g., RNP .3/125 ft.). The term “RNP Type” is generally reserved for future uses, in which future vertical and longitudinal elements or other conditions of RNP may additionally apply. a. Table 4.5.1-1 provides RNP Levels that could support initial, intermediate, final and missed approach segments. These RNP levels have not yet been established as international standards. ### Page 59 Par 4 Page 45 Table 4.5.1-1. RNP LEVELS FOR APPROACH RNP Level Applicability/Operation (Approach segment) Normal Performance (95%) Containment Limit (*) RNP 1 Initial/Intermediate approach +/-1 nm +/-2 nm RNP 0.5 Initial/Intermediate/Final approach [Supports limited Category I minima] +/-0.5 nm +/-1 nm RNP 0.3 Initial/Intermediate/Final approach [Supports limited Category I minima] +/-0.3 nm +/-0.6 nm RNP 0.3/125 ft. Initial/Intermediate/Final approach with specified baro vertical guidance [Supports limited Category I minima] +/-0.3 nm +/-125 ft +/-0.6 nm +/-250 ft RNP 0.03/45 ft. Final approach with specified vertical guidance[Supports Category I minima] +/-0.03 nm (**) +/-45 ft +/-0.06 nm +/-90 ft RNP 0.01/15 ft. Final approach with specified vertical guidance [Supports Category I/II minima] +/-0.01 nm (***) +/-15 ft +/-0.02nm +/-30 ft RNP 0.003/15 ft. Final approach with specified vertical guidance [Supports Category I/II/III minima] +/-0.003 nm +/-15 ft (****) +/-0.006 nm +/-30 ft (*) (*) NOTE: For barometric VNAV, the obstacle assessment methodology described in Appendix 5 may be used to addresses vertical containment limits which consider multiple factors such as altimeter error, temperature, and “along track” fix error. Each of these factors should be considered, as necessary, in determining Required Obstacle Clearance (ROC). Nominal vertical values shown in this Table associated with various levels of RNP are intended to be used in conjunction with and considering factors described in Appendix 5, as applicable to the vertical path specified and the type or types of sensor systems used. For other forms of VNAV (e.g., when using an ECEF coordinate specified geometric path), assurance of vertical containment may be met by any FAA approved method, including the method specified by Appendix 5. Examples of acceptable methods other than that based on Appendix 5 would be methods where containment is considered as a “designed-in capability” of a system or aircraft (e.g., as for GBAS or SBAS), or a specific system/infrastructure/operational assessment method, acceptable to FAA, with potential corresponding operational or procedural requirements. (**) NOTE: Performance consistent with Category I operation based on ILS performance requirements at 200 feet (***) NOTE: Performance consistent with Category II operation based on ILS performance requirements at 100 feet (****) NOTE: Consistent with landing and rollout performance (refer to AC 120-28D). Vertical accuracy does not apply below 100 feet HAT due to the transition to a flare maneuver consistent with reduction in sink rate and landing dispersion requirements. b. RNP is a required navigation performance level described by the specification of a numeric value indicating the required navigation accuracy for a specific operation, typically specified laterally in nautical miles (e.g., RNP 1 is a Required Navigation Performance of +/-1 nautical mile (95% Probability)). c. RNP containment is specified as RNP (X) x 2. ### Page 60 Page 46 Par 4 d. RNP Levels are defined for lateral performance, or lateral and vertical performance, if applicable. Standard values for RNP for general use are as specified in RTCA’s Minimum Airspace Performance Standards (MASPS) for RNP (RTCA DO-236) as amended, this AC, related ACs, or as otherwise specified by FAA through published instrument procedures, the Aeronautical Information Manual (AIM), or by NOTAM. ICAO specified types or levels of RNP as promulgated in ICAO Manuals or ICAO Regional Supplements for International Airspace may also be considered as acceptable RNP levels for Approach operations. e. RNP Levels typically used for various approach and missed approach segments supporting Category I procedures may be based on use of multi-sensor RNAV (e.g., FMS with IRS, VOR, DME, or GNSS inputs), or on other aircraft navigation systems having FMS-like capabilities (e.g., GPS based navigation systems). RNP Levels applicable to Category I may also take advantage of, or also be based on, sensor inputs received from specific landing systems (e.g., ILS, MLS, or GLS). f. RNP Levels typically used for various approach and missed approach segments supporting Category II procedures may be based on the same capability specified above for Category I, except that for any portions of a final approach segment below 200 ft. HAT for Category II, use of specific landing system sensors (e.g., ILS, MLS, or GLS) may be determined to be necessary to achieve the desired level of RNP. Similarly, for portions of any FAS below 200 ft. HAT, use of a multi-sensor RNAV system should have suitable integrity and availability capability (e.g., may require use of multiple FMS with IRS, and suitable ILS, GNSS, or GBAS inputs to achieve the necessary RNP capability). 4.5.2. Other RNP Levels or Types. Other RNP Levels or Types may include types specified by a particular Authority for specific applications (e.g., RNP 5 within certain geographic areas; RNP .15 for a particular air carrier “Special approach procedure”) 4.6. Flight Path Definition. Certain flight segments and waypoints are necessary to effectively implement approach and missed approach operations using landing systems where the required flight path is not inherent in the signal structure of the navigation aid (e.g., integrated multi-sensor area navigation systems and other RNAV systems such as satellite systems). The concepts and criteria described below may be applied to other types of navigation systems when using area navigation and RNP concepts. a. In general, an operator must have an acceptable method to ensure that any waypoints or path points which are considered critical to an instrument procedure (if any) are correctly defined, and are loaded into each applicable aircraft’s database, initially, and at each change cycle. b. RNP-based area navigation systems may use any leg types available and suitable for RNP path definition as specified by acceptable FAA or industry criteria (e.g., RTCA DO-236; ARINC 424) for a particular type of navigation system), or leg types as otherwise approved by FAA for use with RNP. Leg types may be specified to define a suitable path in space in conjunction with established waypoints, new waypoints, or path definition points. c. Levels of RNP may be procedurally specified, may be specified in a data base for automatic call up for an entire procedure when a procedure is loaded, may be specified in a data base for automatic call up for each leg or segment of a procedure, may be entered by the flightcrew into the navigation system for a procedure or leg, or may be based on navigation system default settings if those default RNP settings are found to be acceptable to FAA (e.g., when using standard FMS RNP default values and standard instrument procedures with a compatible RNP level specified). When possible, it is recommended that RNP levels be specified by the instrument procedure, and automatically set for each applicable leg, to minimize flightcrew input workload and potential for FMS or navigation system input error. d. Levels of RNP may be specified for individual path segments, for an entire procedure, or for portions of a procedure (e.g., Intermediate segment, FAS, IMAS, or an entire missed approach path). e. The following criteria and considerations are appropriate to specify the landing and rollout flight path. A graphic depiction of the points, heights, angles or other considerations described below is shown in Figure 4.6-1. ### Page 61 Par 4 Page 47 f. The approach segment connects with the rollout segments. An approach flight path is considered to terminate at the beginning of the rollout segment. 4.6.1. Landing and Rollout Flight Path. The following criteria specifies certain reference points and other criteria necessary to effectively implement landing and rollout operations using a landing system where the required flight path (e.g., FAS and RWS) is not inherent in the signal structure of the navigation aid (e.g., for satellite based sensor systems). 4.6.2. Runway Datum Point (RDP). The RDP is used in conjunction with the FPAP and the vector normal to the WGS-84 ellipsoid at the RDP to define the geodesic plane of a final instrument approach flight path to touchdown and rollout (e.g., FAS). It is a point typically at the designated center of the landing runway. An RDP is defined by a specified latitude, longitude, ellipsoidal height, and orthometric height. The RDP is a reference point used to connect the approach flight path with the runway. The RDP may or may not be coincident with, and need not necessarily be coincident with the designated runway threshold. 4.6.3. Flight Path Alignment Point (FPAP). The FPAP is a point, usually at or near the stop end of a runway, used in conjunction with the RDP and a vector normal to the WGS-84 ellipsoid at the RDP, to define the geodesic plane of a final approach and landing flight path (e.g., FAS and RWS). The FPAP typically may be the RDP for the reciprocal runway. 4.6.4. Flight Path Control Point (FPCP). The Flight Path Control Point (FPCP) is a calculated point located above the RDP in a direction normal to the WGS-84 ellipsoid. The FPCP is used to establish the vertical descent path and descent angle of the final approach flight path (e.g., FAS) to the landing runway. 4.6.5. Datum Crossing Height (DCH). The height of the Flight Path Control Point (FPCP) above the Runway Datum Point (RDP). Note that the FPCP may be specified in units of feet or meters, but is typically specified in units of feet. NOTE: A standard datum crossing height should typically be 50 ft. For sloped runway touchdown zones, a DCH in the range of 50 to 55 ft above the designated datum point is acceptable. Other values are accepted on a case by case basis considering the airport need for a different value, and the type of aircraft and operations to be used (e.g., STOL). Typically a DCH is coincident with the runway threshold (TCH). (Also see Sections 5.12.3 and 5.12.4). 4.6.6. Glide Path Angle (GPA). The glide path angle is an angle, defined at the FPCP, that establishes the descent gradient for the final approach flight path (e.g., FAS) of an instrument approach procedure. It is measured in the geodesic plane of the approach (defined by the RDP, FPAP, and a vector normal to the WGS-84 ellipsoid at the RDP). The vertical and horizontal references for the GPA are a vector normal to the WGS-84 ellipsoid at the RDP and a plane perpendicular to that vector at the FPCP, respectively. 4.6.7. Glide Path Intercept Reference Point (GIRP). a. The GIRP is the point at which the extension of the final approach path (e.g., FAS) intercepts the runway. ### Page 62 Page 48 Par 4 Points, Heights, Angles Or Other Considerations For Definition of An Approach And Landing Flight Path Figure 4.6-1 Datum Crossing Height (DCH) Runway Datum Point (RDP) Glidepath Intercept Reference Point (GIRP) Flight Path Control Point (FPCP) Flight Path Alignment Point (FPAP)η η = Glide Path Angle b. The locations established for, and the values assigned to, the RDP, FPCP, DCH and GPA will be selected based upon the operation need to establish the required GIRP. Operational considerations include: (1) Path of wheels over threshold(s), (2) Need for coincidence with other aids and systems - visual and non-visual, (3) Runway characteristics (upslope and downslope, crown, etc.), (4) Actual threshold, displaced threshold or multiple threshold characteristics, (5) Actual clearway or stopway characteristics. 4.6.8. Approach and Missed Approach Segments. Figure 4.6-2 below shows the applicable reference points, path points, waypoints and leg types typically used to construct instrument approach procedures applicable to air carrier operations. ### Page 63 Par 4 Page 49 Waypoint and Segment Placement Figure 4.6-2 IMAWP GPIWP APIWP FPCP EFAS FAS IMAS RWS FPAP GIRP 4.6.9. Procedure Design Related Waypoint Definitions and Use. The following procedure design-related waypoint definitions and uses are provided: a. Glide Path Intercept Waypoint (GPIWP) - The point at which the established glide slope intercept altitude (MSL) meets the Final Approach Segment (FAS), on a standard day, using a standard altimeter setting (1013.2 HPa or 29.92 in). b. Approach Intercept Waypoint (APIWP) - A variable waypoint used when necessary to link a barometric LNAV/VNAV flight path with a Final Approach Segment (FAS) that is fixed in space (e.g., a xLS final segment). The APIWP permits LNAV and barometric VNAV segments, which may vary vertically in location on an approach as a function of barometric pressure setting or temperature variation from standard, to join or be connected to a FAS which is otherwise fixed in vertical location with respect to a runway. c. Initial Missed Approach Waypoint (IMAWP) - (Used only for MAP) A Waypoint generally aligned with the runway centerline, beyond the touchdown zone, used to establish a suitable initial climb segment beyond the touchdown zone. The IMAWP intends to provide a safe path and altitude, if applicable, in the vicinity of the runway, to be used to establish a safe initial go-around path following a low altitude go-around or rejected landing. d. Procedure Design Related Segment Definitions. The following procedure design related segment definitions are provided: Final Approach Segment (FAS) The segment of an approach extending from the Glidepath Intercept Waypoint (GPIWP) or Approach Intercept Waypoint (APIWP), whichever occurs later, to the Glidepath Intercept Reference Point (GIRP). For the purpose of procedure construction, The Final Approach segment is defined as beginning at the FAF and ending at the Flight Path Control Point (FPCP) or point at which the missed approach segment starts (e.g., point of lowest nominal DA(H)). Extended Final Approach That segment of an approach, co-linear with the Final Approach Segment, but ### Page 64 Page 50 Par 4 Segment (EFAS) which extends beyond the Glidepath Intercept Waypoint (GPIWP) or Approach Intercept Waypoint (APIWP). Runway Segment (RWS) That segment of an approach from the glidepath intercept reference point (GIRP) to Flight Path Alignment Point (FPAP). Initial Missed Approach Segment (IMAS) That segment of an approach from the Glide Path Intercept Waypoint (GIRP) to the Initial Missed Approach Waypoint (IMAWP). Missed Approach Segment (MAS) That segment of an instrument approach procedure from a point on the FAS corresponding to the position where the lowest DA(H) occurs under nominal conditions, to the designated IMAWP, or missed approach holding WP, as specified for the procedure. ### Page 65 Par 5 Page 51 **5. AIRBORNE SYSTEM REQUIREMENTS.** 5.1. General. The following accuracy, integrity and availability criteria are specified for aircraft systems intended for Category I or II. Aircraft related systems are addressed by 5.1.1. Non-aircraft systems (e.g., NAVAIDs) are addressed in 5.1.2. Specification of flight path is addressed in 5.1.3, such as is applicable to defining an RNAV, LNAV, or VNAV path to be followed by an aircraft. Specific airborne equipment requirements for Category I or II authorizations are addressed in 5.2 and 5.3. 5.1.1. Airborne Systems. a. Airworthiness criteria for aircraft systems intended to meet requirements of this AC are specified in paragraph 5.1.3 through 5.19 below, or Appendix 2 or 3 for demonstration of airborne systems for eligibility for Category I or II minima respectively. b. For aircraft which completed an airworthiness demonstration applicable to Category I or II using earlier versions of this AC, or previous applicable ACs, new operational authorizations may be requested or may be continued only as provided for in standard OpSpecs. 5.1.2. Non-Airborne Systems (e.g., NAVAIDs or equivalent GNSS capability). Unless otherwise specified by FAA, NAVAID/landing system characteristics to be used should have been addressed using an acceptable means of facility or capability classification (e.g., For a U.S. ILS facility, and example of a typical classification would be “II/E/2”). a. The classification should be specified in a manner suitable to address: (1) Intended NAVAID performance level (or an equivalent capability for GNSS), (2) Signal or capability coverage with respect to the intended flight path(s) and runway, and (3) NAVAID or capability “availability and integrity” (e.g., considering standby capability and power, as applicable). b. This classification schema should at least be provided for any xLS capability (e.g., ILS, MLS, or GLS). Typically this is done by use of FAA or ICAO criteria such as specified by FAA Order 6750.24 as amended, or ICAO Annex 10 Criteria, as suited to the applicable NAVAID facility or capability. NAVAID facility or capability operational use is then predicated on suitable facility or capability classification respectively for ILS, MLS, or GLS (e.g., for ILS, III/E/2). c. NAVAID classifications or equivalent capability classification schema should be consistent among ILS, MLS or GLS to the maximum extent possible. d. At non-U.S. facilities, consideration of equivalence to U.S. classification may be necessary for operational authorizations. e. For GLS, classification schema are evolving and are expected to continue to do so as new GNSS elements or augmentation methods become operational. Nonetheless, an appropriate classification method equivalent to that used for ILS, or as otherwise specified by FAA or ICAO, should be used (e.g., addressing “Performance Level”/”Coverage”/”Integrity” such as “PL2/T/1”). f. NAVAID facility or capability classification schema or associated airborne system documentation referring to that classification schema for ILS, MLS, or GLS should not be defined or expressed in operational authorization terms (e.g., Category I, II, or III xLS). This is necessary to recognize that operational authorization criteria for Category I, II, or III may change in time, and because authorizations may not be unique to a particular NAVAID classification or capability, and further, may depend on and be a function of evolving airborne system elements, procedures, or other factors. ### Page 66 Page 52 Par 5 5.1.3. Flight Path Specification. 5.1.3.1. Lateral. a. Category I. The following levels of lateral performance shown in Table 5.1.3-1 are acceptable for Category I and corresponding minima may be applied. Any one or more methods listed below may be demonstrated, but the method(s) used should be identified as the basis for the demonstration. Table 5.1.3.1-1. **CATEGORY I - LATERAL PERFORMANCE/MINIMA** 1) ILS/MLS/GLS (any one xLS) [Minima equivalent to ILS at 200 ft. HAT] [Lateral tracking performance from 1000 ft. HAT to 200 ft. HAT should be stable without large deviations (i.e., within +50 microamps deviation) from the indicated course or path, or equivalent; using at least 3 different representative facilities for a minimum of 9 total approaches. System performance should be acceptable without undue oscillation.] 2) “ILS Equivalent” (e.g., SCAT I/ MASPS;WAAS/MOPS) [Minima equivalent to ILS at 200 ft. HAT] 3) RNP RNP < .03 .03 .3 [Minima equivalent to ILS at 200 ft. HAT] [Minima typically not lower than a DA(H) of 250 ft. HAT] [Minima restricted to not lower than a DA(H) of 250 ft. HAT] 4) FMS (LNAV/VNAV or LNAV) [Minima restricted to not lower than a DA(H) of 250 ft. HAT] 5) RNAV [Minima as specified by Standard OpSpecs/SIAP] **6) LOC, LOC BCRS, VOR, VOR/DME,** NDB, ASR, PAR [Minima as specified by Standard OpSpecs/SIAP] b. Category II. The following levels of lateral performance shown in Table 5.1.1-2 are acceptable for Category II. Any one or more methods may be demonstrated, but the method used should be identified as the basis for the demonstration. ### Page 67 Par 5 Page 53 Table 5.1.3.1-2. **CATEGORY II - LATERAL PERFORMANCE/MINIMA** 1) ILS/MLS/GLS (any one xLS) [Minima equivalent to ILS at 100 ft. HAT] See Category I Criteria to 300 ft. HAT, and in addition, [Lateral tracking performance from 300 ft. HAT to 100 ft. HAT within +25microamps deviation from the indicated course or path, or equivalent, (for 95% of the time/per approach) using at least 3 representative facilities and for a minimum of 20 total approaches. System performance should be acceptable without undue oscillation.]* * NOTE: Or using JAA ACJ AWO 231 Method 2) RNP RNP < .01 [Minima equivalent to ILS at 100 ft. HAT] c. Lateral Performance below or beyond DA(H). For either Category I or II procedures with a DA(H) below 250 ft. HAT*, when guidance is provided (e.g., for autoland, or HUD flare/rollout), the lateral performance should at least be equivalent to that attainable using an ILS Type I/E/1 localizer (or RNP .003) from 200 ft. HAT, or 100 ft. HAT as applicable, to the end of rollout. *NOTE: This provision does not apply to systems intended for Category III - see AC120-28D for Category III requirements. d. From 200 ft. HAT or 100 ft. HAT, as applicable, until returning to an established missed approach segment of the approach procedure, if guidance is provided, performance should be at least equivalent to that attainable using an ILS Type I/E/1 localizer front and back course, or RNP.3 as applicable. 5.1.3.2. Vertical. a. Category I. The following levels of vertical performance are acceptable for Category I and corresponding minima may be applied. Any one or more methods listed below may be demonstrated, but the method(s) used should be identified as the basis for the demonstration. ### Page 68 Page 54 Par 5 Table 5.1.3.2-1. **CATEGORY I - VERTICAL PERFORMANCE/MINIMA** 1) ILS/MLS/GLS Glide Slope/Glide Path (any one xLS Glide Slope) [Minima equivalent to ILS at 200 ft. HAT] [Vertical tracking performance from 700 ft. HAT to 200 ft. HAT should be stable without large deviations (i.e., within +75 microamps deviation) from the indicated path, or equivalent, using at least 3 different representative facilities and for a minimum of 9 total approaches. System performance should be acceptable without undue oscillation.] 2) “ILS Glide Slope Equivalent” (e.g., SCAT I/ MASPS; WAAS/MOPS) [Minima equivalent to ILS at 200 ft. HAT] 3) RNP RNP < .03 and ECEF** VNAV .03 .3 with or without BARO VNAV [Minima equivalent to ILS at 200 ft. HAT] [Minima typically not lower than a DA(H) of 250 ft. HAT] [Minima restricted to not lower than a DA(H) of 250 ft. HAT] 4) FMS BARO VNAV [Minima restricted to not lower than a DA(H) of 250 ft. HAT] 5) RNAV [Vertical performance not applicable*] 6) LOC, LOC BCRS,VOR, VOR/DME, NDB, ASR, PAR [Vertical performance not applicable*; except PAR minima equivalent to ILS] *Note: A procedure addressing a stabilized approach from the Final Approach Fix to MDA(H) is recommended for these procedures (except this note does not apply to PAR). **Note: ECEF VNAV - VNAV referenced to “Earth Center Earth Fixed Coordinates,” or geometric height above the “earth reference surface” based VNAV. b. Category II. The following levels of vertical performance are acceptable for Category II. Any one or more methods may be demonstrated, but the method used should be identified as the basis for the demonstration. ### Page 69 Par 5 Page 55 Table 5.1.3.2-2 **CATEGORY II - VERTICAL PERFORMANCE/MINIMA** 1) ILS/MLS/GLS (any one xLS Glide Slope/Glide Path) [Minima equivalent to ILS at 100 ft. HAT] See Category I Criteria to 300 ft. HAT, and in addition, [Vertical tracking performance from 300 ft. HAT to 100 ft. HAT within +35** microamps deviation from the indicated course or path, or +12 ft, which ever is greater, or equivalent, (for 95% of the time/per approach) using at least 3 different representative facilities and for a minimum of 20 total approaches. System performance should be acceptable without undue oscillation.]* * NOTE: Or using JAA ACJ AWO 231 Method ** NOTE: When this provision is applied to path tracking in conjunction with Category III, momentary excursions up to + 75 microamps during test demonstrations may be acceptable if flight guidance system touchdown and landing performance is otherwise shown to be satisfactory. 2) RNP RNP < .01 with ECEF** VNAV [Minima equivalent to ILS at 100 ft. HAT] c. Category I or Category II. (1) Vertical (VNAV) performance at altitude constraints prior to a Final Approach Fix (FAF) or Final Approach Point (FAP), or at an FAF or FAP. For procedures with VNAV segment(s) prior to an FAF or FAP, at an FAF or FAP (e.g., intercepting an FAS from an en route segment, STAR, Profile Descent, initial approach or intermediate approach segment), vertical performance should normally be based on use of a vertical “Fly by” path rather than a “Fly over” path. The small vertical displacement which may occur at a vertical constraint as a result of using a vertical “Fly by” waypoint rather than vertical “Fly over” waypoint is considered operationally acceptable, and desirable, to ensure asymptotic capture of a new (next) vertical segment. This momentary deviation below the published minimum procedure altitude is acceptable provided the deviation is limited to no more than 100 ft. and is a result of a normal VNAV capture. This applies to both “level off” or “altitude acquire” segments following a climb or descent, or vertical climb or descent segment initiation, or joining of climb or descent paths with different gradients. NOTE: A “Fly By” vertical waypoint is a WP for which an aircraft may initiate a vertical rate change and depart the specified vertical path to the active WP prior to reaching that WP, in order to asymptotically capture the next vertical path. A “Fly Over” vertical waypoint is a WP for which an aircraft must stay on the defined vertical path until passing the active WP and may not initiate the necessary vertical rate change to capture the next vertical path until after passing the active WP. Hence, after passing the active WP, as the next WP becomes active, and if there is a vertical path change, the aircraft must re-adjust vertical rate to re-capture the vertical path after having already overshot the first opportunity for an asymptotic capture of that new path. (2) Vertical (VNAV) performance at waypoint altitude constraints near the point at which DA(H) or MDA(H) may occur. For procedures with waypoints at or near the point at which DA(H) may occur, vertical (VNAV) performance should not preclude continuous descent of the aircraft to the runway, following the established VNAV path to the runway (e.g., VNAV should not initiate inappropriate capture of a missed approach segment and ### Page 70 Page 56 Par 5 automatic level off (at MDA(H)) or initiation of MAP climb, without pilot confirmation that a missed approach or go-around is intended (e.g., TOGA initiation). (3) Vertical (VNAV) performance below or beyond DA(H) or MDA(H). For procedures with a DA(H) below 200 ft. HAT* (e.g., for autoland, or HUD flare/rollout), the glide path/glide slope vertical performance should at least be equivalent to that attainable using an ILS glide slope at a facility classified as Type I/E/1, between 200 ft. HAT and 50 ft. HAT. *NOTE: This provision does not apply to systems intended for Category III - see AC120-28D for Category III requirements. 5.1.3.3. Longitudinal. Longitudinal (along track) requirements for Category I or II operations are as specified below. a. Category I. The following longitudinal (along track) requirements are acceptable for Category I. Any one or more methods listed below may be demonstrated, but the method(s) used should be identified as the basis for the demonstration. ### Page 71 Par 5 Page 57 Table 5.1.3.3-1. **CATEGORY I - LONGITUDINAL PERFORMANCE/MINIMA** 1) ILS/MLS/GLS (any one xLS, or any combination provided by MMR) Use of VHF OM/MM Marker Beacons Use of VOR/TACAN Fixes (other than for MM) Use of LOM/LMM NDBs Use of suitable DME Distance Information Use of FMS RNAV Fixes (other than for MM) Use of Distance to “Runway Threshold WP” Other methods (e.g., Radar fixes, Fan Markers) No specific method of assuring along track position [Minima equivalent to ILS at 200 ft. HAT] [Minima equivalent to ILS at 200 ft. HAT] [Minima equivalent to ILS at 200 ft. HAT] [Minima equivalent to ILS at 200 ft. HAT] [Minima equivalent to ILS at 200 ft. HAT] [Minima equivalent to ILS at 200 ft. HAT] [Restricted minima may apply - DA(H)>250 ft. HAT] [Restricted minima may apply - DA(H)>250 ft. HAT] 2) “ILS Equivalent” (e.g., SCATI/MASPS;WAAS/MOPS) [Same as for ILS/MLS/GLS described above 3) RNP* RNP < .03 .03 .3 [Minima equivalent to ILS at 200 ft. HAT] [Minima typically not lower than a DA(H) of 250 ft. HAT] [Minima restricted to not lower than a DA(H) of 250 ft. HAT] *Note: RNP Systems/Procedures that do not provide for display of distance to a “Runway Threshold WP” may have minima additionally restricted. 4) FMS (LNAV/VNAV or LNAV) [Minima restricted to not lower than a DA(H) of 250 ft. HAT] 5) RNAV (Op-Specs Part C; Para C063) [Minima as specified by Standard Op-Specs/SIAP] 6) LOC, LOC BCRS,VOR, VOR/DME, NDB, ASR, PAR [Minima as specified by Standard Op-Specs/SIAP] b. Category II. The following levels of longitudinal (along track) performance are acceptable for Category II. Any one or more methods may be demonstrated, but the method used should be identified as the basis for the demonstration. Table 5.1.3.3-2 **CAT II - LONGITUDINAL PERFORMANCE/MINIMA** 1) ILS/MLS/GLS (any one xLS, or any combination provided by MMR) Same as for Category I, except that an IM or suitable distance readout to a “Runway Threshold WP” is also required. 2) RNP RNP < .01 [Same as for ILS/MLS/GLS above.] ### Page 72 Page 58 Par 5 5.1.3.4. Typical Wind and Wind Gradient Disturbance Environment. The lateral and vertical performance described in paragraph of 5.1.3 above should typically be expected to be achievable in conditions at least as described below. Performance may be estimated, assessed analytically, demonstrated in simulation, or demonstrated in flight. Relevant associated information on demonstrated winds encountered or estimated wind gradient capability may be included in the AFM, as desired by the applicant. a. Systems intended for use with procedures for either Category I or Category II should be capable of coping with at least the following wind, wind gradient, and turbulence conditions: • Reported Surface Headwind Component - 25 kts • Reported Surface Tailwind Component - 10 kts • Reported Surface Crosswind Component - 15 kts b. Wind Gradients/Shear - at least 4 kts per 100 ft. from 500 ft. HAT to the surface; c. Recommended Capability - Ability to cope with 8 kts per 100 ft. for 500 ft., moderate turbulence, knife edge shears of at least 15kts over 100 ft., 20 kts lateral directional vector shears of 90 degrees over 100 ft., and ability to cope with a 20 kt logarithmic shears between 200 ft. and the surface. 5.2. Airborne Equipment for Category I. The following equipment (along with any additional equipment specified by 14 CFR for IFR flight) is the recommended aircraft equipment for an authorization for Category I. a. For ILS, GLS, or MLS approach capability: • Two navigation receivers, or equivalent type of device, of each type intended for use, NOTE 1: The navigation receivers specified above may be provided as two or more integrated multi-sensor units (e.g., MMR), NOTE 2: For GLS, at least one data link receiver capable of receiving GBAS uplinked corrections for GNSS position fix correction data may be considered acceptable, when used with dual navigation receiver capability (e.g., dual GPSSU sensors) receiving GPS SV ranging information. Dual data link receivers capable of receiving GBAS uplinked corrections for GNSS are recommended. NOTE 3: Installation of only one navigation receiver may be authorized by FAA for special circumstances, considering the particular facilities and routes to be used, such as if suitable minima restrictions and requirements for alternate navigation capability are applied (e.g., one GLS receiver if two ILS receivers are installed). • Suitable navigation displays, attitude, vertical speed, and airspeed displays for each pilot (see paragraph 5.9 for details) • Suitable failure annunciation visible to each pilot • One or more Marker Beacon systems (unless an approved RNAV substitute is available, or if not necessary for the route of flight, including alternates) • One or more DMEs (unless an approved RNAV substitute is available, or if not necessary for the route of flight, including alternates) • One or more ADFs (unless an approved RNAV substitute system is available, or unless ADF is not required for the intended route of flight, including alternates). Note that two ADFs may be required IAW paragraph 121.549 for certain international operations, and for certain obstacle or terrain critical departure, approach, or missed approach procedures • For aircraft intended for approval of landing minima below RVR 3000, at least one flight director or one autopilot ### Page 73 Par 5 Page 59 • It is recommended that the following capability be available: - Radar Altimeter - Standby power for at least one pilot’s ILS/GLS navigation receiver and displays - Rain removal capability b. For approaches other than ILS, GLS, or MLS (e.g., RNAV, VOR, VOR/DME, NDB). • 2 navigation receivers and associated displays of the type of the approach system to be used (unless otherwise authorized by FAA for the facilities and route to be used), or • 2 FMS systems (unless use of 1 is authorized by FAA for the facilities and route to be used) which are capable of using the necessary NAVAIDs or equivalent (e.g., space vehicles (SVs)), or which can be monitored by using raw data NAVAID data (e.g., on an associated ND display or RDMI). • Suitable navigation displays, attitude, vertical speed, and airspeed displays for each pilot (see paragraph 5.9 for details) • Suitable failure annunciation visible to each pilot • For ASR or PAR, at least 2 communication radios capable of receiving communications of ASR or PAR information. /elevenoclock It is recommended that the following capability be available: - Radar Altimeter - Standby power for at least one pilot’s VOR or RNAV navigation receiver and displays - Rain removal capability c. For aircraft types and systems approved previously to issuance of this AC using earlier AC120-29A or equivalent criteria, the aircraft must have a system which meets that earlier criteria. While such systems may continue to be produced and installed for retrofit in aircraft, or may continue to be installed in new production aircraft or variants, or future derivatives of those types or variants, any additional credit permitted by this AC for Category I capability may be limited to those aircraft and systems meeting revised provisions of this AC, including those provisions shown in Appendix 2. d. For requirements related to equipment inoperative dispatch pertaining to Category I approach capability see paragraph 5.22 below. For situations involving in-flight failure of equipment pertaining to Category I approach capability see paragraph 5.23 below. 5.3. Airborne Equipment for Category II. The following equipment (along with any applicable equipment otherwise specified above for Category I) is the minimum aircraft equipment considered necessary for an authorization for Category II. a. Two independent navigation receivers, or equivalent, of each type intended for use, NOTE 1: The navigation receivers specified above may be provided as two or more integrated multi-sensor units (e.g., MMR), NOTE 2: For GLS, at least one data link receiver capable of receiving GBAS uplinked corrections for GNSS position fix correction data may be considered to be acceptable, when used with dual navigation receiver capability (e.g., dual GPSSU sensors) receiving GPS SV ranging information. Dual data link receivers capable of receiving GBAS uplinked corrections for GNSS are recommended. b. A suitable Automatic Flight Control System, or manual flight guidance system, or both (e.g., flight director) as follows: ### Page 74 Page 60 Par 5 • A system or systems designed to meet criteria of Appendix 3, or • For aircraft types and systems approved previously to issuance of this AC using earlier AC 120-29A or equivalent criteria, the aircraft must have a system which meets that earlier criteria. While such systems may continue to be produced and installed for retrofit in aircraft, or may continue to be installed in new production aircraft or variants, or future derivatives of those types or variants, any additional credit permitted by this AC for Category II capability may be limited to those aircraft and systems meeting revised provisions of this AC, including those provisions shown in Appendix 3. • At least 1 autopilot (AFGS) and at least dual flight director systems with an independent display for each pilot is recommended. Dual systems which provide the same information to both pilots, with the second system in “hot standby status” may be acceptable only if suitable comparison monitoring between the systems is available, and timely transfer to standby can be completed, and suitable annunciation to the flightcrew is provided. c. A radar altimeter display for each pilot. (Note: At least 2 independent radar altimeters with a display for each pilot are recommended.) d. Rain removal equipment is required for each pilot (e.g., windshield wiper, bleed air). (Note: hydrophobic coating is recommended for each applicable forward windshield, in lieu of rain repellent, due to environmental considerations.) e. Flight instruments and annunciations which can reliably depict relevant aspects of the aircraft position relative to the approach path, attitude, altitude and speed, and aid in detecting and alerting the pilots in a timely manner to failures, abnormal lateral or vertical displacements during an approach, or excessive lateral deviation (see paragraph 5.9 for details). f. Unless otherwise approved by FAA based on demonstration of acceptable pilot workload, an autothrottle system should be provided. g. For requirements related to equipment inoperative dispatch pertaining to Category II approach capability see paragraph 5.22 below. For situations involving in-flight failure of equipment pertaining to Category II approach capability see paragraph 5.23 below. 5.3.1. Standard Category II Minima. Standard Category II minima are a DA(H) of 100 ft. HAT and RVR not less than 1200 ft. (350m). 5.3.2. Special Category II Authorizations. Special Category II minima may be authorized for certain qualifying ILS/GLS facilities (e.g., Type I ILS). Minima at these facilities may be restricted as follows depending on NAVAID, airport facility, and obstacle assessments by FAA. Order 8400.13 addresses certain standard provisions applicable to these authorizations. Other provisions may apply when proposed by the applicant, and approved by FAA. Any authorizations issued should be consistent with one or more of the following DA(H) and RVR paired provisions: • DA(H) 150 ft. HAT RVR 1800 • DA(H) 150 ft. HAT RVR 1600 • DA(H) 100 ft. HAT RVR 1800 • DA(H) 100 ft. HAT RVR 1600 • DA(H) 100 ft. HAT RVR 1200 5.4. Automatic Flight Control Systems and Automatic Landing Systems. Automatic Flight Control Systems, Autoland Systems, or Manual Flight Guidance systems (e.g., HUD) are considered acceptable for use and are ### Page 75 Par 5 Page 61 recommended for Category I or II ILS, MLS, or GLS procedures which do not have NOTAM restrictions on localizer or glide slope or equivalent signals (e.g., Glide Slope unusable below 500 ft. HAT, or Localizer unusable inside threshold). 5.5. Flight Director Systems. Characteristics of Flight Director Systems (head down or head up) used for aircraft authorized for Category I or II should be compatible with the characteristics of any autopilot or autoland system used. Flight control systems that provide both autopilot control and flight director information may display, or may not display, flight director commands as appropriate for the system design and operator requirements. Regardless of whether Flight Director commands are provided, situational information displays of navigation displacement must also be provided to both flight crewmembers. To ensure that unacceptable deviations and failures can be detected, the displays must be appropriately scaled and readily understandable in the modes or configurations applicable. 5.6. Head up Display Systems. Head up Display systems used as the basis for a suitable Category I or II authorizations must provide guidance for one or both pilots as appropriate for the system design. If information is provided to only the flying pilot, then appropriate monitoring capability must be established for the non-flying pilot. Monitoring tasks must be identified, and the non-flying pilot must be able to assume control of the aircraft in the event of system failure or incapacitation of the pilot using the HUD (e.g., for a safe go-around or completion of rollout). Head up Display Systems acceptable for Category I or II must meet provisions of Appendix 2 or 3 respectively, or acceptable earlier criteria specified by the FAA and referenced in an AFM. 5.7. Enhanced/Synthetic Vision Systems. Enhanced/Synthetic Vision Systems based on millimeter wave radar or other such sensors may be used to ensure the integrity of other flight guidance or control systems in use during Category I or II operations. They must be demonstrated to be acceptable to FAA in a proof of concept evaluation and they must otherwise meet the requirements of Appendix 2 or 3 of this AC as applicable. Use of Enhanced/Synthetic Vision Systems for purposes other than establishing the accuracy or integrity of flight guidance system performance must be demonstrated to be acceptable through proof of concept testing prior to identification of specific airworthiness and operation criteria. 5.8. Hybrid Systems. Hybrid systems (e.g., a fail passive autoland system used in combination with a monitored HUD flight guidance system) may be acceptable for Category I or II if the system provides the equivalent performance and safety to a non-hybrid system as specified for the minima sought (e.g., Category I or II). a. Hybrid systems with automatic landing capability should be based on the concept of use of the automatic landing system as the primary means of control, with the manual flight guidance system serving as a backup mode or reversionary mode. b. Any transition between hybrid system elements (e.g., control transition from autoland use to manual control HUD use, or for response to failures) must be acceptable for use by properly qualified flightcrews (e.g., qualified IAW part 121, an approved Advanced Qualification Program (AQP), or equivalent JAA criteria, as applicable, and standard industry practices). Transitions should not require extraordinary skill, training, or proficiency. c. For any system which requires a pilot to initiate manual control at or shortly after touchdown, the transition from automatic control prior to touchdown to manual control using the remaining element of the hybrid system (e.g., HUD) after touchdown must be shown to be safe and reliable. 5.9. Instruments, Systems, and Displays. The following identifies Flight Instrument, Systems, and Display presentations requirements for Category I and Category II operations: 5.9.1. Instruments, Systems, and Displays for Category I. a. Attitude indicators, EADIs or primary flight displays must be provided for each required pilot (pilot flying (PF) and pilot not flying (PNF)), or equivalent electro-mechanical instruments depicting attitude, barometric altitude, airspeed, and vertical speed. ### Page 76 Page 62 Par 5 b. HSIs, EHSIs, NDs, or other equivalent navigation displays, with pertinent, reliable and readily understandable lateral situation information for both normal and non-normal conditions related to Category I landing and missed approach procedures, must be provided for each required pilot. c. Instrument and panel layouts must follow accepted principles of flight deck design (e.g., basic-T format, conventions for airspeed altitude scales). d. The location and placement of situation information/navigation displays must be appropriate for each required flight crewmember, and must be appropriately scaled and readily understandable in presentations or mode of display used. e. Suitable redundant lateral, and where applicable, vertical path displacement information from the final approach course and specified glide path must be provided. (1) For any operation intended for use with a DA(H) below 250 ft. HAT, lateral and vertical displacement information must be provided on the PFD, EADI, ADI, or equivalent to each pilot independently. (2) For RNP operations with minima below 250 ft. HAT, the lateral and vertical displacement full-scale indication on the PFD, EADI, or attitude indicator should be as shown in Figure 5.9.2-1 and 5.9.2-2, unless otherwise approved by the FAA. It is recommended that these displacement indications be provided for any RNP approach operations. (3) Different display sensitivities may be necessary for steep or shallow angle approaches. (4) The 0.7 degree taper prior to the 100 ft. HAT for vertical display sensitivity is acceptable for most glide path angles. A taper of ¼ the glide path angle is an acceptable alternative, and would be preferred for steep or shallow glide path angles. (5) The display sensitivities that are selected should be validated by simulator or flight evaluation. f. Decision Altitude (Height) or Minimum Descent Altitude (Height) advisory indications that are readily understandable and appropriately distinctive plus marker beacon indications (middle marker, and outer marker), or equivalent, should be provided at each required pilot station. NOTE: Unless otherwise approved by FAA, advisory indications should be expressed as either “RH” or “RA” for radar/radio height or altitude, and as “BARO” for barometric altitude. Flightdeck depiction of radio and barometric height or altitude advisories should not typically use the operational designations of “DH” or “MDA.” g. Appropriate system status and failure annunciations suited to the guidance systems used, navigation sensors used, and any related aircraft systems (e.g., autopilot, flight director, electrical system) should be provided. h. Automatic audio call-outs as described in paragraph 5.11 are recommended. i. A suitable rain removal method is recommended for each pilot for Category I operations. Suitable methods typically include windshield wipers, bleed air windshield rain removal, or hydrophobic coatings. 5.9.2. Instruments, Systems, and Displays for Category II. a. Attitude indicators, EADIs or primary flight displays must be provided for each required pilot (PF and PNF), or equivalent electro-mechanical instruments depicting attitude, barometric altitude, airspeed, and vertical speed plus suitable standby attitude information available to each required pilot. ### Page 77 Par 5 Page 63 b. HSIs, EHSIs, NDs or other equivalent navigation displays with pertinent, reliable, and readily understandable lateral situation information for both normal and non-normal conditions related to Category II landing and missed approach procedures, must be provided for each required pilot. c. Instrument and panel layouts must follow accepted principles of flight deck design (e.g., basic-T format, conventions for airspeed altitude scales). d. The location and placement of situation information/navigation displays must be appropriate for each required flight crewmember, and must be appropriately scaled and readily understandable in presentations or mode of display used. e. Suitable redundant lateral and vertical path displacement information from the final approach course and specified glide path must be provided. (1) Lateral and vertical displacement information must be provided on the PFD, EADI, ADI or equivalent to each pilot independently. (2) Lateral displacement expanded scale information must be provided to confirm that the aircraft position with respect to intended flight path and the landing runway on each PFD, EADI, ADI or equivalent (e.g., for ILS, a full scale sensitivity of 1 Dot (0.0775 ddm)), or the following criteria applicable to RNP. (3) For RNP operations, the lateral and vertical displacement full-scale indication on the PFD, EADI, or attitude indicator should be as shown in Figure 5.9.2-1 and 5.9.2-2, unless otherwise approved by FAA. It is recommended that these displacement indications be provided for any RNP approach operations. Figure 5.9.2-1 and 5.9.2-2 shows that for the point on the approach path where the RNP portion of the path meets the angular portion of display limits, the display limit distance from nominal path (zero deviation) to full scale high or to full scale low display deviation is + 250 ft. (vertical displacement), and + 1 x RNP (lateral displacement). At the point on the approach path where the vertical angular display limit converges to a constant value (i.e., nominal path is at 100 ft. HAT), the full-scale displacement is +24' (vertical displacement). At that point on the approach path where the lateral angular display limit converges to a constant value (i.e., runway threshold), the full scale displacement is +175 ft. (lateral displacement). f. An autopilot or flight director system suitable for the minima to be authorized. g. Unless otherwise approved by the FAA for Category II operations based on autopilot use alone, flight director(s), or command guidance information, should be provided for each pilot, suitable for the minima to be authorized - at least dual independent system capability must be installed for Category II operations for aircraft which are certificated with more than one required pilot. NOTE: For Head Up Display (HUD) operations, availability of the information in items a, b, and e above on a HUD does not necessarily substitute for availability of this information on pertinent head-down displays (HDDs). Configurations found acceptable to FAA include use of a compatible HUD and HDDs at the Crewmember 1 (CM1/Captain) flight deck station, and suitable and comparable HDDs at the Crewmember 2 (CM2 /FO) flight deck station, each with adequate flight path display and failure annunciation. Use of other HUD/HDD configurations for CM1 and CM2 must be evaluated by FAA, and be determined to provide acceptable and equivalent or better capability. h. Unless otherwise approved by FAA based on demonstration of acceptable pilot workload, an autothrottle system should be provided. i. Decision Altitude (Height) advisory indications that are readily understandable and appropriately distinctive plus a display of radio altitude and marker beacon indications (inner marker, middle marker, and outer marker), or equivalent, should be provided at each required pilot station. ### Page 78 Page 64 Par 5 NOTE: Unless otherwise approved by FAA, advisory indications should be expressed as either “RH” or “RA” for radar/radio height or altitude, and as “BARO” for barometric altitude. Flight deck depiction of radio and barometric height or altitude advisories should not typically use the operational designations of “DH” or “MDA.” j. Appropriate system status and failure annunciations suited to the guidance systems used, navigation sensors used, and any related aircraft systems (e.g., autopilot, flight director, electrical system) should be provided. k. Automatic audio call-outs as described in paragraph 5.11 are recommended. l. A suitable rain removal method is required for each pilot for Category II operations. m. A demonstration of the suitability of any indications for non-normal configurations for which credit is sought (e.g., electrical configurations, hydraulic power). ### Page 79 Par 5 Page 65 Figure 5.9.2-1 Figure 5.9.2-2 ±1 7 5f t Mini m u m Display Deviation at threshold Maximum Display Deviation = RNP nm2 degree taper Deviation valid 1 mile beyond runway length Lateral Deviation ********** FAC defined by Runway Reference Waypoints ±24 feet Maximum Display Deviation ±250 feet Maximum Display Deviation 0.7 Degree taper Vertical Deviation 100 feet HAT ### Page 80 Page 66 Par 5 5.10. Annunciations. Annunciations must be clear, unambiguous, and appropriately related to the flight control mode in use. The mode annunciation labels should not be identified by landing minima classification. For example, APPROACH, LAND 2, LAND 3, Single Land, Dual Land, are acceptable mode annunciation labels, whereas, “Category II,” “Category III,” etc., should not be used. Aircraft previously demonstrated for Category I or II which do not meet this criteria may require additional operational constraints to ensure the correct use of minima suited to the aircraft configuration. 5.11. Auto Aural Alerts. a. Automatic Aural Alerts (automatic call-outs, voice callouts, etc.) of radar altitude, or call-outs approaching landing minimums, or call-outs denoting landing minimums are recommended and should be consistent with the design philosophy of the aircraft in question. However, any automatic call-outs used should not be of a volume or frequency that interferes with necessary flightcrew communications or normal crew coordination procedures. Recommended automatic call-outs include a suitable alert or tone as follows: (1) At 500 ft. (radar altitude), approaching minimums and at minimums, and (2) Altitude call-outs during flare, such as at “50” ft., “30” ft. and “10” ft., or altitudes appropriate to aircraft flare characteristics. b. Low altitude radio altitude call-outs, if used, should appropriately address the situation of higher than normal sink rate during flare, or an extended flare which may be progressing beyond the touchdown zone. Other alerts may be used when approved by the Administrator, if those alerts are consistent with that Operators approved procedures and minima, and do not impair crew communication. 5.12. Navigation Sensors. a. Navigation sensors as noted in paragraph 4.3.7.1 through 4.3.7.4 and in 5.12.1 or 5.12.2 below may be used to support Category I or Category II Instrument Approach Procedures. b. Navigation systems, procedures, sensors, or NAVAID signals cited in paragraphs 4.3.7.1 through 4.3.7.4 or in 5.12.1 or 5.12.2 may also use and take suitable credit for various forms of inertial or air data system capability when combined with capability of the sensors cited in the above provisions to improve accuracy, integrity, or availability performance (e.g., position or velocity complementary filtering, or Kalman filtering may be used, and appropriate credit taken for performance improvement). 5.12.1. Navigation Sensors for (xLS) - ILS, GLS, or MLS. For ILS, GLS, or MLS, various navigation sensors individually may be acceptable to support Category I or II operations. ILS localizer and glideslope signals are the primary means currently used for the determination of deviation from the desired path for lowest Category I or II operations. Criteria for acceptable ILS and MLS localizer and glide-slope receivers are included in Appendix 2 or 3 or in earlier acceptable criteria used by FAA for previous demonstrations of systems for Category I or II. a. Other navigation information based upon GNSS, or SBAS/GBAS, may be used individually or in combination to satisfy the necessary accuracy, integrity, and availability for Category I or II. Navigation sensors other than ILS must meet equivalent ILS performance or appropriate RTCA or EUROCAE criteria for lowest Category I minima credit, unless otherwise authorized. b. Appropriate marker beacon information, or equivalent, must be displayed to each pilot for the outer, middle and inner markers. The FAA may authorize appropriate substitutes for marker beacons for Category I or II based upon the use of suitable GNSS or SBAS/GBAS capabilities, or DME. c. ADF capability, or equivalent capability, should be available as suitable for the planned route of flight or planned alternates (e.g., 14 CFR sections 91.205 (d)(2) and 121.349). For example, at least 1 ADF should be available for ILS procedures, unless the operator does not use ILS procedures with an NDB facility identified as an ### Page 81 Par 5 Page 67 approach transition or missed approach NAVAID, or if the operator has available and uses an approved RNAV capability providing equivalent or better performance to that provided by ADF/NDB. RNP-qualified aircraft may be considered to be eligible for ADF/NDB waypoint substitution any time the area navigation system (e.g., FMS) is able to provide RNP.3 or better capability, for each applicable equivalent procedure segment, or for use of an equivalent NDB waypoint. Any other RNAV capability substitution for use of ADF/NDB for instrument procedures should be as determined to be acceptable for that operator by the CMO (e.g., GNSS system substitution IAWAIM provisions). Note: PAR may also be considered to be acceptable for Category I (also see 4.3.4.1.c and 4.3.8.8). 5.12.2. Navigation Sensors for Approaches other than ILS, GLS, or MLS. For approaches other than ILS, GLS, or MLS, the following sensors are considered to be acceptable for providing course guidance for Category I Operations (Note: Category II operations are not authorized exclusively using these sensors.): • LOC • LDA • SDF • BCRS • RNAV (e.g., FMS) • GPS • VOR • VOR/DME • TACAN • NDB • NDB/DME • Dual NDB • ASR • KRM (RMS) 5.12.3. Aircraft Navigation Reference Points, Wheel to Eye Height, and Wheel to Navigation Reference Point Height. To ensure suitable wheel height and clearance over the threshold of runways when following an electronic path (e.g., glideslope or VNAV) and when using visual references (e.g., VGSI/PAPI) aircraft manuals should specify and Operators should be aware of the height of the pilots eye reference point and the height of the navigation reference point (e.g., glideslope antenna) above the wheel path during landing. This is usually specific to each aircraft type. This information should be available to the operator and pilot, along with any guidance on the minimum acceptable runway threshold crossing height criteria for procedures, if applicable, and any constraints or recommendations for proper VGSI/PAPI use. 5.12.4. Threshold Crossing Height (TCH). a. Typically, procedures are designated with vertical path runway threshold crossing height in the range of 50 to 55 ft. The maximum TCH for instrument approaches is usually limited to 60 ft. Unless otherwise accepted by FAA, aircraft should be able to use these standard facilities and any other facilities with a vertical path (glideslope or VNAV path) having a threshold crossing height specified as not less than 48 ft. b. For operations on facilities where a threshold crossing height (glideslope or VNAV) is less than 48 ft., the operator and CHDO should consider the advisability of those operations on a case by case basis. Considerations should include any obstructions in the pre-threshold area, the amount the glideslope or VNAV path is below standard values, aircraft type and aircraft characteristics as proposed for the operation, whether the runway under-run area is a full load-bearing surface, placement of lighting aids (threshold lights/approach lights), availability, and suitability of VGSI/PAPI, weather minima to be used, and any other relevant factors. 5.13. Supporting Systems and Capabilities. ### Page 82 Page 68 Par 5 5.13.1. Flight Deck Visibility. Forward and side flight deck visibility for each pilot should be provided as follows: a. The aircraft should have a suitable visual reference cockpit cutoff angle over the nose for the intended operations, at the intended approach speeds, and for the intended aircraft configurations, as applicable (e.g., flap settings); b. The aircraft’s flight deck forward and side windows should provide suitable visibility for taxi and ground operations in low visibility; and c. Placement of any devices or structure in the pilot’s visual field which could significantly affect the pilot’s view for low visibility operations must be acceptable (e.g., HUD drive electronics, sun visor function or mountings). 5.13.2. Rain and Ice Removal. a. Suitable windshield rain removal, ice protection, or defog capability should be provided as specified below: (1) Installation of rain removal capability is recommended for Category I and required for Category II (e.g., windshield wipers, windshield bleed air). (2) Installation of use of windshield hydrophobic coatings, or use of equivalent rain repellent systems which meet pertinent environmental standards are recommended. (3) Installation of suitable windshield anti-ice or de-ice capability is recommended for Category I and required for Category II for aircraft intended to operate in known icing conditions during approach and landing. (4) Installation of at least suitable forward windshield defog capability is recommended for aircraft subject to obscuration of the pilot’s view during humid conditions. b. Aircraft subject to obscuration of the windshield due to rain, ice, or fogging of the pilot’s view which do not have protection, or which do not have adequate protection may require operational limitations on the conditions in which low visibility operations are conducted. 5.13.3. Miscellaneous Systems. Other supporting systems including instruments, radar altimeters, air data computers, inertial reference units, instrument switching, or capabilities such as flight deck night lighting, landing lights and taxi lights, position, turnoff, and recognition lights, flight data recorders, cockpit voice recorders, or other low visibility related aircraft systems must meet any appropriate criteria as specified in Appendix 2 or 3, in basic airworthiness requirements applicable to U.S. certificated aircraft or equivalent, or acceptable earlier criteria authorized by FAA for aircraft previously demonstrated to be acceptable for Category I or Category II operation (See paragraphs 5.20 and 5.21 for GPWS, TAWS and FDR provisions). 5.14. Go-Around Capability. a. For aircraft authorized for instrument approaches, and particularly for aircraft intended for operation to Category II minima, evaluation of go-around capability should be based on both normal and any specified nonnormal operations, down to the lowest minima expected. Assessment should account for factors related to aircraft geometric limitations (e.g., fuselage attitude and potential for tail strike) during the transition to go around, limited visual cues, autoflight system mode switching if applicable, and any other pertinent factors identified by FAA. For aircraft in which a go-around from a very low altitude may result in an inadvertent touchdown, the safety of such a procedure should be established considering its effect on related systems, such as operation of autospoilers, automatic braking systems, autopilot/flight director mode switching, autothrottle operation and mode switching, reverse thrust initiation and other systems associated with, or affected by, a low altitude go-around. ### Page 83 Par 5 Page 69 b. If an automatic or flight director go-around capability is provided, it should be demonstrated that a go-around can be safely initiated and completed from any altitude to touchdown. If an automatic go-around mode can be engaged at or after touchdown, it should be shown to be safe. The ability to initiate an automatic or flight director go-around at or after touchdown is not required or appropriate. Inadvertent selection of go-around after touchdown (either an automatic or flight director go-around capability) should have no adverse effect on the ability of the aircraft to safely rollout and stop. c. Regardless of the flight guidance system used, availability of appropriate information to safely go-around should be available to the flightcrew, and the aircraft should have the capability to go-around. The go-around must be able to be initiated at any time during the approach to touchdown. Although flight guidance system go-around capability is not required, if such go-around capability is supported by a flight guidance system, that capability should be able to be selected at any time during the approach to touchdown. If a go-around mode of a flight guidance system is activated at a low altitude where the aircraft inadvertently touches the ground, the flightcrew should have access to adequate information to accomplish a safe go around, and the aircraft or flight guidance system should not exhibit any unsafe characteristic as a result of an inadvertent touchdown. d. The following factors should typically be considered when evaluating the safety of a go-around from any point in the approach before touchdown: (1) Go-around capability should address normal operating conditions, and may include specified nonnormal conditions (e.g., engine out) down to the lowest expected operating minimum. (2) Factors related to any geometric limitations (such as tail strike) or configuration changes (such as flap retraction, or allowing for any necessary acceleration segment) of the aircraft during the transition to a go-around should be considered. (3) Factors such as the autopilot, flight director, or autothrottle mode switching or automatic disconnect, minimizing altitude loss during transition to a go-around, and addressing any adverse consequences that might result from autopilot, flight director, or autothrottle malfunction should be considered. (4) If a go-around could result in an inadvertent touchdown, the safety of such an event should be considered. The aircraft design and/or procedures used should accommodate relevant factors. Examples of relevant factors to consider include operation and acceleration characteristics of engines, failure of an engine, the operation of autothrottle, autobrakes, auto-spoilers, autopilot/flight director mode switching, and other systems (e.g., ground sensing logic) which could be adversely affected by an inadvertent touchdown. (5) If the occurrence of any failure condition in the aircraft or its associated equipment could preclude a safe go-around from low altitude, then such failure conditions should be identified. In such a case, a minimum height may be specified from which a safe go-around was demonstrated if the failure occurs. If the failure occurs below the specified height, pilots should be made aware of appropriate procedures to be used, and the effects or consequences of any attempt to go-around. e. If necessary, information should be provided to the flightcrew concerning appropriate procedures for low altitude go-around. If the ability to conduct approach and landing operations with an engine inoperative using low minima are intended (e.g., minima below an MDA(H) or DA(H) of approximately 250 ft. HAT), or if procedures for an engine failure during a low altitude go-around require special consideration or are significantly different than for any other go-around, then flightcrew procedures to safely conduct such an engine-out go-around should be addressed. If necessary, suitable information to safely conduct such a low altitude go-around should be provided to the flightcrew (e.g., flap configurations and flap retraction procedures, appropriate acceleration to a suitable goaround speed, appropriate use of auto-feather capability). 5.15. Excessive Deviation Alerting. Some method is recommended for being able to detect excessive deviation of the aircraft laterally and vertically during approach, and laterally during rollout, as applicable. The method used should not require excessive workload or undue attention. This provision does not require a specified deviation ### Page 84 Page 70 Par 5 warning method or annunciation, but may be addressed by parameters displayed on the ADI, EADI, or PFD. When a dedicated deviation warning is provided, its use must not cause excessive nuisance alerts. 5.16. Rollout Deceleration Systems or Procedures for Category I or II. 5.16.1. Stopping Means. A means to determine that an aircraft can be reliably stopped within the available length of the runway, considering ambient conditions, is recommended for any operation. 5.16.2. Antiskid Systems. Unless otherwise specified by FAA, aircraft authorized for Category I or Category II do not have specific antiskid system installation or use requirements beyond those specified in the applicable AFM, applicable FAA MMEL and MEL, and applicable field length operating rules. 5.17. Engine Inoperative Category II Capability. The following criteria are applicable to aircraft systems intended to qualify for “engine inoperative Category II” authorizations. Aircraft demonstrated to meet the provisions of Appendix 2 with an “engine inoperative” and have an appropriate reference to engine inoperative Category II capability in the FAA approved AFM are typically considered to meet the provisions listed below. Other aircraft which have an AFM showing only all-engine Category II capability may be operationally demonstrated for engine inoperative Category II capability IAW paragraph 5.19.1 through 5.19.3 and paragraph 10.5. a. The AFM or equivalent reference (e.g., Operators manual) must suitably describe demonstrated approach and missed approach performance for the engine inoperative configuration, and the aircraft must meet pertinent criteria otherwise required for all-engine Category II or equivalent criteria. Suitable performance information should also be available to the pilot and, if applicable, the aircraft dispatcher, to ensure safe landing capability in the anticipated configuration and with anticipated speeds, and to establish safe go-around capability from DA(H) and, if applicable, for a balked landing from the TDZ (e.g., equivalent to an obstacle clearance takeoff procedure). When assessing engine out Category II capability, the following exceptions to all-engine Category II criteria may be used: (1) The effects of a second engine failure when conducting Category II operations with an engine inoperative need not be considered, (2) Crew intervention to re-trim the aircraft to address thrust asymmetry following engine loss may be permitted, (3) Alternate electrical and hydraulic system redundancy provisions may be acceptable, as suited to the type design (e.g., bus isolation and electrical generator remaining capability must be suitable for the engine out configuration), (4) Requirements to show acceptable approach performance may be limited to demonstration of acceptable performance during engine-out flight demonstrations (e.g., a safe approach to minima), and (5) Approach or Landing system “status” should accurately reflect the aircraft configuration and capability. b. Suitable information about flight guidance system capability must be available to the flightcrew in flight, particularly at the time of a “continuation to destination” or “diversion to alternate” decision. This is to determine that the aircraft can have an appropriate Category II approach capability when the approach is initiated (e.g., Nonnormal checklist specification of expected configuration during approach, autopilot or flight director status annunciation of expected mode capability). c. The operator should consider system performance in appropriate weather conditions (e.g., winds, turbulence or wind gradients) to make a determination as to whether any weather related restrictions or limitations are appropriate. 5.18. Special Airports with Irregular Pre-Threshold Terrain. Not withstanding the fact that most aircraft systems that have completed airworthiness demonstrations consider irregular terrain in the pre-threshold area, special ### Page 85 Par 5 Page 71 operational evaluations are nonetheless appropriate for certain airports having difficult pre-threshold terrain conditions. These special evaluations consider each particular aircraft type, the particular flight control system, and may include consideration of particular system elements such as the type of radar altimeters installed or other equipment. The need for such a special evaluation of a part 97 instrument approach procedure is identified by FAA order 8400.8, Procedures for Approval of Facilities for FAR Part 121 & Part 135 CAT III Operations. Criteria for the evaluation of irregular Pre-threshold terrain airports is contained in FAA Appendix 8 of AC 120-28D. Criteria for approval of Operators or procedures regarding operations at runways with irregular Pre-threshold terrain are addressed in paragraphs 6.2.5 and 10.7. 5.19. Airborne System Evaluation and Approval. Category I and Category II airborne systems may be IAW the applicable airworthiness criteria contained in Appendix 2 or 3 during type certification or STC approval, or they may be evaluated in conjunction with a FAA-approved program with an air carrier. To be acceptable for Category I or II landing minima, the airborne equipment should meet the criteria in Appendix 2 or 3 of this AC and be able to conduct Category I or II operations IAW the operational concepts discussed in Paragraph 4 above. However, if a determination of compliance with Appendix 2 or 3 has not been made, airborne equipment which is shown to meet the operational demonstration criteria in the applicable subparagraphs below may also be acceptable for Category I (e.g., RNP Operations) or Category II landing minima if it is demonstrated that this equipment permits safe Category I or II operations, as applicable, IAW the operational concepts discussed in Paragraph 4 above. 5.19.1. “Operator Use Suitability” Demonstrations - Applicability. The following criteria in paragraphs 5.19.2 through 5.19.3 (also see paragraph 10.5) apply to applicants desiring airborne equipment approval for those systems which do not have a statement in the approved airplane flight manual which indicates that the equipment meets the relevant performance standards of this AC, previous editions of this AC, or equivalent criteria (e.g., either for Category I such as applicable to FTE demonstrations for RNP, or for Category II). The criteria of paragraphs 5.19.2 and 5.19.3 are not intended to apply to those aircraft types or variants which already include a statement in the approved airplane flight manual indicating that the airborne flight guidance system was evaluated IAW criteria of this AC. 5.19.2. Airborne Equipment Operational Validation. The applicant should provide an acceptable test and evaluation plan which establishes satisfactory performance of the flight guidance system for either the Category I or Category II operations intended, as applicable. To be acceptable, the applicant should conduct an appropriate number of approaches and missed approaches, or other applicable operations, for representative instrument procedures to be flown. For such assessments under this provision, an applicant may be considered to be an operator, a group of Operators, or an aircraft manufacturer or avionics manufacturer in conjunction with one or more Operators. An aircraft manufacturer or avionics manufacturer seeking to demonstrate alternate levels of FTE without involvement of an operator would normally be expected to do so as part of a TC or STC process, IAW criteria of an Appendix of this AC. 5.19.2.1. Category II Assessments. For Category II, the applicant should typically be expected to perform at least 300 successful approaches to appropriate Category II DA(H) minima, in each aircraft type intended. The 300 approaches may be allocated to several variants within a type if the flight guidance systems used by each variant are the same or similar. If a related or similar aircraft type is configured with the same or a similar flight guidance system and is already approved for Category II, or for special case consideration such as consideration of an engine inoperative Category II approach, the number of approaches for a particular type or variant may be reduced by an appropriate amount depending on the degree of system similarity, flight guidance performance similarity, or aircraft similarity, as determined appropriate by the CMO, AEG, or AFS-400. Approaches may be accomplished in line operations, during training flights, or during specific demonstration flights, or in any combination. Not less than ninety percent of the total demonstrated approaches conducted should be successful. No unsafe approaches or missed approaches should occur. (See 5.19.3.3 for a definition of a successful approach). Approaches should be accomplished IAW the following criteria: a. A minimum of three facilities/runways should be used during the demonstrations, unless Category II operations will be conducted only at fewer than 3 facilities by that operator. At least 10 percent of the total number ### Page 86 Page 72 Par 5 of approaches should be conducted on each of at least three of the facilities selected. The number of approaches conducted on additional facilities may be at the applicant’s discretion. b. At least some approaches should be accomplished using facilities approved for Category II or Category III Procedures. However, at the applicant’s option, demonstration may be made using facilities used only for Category I Procedures. c. No more than 15 approaches per day should be conducted on a single facility. d. No more than 60 percent of the approaches should be conducted in any single aircraft, unless the operator has 3 or fewer aircraft to be evaluated, and performance of the other aircraft may be considered to be equivalent. e. Where an applicant has different variants of a type aircraft which utilize the same or similar flight guidance system, the applicant should ensure that each of the variants can meet the necessary performance criteria. f. If flight director performance is to be assessed, a representative number of pilots should be used to conduct the necessary approaches. No single pilot should perform more than 20 percent of the approaches, unless a small total number of pilots assigned to the aircraft type requires the use of a greater percentage. g. An acceptable sample of the approaches conducted should be observed by an FAA Aviation Safety Inspector or other suitably qualified evaluator(s) (e.g., a check airman representatives of the operator, an APD or equivalent, or representatives from the aircraft or avionics manufacturer), as determined acceptable by FAA. 5.19.2.2. Flight Technical Error (FTE) Assessments. Flight Technical Error (FTE) assessments for approach or missed approach, or other defined operations, may be made by an aircraft manufacturer, an avionics manufacturer, or an operator to establish alternate levels of expected FTE to be used for navigation system or procedure authorization. Alternate levels of FTE may then be applied to instrument procedure development or authorization, in lieu of standard assumed FTE values, when the assumptions or conditions of the alternate FTE levels can be met or satisfied. a. FTE levels may be established by analysis (e.g., of existing data), by simulation (e.g., in a suitable flight training simulator), through flight verification (e.g., data collected from flight demonstration(s) with an appropriately configured aircraft), or in any combination of these methods. Regardless of the method(s) used, sufficient assessment should take place to ensure that any resulting FTE information or values are valid for the navigation conditions or procedures to which they are to be applied. The assessment should key to types of procedures to be flown, appropriately consider normal, non-normal and rare normal operations, should address pilot capability or system variability to the extent necessary, and should have sufficient repeatability to have confidence in the FTE level(s) that result. b. Any FTE assessment related exceptions to industry criteria found in sources such as RTCA DO-236 for RNP should be clearly identified, if necessary (e.g., navigation systems for which 22nm constant radius turns are not intended to be applicable). 5.19.3. Data Collection and Analysis for an Airborne System Evaluation. 5.19.3.1. FTE Data Collection and Analysis. For an FTE assessment demonstration, sufficient data should be collected to establish the suitability of the levels of FTE sought. The data collection and consequent analysis should match and at least consider the types of procedures to be flown (e.g., representative leg types and leg geometry), aircraft configurations to be used (e.g., map display, flight director, autopilot), representative environmental conditions, pertinent normal or non-normal conditions, and representative pilot qualification and experience. Data collection may be from a dedicated FTE assessment, or from data collected during line operations, if appropriate conditions are experienced (e.g., weather) and assumptions satisfied (e.g., pilot sample variability). FTE data collection and analysis may separately address flight on stabilized portions of straight segments, and flight during curved segments or during leg to leg captures. Use of statistical methods for analysis of data is acceptable, but is not ### Page 87 Par 5 Page 73 necessarily required (e.g., for treatment of certain rare normal or non-normal conditions). The analysis methods or techniques to be used by the applicant and any demonstration program to be used should be determined to be acceptable to FAA prior to commencement of the FTE assessment program. 5.19.3.2. Data Collection for a Category II Demonstration. For a Category II system suitability demonstration, each applicant or designated representative should provide the information listed below, as necessary and as requested by the CHDO. This information should be related to performance of the airborne flight guidance system and display system regardless of whether an attempted approach demonstration is successful, unsuccessful, or discontinued. The information, along with recommendations and any clarifying information regarding unsuccessful or discontinued approaches should be provided to the FAA CHDO: a. Specify the total number of approaches attempted, the number of successful approaches, and the number of and reasons for unsuccessful or discontinued approaches, if known. b. If an approach is discontinued, specify the height above the runway at which the approach was discontinued. c. Specify the acceptability of lateral position, vertical position, track, vertical path/vertical speed, speed error, and pitch trim acceptability at 200 ft. HAT, 100 ft. HAT or at DA(H), and note if the approach was in any way inconsistent with continuing an approach to a normal landing within the touchdown zone. d. Specify the NAVAIDs and runway facilities used and the reported weather and wind conditions in which the assessment was conducted. e. Evaluate the tracking performance stability, and suitability of the flight director or autopilot, as applicable, for the intended operation. f. If not otherwise based on data recording, the evaluator(s) should note and record the lateral and vertical position of the airplane relative to the localizer and glide slope at least at the 200 ft. HAT, 100 ft. HAT or at DA(H), and the estimated runway touchdown point achieved consistent with following the flight guidance system, as applicable to the system used. g. If unable to initiate an approach due to a deficiency in the airborne equipment, note the reason for the deficiency and any recommendation for addressing the deficiency. h. Provide any other relevant associated recommendations or circumstances. NOTE: Unsuccessful approaches attributed solely to Air Traffic Service (ATS) circumstances may be excluded from the data (e.g., flights vectored too close to a final fix or at large angles preventing adequate localizer and glide slope capture; termination of an approach at the request of an Air Traffic Facility or due to an amended air traffic clearance; evidence of inappropriate ILS critical area protection). Also, unsuccessful approaches may be excluded from consideration due to faulty NAVAID or non-aircraft sensor signals. Airborne system failures attributed to maintenance failures or maintenance factors should be documented for subsequent joint resolution by FAA and the operator. 5.19.3.3. Definition of a Successful Approach for a Category II Demonstration. For the purpose for the airborne system suitability demonstration for Category II, a successful approach is one in which, at least at the 100 ft. HAT point or DA(H), through touchdown, meets the following criteria: a. The airplane is continuously in a position to complete a normal landing using normal maneuvering. Typically this is considered to require that below 200 ft. HAT the flight deck is positioned within and is tracking to remain within, the lateral confines of the extended runway. ### Page 88 Page 74 Par 5 b. The deviation from glide slope does not exceed + 75 microamps (1/2 scale) as displayed on the ILS, MLS, GLS, or equivalent system/indicator at least down to the DA(H). Below the DA(H) a normal approach path is followed and a normal flare occurs, with a landing safely within the touchdown zone at normal sink rates and attitudes. c. The indicated airspeed, track, vertical speed, alignment, and heading are satisfactory. Indicated air speed does not exceed + 5 knots of planned approach airspeed but may not be less than computed threshold or reference speed. d. No unusual maneuvers or excessive attitude changes or attitude rates occur. e. The airplane is generally in trim so as to preclude any excessive control forces. 5.20. Ground Proximity Warning System (GPWS) or Terrain Awareness Warning System (TAWS) Interface. Airborne equipment used for approach should have appropriate interfaces with or compatibility with GPWS and TAWS. This is to ensure nuisance free operation at routine airports. Special procedures may be used for non-normal procedures or at airports with unusually difficult underlying terrain, or other such factors. 5.21. Flight Data Recorder (FDR) Interface. Airborne equipment used for approach should have appropriate interfaces with or compatibility with flight data recorders, and if applicable cockpit voice recorders (e.g., alerting audio audibility on CVR). 5.22. Takeoff, or Dispatch, with Inoperative Navigation Receivers, Instruments, or Displays for Category I or II. Notwithstanding the airborne equipment installation provisions of paragraphs 5.2 and 5.3 above, and IAW any other FAA applicable MMEL and MEL provisions (e.g., as specified by the FAA FOEB or FSB for the type), a pilot may depart or an operator may dispatch an aircraft for Category I or Category II using the following guidelines (e.g., the operator may address MEL provisions stating “As required by the CFR,” or equivalent provisions, as shown below): 5.22.1. Inoperative System Departure or Dispatch for Category I. For departure, or dispatch for Category I, if applicable, two navigation receivers are typically required, with each suitable for the route of flight and expected approaches to be conducted (e.g., dual ILS, if flying a route based on expected use of ILS for landing). a. If the flight is based on use of a planned approach procedure that specifically requires dual navigation capability (e.g., /E required, or dual NDB required, or dual VOR required) then two pertinent systems are required for takeoff or dispatch. b. If an approach procedure planned for use is not precluded from being conducted using one navigation source (e.g., one NDB, one FMS, one ILS), a minimum of one navigation receiver, or equivalent, of each type required for the intended flight is required. That navigation receiver’s indication, or equivalent, should be able to be displayed at or be visible to each required pilot station, for each type of facility(s) intended for landing. Use of this provision requires considering subsequent failure of the one system intended for use (e.g., the ILS) and the need to be able to safely use any alternate remaining navigation system(s) (e.g., VOR or RNAV) while enroute, during approach, or during missed approach. In any instance, after the first failure in flight, there must still be another suitable navigation capability available to the aircraft to safely land. The other navigation capability required above may be based on use of a different NAVAID type, use of acceptable RNAV capability, or use of an alternate airport with the same or a different type of instrument procedure. c. Instruments, or displays, or display elements may be inoperative if, considering the remaining instruments or displays, each pilot can accomplish that pilot’s respective assigned crew duties for flying and monitoring the flight (e.g., failure of an ILS raw data display on the F/O’s ADI or PFD may be permissible if that information or equivalent is available by other acceptable means - such as by using the F/O’s HSI LOC or ND LOC indication in lieu of the ADI LOC indication). When considering inoperative component(s), subsequent failure of any single additional instrument, or display, or display component must not put the aircraft or crew in an unsafe situation for ### Page 89 Par 5 Page 75 which the pilots cannot safely compensate (e.g., it is determined to be acceptable in the above example that after a subsequent failure the F/O will be able to acceptably monitor the Captain’s corresponding instruments, or standby instruments). 5.22.2. Inoperative System Departure or Dispatch For Category II. For departure, or dispatch, for Category II, a minimum of two LOC or GLS navigation receivers of each type to be used are normally required for Category II. The receiver’s indications to be used should be able to be independently displayed at or be visible to each respective pilot station, for each type of facility(s) intended for landing (e.g., ILS, MLS, or GLS). For ILS glide slope, only one receiver need be operative for departure or dispatch, if that receiver is a self monitored receiver with reliable failure indication, if the receiver information can be displayed at each pilots station, and if any other systems required for the Category II minima do not depend on having dual glideslope capability available (e.g., autoland, alerting and warning or monitoring systems). a. Use of the “departure or dispatch with a single glideslope receiver” provision requires considering subsequent failure of the one GS system intended for use while enroute or on approach, and the need to be able to safely use alternate remaining navigation system(s) to safely land, after failure of the glideslope receiver in flight. b. Instruments and displays provisions are the same as for Category I, except that at least one operative radar altimeter must be provided, and that one radar altimeter must at least be able to be displayed at each pilot station, or be easily visible to each pilot station. NOTE: For Category II minima, if minima are intended to be based on use of an Inner Marker in lieu of a radar altimeter(s), and if the operator is not otherwise precluded from using the Inner Marker as a means to establish Category II minima, the radar altimeter need not be operative for takeoff or dispatch for purposes of establishing landing minima (e.g., for DA(H)). This provision does not address other MMEL/MEL provisions that may otherwise independently apply to radar altimeter availability, however, such as for appropriate GPWS function. c. In addition to instruments and displays for Category II, there must be acceptable ice and rain removal protection available for the expected conditions during approach (e.g., windshield anti-ice for icing conditions, windshield wipers or equivalent for rain). 5.22.3. Inoperative System Departure or Dispatch for Either Category I or Category II. a. For departure or dispatch for either Category I or II, for EFIS aircraft that have capability to switch entire display formats to different flight deck display locations, these systems typically may be dispatched with an inoperative display or with displays in alternate locations. For an alternate location, each pilot must be able to acceptably perform respective PF or PNF duties for approach and missed approach. Following failure of an additional display or display in an alternate position, the aircraft must still be able to be safely flown and landed using available instrument approach NAVAID capability and remaining displays. b. Operators should ensure that planned operations consider any pertinent AFM or FCOM provisions for flight guidance system use that may relate to inoperative components (e.g., altimeter source, navigation source, or instrument source switching, and available flight director or autopilot modes, as applicable). 5.23. Continuation of Flight after Navigation System Failure Enroute, or During Approach for Category I or II. Notwithstanding the airborne equipment installation provisions of paragraphs 5.2 and 5.3 above, MMEL and MEL provisions of paragraphs 5.22 above, and any other FAA applicable FSB provisions for the type aircraft, a pilot may continue enroute or initiate an approach to Category I or Category II minima using the following guidelines of 5.23.1 through 5.23.3. 5.23.1. Continuation of a Flight After Failures For Category I. ### Page 90 Page 76 Par 5 a. The operator should establish a policy addressing typical failure conditions for which initiation or continuation of an approach in low visibility conditions is considered acceptable (e.g., failure of a single flight director, FCC, or instrument, for which switching to an alternate or common source still provides adequate information). Operators should also describe typical conditions for which the operator would expect that a pilot would divert to a different airport with better weather conditions, if possible (e.g., for complex engine or hydraulic failures where flight guidance or go-around performance may be significantly degraded). b. Unless dual capability is specifically required for a particular procedure (e.g., /E required, dual NDB required), for initiation or continuation of approach, a minimum of at least one navigation receiver or sensor of each type required for the intended approach procedure is required. If an approach is initiated with only one receiver or sensor, the pilot should, to the extent possible, consider the potential consequence of subsequent failure of that system or sensor. 5.23.2. Continuation of a Flight after Failures For Category II. For continuation enroute or initiation of an approach, a minimum of one LOC or GLS navigation receiver of each type to be used is normally required for initiation or continuation of Category II approach. The receiver’s displacement indications, if applicable, should, however, be able to be independently displayed at or be visible to each respective pilot station, for each type of facility(s) intended for landing (e.g., ILS, MLS, or GLS). For ILS glide slope, only one receiver need be operative for approach if the receiver information can be displayed at each pilot’s station, and if any other systems required for the Category II minima do not depend on having dual glideslope capability available (e.g., autoland, alerting and warning or monitoring systems). a. Instruments and displays provisions are the same as for Category I, except that at least one operative radar altimeter must be provided, and that one radar altimeter must at least be able to be displayed at each pilot station, or be easily visible to each pilot station. NOTE: For Category II minima, if minima are intended to be based on use of an Inner Marker in lieu of a radar altimeter(s), and if the aircraft and crew are not otherwise precluded from using the Inner Marker as a means to establish Category II minima, the radar altimeter need not be operative for approach, for purposes of establishing landing minima (e.g., for DA(H)). b. In addition to suitable instruments and displays, there must be acceptable ice and rain removal protection available for the expected conditions during approach (e.g., windshield anti-ice for icing conditions, windshield wipers or equivalent for rain). 5.23.3. Continuation of a Flight after Failures for either Category I or Category II. If a flight is to be continued to destination and the originally planned instrument approach procedure(s) (IAP) used after a failure enroute, or if an approach is to be continued, the pilot should consider the consequence to and alternatives available for the flight if remaining navigation receiver or sensor capability should subsequently fail. a. For EFIS aircraft that have capability to switch entire display formats to different flight deck display locations following a failure, these systems typically may be switched to an operative display, or display in an alternate location. For a failed display or an alternate location, each pilot must be able to acceptably perform respective PF or PNF duties for approach and missed approach. Following failure of an additional display or display in an alternate position, the aircraft must still be able to be safely flown and landed using available instrument approach NAVAID capability and remaining displays. b. Pilots should ensure that planned operations consider any pertinent AFM or FCOM provisions for flight guidance system use that may relate to inoperative components (e.g., altimeter source, navigation source, or instrument source switching, and available flight director or autopilot modes, as applicable). c. A pilot exercising emergency authority may deviate from the above or any other provisions of this AC to the extent necessary to ensure safe flight and landing. ### Page 91 Par 6 Page 77 **6. PROCEDURES.** 6.1. Operational Procedures. Appropriate operational procedures based on the approved operator program should be addressed. Operational procedures should consider the pilot qualification and training program, airplane flight manual (AFM), crew coordination, monitoring, appropriate takeoff and landing minima including specification of either a DA(H) or MDA(H), as applicable, for landing, crew call-outs, and assurance of appropriate aircraft configurations. Suitable operational procedures must be implemented by the operator and be used by flightcrews prior to conducting low visibility Category I or II landing operations. 6.1.1. AFM Provisions. The operator’s procedures for low visibility takeoff or Category I or II landing should be consistent with AFM provisions specified during airworthiness demonstrations. Adjustments of AFM procedures consistent with operator requirements are permitted when approved by the POI. Operators should ensure that no adjustments to procedures are made which invalidate the applicability of the original airworthiness demonstration. 6.1.2. Crew Coordination. Appropriate procedures for crew coordination should be established so that each flight crewmember can carry out their assigned responsibilities. Briefings prior to the applicable takeoff or approach should be specified to ensure appropriate and necessary crew communications. Responsibilities and assignment of tasks should be clearly understood by crewmembers. Tasks should be accomplished consistent with the operator’s specified provisions for the aircraft type or variant and each crewmember position unless otherwise approved by the POI (duties of each pilot, monitored approach, etc.). 6.1.3. Monitoring. Operators should establish appropriate monitoring procedures for each type of low visibility approach, landing, and missed approach. Procedures should ensure that adequate crew attention can be devoted to control of aircraft flight path, displacements from intended path, mode annunciations, failure annunciations and warnings, and adherence to minima requirements associated with DA(H) or MDA(H). a. In the event that a “monitored approach” is used, (e.g., where the first officer is responsible for control of the aircraft flight path by monitoring of the automatic flight system) appropriate procedures should be established for transfer of control to the pilot who will be making the decision for continuation of the landing at or prior to DA(H) or MDA(H). b. Monitoring procedures should not require a transfer of responsibility or transfer of control at a time that could interfere with safe landing of the aircraft. Procedures for calling out failure conditions should be preestablished, and responsibility for alerting other flight crewmembers to a failure condition should be clearly identified. 6.1.4. Use of the DA(H) and MDA(H). Decision Altitude (Height) is used for Category I and II operations. Decision Altitude (Height) is used when vertical path guidance is available (e.g., ILS, GLS, MLS, VNAV). Decision Altitude (DA) is used for barometrically determined altitude minima (MSL), typically associated with Category I procedures where vertical guidance is available. If specifically authorized by FAA (rare uses) a DA may in some circumstances be used for Category II. a. Decision Height (DH) is used for Category II operations, except where use of an Inner Marker is authorized in lieu of a DH, or where a DA is authorized (rare use). b. When DAs or DHs are specified, procedures for setting various reference bugs in the cockpit should be clearly identified, responsibilities for DA or DH call-outs should be clearly defined, and visual reference requirements necessary at DA or DH should be clearly specified, so that flightcrews are aware of the necessary visual references that must be established by and maintained after passing DA or DH. c. MDA(H) is typically used for procedures that do not have vertical path guidance (e.g., VOR, NDB, 2D- RNAV, Circling). U.S. Operators are authorized to use MDA. MDH may be used internationally by non-US Operators, and U.S. Operators may need to be aware of its existence and use when operating to international locations even though U.S. Operators are not typically authorized to use MDH. Any request for use of MDH must ### Page 92 Page 78 Par 6 be coordinated with AFS-400. Also the “height element (H)”, used with MDA(H), provides an advisory value for RA relative to the airport or TDZ elevation, and may be used for situation awareness, even if not used to actually define minima. Caution should be noted however, since irregular terrain in the vicinity of the airport may result in observed RA values that are significantly different than expected height (H) derived from the published procedure when not over or near the airport surface. d. Procedures should be specified for call-out of the DA, DH, or MDA(H). e. Procedures should be specified for conversion of the DA or DH to an MDA(H) in the event that the aircraft reverts from or loses vertical path guidance. However, any adjustments to approach minima or procedures made on final approach should be completed at a safe altitude (e.g., above 1000 ft. HAT). f. Any use of QFE procedures for DA or DH for Operators that are not already so authorized (applicable to either Category I or II, whether inside the United States or outside the United States) must be specifically approved by the CHDO, after coordination with AFS-400. g. For Category II, the operator should ensure that at each runway intended for Category II operations, the radar altimeter systems used to define DH provides consistent, reliable, and appropriate readings for determination of DH. In the event of irregular terrain underlying the approach path an alternate method should be used. DH may be based on other means (e.g., inner marker) when specifically approved by FAA. 6.1.5. Callouts. Altitude/Height callouts should be developed, implemented, and used for Category I and Category II operations. When more than one Category of operation is used (e.g., Category I or II) callouts should be compatible, consistent, and preferably common to as many Categories of Operation as practicable. a. Callouts may be accomplished by the flightcrew or may be automatic (e.g., using synthetic voice call-outs or a tone system). Typical call-outs acceptable for Category I or Category II include the following: • “1000 ft.” above the touchdown zone, • “500 ft.” above the touchdown zone, • “approaching minimums,” • “at minimums,” as applicable, • any pertinent visual reference(s) observed, and resulting crew action, as applicable (e.g., “runway in sight,... landing”), • key altitudes during flare, (e.g., 50, 30, 10) or AFGS mode transitions (e.g., flare, rollout), and • as appropriate, auto spoiler, reverse thrust deployment and autobrake disconnect. b. Combinations of these calls may also be used as appropriate. In any event, the calls made by the flightcrew should not conflict with the automatic systems or auto call-outs of the aircraft, and conversely the configuration selected for the aircraft should not conflict with expected call-outs to be made by the flightcrew. Compatibility between the automatic call-outs and the crew call-outs must be ensured. The number of call-outs made automatically, manually or in combination should not be so frequent as to interfere with necessary crew communication for abnormal events. c. Also, call-outs should be specified to address any non-normal configurations, mode switches, failed modes, or other failures that could affect safe flight, continuation of the landing, or the accomplishment of a safe missed approach. Any use of crew initiated call-outs at altitudes below 100 ft. during flare should ensure that the call-outs do not require undue concentration of the non-flying pilot on reading of the radar altimeter rather than monitoring the overall configuration of the aircraft, mode switching, and annunciations. Automatic altitude call-outs or tones are recommended for altitude awareness, at least at and after passing DA(H) or MDA(H). ### Page 93 Par 6 Page 79 6.1.6. Configurations. a. Operational procedures should accommodate any authorized aircraft configurations that might be required for Category I or Category II approaches or missed approaches. Examples of operational procedures that an operator may need to accommodate include: (1) Alternate flap settings, (2) Use of alternate AFGS modes or configurations (e.g., with or without autopilot(s) or flight director(s), autoland, HUD), (3) Inoperative equipment provisions related to engine(s) inoperative, or the minimum equipment list, such as a non-availability of certain, inoperative instruments (e.g., PFD, radar altimeter), air data computers, hydraulic systems or instrument switching system components, (4) Availability and use of various electrical system components (e.g., generator(s) inoperative), alternate electrical power sources (e.g., APU) if required as a standby source, and (5) If applicable, describing the relationship of approach minima to any decision or commit points for critical aircraft configurations that are identified by the operator (e.g., two engines inoperative procedures for three or four engine aircraft, or abnormal flight control configuration procedures) b. Procedures required to accommodate various aircraft configurations should be readily available to the flightcrew to preclude the inadvertent use of an incorrect procedure or configuration. Acceptable configurations for that operator and aircraft type should be clearly identified so that the crews can easily determine whether the aircraft is or is not in a configuration to initiate a low visibility approach using a pertinent Category I or Category II procedure. c. Configuration provisions must be consistent with, but are not limited to, those provided in the OpSpecs for that operator. 6.1.7. Compatibility between Category I, Category II, and Category III Procedures. a. The operator should ensure that to the extent possible, flightcrew and operational procedures for Category I and Category II are consistent with the procedures for that operator for Category III, particularly to minimize confusion about which procedure should be used in variable weather. b. The operator should to the extent practical, minimize the number of procedures that the crew needs to be familiar with for low visibility operations so that, regardless of the landing category necessary for an approach, the correct procedures can be used consistently and reliably. 6.1.8. Procedure Considerations During Non-Normal Operations. When procedures or configurations have been specified for non-normal situations, flightcrews are expected to apply those procedures and use good judgment in making the determination of any appropriate adjustments to safely use an instrument approach procedure. This may include identifying any necessary adjustments to DA(H), MDA(H), approach path, missed approach path, or required visibility believed to be necessary (e.g., assessing the climb gradient that can be achieved, identifying a safe engine out lateral and vertical flight path, requesting an appropriate length of final approach). Guidelines for nonnormal configurations, situations, or procedures may be provided by the aircraft flight manual or by the operator. Crews are expected to be familiar with these guidelines and apply them to the extent practical. a. Specific guidelines for initiation for a Category II approach with an inoperative engine are provided in paragraph 5.17. ### Page 94 Page 80 Par 6 b. When procedures or configurations have not been specified for a non-normal situation or configuration, flightcrews are expected to use good judgment and select the safest course of action in making the determination of appropriate configurations or margins for an approach. The decisions to initiate, continue, or to discontinue an approach, divert to an alternate, and any adjustments to minima should be made considering relevant factors such as: • Seriousness of the emergency • Failure status of the aircraft • Potential for unknown damage or further failures • Navigation system status • Runway, visual aid, and NAVAID status • Procedure flight path and minima to be used • Proximity to high terrain, obstacles, or adjacent approaching aircraft • Potential altitude loss, flight path required, or cleanup altitude needed to change configuration and accelerate for a missed approach • Obstacle clearance during transition to a missed approach (including the possible need to reject the landing from below DA(H) or MDA(H) • Fuel on board • Distance and suitability of alternate airports • Likelihood of changing weather, NAVAID, or runway conditions, c. It is not the intent of this AC to comprehensively define guidelines for each circumstance that might be possible (e.g., serious in-flight fire, minimum fuel). It should be noted, however, that flightcrews have both the authority and responsibility to consider relevant factors, such as those identified above, when deciding the safest course of action. If doubt exists on a course of action (e.g., initiating or continuing an approach with conditions potentially below minima), it is the flightcrews responsibility to exercise any necessary emergency authority to ensure safe flight. 6.2. Category I or Category II Instrument Approach Procedures. 6.2.1. Acceptable Procedures for Category I. Procedures acceptable for a Category I authorization for a U.S. Operator in the Unites States, or internationally, under provisions of part 121, 125, or 135, or for a Foreign Operator under provisions of part 129 at U.S. Airports, are those listed in paragraphs 4.3.1.4, 4.3.2, and 4.3.3, and any others found acceptable to FAA and listed in Standard OpSpecs, Part C. 6.2.2. Acceptable Procedures for Category II. Procedures acceptable for a Category II authorization for a U.S. Operator in the United States, or internationally, under provisions of part 121,125, or 135, or for a Foreign Operator under provisions of part 129 at U.S. Airports, are those listed in Paragraphs 4.3.1.4 and 4.3.2 above, and any others found acceptable to FAA and listed in Standard OpSpecs, Part C. 6.2.3. Standard Obstacle Clearance for Approach and Missed Approach. Standard approach and missed approach criteria for obstacle clearance for normal operations are as specified in FAA Order 8260.3, United States ### Page 95 Par 6 Page 81 Standard for Terminal Instrument Procedures, or as referenced in FAA Air Traffic criteria for terminal procedures (FAA Order 7100.11, Flight Management System Procedures Program), or for non-U.S. airports, ICAO PANS-OPS. a. Standard VNAV criteria may be applied as specified in FAA Order 8260.40, Flight Management System (FMS) Instrument Procedures Development. b. Standard RNP criteria may be applied as specified in Appendix 5 of this AC or pertinent paragraphs of AC 120-28D. c. For non-normal operations (e.g., engine inoperative), criteria equivalent to that specified in 14 CFR for takeoff (e.g., section 121.189) may be applied for those portions of an approach or missed approach not otherwise addressed by procedure design for normal operations (e.g., engine out missed approach gradients, or engine inoperative flap retraction and acceleration segments, or a rejected landing climb back to procedurally protected airspace after loss of visual reference at an airport with significant nearby obstacles or mountainous terrain) d. Regardless of criteria used, the operator should ensure appropriate consistency between obstacle clearance criteria used for takeoff, en route operations, terminal procedures, instrument approach procedures, engine inoperative procedures, and drift down procedures, as applicable. 6.2.4. Special Obstacle Criteria. Obstacle criteria for RNP is as identified in Appendix 5. a. Obstacle clearance criteria for Category II procedures is identified in Appendix 6. b. Obstacle clearance criteria to facilitate implementation of VNAV paths for approaches other than xLS are contained in FAA Order 8400.10 c. Other obstacle clearance criteria may be requested for use by an applicant and authorized by FAA, for specific applications (e.g., international operations, operations at military facilities, disaster relief). When other criteria are used, related compensating factors are typically considered, to ensure equivalent safe terrain or obstacle clearance. 6.2.5. Irregular Pre-threshold Terrain Airports. Irregular pre-threshold terrain airports identified by a 14 CFR part 97 procedure, or by FAA Order 8400.8, must be evaluated IAW FAA approved procedures prior to incorporation in OpSpecs for use by air carriers operating to Category II minima. (See the FAA worldwide web site for Category II/II Status L, for Restricted (irregular pre-threshold terrain) airports: http://www.faa.gov/avr/afs/afs410/afs410.htm). Acceptable procedures for evaluation of use of these airports may be found in AC 120-28D, Appendix 8. For aircraft not using autoland, this evaluation consists primarily of ensuring availability of an appropriate method for identification of DA(H) (e.g., assessing acceptable radar altimeter indications approaching and at DA(H), or substituting use of “Inner Marker” in lieu of Radio Altimeter). Assessing acceptable radar altimeter indications is done by ensuring sufficient Radio Altimeter display readout stability and continuity to be able to be easily read the Radar Altimeter when approaching DA(H) and at DA(H), while over-flying the irregular underlying terrain. This assessment may typically be done during operations using minima no lower than Category I, or may be based on operations at that runway by that operator with an equivalent radio altimeter installation (e.g., previously in a B757, for new B767 operations), or may be based on other U.S. Operators who have completed an assessment using the same aircraft type and radio altimeter system combination, or equivalent. 6.2.6. Airport Surface Depiction for Category I or II Operations. a. Unless otherwise authorized for a particular airport or series of airports, a suitable airport surface depiction should be available to flightcrews for each regular, provisional, or alternate airport or any airport the operator could reasonably expect operations (e.g., section 121.161 ETOPS diversion airports, designated emergency airports), to ### Page 96 Page 82 Par 6 ensure appropriate identification of visual landmarks or lighting to safely accomplish taxing from the gate to the runway and from the runway to the gate. Airport depiction should be on an appropriate scale with suitable detailed information on gate locations, parking locations, holding locations, critical areas, obstacle free zones, taxi way identifications, runway identifications, and any applicable taxiway markings for designated holding spots or holding areas. Standard depictions provided by commercial charting services may be acceptable if they provide sufficient detail to identify suitable routes of taxi to and from the runway and gate positions for departure or arrival. b. Electronic presentations of airport diagrams are considered an acceptable substitute for paper (hard copy) depictions if acceptable operational provision is made for failure of the electronic device providing the airport depiction, if each necessary flight crewmember can have access to the depiction when needed, and if equivalent scaling, orientation, chart detail, and information content is provided. 6.2.7. Continuing Category I or Category II Approaches in Deteriorating Weather Conditions. The following procedures are considered acceptable in the event that weather conditions are reported to drop below the applicable Category I or II minima after an aircraft has passed the final approach point or final approach fix, as applicable (reference section 121.651). a. Operations based on a DA(H) may continue to the DA(H) and then land, if the specified visual reference is subsequently established by the pilot no later than the DA(H). b. Operations based on an MDA(H) may continue to the MDA(H), and then to the point of intercept of the VNAV path to the runway, to the VDP, or equivalent, or to the MAP, as applicable, then land, if the specified visual reference is established by the pilot no later than point at which descent below the MDA(H) commences. NOTE: For wind constraint applicability on final approach see paragraph 6.2.11. 6.2.8. “Approach Ban” Applicability. Sections 121.651, 125.381, and 135.225 generally require that weather conditions be at or above takeoff minima prior to takeoff, and above landing minima prior to initiating the final segment of an instrument approach. However the applicability of these rules can be different for certain Domestic and International Operations (e.g., pilots authority to initiate “Look-See” Approaches at non-U.S. airports when weather is reported below minima). This paragraph explains and clarifies applicability of weather reporting for takeoff minima, and applicability of the “approach ban” provision related to sections 121.651, 125.381, or 135.225 at U.S. and non-U.S. airports. a. Accordingly, an instrument approach should not be continued beyond the applicable outer marker, final approach fix, or equivalent position in the final approach segment unless the reported visibility or controlling RVR is above the specified minimum. If no outer marker, final approach fix, or equivalent fix is available, or if such a fix is not used as the point of application of an approach ban when weather is reported below minima, the aircraft should in no case descend below an altitude of 1,000 ft. above the TDZE for the runway of intended landing, unless weather is reported to be at or above minima. Equivalent positions to the outer marker are considered to be, but are not limited to: DME, VOR, non-directional beacon, or other such fixes authorized in the standard instrument approach procedure (SIAP), which are located at a position similar to an outer marker, outer compass locator, or final approach fix. A corresponding surveillance radar fix may also be used as a point of application of an approach ban, in lieu of an outer marker, final approach fix, or such equivalent fix. b. If, after passing the applicable approach ban fix or point (e.g., outer marker, equivalent fix, or an altitude 1,000 ft. above the TDZ Elevation), and the reported visibility or controlling RVR falls below the specified minimum, the approach may be continued to DA(H) or MDA(H). If suitable visual reference can be established prior to descending below DA(H) or MDA(H), a landing may be completed. c. Controlling RVR means the reported values of one or more RVR reporting locations (touchdown, midpoint, rollout, or equivalent international locations) used to determine whether operating minima are or are not met. Where RVR is used, the controlling RVR is the touchdown RVR, unless otherwise specified by FAA (e.g., through operations specifications). ### Page 97 Par 6 Page 83 d. Differences in application of the approach ban between U.S. airports and non-U.S. airports stems from the recognition that there may be differences in non-U.S. and U.S. methods to determine and report weather conditions. On a worldwide basis, differences exist in types and characteristics of meteorological devices used, measurement techniques and policies, or processes for categorizing, reporting, or disseminating weather (e.g., different methods of determining and reporting RVR or meteorological visibility). e. An approach ban is applicable at U.S. airports. It may also apply at airports in countries outside the United States where that state or airport authority specifically precludes “look-see” authorization when weather is below minima. Operators should be familiar with such policies of states outside the United States, or for non-US airports, and appropriately apply those states or airports policies. f. 14 CFR and FAA policies require that for airports within the United States and its territories (e.g., Puerto Rico) or at U.S. military airports (e.g., airports at which U.S. military forces manage the facility or have a designated U.S. base or facility) it is necessary to have reported weather at a value at or above landing minima prior to initiating an approach (section 121.651). g. The latest weather report from the most reliable source is considered to be the applicable controlling weather report as follows: (1) Report from a co-located Air traffic Facility (e.g., Tower Local Control, Approach control), or (2) ATIS Report, or (3) Airline or FSS report from NWS or an approved source 6.2.9. Approach Operations at Non-U.S. Airports, when Weather is Reported “Below Minima.” This paragraph describes the regulatory basis for executing an instrument approach procedure (IAP) at a non-U.S. airport when it is previously known that the weather at that airport may be, or is below the charted weather minima or approach ban weather criteria for that IAP. a. When an aircraft approaches an airport, a decision typically must be made whether or not to initiate the approach and whether it is permissible to proceed beyond the FAF or FAP on an IAP, based on specified “approach minima.” b. These criteria are not necessarily the same as the charted criteria at the bottom of the approach plate, since in ICAO compliant publications, some States set approach minimums for an IAP by specifying an “approach ban” at weather minima different than that specified on the approach plate or OpSpecs for continuing below or beyond DA(H) or MDA(H). c. The approach initiation minimums for an IAP may or may not be the same as the landing minimums shown on the IAP. d. The following criteria are considered to apply as noted below (reference 14 CFR sections 91.703, 121.11, 135.3, 135.225, 125.23, 125.381). (1) Operations Specifications: Always apply, domestic and international. (2) State of the Aerodrome criteria if promulgated as rules or regulations: Typically always apply in the national airspace of that state, as an agreed sovereign right. (3) 14 CFR parts 121, 125, or 135 always apply to domestic operations, and always apply internationally unless the State of the Aerodrome specifically prohibit use of a particular part or provision of 14 CFR, or promulgates a rule contradicting a regulation, and the FAA agrees to apply the overriding provision of the State of the Aerodrome rather than the regulation. Typically State of the Aerodrome provisions may be more restrictive than the regulation, but may not provide relief from a U.S. regulation that applies to international operation. ### Page 98 Page 84 Par 6 (a) Section 121.651, 125.381 and 135.225 address approach minimums. A weather report for that airport is required prior to commencing an IAP. This is required worldwide. (b) Reported visibility is required to be at least as good as the “visibility minimums prescribed for that approach” prior to commencing an IAP. This visibility requirement applies to airports in the United States, its territories, and U.S. military airports (whether in the United States or outside the United States), and to any airport in a foreign country where the country’s operating rules require that the prescribed visibility be available prior to commencing the approach. (c) Parts 121, 135, and 125 allow the crew to continue an IAP to DA(H) or MDA(H) if a below minimums weather report is received while already on the final segment of the approach. (d) Part 121 allows an ILS Category I Procedure to be conducted with below minimums weather if both the ILS and a PAR are used simultaneously by the pilot. This does not apply to an operator not authorized for use of PAR, since that operator may not train for PAR approaches. (e) Accordingly, there is no requirement for an above minimums weather report to commence an IAP in a foreign State (e.g., using a weather source other than the NWS or a source approved by the NWS) unless FAA has specifically precluded use of the look-see provision for a particular State or States. (Note: The State of the Aerodrome or Airport may additionally preclude such below minima operations, and U.S. Operators are expected to abide by such provisions, unless otherwise approved by FAA (e.g., through an emergency authorization in time of conflict or natural disaster). (4) ICAO Standards apply over the high seas (international airspace), and in the airspace of a State which adheres to the ICAO Convention, subject to modification by that State, or ICAO filed “Difference.” ICAO Standards and Recommended Practices (e.g., ICAO Annex 2, Annex 6, and PANS-OPS) do not address “approach minimums,” or any particular weather criteria applying to the decision whether to initiate or continue an IAP. (Also see “ICAO Manual of All Weather Operations” DOC 9365 AN/910.) (5) Part 91 always applies to domestic operations unless superseded by part 121, 125, or 135 provisions. Internationally certain provisions of part 91 apply when not otherwise superseded by part 121, ICAO, or State of the Aerodrome rules. Section 91.175 does not specifically address minimums related to initiation of an approach, or any weather criteria for initiating an IAP. All references are to landing minimums and the required visual references to continue below DA(H) or MDA(H). For operators conducting operations under part 91 (e.g., training, ferry, aircraft functional flight test), the approach ban provisions of part 121, 125, or 135 may thus not necessarily apply if the particular operation is considered to be conducted under part 91 by the CMO. Also, for flight test and POC demonstration purposes, waivers to provisions of section 91.175 may be requested from FAA (e.g., such as to authorize limited use of reduced weather minima for test or evaluation purposes). 6.2.10. IFR Approaches or Low Visibility Takeoffs in Class G Airspace. An operator may be authorized to conduct IFR approaches to Category I or Category II minima, or low visibility takeoffs, in Class G airspace, if the requirements of the applicable OpSpecs are met. a. Nonscheduled Operations. For nonscheduled operations, the CHDO must ensure that the operator's Category I or II operations program provides the policy, and direction and guidance necessary to safely conduct these operations. The CHDO must also ensure that the certificate holder's manuals cover the specific procedures which must be used, and the facilities and services which must be available and operational for the safe conduct of instrument approach operations in Class G airspace (e.g., weather reporting, advisory frequencies, and NAVAID critical area protection, as applicable). b. Scheduled Operations. In addition to meeting the requirements for nonscheduled operations, the CHDO must ensure that the facilities and services necessary for the safe conduct of instrument approach procedures in Class G airspace are available during the times of scheduled operations, and are specified in the OpSpecs. ### Page 99 Par 6 Page 85 c. Method of Approval. The authorizations to conduct instrument approach procedures in Class G airspace are addressed by issuing Special Non-14 CFR part 97 OpSpecs. 6.2.11. Wind Constraint Applicability. When wind constraints apply to Category I or Category II procedures (e.g., an OpSpec 15 knot crosswind component limit) the limit is considered to apply to the point of touchdown. If a report of a crosswind component value greater than the limit is received while on approach, an aircraft may continue an approach, but a subsequent wind report indicating winds are within limits or a pilot determination that actual winds are within limits must be made prior to touchdown. a. The flightcrew should use the most recent, reliable and appropriate information. Acceptable methods for a wind determination may include ATS reports, reports of other aircraft with reliable means of wind determination (e.g., IRS), pilot use of on-board IRS or FMS wind readout capability, data link of recent winds, or pilot confirmation of an acceptable visual indication of winds on the surface by a wind sock, wind indicator or equivalent wind indicating device. b. When an Airplane Flight Manual or other manufacturer’s reference (e.g., FCOM) references “Maximum wind component speeds when landing weather minima are predicated on autoland operations,” or an equivalent statement, an operator or flightcrew may consider those wind values to apply to “steady state” wind components. c. It is considered acceptable for the flightcrew to land when gust values are reported to exceed the steady state wind limit if the flightcrew considers the gust exceedance to be: • insignificant in magnitude • variable in direction • occasional, or • the wind report is not applicable (e.g., obviously outdated, measured at a location considered too far from the runway or touchdown zone, or gusts considered not pertinent during the period of touchdown or rollout.) 6.2.12. Crosswind Component Determination at Airports with Significant Magnetic Variation (Polar Regions). Operators, flightcrews, and dispatchers (if applicable) of air carriers operating in polar regions or having ETOPS or EROPS alternates in these polar regions should be familiar with appropriate methods to determine wind components and particularly tailwind and crosswind components at airports with significant magnetic variation, or with runways oriented to true north. Due to METAR, TAF, and ATS Tower reported winds and runways potentially having different magnetic or true north reference, caution must be exercised where significant magnetic variation values exist, to correctly determine applicable crosswind and tailwind component limits. 6.2.13. Unusual or Extreme Temperatures or Pressures. 6.2.13.1. General Cold Temperature Considerations. Appropriate “cold temperature” altitude adjustments for instrument procedure minimum segment altitudes (e.g., initial or intermediate segments) should be made when altitude errors resulting from unusually cold airport surface temperatures are considered significant, and are needed to ensure terrain or obstacle clearance. Instrument procedure designers, airspace planners, Authorities, Air Traffic Service (ATS), Operators or pilots may make appropriate corrections, as necessary. Altitude errors typically may be considered significant in mountainous regions when surface temperatures are below -22F/-30C, when significant terrain or obstacle clearance is a factor, and when temperature considerations have not otherwise been addressed by instrument procedure design. Flightcrews should not additionally make corrections if instrument procedures already address temperature related terrain or obstacle clearance to the degree necessary, or if ATS has addressed cold temperature considerations in their assigned clearance altitudes. Use of any altitude corrections made by flightcrews should be consistent with ATS cold temperature altitude correction policies when such policies are promulgated, and when safe clearance is ensured by those ATS policies. (Also see paragraphs 4.3.1.1 item g, 4.3.4. item c., 7.1.3. items d, and 8, 8.13, and 8.14 for related information). ### Page 100 Page 86 Par 6 6.2.13.2. Temperatures Below Those Used in Procedure Design. In some countries, cold temperature errors are considered during procedure design, and are addressed in published instrument procedures, MEAs, and Air Traffic Service (ATS) minimum clearance altitudes such as MVAs when necessary. If temperatures are significantly below the reference temperature considered during procedure design, it may be appropriate for pilots or Operators to apply altitude corrections to the specified (published or charted) procedure minimum altitudes while in flight. This may be done using an appropriate altitude correction table as provided in Table 6.2.13-1 below, or through an equivalent table or method, to ensure terrain or obstacle clearance. 6.2.13.3. Segments which may need to be Corrected for Temperature. Altitude corrections are particularly important on initial or intermediate approach segments in areas of mountainous terrain when there is a significant difference between true altitude and indicated altitude due to unusually cold surface temperatures. Additionally, the size of any temperature-induced altitude or height error decreases in magnitude as the height above the airport surface decreases. Corrections may also be appropriate for MEAs, MVAs, “driftdown” flight paths in mountainous terrain, or missed approach or takeoff flight paths, when extreme cold temperature effects are not otherwise considered. When a U.S. Air Traffic Facility, or international ATS facility already considers cold temperature effects in clearances, additional corrections by flightcrews should not normally be made (e.g., for a radar vector altitude clearance). 6.2.13.4. Uncorrected Procedures. In certain states, cold temperature correction may need to be applied any time temperature is below ISA (e.g., Canada, Northern Europe, when using ICAO criteria). When flying to such states, it is important for the operator and pilots to be aware of that state’s cold temperature instrument procedure correction policy, and to operate consistent with that policy. This may be accomplished by an operator applying that state’s policy, or by the operator using the operator’s own policy, if that policy provides for safe clearance and is suitable for use within that state (e.g., the operator’s altitude correction policy for cold temperature is compatible with that state’s ATS procedures or requirements). 6.2.13.5. VNAV Path and Visual Guidance (VGSI) Temperature Considerations. Pilots and Operators should be aware that temperature-related effects on VNAV path formulation can occur when operating well below or above ISA. For example, in extreme cold temperatures, VNAV descent gradients may be more shallow than usual and visual aids (e.g., VGSI, VASI, PAPI) may not necessarily show “on path” indications when visual reference is first acquired, even though the aircraft is correctly flying the FMS-indicated VNAV path. In such cases, pilots should be alert for the need to adjust and ensure a safe flight path. Similarly, pilots and operators should be aware that unusually shallow VNAV gradients could be lower than “step down” crossing altitudes if temperature considerations have not been addressed. For temperatures well above ISA, VNAV descent angles may be correspondingly steeper than nominal. While obstacle clearance would not be an issue, aircraft descent gradient capability could be a factor if operating near descent gradient limits for the aircraft (e.g., with unusual tailwind conditions at altitude, or with reduced flap settings with an engine inoperative). 6.2.13.6. Unusual Cold Temperature Operations within the Unites States. Within the United States, cold temperature factors and related altitude additives should be considered by procedure designers when necessary (e.g., during procedure design) or are considered by airspace planners to the extent necessary (e.g., when establishing MVAs in cold climates and mountainous areas). However, since assessments for cold temperature correction may vary for particular procedures or situations, if an operator has questions as to the suitability of a particular procedure in extreme cold conditions. Operators may consult the appropriate FAA procedure design office through their respective POI or CMO to determine what additional precautions or adjustments may be appropriate in extreme cold temperature conditions, if any. 6.2.13.7. Unusual Cold Temperature Operations Outside of the Unites States. a. It is particularly important to note these temperature effects when operating outside of the Unites States. Not all states necessarily address temperature compensation within instrument procedure development or in airspace procedure planning. If a flightcrew or operator is in doubt regarding safe obstacle clearance, additional margin should be provided (e.g., requested from ATS, if applicable). Operators may elect to coordinate with authorities or ATS facilities in countries outside of the Unites States which have unusually cold temperatures to determine which procedure-specified altitudes include extreme cold temperature considerations, if any, and which do not. If a pilot is ### Page 101 Par 6 Page 87 in doubt as to safe altitude clearance, corrections should be considered and applied, and ATS should be advised of the use of corrected altitudes, if applicable. b. Where temperature constraints are placed on instrument approach procedures, operators and pilots should be familiar with and properly apply those constraints. Pilots and operators should also be familiar with any temperature correction table(s) provided by the “State of the Aerodrome” (ICAO) or aircraft manufacturer. For FMS, pilots should be familiar with any temperature correction methods that apply to proper FMS use, if provided. 6.2.13.8. Use of Standard Cold Temperature Correction Table (Table 6.2.13-1). Extreme cold temperature corrections may be made within the United States, or by U.S. operators when flying internationally, IAW the standard temperature correction table shown in Table 6.2.13-1, or through an equivalent table. International operators flying to the Unites States (e.g., part 129) may use methods acceptable to the authority of the State of the operator, or methods equivalent to those found acceptable for U.S. operators by FAA. a. Table 6.2.13-1 provides altitude correction values in feet, related to reported airport surface temperature, to be added to various published instrument procedure-related altitudes. The amount of altitude correction to be applied depends on the height of the published segment above the airport. b. For example, using Table 6.2.13-1, an altitude correction of 280 ft. would apply for (see highlighted values in Table 6.2.13-1): (1) a reported airport surface temperature of -30C, and (2) a published instrument procedure segment altitude of 1500 ft. above the airport elevation, 6.2.13.9. Use of Other Cold Temperature Correction Tables. In the event that different cold temperature altitude correction table(s) or methods are provided by a “State of the Aerodrome,” an aircraft manufacturer, ICAO, another authority for that State, or by the operator (e.g., simplified table(s) or methods), pilots or operators may use that alternate table or method in lieu of Table 6.2.13-1. The alternate table(s) or methods should, however, ensure suitable terrain and obstacle clearance, and its use must be compatible with any applicable ATS procedure or clearance. 6.2.13.10. Altimeter Settings. Pilots and operators should be familiar with the proper altimeter settings to use and should take necessary precautions to switch altimeter settings at appropriate times or locations, considering possible multiple sources for altimeter settings including ATS-issued altimeter settings, company or airport reported settings, or settings broadcast over ATIS, or automated settings received by radio based on AWOS, or ASOS. 6.2.13.11. Altimeter Settings (Not Recent). Pilots and Operators should also take necessary precautions when using altimeter settings that may not be recent, or settings from remote locations, or rapidly varying settings, particular at times when pressure is reported or is expected to be rapidly decreasing. 6.2.13.12. Precautions for Unusually High or Low Temperatures or High or Low Pressures. Aircraft performance or procedure adjustments may need to be considered for unusually high or low temperatures or high or low pressures (e.g., temperatures or pressures above or below available AFM data). In such situations, operators may need to request suitable additional information or AFM provisions from the manufacturer, if temperatures or pressures exceed available AFM information or limitations. Data may be provided by the aircraft manufacturer or other approved source (e.g., if the aircraft manufacturer no longer exists or does not support the aircraft type) for such unusual temperatures or surface pressures. In addition to acquiring the necessary data and revised limitations, these situations can also be an important additional consideration for go-around or missed approach assessment. ### Page 102 Page 88 Par 6 Table 6.2.13-1 Cold Temperature Altitude Corrections Note: Values are to be added to published altitudes. Arpt Temp (°°°°C) Height Above Altimeter Source (feet) 200 300 400 500 600 700 800 900 1000 1500 2000 3000 4000 5000 0 20 20 30 30 40 40 50 50 60 90 120 170 230 290 -10 20 30 40 50 60 70 80 90 100 150 200 290 390 490 -20 30 50 60 70 90 100 120 130 140 210 280 430 570 710 -30 40 60 80 100 120 130 150 170 190 280 380 570 760 950 -40 50 80 100 120 150 170 190 220 240 360 480 720 970 1210 -50 60 90 120 150 180 210 240 270 300 450 600 890 1190 1500 6.2.14. Metric Altitudes. When used, the operator should address appropriate flightcrew and dispatch procedures for identification of and appropriate setting and use of altimeters, altitude alert systems, and altitude reference bugs for metric altitude use. This should include emphasis on distinguishing appropriate use of metric versus non-metric units for altimeter settings, change over points, and callouts as used by that operator, and as applicable to the metric altitude routes and procedures used. 6.2.15. International “Approach Procedure Title” Requirements for or Limitations on NAVAID Use. The operator should address appropriate flightcrew and dispatch procedures (if applicable) for identification of and appropriate use of international approach procedures which may or may not have all necessary NAVAIDs listed in the “procedure title” (e.g., NDB ILS Runway 16). For some of these procedures, NAVAIDs may be required which are not necessarily shown in the procedure title. For these procedures the operator should ensure that appropriate airborne equipment is operating for dispatch (if applicable), and crews should verify that appropriate navigation equipment is operating to safely conduct the approach and missed approach. Where substitutions are approved for U.S. Operators (e.g., FMS based RNAV for NDB, VOR, or DME, or GPS for NDB) the operator should ensure flightcrews are familiar with substitutions allowable for that region, state, or procedure. 6.2.16. “U.S. TERPS” or “ICAO PANS-OPS” Obstacle Clearance Procedural Protection Limitations. The operator should be aware that U.S. Standards for Terminal Instrument Procedures (TERPS) and ICAO PANS-OPS-based instrument procedures principally address normal operations, including flight above DA(H) or MDA(H), and above any specified or assumed climb gradients. Operations in non-normal configurations or at unusual speeds (e.g., operations with an engine inoperative, particularly for twin engine aircraft, or in unusual flap or flight control configurations) do not necessarily ensure compliance with climb gradients assumed for TERPS or PANS-OPS-based standard procedures. Accordingly, operators, flightcrews, and dispatchers (if applicable) should consider any necessary aircraft type specific or weight/altitude/temperature (WAT) specific procedures (e.g., similar to takeoff procedures) that may be necessary to ensure safe obstacle clearance, for at least the following situations: a. Engine failure prior to initiation of or during approach or missed approach, b. Balked landing or go-around from below DA(H) or MDA(H) (e.g., as for inadvertent loss of visual reference) ### Page 103 Par 6 Page 89 c. Any special precautions that may be needed if a crew follows a published missed approach procedure or ATS instruction for a turn from below DA(H) or MDA(H), and before climbing to a safe altitude protected by the procedure or MVA, d. Any necessary consideration of an associated “IFR departure procedure” as an aid to ensure safe obstacle clearance, if initiating a go-around from below DA(H), MDA(H), or during a circling approach, e. Any special limitations that may be necessary for safe operations into section 121.445 designated airports.(e.g., Reno, NV [KRNO]). 6.2.17. Navigation Reference Datum Compatibility (e.g.,WGS-84/Other Datum). Outside the Unites States, it is important for operators using FMS, GPS, and RNAV to be aware of, and where necessary, take precautions to address potential differences in the Navigation Data Base (NDB) “reference datum” used by their aircraft’s navigation system, and the datum used locally by States for aeronautical data (e.g., NAVAID locations, runway waypoint locations) and specification of instrument procedures. a. This is important to preclude significant navigation errors. If not appropriately addressed, the actual position of the aircraft may significantly differ from the indicated position. Aircraft may experience incorrect FMS position updating, may fly to an incorrect geographic location for a waypoint, NAVAID, or runway, may violate obstacle clearance during approach or missed approach, or may complete an instrument procedure displaced from the airport or runway intended. Significant map shifts can occur if FMS position estimates are based on use of a NAVAID using a different reference datum than the aircraft’s NDB presumes. Similarly, GPS stand alone systems, while accurately flying to locations specified in a WGS-84 coordinate frame, may not necessarily fly the path over the ground intended by the procedure if the specification of that path uses a datum significantly different than WGS-84. This also can be important when flying with a navigation data base using WGS-84 as the basis for a procedure, but the aircraft is not using GPS or GPS updating, and is depending on local NAVAID updating with those NAVAIDs referenced to a different datum (e.g., as for a GPS inoperative MEL dispatch case with FMS). b. For Category I or II procedures, the issue of use of an appropriate Navigation “Reference Datum” principally applies to flying procedures as follows: • RNAV approach or missed approach procedures • RNAV Initial or intermediate segments ILS or MLS procedures, or • RNAV missed approach segments ILS or MLS procedures c. The final approach segment of ILS or MLS typically is not adversely affected by a difference in reference datum. d. GLS or RNP procedures, while depending on specification of an appropriate reference datum for final approach, are protected through other criteria to ensure consistent navigation. e. Information about the Navigation Reference Datum used in a particular location outside of the United States is typically available on the Internet. An example of a web site containing this information is: http://www.jeppesen.com/wgs84.html f. Accordingly, when outside United States airspace and when WGS-84 is not used as the reference datum locally for NAVAID’s or procedures, or a reference datum equivalent to WGS-84 is not used, and RNAV segments are flown as part of an instrument approach or missed approach procedure for: • FMS-equipped aircraft • FMS-equipped aircraft using GPS updating, or • GPS “stand alone” equipped aircraft ### Page 104 Page 90 Par 6 Operators should take suitable precautions, as described below: (1) Aircraft Equipped With FMS Having GPS Updating Capability, or Equipped With “GPS Stand Alone” Navigation Systems. (a) For aircraft having FMS capability with GPS updating, or a “GPS Stand Alone” navigation systems, for each approach outside the United States where the local datum is not WGS-84, or WGS-84 equivalent, or where the operator is uncertain as to whether the local datum is significantly different than WGS-84, the operator should take one or more of the following precautions, as necessary: i. Verify that the datum is WGS-84, or equivalent, ii. Conduct an assessment of the difference in the datum used, to determine that any difference is not significant for the procedures to be flown, iii. Develop and use special RNAV procedure segments or aeronautical data referenced to WGS- 84 or equivalent, as necessary, iv. Manually inhibit GPS updating of the FMS while flying the approach, or segments of the approach affected by the difference in reference datum, v. Only use FMS or GPS Stand Alone systems to fly pertinent RNAV segments of the approach where it is possible to use other NAVAID raw data to confirm correct aircraft position along the flight path, vi. Conduct simulation verification, or in-flight verification or confirmation of suitable navigation performance, vii. Preclude FMS or GPS use on segments of the approach affected by the difference in reference datum, or viii. Use any other method proposed by the operator, and found acceptable to FAA, to ensure that a difference in the NDB Reference Datum from the local datum does not cause loss of navigation integrity. (b) For GLS or RNP procedures or procedure segments, since the reference datum is consistent with WGS-84 by procedure design, Operators of aircraft using GPS updating of FMS need not apply the special precautions listed above, unless otherwise advised (e.g., by NOTAM or equivalent). (2) FMS Aircraft That Do Not Have GPS Updating Capability. (a) While possible, FMS-equipped aircraft that do not have GPS updating capability may be less likely to experience this particular datum reference difference issue. This is because navigation databases, local NAVAIDs, and local instrument procedures typically address and resolve datum issues consistently on a local basis, and in a consistent manner within the locally used coordinate frame of reference. However, even though the datum difference issue may be less likely, it nonetheless may occur. Operators should apply precautions, as necessary, if there is significant doubt as to Navigation Data Base datum differences. (b) The precautions listed above in item (1) should not be interpreted to discourage GPS installation and use. GPS updating of FMS can significantly increase both navigation accuracy and integrity, and reduce the risk of other types of navigation errors, including map shifts, yielding a significant safety increase. 6.2.18. Alternative Use of FAA/JAA Harmonized Minima. This AC provides for use of optional “FAA/JAA harmonized operating minima” when authorized by OpSpecs or an LOA, in lieu of otherwise published minima based on U.S. TERPS or ICAO PANS-OPS. Use of these minima is limited to use within the United States, within any JAA (European) State that authorizes use of these minima or equivalent, or in other States that accept or apply FAA or JAA criteria. These minima have been determined to be acceptable for use by U.S. Operators or JAA ### Page 105 Par 6 Page 91 supervised Operators within the United States who have implemented applicable provisions and criteria of Appendix 8, or its equivalent. a. Minima based on values provided in Appendix 8 should not be below the lowest minima authorized through a Category I Standard OpSpecs authorization, or below any applicable published foreign aerodrome minima when operating outside the United States. b. These minima provide for a single table for Aerodrome Operating Minima regardless of approach type, and are intended for use by aircraft and procedures which are based on a stabilised descent path to the runway (e.g., using an xLS glide slope, VNAV, or other specifically approved method for maintaining a constant vertical descent path or rate during final approach). Use of minima in this table for other procedures not using a glide slope or constant VNAV descent path to minima is considered only on a case-by-case basis by the FAA. c. The harmonized minima are intended to cover all categories of straight-in approach procedures including xLS (e.g., ILS GLS, MLS) and approaches other than xLS (e.g., RNAV, LOC, BCRS, VOR, NDB). Any procedure based on U.S. TERPS or ICAO PANS-OPS, or special procedures otherwise approved by FAA are eligible to use these harmonized minima. d. Approaches with glide slope angles or VNAV descent paths in excess of 3.77 degrees, or special procedures at certain airports that require specific knowledge or training, are not typically eligible for use of these special approach minima. e. The FAA/JAA Harmonized Approach minima which may alternately be approved through OpSpecs for use by U.S. Operators, or JAA supervised Operators, or equivalent authority/operators determined acceptable by FAA (e.g., Canada), are as listed in Appendix 8. 6.2.19. Assessment of Threshold Crossing Height (TCH), Approach Descent Gradient, and Runway Slope. a. Operators should assess instrument procedures to be used at regular, alternate, and provisional airports, and at planned diversion contingency airports to ensure satisfactory Threshold Crossing Height (TCH) for the type of aircraft to be flown (see 5.12.3 and 5.12.4). Typically, TCHs of less than 48 ft. should not be used by wide body air carrier aircraft without special review by the operator. b. Operators should assess instrument procedures to be used at regular, alternate, and provisional airports, and at planned diversion contingency airports to ensure that final approach descent gradients specified are appropriate for the type of aircraft to be flown, and for conditions expected to be encountered (e.g., engine-out flap settings and speeds, anti-ice operating). For facility, obstacle, or terrain constraints, certain airports served by air carrier aircraft have unusually steep gradients (Stephenville, Newfoundland. - CYJT) or unusually shallow gradients (Kodiak, Alaska - PADQ) that may have operational consequence for certain aircraft types. c. Under extreme cold temperature conditions certain VNAV paths may be more shallow than normal, and under extreme high temperatures these VNAV paths may be steeper than normal (see paragraph 6.2.13). In either case the paths may not closely align with fixed visual aids such as VGSI/PAPI. d. Certain runways have unusual general slope, or complex varying slope that should be assessed by the operator for pilot awareness, or for operational consequence (e.g., operator specifies that the aircraft must touchdown by a certain point on the runway, or the last portion of the runway is not visible during flare in the TDZ due to changing slope). ### Page 106 Page 92 Par 7 **7. TRAINING AND CREW QUALIFICATION.** a. Training and crew qualification programs pertinent to Category I, Category II, or lower than standard takeoff minima should include appropriate ground training (e.g., knowledge assurance) and flight training (e.g., skill or maneuver experience in simulation or an aircraft) to ensure safe aircraft operation for instrument procedures and low visibility operations in normal, rare normal (e.g., winds, turbulence, restricted visibility), and specified non-normal conditions (e.g., engine or various systems inoperative). Although training is not required for part 125, Operators are encouraged to prepare a training and qualification program for all flight crewmembers IAW this paragraph. b. This is typically accomplished through appropriately addressing initial qualification, recurrent qualification, upgrade qualification, differences qualification, recency of experience, and re-qualification. The Operator’s program should provide appropriate training and qualification for each pilot in command (PIC), second in command (SIC) and any other pilot or flight crewmember expected to have knowledge of or perform duties related to Category I or Category II landing operations (e.g., Flight engineer, augmented flight crewmember). c. Each PIC, and each other pilot or dispatcher, if applicable, having duties related to flight planning or use of Category I or Category II instrument procedures is expected to have comprehensive knowledge of areas described in paragraph 7.1 below. Each pilot expected to perform instrument procedures in normal or specified non-normal operations or perform duties associated with those procedures, should have successfully demonstrated the necessary skills in accomplishing those designated maneuvers or procedures as shown in paragraphs 7.2 through 7.4 below. Demonstration of skill in performing instrument procedures typically is accomplished through simulator training, checking, or during line operating experience or evaluations. Pilots other than a PIC or SIC may only be expected to perform those relevant duties, procedures or maneuvers related to instrument procedures that are applicable to their own crew position or assigned duties (e.g., international relief officers). 7.1. General Knowledge (Ground) Training for All Weather Operations (AWO). a. Appropriate ground training should be conducted suitable for the “All weather Operations,” instrument procedures, aircraft type(s) or variants, crew positions, airborne systems, NAVAIDs, and ground systems used. b. Topics should be addressed to include at least those listed in paragraphs 7.1.1 through 7.1.3, and be addressed or tailored to suit application to initial qualification, recurrent qualification, re-qualification, upgrade, or differences qualification, as applicable. c. Topics should be addressed for each PIC and any other pilots having assigned duties (e.g., SIC) as a PF or PNF during conduct of IAP. When duties are specifically assigned to a PF or PNF (e.g., monitored approach, Category II), only those duties applicable to the assigned crew position need be addressed for that crew position. When instrument approach-related duties are specifically assigned to other than the PIC or SIC, such as a flight engineer or relief pilot duties applicable to the assigned crew position should be addressed. When flight crewmembers other than a PIC or SIC are not assigned duties associated with an IAP but are expected to be present on the flight deck during an instrument approach, it is recommended, but not required, that they also receive suitable academic training. d. Acceptable methods to address ground training topics include classroom instruction, self guided slide/tape presentation, or computer-based instruction, or self-instruction using appropriate reference materials. e. If the method of satisfying ground training requirements is exclusively through self guided learning or review from appropriate reference materials (e.g., flightcrew operating manual, Aeronautical Information Manual, and commercially available instrument procedure charts), the operator should use some clearly identified method (e.g., periodic written examination) to verify that each pilot has acquired or has retained the necessary knowledge. ### Page 107 Par 7 Page 93 7.1.1. Ground Systems and NAVAIDs for Category I or Category II. a. Ground systems and NAVAIDs are considered to include characteristics of the airport, electronic navigation aids, lighting, marking, and other systems (e.g., RVR) and any other relevant information necessary for safe Category I or Category II landing or low visibility takeoff operations. b. The training and qualification program should appropriately address the operational characteristics, capabilities and limitations of at least each of the following: (1) NAVAIDs. The navigation systems or NAVAIDs to be used, such as the instrument landing system (ILS) with its associated critical area protection criteria, GPS Landing System (GLS), or Microwave Landing System (MLS) characteristics, as applicable, marker beacons, VOR, DME, NDB, DME, compass locators or other relevant systems should be addressed to the extent necessary for safe operations. If area navigation systems, or other nonground based NAVAID systems (e.g., GNSS, LORAN) are used, any characteristics or constraints regarding that method of navigation or associated supporting elements (e.g., GBAS, WAAS), must be addressed. (2) Visual Aids. Visual aids include approach lighting system, TDZ, centerline lighting, runway edge lighting, taxiway lighting, standby power for lighting and any other lighting systems that might be relevant to a Category I or Category II environment, such as pilot control of lighting aids, or coding of the center line lighting for distance remaining, and lighting for displaced thresholds, land and hold short lighting, or other relevant configurations should be addressed. (3) Runways and Taxiways. The runway and taxi way characteristics concerning width, safety areas, obstacle free zones, markings, hold lines, signs, holding spots, runway slope, suitability of TCH, unusual friction, grooving, or PFC characteristics, critical area protection areas, or taxi way position markings, runway distance remaining markings and runway distance remaining signs should be addressed. (4) Meteorological Information. METARs, TAFs, visibility reporting, Transmissometers systems, including RVR locations, readout increments, sensitivity to lighting levels set for the runway edge lights, variation in the significance of reported values during international operations, controlling and advisory status of readouts, and requirements when transmissometers become inoperative; appropriate use of Temperatures in C or F, conversion of temperatures between C and F; appropriate use of pressure information including altimeter settings in units of HPa or inches, QNE, QNH, QFE (if applicable); appropriate use of Transition Level and Transition Altitude; appropriate interpretation and use of reported wind and gust information, in true or magnetic direction, as applicable to the source and circumstance. (5) NOTAMs and other Aeronautical Information. Facility status, proper interpretation of outage reports for lighting components, standby power, or other factors and proper application of NOTAMs regarding the initiation of Category I or Category II approaches or initiation of a low visibility takeoff. (6) Flight Planning and Flight Procedures Related to Inoperative or Unsuitable NAVAIDs. When NAVAID position updating is used in support of area navigation position determination (e.g., VOR, VOR-DME, DME-DME, GNSS updating), Operators and flightcrews should be aware of when and how to disable use of an unsuitable NAVAID or updating method within the airborne navigation system. This is especially true for NAVAID failure conditions that are probable to cause a significant map (position) shift (e.g., movement of a NAVAID to a new location without corresponding update of the NAVAID position in a database, significant numbers of space vehicle outages, or areas of interference). 7.1.2. The Airborne System. a. The training and qualification program should address the characteristics, capabilities, and limitations of each appropriate airborne system element applicable to Category I or Category II landing including the following: ### Page 108 Page 94 Par 7 (1) Flight guidance system. The flight guidance system, including appropriate modes to be used for different circumstances or procedures (e.g., APPROACH, HDG, V/S, LNAV/VNAV), and any associated landing system or landing and roll out system, or go-around capability, if applicable (e.g., autopilot, autoland); (2) Flight director system. The flight director system, including appropriate modes to be used for different circumstances or procedures (e.g., APPROACH, HDG, V/S, LNAV/VNAV), and including any associated landing or landing and roll out capability, or go-around capability, if applicable (e.g., HGS); (3) Automatic throttle. The automatic throttle control system, if applicable. Mixed mode autoflight/autothrottle operation should be addressed (e.g., manual flight, but with autothrottles on, or vice versa), if pertinent to the aircraft type, (4) Displays. Situation information displays, as applicable, including any applicable limits for acceptable approach performance to continue an approach, flare, rollout, or go-around (e.g., typically 1/2 dot or less lateral or vertical displacement below 500 ft. HAT down to DA(H), and (5) Status, Alerting and Warning Displays. Other associated instrumentation and displays, as applicable, including any monitoring displays, status displays, mode annunciation displays, failure or warning annunciations, and associated system status displays that may be relevant. (6) Means for determining DA(H) or MDA(H). The means for determining DA(H) or MDA(H) as follows: (a) DA(H) as applicable to the particular Category I ILS, GLS, or MLS procedure (e.g., as an applicable DA, or Marker Beacon substitute for a DA when authorized); (b) DA(H) as applicable to the particular Category I RNAV or RNAV RNP procedure with VNAV (e.g., as an applicable DA); (c) MDA(H) as applicable to the particular Category I procedure other than ILS, GLS, or MLS (e.g., as an applicable MDA, and any associated missed approach point); and (d) DA(H) as applicable to the particular Category II ILS, GLS, or MLS procedure (e.g., as an applicable DH, or Marker Beacon substitute for a DH, when authorized). (7) Other Flight Deck Systems. Other flight deck systems operations or use, as may be related to low visibility operations (e.g., autobrakes, autospoilers), and any associated limitations, characteristics, or constraints (e.g., touchdown pitch up or pitch down tendency of certain autospoiler or autobrake settings or non-normal conditions, time delays, auto-deactivation features with go-around). (8) Other aircraft characteristics. Any system or aircraft characteristics that may be relevant to Category I or Category II operations, such as cockpit visibility cutoff angles and the effect on cockpit visibility of proper eye height, seat position or instrument lighting intensities related to transition through areas of varying brightness visual conditions change. Crews should be aware of the effects on flight deck visibility related to use of different flap settings, and approach speeds. Minimum usable TCH and minimum or maximum final approach descent gradients should be addressed, if applicable. (9) Lighting. Proper use of various landing, taxi, turnoff, wing, logo, or strobe lights for approach visibility, taxi, or collision avoidance conspicuity. (10) Rain Removal and De-fog. Proper procedures for use of rain removal/defog (e.g., windshield wipers). If windshield defog, anti-ice, or de-icing systems affect forward visibility, crews should be aware of those effects and be familiar with proper settings for use of that equipment related to low visibility landing. ### Page 109 Par 7 Page 95 (11) Course and Frequency Selection. For automatic or manual systems which require crew input for parameters such as inbound course or automatic or manually tuned navigation frequencies, the crew should be aware of the importance and significance of any incorrect selections or settings, if not obvious, to ensure appropriate system performance. (12) Environmental Limits. Description of the limits to which acceptable system performance has been demonstrated for headwind, tailwind, crosswind, and wind shear as applicable, and recognition of unacceptable performance in the case of adverse weather (e.g., windshear, turbulence). (13) Non-normal or Failure Conditions. Recognition and response to pertinent non-normal or failure conditions, and related non-normal procedure and checklist use for flight guidance, instrument, and supporting systems (electrical, hydraulic, and flight control systems). (14) Go-Around. Proper airborne system use for go-around, including consideration of height loss during transition to a go-around, performance assurance for obstacle clearance, management of any necessary mode changes, and assurance of appropriate vertical and lateral flight path tracking. b. As applicable, the operator may consult the CHDO/POI to ensure that information presented by the operator about any training or qualification items or issues referenced above, or any additional issues pertinent to the type aircraft or system used, are consistent with the pertinent FAA Flight Standardization Board (FSB) Report for the applicable aircraft type. 7.1.3. Flight Procedures, Operations Specifications, and Other Information. a. Regulations and OpSpecs. Pilots, and dispatchers if applicable, should be familiar with FAA regulations pertinent to their operation (e.g., sections 91.175, 121.651, 125.381 and 135.225) and OpSpecs applicable to Category I or Category II landing, or lower than standard takeoff minima, as applicable. b. Crew Duties. Pilots should be familiar with appropriate crew duties, monitoring assignments, transfer of control during normal operations using a “monitored approach” appropriate automatic or crew initiated call-outs to be used, proper use of standard IAPs, special IAPs, applicable minima for normal configurations or for alternate or failure configurations and reversion to higher minima in the event of failures. c. Visibility and RVR. Pilots, and dispatchers if applicable, should be familiar with proper application of meteorological visibility, METARs, TAFs, RVR, RVV (if applicable), including their respective use and limitations, the determination of controlling RVR and advisory RVR, required transmissometers, appropriate light settings for correct RVR readouts and proper determination of RVR values reported at foreign facilities. Pilots should be familiar with any authorized methods for pilot assessment and reporting of visibility at non-U.S. facilities. d. Procedures and Charts. (1) Pilots, and dispatchers if applicable, should be familiar with the proper use of instrument procedures and charts including application of DA(H) and MDA(H), and when to use DA, DH, or an equivalent (e.g., OCA (H)), or MDA as applicable, including proper use and setting of barometric or radar altimeter bugs, use of the inner marker where authorized or required due to irregular underlying terrain and appropriate altimeter setting procedures for the barometric altimeter consistent with the Operators practice of using either QNH or QFE, and if applicable. (2) Pilots should be aware of when to make suitable cold weather temperature corrections for altimeter systems and procedures, if necessary. e. Visual references. Pilots should be familiar with the availability and limitations of visual references encountered, both on approach before and after DA(H), if a DA or DH is applicable. Pilots should be familiar with the expected visual references likely to be encountered. Pilots should be familiar with procedures for an unexpected deterioration of conditions to less than the minimum visibility specified for the procedure during an approach, flare ### Page 110 Page 96 Par 7 or roll out including the proper response to a loss of visual reference or a reduction of visual reference below the specified values when using a DA(H) or MDA(H) and prior to the time that the aircraft touches down. The operator should provide some means of demonstrating the expected visual references where the weather is at acceptable minimum conditions and the expected sequence of visual queues during an approach in which the visibility is at or above the specified landing minimums. This may be done using simulation, video presentation of simulated landings or actual landings, slides showing expected visual references, computer based reproductions of expected visual references or other means acceptable to the FAA. f. Visual Transition. Procedures should be addressed for transitioning from non-visual to visual flight for both the PIC, SIC, as well as the pilot flying and pilot not flying, during the approach. For systems that include electronic monitoring displays, as described in item e above, procedures for transitioning from those monitoring displays to external visual references should be addressed. g. Unacceptable Displacements. Pilots should be familiar with the recognition of the limits of acceptable aircraft position and flight path tracking during approach, flare and, if applicable, roll out. This should be addressed using appropriate displays or annunciations for the aircraft type. h. Environmental Effects. Environmental effects should be addressed. Environmental effects include appropriate constraints for head winds, tail winds, cross winds, and the effect of vertical and horizontal wind shear on automatic systems, flight directors, or other system (e.g., HGS) performance. For systems such as head up displays which have a limited field of view or synthetic reference systems (e.g., EVS or SVS) pilots should be familiar with the display limitations of these systems and expected crew actions in the event that the aircraft reaches or exceeds a display limit capability. Extreme temperature or pressure effects should be considered, if necessary. i. Operator Policies. Pilots, and dispatchers if applicable, should be familiar with the Operators policies and procedures concerning any constraints applicable to Category I or Category II landings, or low visibility takeoff including constraints for operations on contaminated or cluttered runways. Procedures to be used when obscuring of appropriate lighting or markings occurs, and limits should be noted for operations on slippery or icy runways regarding both directional control and stopping performance. Pilots, and dispatchers if applicable, should be familiar with appropriate constraints related to use of braking friction reports. Pilots, and dispatchers if applicable, should be familiar with the method of providing braking friction reports applicable to each airport having instrument landing operations. j. Response to Aircraft or System Failures. Pilots should be familiar with the recognition and proper reaction to significant aircraft system failures experienced prior to and after reaching the final approach fix and experienced prior to and after reaching DA(H), as applicable. Expected crew response to failures prior to touchdown should be addressed, particularly for Category II operations. k. Ground or Navigation System Faults. Pilots are expected to appropriately recognize and react to ground or navigation system faults, failures, or abnormalities at any point during the approach, before and after passing DA(H) and in the event an abnormality or failure which occurs after touchdown. Pilots should be familiar with appropriate go-around techniques, systems to be used either automatically or manually, consequences of failures on go-around systems which may be used, the expected height loss during a manual or automatic go around considering various initiation altitudes, and appropriate consideration for obstacle clearance in the event that a missed approach must be initiated below DA(H). l. Navigation Anomalies or Discrepancies. Pilots, and dispatchers if applicable, should be familiar with the need to report navigation system anomalies or discrepancies, or failures of approach lights, runway lights, touchdown zone lights, center line lights or any other discrepancies which could be pertinent to subsequent Category I or Category II operations. m. International Procedures. Pilots, and dispatchers if applicable, should be familiar with any applicable international procedures including application of OCA, OCH, the applicable State AIP, or regional supplements (if not otherwise addressed by the operator in the FCOM or equivalent), pertinent excerpts from ICAO references (e.g., ### Page 111 Par 7 Page 97 Manual for All Weather Operations - ICAO DOC 9365AN/910). Regulatory requirements and responsibilities at non-U.S. international airports (e.g., approach ban and “look see” provisions). n. Performance and Obstacle Clearance. Pilots, and dispatchers if applicable, should be familiar with any applicable aircraft performance or weight limit information to ensure safe obstacle clearance for “all engine,” or “engine inoperative” missed approach, or rejected landing. Applicable performance information should consider applicable flap settings to be used, go-around procedures, acceleration segments if applicable, transition at any time following an engine failure between the specified “all-engine lateral flight path” (or radar vectors) and any specified “engine-inoperative lateral flight path,” using acceptable flap retraction and cleanup height procedures. o. Flight Plans and Equipment Classification. Pilots, and dispatchers if applicable, should be familiar with use of appropriate flight plan equipment classifications (e.g., Required System Performance (RSP)) affecting eligibility for various takeoff or landing procedures (e.g., flight plan /F, /E designations), and proper alternate airport identification and use, including any takeoff, en route ETOPS, or destination alternates, as applicable. p. EVS, SVS, or ILM. When a synthetic reference system such as a “synthetic vision system” (SVS) or “enhanced vision system” (EVS) or “Independent Landing Monitor” (ILM) system is used, pilots should be familiar with the interpretation of the displays to ensure proper identification of the runway and proper positioning of the aircraft relative to continuation of the approach to a landing. Pilots should be briefed on the limitations of these systems for use in various weather conditions and specific information may need to be provided on a site-specific basis to ensure that misidentification of taxiways or other adjacent runways does not occur when using such systems. 7.2. Maneuver or Procedure (Flight) Training for All Weather Operations (AWO). a. Aircraft or Flight Simulator Use. Maneuver/Procedure (Flight) training and evaluation should be provided, and should use appropriate simulation capability. If simulation capability is not available, training or evaluation may be accomplished partially with training devices, or partially or completely in an aircraft. However, when training or evaluation is done using training devices, or with simulators with limited capability (e.g., not Level C or D), or with an aircraft, additional factors or techniques (e.g., use of CBT) may need to be considered by the operator to ensure effective training. b. Addressing Applicable Regulations. Maneuver or procedure training should generally address applicable part 121 Appendix E or F provisions, an approved AQP Program as applicable, approach and landing events specified in part 61, relevant FAA Order 8400.10 airman certification takeoff and landing provisions, FAA Order 8700.1 for part 125 competency or instrument checks, or FAA ATPC Practical Test Standards (PTS) as applicable, as described or credited below. c. Types Of Procedures and Conditions to be Addressed. Maneuvers and procedures trained should be keyed to the types of instrument procedures used by the operator, the environment in which they are flown, and any special considerations that may apply to their safe application. Operating policies, procedures, and documentation representative of that applicable to the particular operator should be used. Maneuver and Procedure Training and any necessary evaluation should ensure that instrument procedures can be safely flown considering at least the following factors, as applicable to the specific operator: (1) Types of instrument procedures used (standard and special, if applicable); (2) That operator’s manuals, charts, and checklists; (3) Aircraft type(s) and variants flown; (4) Flight guidance system(s) used; (5) NAVAID(s) and visual aids used; (6) Flightcrew procedures used (e.g., PF/PNF duties, monitored approach, callouts); ### Page 112 Page 98 Par 7 (7) Airport characteristics typically experienced (e.g., Visual aids, transition level, air traffic procedures, meteorological procedures, signs and markings, unusual airport features (elevations, slope) as applicable); (8) Runway characteristics typically experienced (e.g., representative field lengths, grooving, marking); (9) Nearby critical terrain or obstruction environment, if applicable; (10) Relevant environmental conditions (e.g., wind, turbulence, shear, visibility and ceiling conditions, slippery runways, rain or snow effects on visibility); (11) Lowest Category I or Category II straight-in, or Category I circling minima as applicable; and (12) Other relevant AWO characteristics (e.g., special instrument procedures). d. Use of Part 121.Appendix H Level C or D Simulators. (1) When simulation (e.g., part 121, Appendix H level C or D) is the primary method used for flight training or evaluation for takeoff, approach and landing procedures, appropriate normal, non-normal, and environmental conditions (relevant wind, turbulence, visibility, and ceiling conditions) should be simulated. In this instance, training and evaluation need only be conducted using applicable landing minima and relevant and representative procedures and conditions (e.g., a representative mix of day, night, dusk, variable/patchy conditions, representative temperatures, landing runway altitudes, precipitation conditions, turbulence, and icing conditions). Multiple requirements for maneuvers may be combined at the discretion of the POI/APM/CMO/CMU, subject to the constraints below (e.g., to preclude the need to repeat various Category I/II/III, approach scenarios for normal approaches, approaches with an engine(s) out, missed approach, landing, rejected landing, and various go-around events). The training benefit of realistic simulation is acknowledged, and credit for use of a representative sample of conditions to be flown, directly using pertinent minima, is considered to be acceptable. Accordingly, when level C or D simulation is used, only a sample of procedural types, environmental conditions, successful crew performance, and other factors listed in c. above need be assessed. However, when such credit for combining events is permitted, the operator and CMO/CMU/POI/APM should nonetheless ensure that the program used leads to flightcrews reliably performing the necessary low visibility procedures under both normal and anticipated non-normal conditions in line service. Acceptable numbers and types of training or demonstration instrument approach procedure events for various types of training or checking or qualification programs are listed in paragraphs 7.2.1 through 7.2.7 below. (2) In instances where Level C or D simulation is typically used IAW this provision, but the level of simulation capability is temporarily degraded to Level A or B, the operator with CMO concurrence may nonetheless apply provisions of this paragraph on a temporarily basis, until the simulation capability can be returned to level C or D status. e. Use of Simulators other than Part 121 Appendix H Level C or D, use of Training Devices, or use of an Aircraft. When part 121, Appendix H level C or D simulation (or equivalent) is not used for All Weather Operations (AWO) Qualification (e.g., when an aircraft is used, or a training device(s) level 2 through 7, or visual simulator, or non-visual simulator, or Level A or B simulator, or a simulator qualified for Level C or D but used as an FBS is used) certain restrictions and additional provisions may apply to training or qualification, as follows: (1) The POI or CMO/CMU may require that during training or evaluations the flightcrew demonstrate satisfactory lateral and vertical flight path tracking performance, to an appropriate tolerance, and to ensure flight path stability after passing DA(H). This is to address the possible lack of visual reference or external environmental disturbances that may exist in real operations but that may be minimal or absent during training or testing in limited capability simulators or simulation devices (e.g., due to lack of visual reference, turbulence or other disturbances being faithfully represented). (2) The POI or CMO/CMU may require that additional procedures or combinations of procedures be demonstrated, or that limitations apply to credits allowed by this AC in terms of credit for combining maneuvers or ### Page 113 Par 7 Page 99 types of procedures trained, maneuvers demonstrated, or other events evaluated (e.g., for combinations of various Category I, II, or III procedures for ILS, VOR, VOR/DME, NDB, Back Course Localizer, or engine inoperative missed approach or landing procedures). (3) The POI or CMO/CMU may require additional training or checking event items beyond those identified in this AC below, or those addressed only generically in part 121 Appendix E or F, or in part 61 if applicable (e.g., providing for HUD or autoland qualification where part 121 or 91 only make general reference to items like other special characteristics as necessary). (4) When using an aircraft for training or testing, the POI or CMO/CMU may require that provision be made for use of a view limiting device for any necessary competency demonstrations. This is particularly applicable to any evaluation of a pilot that has not previously qualified to fly a similar class of aircraft (e.g., large turbojet aircraft), or for a pilot that does not have significant instrument experience beyond that necessary to satisfy minimums for issuance of an FAA commercial pilot’s license with instrument rating. (5) For use of Level A or B Simulation in lieu of Level C or D Simulation that is temporarily not available, see paragraph 7.2 d. above. f. Flight Training Maneuvers for Category I or II Landings. Maneuvers may be addressed individually as a respective Category I or Category II maneuver, or an appropriate sample of Category I and Category II maneuvers may be trained and evaluated, if crews are to be both Category I and II qualified. When flightcrews are authorized to use minima for Category III, as well as Category II, samples of maneuvers selected to be performed for training and evaluation may be from appropriate combinations of Category I, II, and III procedures. When found acceptable to the CHDO/POI, each maneuver need not be repeated for each Category of landing weather minima to be authorized. Flight training for Category I or Category II landing should address at least the following maneuvers: (1) Normal landings. Normal landings at the lowest applicable Category I or Category II minima, using representative autoflight configurations or combinations of configurations authorized for use (e.g., flight director, autopilot, autothrottles); (2) Missed approach. A missed approach from the lowest applicable DA(H) and MDA(H), (may be combined with other maneuvers); (3) Balked landing. A balked landing or missed approach from a low altitude that could result in a touchdown during go-around (balked landing or rejected landing - may be combined with other maneuvers); (4) System or NAVAID Failures. Appropriate aircraft and ground system NAVAID failures (may be combined with other maneuvers); (5) Engine Failures. Engine failure prior to or during approach (if specific flight characteristics of the aircraft or operational authorizations require this maneuver); (6) Low Visibility Rollout. Manual roll out with low visibility at applicable minima (may be combined); (7) Realistic Environmental Conditions. Landings (in simulation) with environmental conditions at a representative sample of limiting values authorized for applicable Category I or II minima for that operator (e.g., regarding wind magnitude, headwind and crosswind components, turbulence, and runway surface friction characteristics (wet, snow, slippery) may be combined); and (8) Non-normal configuration approaches and landings. Representative non-normal configuration approaches and landings in instrument conditions should be demonstrated. For these approaches, the simulated weather minima may be above, or well above, the lowest Category I or Category II minima authorized. Minima should be at levels that might typically be experienced in line operations, for a landing with the non-normal condition used. During these approaches, representative autoflight, instrument, and aircraft system configurations or ### Page 114 Page 100 Par 7 combinations of configurations should be demonstrated (e.g., flight director, autopilot, autothrottles, raw data, inoperative electrical or hydraulic components). (9) Basic Airmanship Skills. In accomplishing items (1) through (8) above, each pilot should demonstrate competence, or be judged to have the necessary competence in “basic airmanship skills” to adequately address: (a) Manual Control. Manual control, or reversion to manual control of the aircraft, if necessary, (for FBW aircraft, normal law or configuration is acceptable) (b) Automation. Proper use of automation, (c). Situation Awareness. Appropriate planning and situation awareness, including terrain awareness, (d) Detection and coping with adverse environmental factors. Ability to detect and cope with adverse environmental conditions (e.g., applicable crosswinds, turbulence, windshear, convective weather, or adverse airport conditions (e.g., slippery runways)), (e) Detection and coping with adverse NAVAID factors. Detection Ability to detect and cope with adverse ground system, space system, or NAVAID failures or anomalies), and (f) Crew coordination and CRM. Proper crew coordination, and crew resource management. (g) Flight Training Maneuvers for Takeoffs. For low visibility takeoff (RVR less than 2400 RVR), the following maneuvers and procedures should be addressed (may be combined): i. Normal takeoff, ii. Rejected takeoff from a point prior to V1 (including an engine failure), iii. Continued takeoff following failures including engine failure, and any critical failures for the aircraft type which could lead to lateral asymmetry during the takeoff, or iv. Limiting conditions. The conditions under which these normal and rejected takeoffs should be demonstrated include appropriate limiting cross winds, winds, gusts, and runway surface friction levels authorized. A demonstration should be done at weights or on runways that represent a critical field length. h. Demonstration of Appropriate PF or PNF Duties By Each Pilot. During each of the specified maneuvers or procedures, flight crewmembers are expected to perform their respective assignments or duties (e.g., Captain, First Officer, PIC, SIC, Pilot-Flying (PF), Pilot-Not-Flying (PNF)), as applicable. However, PICs and SICs should typically be able to perform either PF or PNF duties, unless otherwise limited by the Operators policies or aircraft characteristics (e.g., if F/Os are precluded by operator policy or system installation (HUD) from serving as PF during certain adverse weather takeoffs or landings). In situations where flight crewmembers are being qualified other than as part of the complete flightcrew (e.g., when two pilots in command are being qualified) or when a pilot other than the PIC is also to be authorized to serve as the PF for low visibility operations, each flight crewmember should individually demonstrate the required maneuvers or procedures, or an acceptable sample of procedures. Relevant procedures are those involving manual control of the aircraft, rather than procedures such as autoland, which may not involve significant differences in PF or PNF skills. 7.2.1. Initial Qualification. Prior to maneuver or flight training, Initial General Knowledge (Ground) Training for “All Weather Operations (AWO)” should be addressed. Coverage of those subjects specified in 7.1 should typically be completed for each pilot having assigned AWO responsibilities. a. Maneuver or Procedure (Flight) Training addressing suitable for that operator’s Initial Qualification for “All Weather Operations (AWO)” should be conducted. While the number of procedure types covered, number of The text continues at https://openairdocs.org/ac/120-29.md?from=115 --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.