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1-6. RELATED REGULATIONS AND REFERENCES.
a. Title 14 CFR:
• Part 23, § 23.2510.
• Part 25, §§ 25.1309, 25.1322, 25.1329, 25.1581 and 25.1583.
• Part 61, §§ 61.21 and 61.66.
• Part 91, §§ 91.175, 91.176, 91.189, 91.191, 91.193 and Appendix A.
• Part 121, §§ 121.579 and 121.651.
• Part 125, §§ 125.379 and 125.381.
• Part 129, § 129.11.
• Part 135, § 135.225.
b. ACs, FAA Orders, and Operational Authorizations. Unless a specific reference is made to a particular version of a rule or AC, current editions of the following FAA orders, operational authorizations, and ACs should be used:
(1) ACs:
• AC 20-153, Acceptance of Aeronautical Data Processes and Associated Databases.
• AC 20-185, Airworthiness Approval of Synthetic Vision Guidance System.
• AC 25-7, Flight Test Guide for Certification of Transport Category Airplanes.
• AC 25-31, Takeoff Performance Data for Operations on Contaminated Runways.
• AC 25-32, Landing Performance Data for Time-of-Arrival Landing Performance Assessments.
• AC 90-101, Approval Guidance for RNP Procedures with AR.
• AC 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace.
• AC 90-106, Enhanced Flight Vision Systems.
• AC 90-107, Guidance for Localizer Performance with Vertical Guidance and Localizer Performance without Vertical Guidance Approach Operations in the U.S. National Airspace System.
• AC 90-108, Use of Suitable Area Navigation (RNAV) Systems on Conventional Routes and Procedures.
• AC 90-112, Development and Submission of Special Instrument Procedures to the FAA.
• AC 91-79, Mitigating the Risks of a Runway Overrun Upon Landing.
• AC 120-53, Guidance for Conducting and Use of Flight Standardization Board Evaluations.
• AC 20-191, Criteria for Airworthiness Approval of Low Visibility Takeoff and CAT II/III Approaches.
• AC 120-57, Surface Movement Guidance and Control System.
• AC 120-62, Takeoff Safety Training Aid.
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• AC 120-71, Standard Operating Procedures and Pilot Monitoring Duties for Flight Deck Crewmembers.
• AC 120-76, Guidelines for the Certification, Airworthiness, and Operational Use of Electronic Flight Bags.
• AC 120-91, Airport Obstacle Analysis.
• AC 120-105, Foreign Terminal Instrument Procedures (FTIP) Acceptance/Review.
• AC 121.195-1, Operational Landing Distances for Wet Runways; Transport Category Airplanes.
(2) FAA Orders:
• FAA Order 8400.13, Procedures for the Evaluation and Approval of Facilities for Special Authorization Category I Operations and All Category II and III Operations.
• FAA Order 8900.1, Flight Standards Information Management System (FSIMS).
• FAA Order 6750.16, Siting Criteria for Instrument Landing Systems.
• FAA Order 6750.24, Instrument Landing System and Ancillary Electronic Component Configuration and Performance Requirements.
• FAA Order JO 7110.65, Air Traffic Control.
• FAA Order 8260.3, United States Standard for Terminal Instrument Procedures (TERPS).
• FAA Order 8260.60, Special Instrument Procedures.
• RTCA DO-253, Minimum Operational Performance Standards for GPS Local Area Augmentation System Airborne Equipment.
• RTCA DO-359, Minimum Aviation System Performance Standards (MASPS) for Synthetic Vision Guidance Systems.
c. OpSpecs/MSpecs/LOAs:
• Standard OpSpecs Parts A and C.
• OpSpec C048, Enhanced Flight Vision System Operations.
• OpSpec/MSpec/LOA C051, Terminal Instrument Procedures.
• OpSpec C052, Straight-in Non-Precision, APV, and Category I Precision Approach and Landing Minima—All Airports.
• OpSpec C055, Alternate Airport IFR Weather Minimums.
• OpSpec C056, IFR Takeoff Minimums, Airplane Operations—All Airports.
• OpSpec C057, IFR Takeoff Minimums, 14 CFR Part 135 Airplane Operations—All Airports.
• OpSpec C060, Category II and Category III Instrument Approach and Landing Operations.
• OpSpec C061, Flight Control Guidance Systems for Automatic Landing Operations Other Than Categories II and III.
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• OpSpec C062, Manually Flown Flight Control Guidance System Certified for Landing Operations Other Than Categories II and III.
• OpSpec C078, IFR Lower Than Standard Takeoff Minima, Airplane Operations— All Airports.
• OpSpec C079, IFR Lower Than Standard Takeoff Minima, 14 CFR Part 135 Airplane Operations—All Airports.
• OpSpec D072, Aircraft Maintenance – Continuous Airworthiness Maintenance Program (CAMP) Authorization.
Par 2-1 Page 7 (and 8) CHAPTER 2. BACKGROUND
2-1. OPERATIONAL AUTHORIZATIONS VERSUS AIRWORTHINESS DEMONSTRATIONS. Takeoff and approach weather minima are approved through applicable operating rules, use of approved instrument procedures, and issuance of operations specifications (OpSpecs), management specifications (MSpecs), and letters of authorization (LOA).
Airworthiness demonstration of aircraft equipment is usually accomplished 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 may change after airworthiness demonstrations are conducted, additional operational credit may be applied. In general, information related to operational approvals is contained in the main body of this AC and criteria related primarily to the airworthiness demonstration of systems or equipment is contained in AC 20-191.
2-2. EXPLANATION OF TERMS. A comprehensive list of definitions pertinent to this AC is included in Appendix 1. Within this AC, RVR values are specified in units of feet unless otherwise noted. A conversion table may be found in OpSpec C051. Minima typically used during LVO are provided in the appropriate OpSpecs.
2-3. APPROACH TERMINOLOGY. Terminology used in this AC is consistent with current OpSpecs, MSpecs, and LOAs. Definitions of instrument approach categories are listed in Appendix 1, Definitions and Acronyms. While there are slight variations of these definitions as used within International Civil Aviation Organization (ICAO) and various countries internationally, the broad objectives and practical operational applications are similar. Also, in certain states, lowest authorized minima may be slightly different than as specified by the U.S. or ICAO criteria. 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.
Par 3-1 Page 9 CHAPTER 3. OPERATIONAL CONCEPTS
3-1. INSTRUMENT OPERATIONS. This AC addresses operational authorization for terminal instrument operations using ground-based Navigational Aids (NAVAID) or space-based NAVAIDs augmented by ground-based equipment. These operations include takeoff in lower-than-standard visibility conditions, Category (CAT) I, CAT I Landing Minima with Reduced Lighting (Runway Visual Range (RVR) 1800), Special Authorization (SA) CAT I, CAT II, SA CAT II, and CAT III. Some of these operations require special aircrew and aircraft certification. These operations are collectively referred to as AWO throughout the course of this document.
a. Airborne Systems. Basic airworthiness certification for instrument flight rules (IFR) is typically considered acceptable for operational approval of an aircraft for standard CAT I.
However, CAT II and III airborne system requirements, as well as those for takeoff guidance systems used for lower-than-standard minima, are specified in AC 20-191. Airborne systems intended to meet CAT I Landing Minima with Reduced Lighting (RVR 1800) and SA CAT I/II requirements, while not addressed in AC 20-191, are specified in paragraph 3-7 below.
(1) For aircraft intended for AWO operations and previously approved using AC 120-29 and/or AC 120-28, the airworthiness criteria for airborne systems specified in the approved Airplane Flight Manual (AFM) are still valid.
(2) Airborne equipment listed in AC 20-191 must be operative in accordance with provisions of applicable standard operations specifications (OpSpecs). Airframe manufacturers and individual operators may also include other optional equipment as part of the CAT II/III configuration; however, that equipment does not need to be operative to conduct a CAT II/III approach unless required by that operator's OpSpecs and consistent with the FAA-approved minimum equipment list (MEL).
b. Magnetic Variation (MagVar) Data and Onboard Database. Issues with MagVar primarily occur when the MagVar data being used internally in the aircraft is not close enough to the current MagVar at a location, or when it is not close enough to the MagVar used in the approach procedure.
(1) Some avionics convert true heading references to magnetic heading references by using worldwide MagVar data contained in an onboard database. Algorithms convert the data into a specific magnetic heading reference for a specific geographic reference point. However, since the Earth’s magnetic fields constantly change, MagVar databases need periodic updates to provide accurate magnetic heading references. The National Oceanic and Atmospheric Administration (NOAA) offers a World Magnetic Model available at http://www.ngdc.noaa.gov/geomag/geomag.shtml. This product is one acceptable source for MagVar information.
(2) The MagVar update is generally only critical for CAT II/III operations, coupled approach, and practice autoland CAT I operations. When flying these procedures, the aircraft systems construct a track in True, used for guidance during rollout and as a cross check on final, apply MagVar from the onboard source(s), and compare the resulting magnetic course to the
Par 3-1 Page 10 published Final Approach Course (FAC). If the difference is greater than some predetermined value (typically three or four degrees) the system may flag or disengage the autopilot. The difference between the onboard source and the published procedure may be in the opposite direction from the current MagVar at the location, one leading and one lagging. Therefore, the total amount of difference must be considered, not just the difference from the current local MagVar.
(3) Aircraft design approval holders should identify any operating limitations of their aircraft associated with application of the MagVar data to ensure sufficiently accurate magnetic heading references are presented and used in the aircraft. Consider at least the following in determining the operating limitations: the error characteristics of magnetic heading references, especially where local magnetic anomalies occur or in regions of high magnetic field inclination or high secular rates of change; intended operation (instrument landing system (ILS) approach, automatic landing, en route navigation, display of course/track to the pilot, etc.); errors in the magnetic reference of any radio navigation aid used; and/or the accuracy of the magnetic reference of the procedure. Operational limitations need to be re-evaluated commensurate with the intended use and the dynamics of error associated with the magnetic heading reference.
Conditions under which operations do not meet the intended function must be clearly identified.
(4) Avionics may use values other than the Localizer (LOC) MagVar, such as the aerodrome magnetic or the on aerodrome NAVAID, or a calculated value, as the onboard source.
Also, some aircraft have more than one onboard source of MagVar data, which may cause an internal MagVar disagreement when one database is updated and the other is not. This internal disagreement may cause flags and disconnects. Some aircraft seem to experience problems only when there is a strong crosswind. The MagVar on the aerodrome diagram is not related to instrument procedures, and is updated on a different schedule. Therefore, it should not be used in any determination of coupled approach and autoland capability.
(5) While issues with MagVar have occurred mostly at aerodromes with a high rate of change, most of which are located at higher latitudes, they can occur at any location where the onboard MagVar data and the published procedures are further apart than the avionics tolerance.
Operators should consult manufacturer guidance concerning the onboard MagVar database and its suitability for autoflight and autoland at aerodromes they intend to operate. The aircraft design approval holders’ continuing airworthiness requirements must define the conditions under which the MagVar database and, if applicable, conversion algorithms or hardware, must be updated. This could be contained in a periodic airplane flight manual update or other Original Equipment Manufacturer (OEM) documentation. These requirements should also define the maintenance procedures necessary to update the onboard MagVar database for their avionics.
(6) In some instances, Notices to Airmen (NOTAM) may contain MagVar restrictions.
A change in the ILS procedure or aerodrome MagVar should be evaluated to determine whether autoflight is still supported with the current onboard MagVar data. Also, updating the onboard data may cause issues at an aerodrome where the procedure MagVar has not been updated. When conducting autoflight and autoland operations at any new aerodrome, it is therefore imperative that flightcrews should use caution. Company/operator training and procedures should adequately cover this potential issue.
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c. Airborne Databases and Interface. It is highly recommended that all airborne databases (e.g., Terrain Awareness and Warning System (TAWS), Enhanced Ground Proximity Warning System (EGPWS), Synthetic Vision Guidance System (SVGS)) be current with the intended area of operation for AWO operations. Terrain, runway, and obstacle database requirements must support the intended function. Valid and compatible databases for SVGS must be installed and contain current data. Refer to AC 20-153 for guidance on the importance of database currency and integrity. Additionally, to ensure continued airworthiness and nuisance-free operation, airborne equipment used for approach operations should be compatible with systems using airborne databases.
3-2. TAKEOFF.
a. Takeoff Minima. Takeoff minima are addressed by §§ 91.175(f), 91.1039; §§ 121.649,
121.651; 125.381; § 135.225 and standard OpSpecs; MSpecs and/or letters of authorization (LOA).
(1) When lower-than-standard minima are necessary, applicable criteria for use of those OpSpec minima are specified in this AC. When appropriate, principal operations inspectors (POI) issue OpSpecs specifying the lower minima through paragraph C056 and C078 for part 121 and 125 operators and OpSpecs paragraphs C057 and C079 for part 135 operators.
OpSpecs specifying the lower minima through paragraph C056 may be issued to part 129 operators. OpSpecs/MSpecs or LOAs contain specific guidance regarding pilots, aircraft, and airports when lower-than-standard takeoff minima are used. Authorization of takeoff minima below the level supported by use of visual reference alone requires the use of a guidance system that has been demonstrated to provide an acceptable level of performance and satisfactory workload for the minima approved, with or without the use of visual reference. The performance and workload assessment of such a system must have considered any compensation that may be introduced by the pilot for particular guidance system characteristics (e.g., coping with a slight LOC signal offset during initial runway alignment) or concurrent use of the guidance system with limited or patchy visual references.
(2) Provisions for demonstration of systems eligible for takeoff minima below the level supported by use of visual reference alone may be found in AC 20-191.
(3) An NTD is necessary for initial authorization of takeoff minima less than RVR 300.
b. Pilot Assessment of Equivalent RVR. For takeoff circumstances where touchdown zone (TDZ) RVR is inoperative or is determined by the pilot to be significantly in error
(e.g., patchy fog obscuring an RVR Visibility Sensor (VS) but not the runway, snow on transmissometer causing erroneous readings), operators may be authorized to make a pilot assessment in lieu of RVR (see subparagraph 6-4c.).
(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 which is specified to ensure adequate visual reference for the takeoff.
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(2) When any pilot assessment of equivalent RVR is made, the pilot must be able to positively determine position on the airport, the correct runway, and positively establish that the aircraft is at the correct position for initiation of takeoff. A pilot may assess visibility at the takeoff position in lieu of reported TDZ RVR (or equivalent) in accordance with OpSpec C078/C079 and subparagraph 6-4c.
3-3. LANDING.
a. Approach and Landing Concepts.
(1) CAT I operations are considered to be any Standard Instrument Approach Procedure (SIAP) with a decision altitude (DA) or minimum descent altitude (MDA) greater than or equal to 200 feet height above touchdown (HAT) and a visibility requirement greater than or equal to RVR 1800.
NOTE: With SA, CAT I minima below RVR 1800 and 200 feet HAT may be authorized via OpSpec, MSpec, or LOA (See subparagraph (4) below).
NOTE: For enhanced flight vision system (EFVS) considerations during CAT I approach operations to reduced visibilities, refer to AC 90-106.
(2) CAT II operations are considered to be any SIAP with a DA/decision height (DH) or visibility requirement less than that specified for CAT I, but greater than or equal to 100 feet HAT and RVR 1000.
(3) CAT III operations are considered to be any SIAP with a DH less than that specified for CAT II (or with no DH, or with an Alert Height (AH)) and a visibility less than that specified for CAT II).
(4) SA CAT I/II operations described in this AC are considered nonstandard with respect to minima historically associated with their approach category. These operations may require additional aircraft equipment and aircrew qualifications, and may allow the use of runways with less than the normal lighting facilities required for their approach category.
(See subparagraphs 3-7e and f for further guidance).
(5) CAT II operations are restricted by standard OpSpec C060 authorizations to be flown using a Head-Up Display (HUD), an autopilot coupled to DH, or an autoland system.
However, if an operator of aircraft with advanced approach and landing systems desires the option of flying a manual approach using head-down guidance (e.g., flight director (F/D)), nonstandard OpSpec language authorizing this is required and additional operating restrictions and pilot training may be required.
(6) Additional demonstration or operational assessment beyond that required for basic IFR flight, under provisions of basic aircraft part 25, typically is necessary for operational authorization of an aircraft for CAT II/III. For CAT II/III 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 CAT II/III authorization (e.g., electrical component failure or engine inoperative CAT II/III). For failures other than those addressed by
Par 3-3 Page 13 the CAT II/III 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. Specific criteria for airworthiness demonstration of systems or capabilities for CAT II/III are included in AC 20-191.
b. Acceptable Instrument Approach Procedure (IAP) Basis. IAPs used by operators in accordance with this AC should be based on:
(1) U.S. SIAPs (i.e., 14 CFR part 97 instrument procedures designed to conform to Order 8260.3 and other related 8260 series orders).
(2) For non-U.S. airports, foreign IAPs acceptable to FAA promulgated by the state of the airport of landing (i.e., International Civil Aviation Organization (ICAO), State of the Aerodrome). Refer to AC 120-105.
(3) Terminal IAPs at U.S. Military airports, regardless of their physical location
(e.g. Ramstein Air Base in Germany), when authorized by the Department of Defense (DOD) and the terminal instrument procedure are constructed using criteria based on Order 8260.3;
ICAO Document 8168-OPS, Procedures for Air Navigation Services—Aircraft Operations (PANS-OPS), Volume II; or Military Instrument Procedures Standardization (MIPS); or other special criteria approved by the Flight Technologies and Procedures Division.
(4) Special IAPs developed and approved by the FAA.
(5) Special IAPs developed by an FAA-approved third party and approved by FAA.
c. Considerations for the Use of Procedures Other Than U.S. Standard Procedures.
For procedures other than those developed in accordance with Order 8260.3 or other pertinent FAA 8260 series orders, 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 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 navigation facilities used);
(5) Suitability of ground systems/equipment (e.g., lighting, RVR sensors, and pilot control of lighting);
(6) Suitability of NAVAIDs (e.g., maintenance and monitoring);
(7) Suitability of airport/runway (e.g., obstructions, clear zones, and markings);
(8) Availability of Aeronautical Information (AI) (e.g., timely NOTAM availability);
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(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.
d. Special IAPs. Special procedures are approved by the Flight Technologies and Procedures Division and issued/authorized by the POI after coordination with pertinent FAA organizations (refer to AC 90-112). Operator requests for the use of special procedures should be coordinated by the POI with the Flight Standards office having responsibility for the airport of the procedure. If applicable, these special procedures should address any provisions associated with application of § 121.445 for special airport qualification.
e. Glide Path Angle (GPA) and Vertical Descent Angle (VDA). Operators must consult the FAA-approved AFM for aircraft limitations which may apply to use of GPAs and/or VDAs other than standard.
(1) CAT I straight-in approaches are normally constructed with a standard GPA or VDA of 3.0° whenever practical. Standard GPAs should not be less than 3.0° and should not exceed the values stipulated in Table 3-1, Maximum Standard Approach Design Glide Path Angles/Vertical Descent Angles. Standard VDAs should not be less than 2.75° and should not exceed the values stipulated in Table 3-1.
TABLE 3-1. MAXIMUM STANDARD APPROACH DESIGN GLIDE PATH
ANGLES/VERTICAL DESCENT ANGLES CAT Maximum Angle A (80 knots or less) 6.40 A (81-90 knots) 5.70 B 4.20 C 3.77 D 3.50 E 3.10* *USAF/USN CAT E maximum is 3.50°
(2) SA CAT I/II and CAT II/III approaches are constructed with a standard GPA of
3.0°. U.S. domestic approach angles for SA CAT I/II and CAT II/III approaches other than 3.0° require approval of the Flight Technologies and Procedures Division.
f. Steep Angle Approach. A procedure with a GPA or VDA at or above 4.5° is considered to be a steep angle approach for operations using transport category airplanes. Refer to AC 25-7 for detailed guidance on required certification and AFM documentation. The use of any steep approach will require specific AFM supplemental information including operational procedures and restrictions, any limitations, airplane configurations (e.g., flaps, gear, inoperative engines, etc.), performance information, as well as any flightcrew training necessary.
Par 3-3 Page 15 Historically, some airport authorities may also require a letter of written approval from the certificating body. Authorization will be required for the use of a non-part 97 or non-PANS-OPS procedure (refer to Order 8260.60 and AC 90-112). Contact the responsible Flight Standards office for further guidance.
3-4. ENGINE INOPERATIVE CAT II/III. See Appendix 2, Engine Inoperative Category (CAT) II/III Approach Operations.
3-5. GO-AROUND SAFETY. A multiengine aircraft conducting an instrument approach should be capable of safely executing a go-around from any point on an approach prior to touchdown with the aircraft in both normal and specified non-normal configurations (e.g., engine out). This capability is necessary to provide for go-around safety due to missed approaches or rejected landings for a variety of circumstances.
a. CAT I Go-Around. Pilots must be aware that after the aircraft has passed the DA/DH or missed approach point (MAP), the published missed approach does not guarantee standard missed approach obstacle clearance. Pilot preplanning for such non-normal events is discussed further in the Aeronautical Information Manual (AIM).
b. CAT II/III Go-Around. The evaluation of this capability is based on normal or specified non-normal CAT III operations at the lowest controlling RVR authorized. This should account for factors related to geometric limitations during the transition to go-around, limited visual cues, autopilot mode switching, and other pertinent factors. For aircraft in which a go-around from a very low altitude may result in touchdown, the safety of such a procedure should be established considering its effect on related systems. This includes operation of auto spoilers, automatic braking systems, autopilot mode switching, auto-throttle mode, reverse thrust initiation, and other systems affected by a low altitude go-around. Except for failure conditions shown to be extremely improbable, a safe go-around must be possible from any point on the approach.
c. Automatic Go-Around. If an automatic go-around capability is provided, it should be demonstrated that a go-around can be safely initiated and completed from any point on an approach prior to touchdown. If the automatic go-around mode can be engaged at or after touchdown, it should be shown to be safe. The ability to initiate an automatic go-around at or after touchdown is not required.
3-6. REQUIREMENTS FOR CAT I OPERATIONS.
a. General Requirements. In general, authorization for standard CAT I operations do not require airworthiness, maintenance, equipage, qualification, or training provisions beyond those required for basic IFR operations under the appropriate 14 CFR part (e.g. part 91, 121) and appropriate for the type of operation being flown. However, parts 121, 125, 129, and 135 operators may only conduct CAT I instrument approaches in accordance with the minima and procedures set forth in their OpSpecs, which should be completed in accordance with Chapter 8 and/or Chapter 9.
b. CAT I Landing Minima with Reduced Lighting (RVR 1800). These operations differ from standard CAT I by allowing for reduced runway lighting requirements (CL and TDZ lights
Par 3-6 Page 16 not required), mitigated by the use of additional onboard equipment. Along with any applicable equipment otherwise specified for CAT I, these operations require an F/D, autopilot, or HUD approved for at least CAT I. The equipment used must provide course and glide path guidance to the DA or until initiation of a missed approach. When authorized by an OpSpec, commercial operators may conduct these operations where designated by a note on a SIAP or on regular RVR 1800 approaches when installed CL and/or TDZ lighting is inoperative. Commercial single-pilot operations are prohibited from using the F/D to conduct these operations without the accompanying use of an AP or HUD.
3-7. REQUIREMENTS FOR OPERATIONS BELOW RVR 1800 TO 1000.
a. General Requirements.
(1) Flightcrew training and qualification consistent with provisions of Chapter 5 for these operations have been completed;
(2) Appropriate NAVAIDs and airport/lighting facilities for the procedures to be flown should be consistent with Chapter 6 of this AC;
(3) With the exception of SA CAT I-only operations, an acceptable continuing airworthiness/maintenance program for the airborne system is provided in accordance with Chapter 7; and
(4) An operational authorization has been completed in accordance with Chapter 8 for a U.S. operator or Chapter 9 for a non-U.S. operator.
NOTE: See Table 3-2, Special Authorization Category II and Category II Minima Matrix, for associated approach RVR minima.
b. Specification of CAT II DA/DH. The lowest authorized DA/DH is cited in this paragraph as an equivalent DH related to height above TDZ elevation (e.g., HAT value of 100 feet). This is done even though operational minima for these operations are typically specified as an equivalent DH value based on radio altitude height above the underlying approach terrain. While a DA is conceptually not precluded for use with CAT II, DAs are not routinely used for these operations, except as a backup for inner marker (IM)-based minima when irregular terrain precludes reliable radio altimeter use to determine minima.
c. Eligibility for CAT II Minima Not Less Than 100 Feet DA/DH. Instrument approach operations that may be authorized CAT II minima currently include only ILS. The FAA may authorize CAT II operations based on Ground Based Augmentation System (GBAS) Landing System (GLS) at a future date.
d. Use of IM. Use of the IM or approved substitute may be authorized in lieu of a DA/DH.
An IM is typically used at runways designated by the applicable procedure, such as where radio altimeter (RA) use is limited or Not Authorized (NA) due to irregular underlying terrain
(e.g., RA NA).