AC 27-1B, Chg 4 2/27/2014 reducing spatial envelopes around obstacles and the resulting warning times may lead to flight unnecessarily close to obstacles.
(4) The applicant should perform sustained standard rate turns, climbs, and descents to evaluate:
• Symbol stability.
• Flicker.
• Jitter.
• Display update rate.
• Color cohesiveness.
• Readability.
• The use of color to depict relative elevation data.
• Caution and warning alert area depictions.
• Normal mode.
• Reduced Protection mode if installed.
• Map masking.
• Overall suitability of the display.
(5) Perform compatibility evaluation of HTAWS equipment lighting with previous NVIS lighting modifications and NVG compatibility that could not be evaluated during ground test.
(6) Perform EMI and EMC testing, and VHF harmonic tests for HTAWS with internal GPS receivers that could not be evaluated during ground test.
k. Rotorcraft Flight Manual (RFM) or RFMS. The applicant should make an evaluation to determine if there are any limitations of the system and, if so, how they will affect rotorcraft operations. Any limitations affecting operations should be included in the RFM or RFMS. As a minimum, the applicant should provide instructions in the Limitations Section of the RFM or RFMS that include the following, as appropriate:
(1) Limitations. The following instructions should be included in the Limitations section of the RFM or RFMS:
(i) Navigation must not be predicated upon the use of the HTAWS information.
Note: The terrain and obstacle display is intended to serve as a terrain and obstacle awareness tool only. The display and database may not provide the accuracy or fidelity on which to base routine navigation decisions and plan routes to avoid terrain or obstacles.
(il) The status of the inclusion of power lines in the obstacle database must be stated.
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(iii) Reduced protection mode must not be selected when operating under IMC conditions except as required when performing offshore platform IFR approach procedures or other special IFR procedures.
(2) Operational Considerations for Normal and Abnormal Procedures. In addition to the HTAWS operational procedures, consider the following:
(i) Terrain or Obstacle Caution Alert. When this alert occurs, verify the rotorcraft flight path and correct it, if required.
(ii) Terrain or Obstacle Awareness Warning Alert. When this alert occurs, immediately initiate a maneuver that will provide maximum terrain or obstacle clearance, until all warning alerts cease.
(ili) Inhibit. For those installations that include the ability to inhibit all or some of the HTAWS audio alerts, the RFM (or RFMS) should address:
(A) When should the audio inhibit function be used?
(B) What alerts are inhibited?
(C) How long the alerts are inhibited?
(D) How to re-establish the alerts?
I. Instructions for Continued Airworthiness. CAs are required by 14 CFR 27.1529, as appropriate and in accordance with part 27 Appendix A. In addition to Appendix A requirements, the applicant should indicate when and how the terrain and obstacle databases need to be updated.
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AC 27-1B, Chg 4 2/27/2014 Page MG 18 - 14
CHAPTER 3
AIRWORTHINESS STANDARDS
NORMAL CATEGORY ROTORCRAFT
MISCELLANEOUS GUIDANCE (MG) AC 27 MG 19. GUIDANCE ON ELECTRONIC DISPLAY SYSTEMS (EDS) FOR ROTORCRAFT
INSTALLATIONS
a. Background.
(1) The increased use of microprocessor technology in avionic systems has resulted in the use of computer-generated graphics to replace conventional electromechanical instruments required by 14 CFR
27.1303 to present information to the pilots. Simple systems use electronic displays to replace electromechanical horizontal situation indicators (HSI) and attitude direction indicators (ADI). Other electronic displays combine ADI and HSI displays on one display. These electronic display systems (EDS) normally include a primary flight display (PFD) displaying primary flight information (attitude, airspeed, altitude, vertical speed and basic navigation course deviation indication (CDI) and for precision or precision-like approaches, vertical deviation indications (VDI)). EDS can include multi-function displays and engine indication caution advisory system (EICAS) displays. Additionally, some EDS also incorporate flight management system logic, which increases the level of integration complexity.
(2) The EDS for which approval is sought must meet the minimum performance standards prescribed in the corresponding technical standard order (TSO) for the features the system provides (e.g., airspeed, attitude, flight guidance, color, symbology, operation, and accuracy). Information pertaining to the flight director function performed by the EDS can be found in section 27.1335 of this AC. Information pertaining to the location of the displays is contained in section 27.1321 of this AC. Additional discussion of the recommendations for an EDS is contained in the latest versions of AC 25-11, Electronic Flight Deck Displays and AC 23.1311-1, Installation of Electronic Display in Part 23 Airplanes. There should be an evaluation of the integration of EDS into existing cockpits along with previously installed avionics and autoflight systems to ensure the resulting pilot-system interface does not increase pilot workload or reduce system safety margins.
b. Reference Materials.
(1) Regulatory and Guidance material.
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AC 27-1B, Chg 7 2/4/2016
(i) Relevant 14 CFR part 27 regulations:
Sections Title § 27.771 Pilot compartment.
§ 27.773 Pilot compartment view.
§ 27.711 Cockpit controls.
§ 27.1301 (Equipment) Function and installation.
§ 27.1303 Flight and navigation instruments.
§ 27.1305 Powerplant instruments.
§ 27.1309 Equipment, systems, and installations.
§ 27.1317 High-intensity Radiated Fields (HIRF) Protection.
§ 27.1321 Arrangement and visibility.
§ 27.1322 Warning, caution, and advisory lights.
§ 27.1323 Airspeed indicating system.
§ 27.1329 Automatic pilot system.
§ 27.1335 Flight director systems.
§ 27.1337 Powerplant instruments.
§ 27.1351 (Electrical Systems and Equipment) General.
§ 27.1353 Storage battery design and installation.
§ 27.1357 Circuit protective devices.
§ 27.1361 Master switch.
§ 27.1365 Electric cables.
§ 27.1367 § 27.1381 Instrument lights.
§ 27.1501 (Operating Limitations and Information) General.
§ 27.1523 Minimum flight crew.
§ 27.1525 Kinds of operations.
§ 27.1529 Instructions for Continued Airworthiness.
§ 27.1541 (Markings and Placards) General.
§ 27.1543 Instrument markings: General.
§ 27.1545 Airspeed indicator.
§ 27.1549 Powerplant instruments.
§ 27.1551 Oil quantity indicator.
§ 27.1553 Fuel quantity indicator.
§ 27.1555 Control markings.
§ 27.1559 Limitations placard.
§ 27.1581 (Rotorcraft Flight Manual and Approved Manual Material) General.
§ 27.1583 Operating limitations.
§ 27.1585 Operating procedures.
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(ii) Other relevant 14 CFR regulations:
Sections Title § 91.205 Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment requirements.
§ 135.149 Equipment requirements: General.
§ 135.159 Equipment requirements: Carrying passengers under VFR at night or under VFR over-the-top conditions.
§ 135.163 Equipment requirements: Aircraft carrying passengers under IFR.
(il) Advisory Circulars, TSOs, Orders, Policy.
The ACs, Order, and policy memoranda are available on the FAA website: www.faa.gov. Copies of current editions of the following publications may be obtained free of charge from the U.S.
Department of Transportation, Subsequent Distribution Office, M-30, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, MD 20785.
Document Title AC 20-88A Guidelines on the Marking of Aircraft Powerplant Instruments (Displays) AC 20-115C Airborne Software Assurance AC 20-136B Aircraft Electrical and Electronic System Lightning Protection AC 20-138C Airworthiness Approval of Positioning and Navigation Systems AC 20-152 RTCA, Inc., Document RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware AC 20-167 Airworthiness Approval of Enhanced Vision System, Synthetic Vision System, Combined Vision System, and Enhanced Flight Vision System Equipment AC 21-16G RTCA Document DO-160 versions D, E, F, and G, "Environmental Conditions and Test Procedures for Airborne Equipment" Airworthiness Guidance for Rotorcraft Instrument Flight Appendix B Certification Procedure For Rotorcraft Avionics Equipment.
Systems Certification Considerations AC 27-1 MG 18 Helicopter Terrain Awareness and Warning System (HTAWS) Operational Use and Modification of Electronic Checklists AC 120-76B Guidelines for the Certification, Airworthiness, and Operational Use of Electronic Flight Bags Order 8110.49 Software Approval Guidelines Page MG 19 - 3
AC 27-1B, Chg 7 2/4/2016
(iv) Industry and Other Technical Documents.
(A) Radio Technical Commission for Aeronautic (RTCA) Documents:
Document Title RTCA/DO- Environmental Conditions and Test Procedures for 160G Airborne Equipment RTCA/DO-178B & C Software Considerations in Airborne Systems and Equipment Certification RTCADO-187 Minimum Operational Performance Standards for Airborne Area Navigation Equipment using Multi-Sensor Inputs RTCA/DO-200A Standards for Processing Aeronautical Data RTCA/DO-201A Standards for Aeronautical Information RTCA/DO-254 Design Assurance Guidance for Airborne Electronic Hardware RTCA/DO-257A Minimum Operational Performance Standards for the Depiction of Navigation Information on Electronic Maps RTCA/DO-267A Minimum Aviation System Performance Standards (MASPS) for Flight Information Services-Broadcast (FIS-B) Data Link (B) Society of Automotive Engineers, International (SAE) Documents (use the current versions). The following SAE documents are available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, or from their website at www.sae.org.
Document Title ARP 926B Fault/Failure Analysis Procedure AIR 1093A Numeral, Letter and Symbol Dimensions for Aircraft Instrument ARP 1782B Photometric and Colorimetric Measurement Procedures for Airborne Direct View CRT Displays ARP 1834A Fault/Failure Analysis for Digital Systems and Equipment ARP 4032B Human Engineering Considerations in the Application of Color to Electronic Aircraft Displays ARP Pilot System Integration 4033 ARP 4067 Design Objectives for CRT Displays for Part 23 Aircraft ARP 4101 Flight Deck Layout and Facilities ARP 4102 Flight Deck Panels, Controls, and Displays ARP 4102/7 Electronic Displays ARP 4103 Flight Deck Lighting for Commercial Transport Aircraft ARP 4105C Abbreviations, Acronyms, and Terms for Use on the Flight Deck ARP 4155A Human Interface Design Methodology for Integrated Display Symbology ARP 4256A Design Objectives for Liquid Crystal Displays for Part 25 (Transport) Aircraft ARP 4260A Photometric and Colorimetric Measurement Procedures for Airborne Flat Panel Displays ARP 4754A Guidelines for Development of Civil Aircraft and Systems ARP 4761 Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment Page MG 19 -4
Document Title ARP 5289A Electronic Aeronautical Symbols ARP 5364 Human Factor Considerations in the Design of Multifunction Display Systems for Civil Aircraft ARP 5365 Human Interface Criteria for Cockpit Display of Traffic Information AS 8034B Minimum Performance Standard for Airborne Multipurpose Electronic Displays AS 8055 Minimum Performance Standard for Airborne Head Up Display (HUD) ARD 50017 Aeronautical Charting ARD 50062 Human Factors Issues Associated With Terrain Separation Assurance Display Technology (C) Other Documents.
Document Title DOT/FAA/CT- Human Factors Design Standard For Acquisition of 03/05 Commercial Off-The-Shelf Subsystems, Non- Developmental Items, and Developmental Systems.
DOT/FAA/AM-13- Multi-Function Displays: A Guide for Human Factors Evaluation 21 DOT/FAA/AAR- FAA Aircraft Certification Human Factors and Operations 95/3 Checklist for Standalone GPS Receivers ICAO 8400/5- Procedures for Air Navigation Services ICAO Abbreviations and 1999 Codes Page MG 19 - 5
AC 27-1B, Chg 7 2/4/2016
(v) Miscellaneous Documents.
Note: The part 23 and part 25 ACs and the GAMA publications listed below are not intended to serve as means of compliance for part 27 requirements. However, these documents may contain usetul reference information that may be acceptable to the certificating authority on rotorcraft certification projects. When referencing these documents, ensure part 27 requirements are adequately addressed, particularly for part 27 FR certifications. Coordinate early with the certificating authority if part 23, 25, or GAMA guidance is proposed to be used.
Document Title PS-ACE100-2001-004 Guidance for Reviewing Certification Plans to Address Human Factors for Certification of Part 23 Small Airplanes AC 23-23 Standardization Guide For Integrated Cockpits In Part 23 Airplanes AC 23.1311-1C Installation of Electronic Display in Part 23 Airplanes AC 25-11B Electronic Flight Deck Displays AC 25.1322-1 Flightcrew Alerting GAMA Pub 10 (Version 1.0) Recommended Practices and Guidelines for Part 23 Cockpit/Flight Deck Design GAMA Pub 12 (Version 2.0) Recommended Practices and Guidelines for an Integrated Cockpit/Flightdeck in a Part 23 Airplane
(2) Acronyms and Descriptions.
(i) Acronyms:
Acronym Description AC Advisory Circular ACO Aircraft Certification Office ADC Air Data Computer ADI Attitude Director Indicator ADDS Aviation Digital Data Service AFM Aircraft Flight Manual AFMS Aircraft Flight Manual Supplement AHRS Attitude Heading Reference System ARD Aerospace Research Document ARP Aerospace Recommended Practice AS Aerospace Standard ASTC Amended Supplemental Type Certificate CA Certification Authority (ies) CAR Civil Air Regulations CFR Code of Federal Regulations CIP Current Icing Potential CS Certification Standard (EASA) Page MG 19 -6
Acronym Description EADI Electronic Attitude Direction Indicator EHSI Electronic Horizontal Situation Indicator EICAS Engine Indication and Crew Alert System ELOS Equivalent Level of Safety EVS Enhanced Vision Systems FAA Federal Aviation Administration FD Flight Director FHA Functional Hazard Assessment FLS Field-Loadable Software FMEA Failure Modes and Effects Analysis FOV Field-Of-View GPS Global Positioning System HIRE High Intensity Radiated Fields HUD Head-Up Display HSI Horizontal Situation Indicators ICAO International Civil Aviation Organization JER Instrument Flight Rules ILS Instrument Landing System IMC Instrument Meteorological Conditions JAR Joint Aviation Requirements LCD Liquid Crystal Displays LED Light Emitting Diodes LNAV Lateral Navigation (Used with GPS) LPV Localizer Performance with Vertical Guidance (Used with GPS) METAR Meteorological Aviation Report MFD Multifunction Flight Display MG Miscellaneous Guidance ND Navigation Display PFD Primary Flight Display PFI Primary Flight Information POH Pilot's Operating Handbook RAIM Receiver Autonomous Integrity Monitoring (used with GPS) SAE Society of Automotive Engineers STC Supplemental Type Certificate SVS Synthetic Vision Systems Page MG 19 - 7
AC 27-1B, Chg 7 2/4/2016 Acronym Description TAS Traffic Advisory System HTAWS Helicopter Terrain Awareness Warning System TC Type Certificate TCAS Traffic Alert and Collision Avoidance System TSO Technical Standard Order VOR Very High Frequency Omnidirectional Range VER Visual Flight Rules VMC Visual Meteorological Conditions WAAS Wide Area Augmentation System
(ii) Definitions. This paragraph contains definitions for terms used in this guidance. For the purposes of this guidance, a "display system" includes not only the display hardware and software components, but also the entire set of avionic devices implemented to display information to the flightcrew. Hardware and software components of other systems that affect displays, display functions, or display controls have to take into account the display aspects of this guidance. For example, this guidance would be applicable to a display used when setting the barometric correction for the altimeter, even though the barometric set function may be part of another system.
Accuracy: A degree of conformance between the estimated or measured value and the true value.
Adverse Operating Condition: A set of environmental or operational circumstances applicable to the aircraft, combined with a failure or other emergency that results in a significant increase in normal flight crew workload.
Certification authority: The guidance in this FAA AC has been harmonized with that of Transport Canada and EASA. The certification authority is that agency to which an applicant applies for airworthiness certification of their product. The term also applies when an applicant wishes to have a product validated in the U.S., Canada, or Europe.
Component: Any self-contained part, combination of parts, subassemblies, or units that perform a distinct function necessary for the operation of the system.
- Continued Safe Flight and Landing: This phrase means that the aircraft is capable of continued controlled flight and landing, possibly using emergency procedures, without requiring exceptional pilot skill or strength. On landing, some aircraft damage may occur because of a Failure Condition.
- Conventional: A system is considered "conventional" if its function, the technological means to implement its function, and its intended usage are all the same as, or closely similar to, that of previously approved systems that are commonly used. The systems that have established an adequate service history and the means of compliance for approval are generally accepted as "conventional."
- Critical: A function whose loss or failure to properly perform would prevent the continued safe flight and landing of the aircraft. Note: The term "Critical Function" is associated with a Catastrophic Failure Condition. Newer documents may not refer specifically to the term "Critical Function."
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Criticality: The level of hazard associated with loss or malfunction of a system function, hardware, software, etc., either alone, in combination with other systems, or in combination with events external to aircraft systems.
- Design-Eye Box: A three-dimensional volume of space surrounding the Design Eye Reference Point used to determine the acceptability of display and control locations.
Design-Eye Reference Point: A designer-selected single reference point in space where the assumed midpoint location is between the pilot's eyes when seated properly at the pilot's station.
Development Assurance: All planned and systematic actions used to substantiate, to an adequate level of confidence, that the system satisfies the applicable certification basis after correction of the identified errors in requirements, design, and implementation.
- Enhanced Vision System: An electronic means to provide a display of the forward external scene topography (the natural or manmade features of a place or region), especially in a way to show their relative positions and elevation, through the use of imaging sensors such as a forward looking infrared, millimeter wave radiometry, millimeter wave radar, and low light level image intensifying.
- Failure: An occurrence that affects the operation of a component, part, or element such that it can no longer function as intended. This includes both loss of function and malfunction. Errors may cause failures, but they are not considered failures.
Failure Condition: A condition having a direct or consequential effect on the aircraft, its occupants, or both, and that is caused or contributed to by one or more failures or errors. Failure Conditions may be classified according to their severity. See section 27.1309 of this AC for more information on failure conditions.
Field-of-View: The angular extent of the display viewable with either pilot's eye when seated at the pilot's station. See figures AC 27 MG 19-1 and AC 27 MG 19-2 for more information on the field-of view.
Function: The lowest defined level of a specific action of a system, equipment, or flight crew performance aboard the aircraft that, by itself, provides a complete recognizable operational capability (for example, an aircraft heading is a function). One or more systems may contain a specific function or one system may contain multiple functions.
- Functional Hazard Assessment: A systematic, comprehensive examination of aircraft and system functions to identify potential Failure Conditions that will have an impact on the aircraft, the flight crew, or the occupants.
- Fix: A generic name for a geographical position also referred to as a waypoint, intersection, reporting point, etc.
Flight Plan: A sequence of fixes interconnected by the desired path. Flight plans may range from the simplest that include only the aircraft's present position, the active waypoint, and the desired path in between, to more complicated plans that include departure and destination airports with multiple intermediate fixes.
- Hardware: An object that has physical being. Generally refers to circuit cards, power supplies, etc.
Hazard: Any condition that compromises the overall safety of the aircraft or that significantly reduces the ability of the flight crew to cope with adverse operating conditions.
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