AC 20-199 Appendix C
• DO-197A, Minimum Operational Performance Standards for an Active Traffic Alert and Collision Avoidance System I (Active TCAS I).
• DO-220B, Minimum Operational Performance Standards (MOPS) For Airborne Weather Radar Systems.
• DO-254, Design Assurance Guidance for Airborne Electronic Hardware.
• DO-300A, Minimum Operational Performance Standards (MOPS) for Traffic Alert and Collision Avoidance System II (TCASII) Hybrid Surveillance.
• DO-309, Minimum Operational Performance Standards (MOPS) for Helicopter Terrain Awareness and Warning System (HTAWS) Airborne Equipment.
• DO-315B, Minimum Aviation System Performance Standards (MASPS) for Enhanced Vision Systems, Synthetic Vision Systems, Combined Vision Systems and Enhanced Flight Vision Systems.
• DO-325, Minimum Operation Performance Standards (MOPS) for Automatic Flight Guidance and Control Systems and Equipment.
• DO-326B, Airworthiness Security Process Specification.
• DO-355A, Information Security Guidance for Continuing Airworthiness.
• DO-356A, Airworthiness Security Methods and Considerations.
• DO-359, Minimum Aviation System Performance Standards (MASPS) for Synthetic Vision Guidance Systems.
• DO-367, Minimum Operational Performance Standards (MOPS) for Terrain Awareness and Warning Systems (TAWS) Airborne Equipment.
• DO-376, Minimum Operational Performance Standard for Offshore Helicopter Terrain Awareness and Warning System (HTAWS).
• DO-385A, Minimum Operational Performance Standards for Airborne Collision Avoidance System X (ACAS X) (ACAS Xa and ACAS Xo).
• DO-391, Aeronautical Information System Security Framework Guidance.
• DO-392, Guidance for Security Event Management.
• DO-405, Minimum Operating Performance Standard (MOPS) for Helicopter Terrain Awareness Warning System (HTAWS) for Onshore Helicopter Operations.
C.10 European Organization for Civil Aviation Equipment (EUROCAE).
The following EUROCAE documents are related to the guidance in this AC. Unless otherwise specified, use the latest FAA-accepted revision for guidance. If the document is revised after publication of this AC, you should verify that the FAA accepts the subsequent revision or update as an acceptable form of guidance. The documents are available online at https://www.eurocae.net.
• ED-14G, Environmental Conditions and Test Procedures for Airborne Equipment.
• ED-30, MPS for Airborne Low Range Radio (radar) Altimeter Equipment.
• ED-202B, Airworthiness Security Process Specification.
• ED-203A, Airworthiness Security Methods and Considerations.
• ED-204A, Information Security Guidance for Continuing Airworthiness.
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AC 20-199 Appendix C C.11 Society of Automotive Engineers (SAE) International.
The following SAE Aerospace Recommended Practice (ARP) documents are related to the guidance in this AC. Unless otherwise specified, use the latest FAA-accepted revision for guidance. If the document is revised after publication of this AC, you should verify that the FAA accepts the subsequent revision or update as an acceptable form of guidance. The documents are available online at https://www.sae.org.
• AS6296, Electronic Flight Instrument System (EFIS).
• AS8034B, Minimum Performance Standard for Airborne Multipurpose Electronic Displays.
• ARINC 707-7, Radio Altimeter.
• ARP4102-7, Electronic Displays.
• ARP4754B, Guidelines for Development of Civil Aircraft and Systems.
• ARP4761A, Guidelines for Conducting the Safety Assessment Process on Civil Aircraft, Systems, and Equipment.
C.12 International Civil Aviation Organization (ICAO).
• ICAO Doc 9718, Handbook on Radio Frequency Spectrum Requirements for Civil Aviation.
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AC 20-199 Appendix D APPENDIX D. DEFINITION OF KEY TERMS The following definitions apply for the purpose of this AC:
D.1 Decision Height (DH).
See 14 CFR 1.1, General Definitions.
Note: During operation of the approach procedure, the RA system is the only source of determining (or annunciating) when the decision height has been reached.
D.2 Electrical Height Output.
The reported RA quantity from the RA system provided as an electrical output interface signal. Note: The output interface may be analog or digital.
D.3 Height Above Ground Level (HAGL).
The distance from the portion of aircraft structure in which the RA antenna(s) is/are installed to the terrain surface at a given point along a flight path.
D.4 In-Band Radio Frequency Interference (RFI).
External RFI signals within the RA operating frequency (4.2–4.4 GHz).
D.5 Installation Time Delay.
The actual round-trip RF signal propagation time delay in an RA system installation on an aircraft relative to the desired zero-height reference point. This may include, for example, the propagation delays in the coaxial cables or transmission lines between the RA transceiver and the RA antenna(s), and the free-space propagation from the RA antenna(s) to the terrain surface when the aircraft is on the ground with the main landing gear touching in a pre-established aircraft attitude (i.e., nose gear may not be touching).
D.6 Installation Height Offset.
A value, determined by calibration, configuration, or installation of the RA system, which defines a constant bias to be subtracted from the measurement result of the RA transceiver in order to account for the height of the RA antenna(s) above the terrain while the aircraft is on the ground (with the main landing gear touching in a preestablished aircraft attitude, the length of coaxial cables or transmission lines between the RA transceiver, and the RA antenna(s) and any other system delays as needed).
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AC 20-199 Appendix D D.7 Installation Manual (IM).
A document developed and made available by the equipment manufacturer of a system, subsystem, or component that specifies the performance characteristics, interface specifications, installation constraints and limitations, installation requirements, calibration (if applicable), on-aircraft testing, maintenance, troubleshooting procedures, and any necessary requirements for other integrated equipment.
D.8 Interference Tolerance Mask (ITM).
The specification that defines the maximum amount of RFI at the surface of the RA antenna(s) that the RA system can safely tolerate.
D.9 Irregular Approach Terrain.
Includes cliffs, valleys, sea-walls, hilltops, and sloping runways, in the area of final approach, within a pproximately 1500 ft of the landing threshold.
D.10 Loop Loss.
The round-trip attenuation of the RF signal received by the radio altimeter system consisting of a delayed, attenuated, and possibly dispersed or modulated version of the transmitter output waveform due to propagation of this signal through space and interaction of the signal with one or more radar targets (i.e., sources of radar reflectivity).
D.11 Multiplex Installation.
An installation of more than one RA system of the same type onboard a single aircraft.
Typically, this will consist of either dual or triplex installation.
D.12 Out-of-Band Radio Frequency Interference (RFI).
External RFI signals outside the RA operating frequency band (i.e., at frequencies less than 4.2 GHz or greater than 4.4 GHz).
D.13 Radio Altimeter Antenna.
The subsystem or component of the RA system that takes a conducted RF signal provided by the transceiver and radiates it toward the terrain and receives a radiated RF signal reflected from the terrain and provides a conducted RF signal to the transceiver.
An RA system will include one or multiple RA antennas.
D.14 Radio Altimeter Indicator or Display.
The subsystem or component of the RA system provides a visual indication of the measured altitude result determined by the RA transceiver. An RA system may include D-2
AC 20-199 Appendix D one, multiple, or no RA indicators or displays. It may be a standalone indicator or display component for the sole purpose of displaying RA system outputs, or it may be a function incorporated into an MFD system, such as an EFIS.
D.15 Radio Altimeter System.
A complete system consisting of receiver and transmitter, one or more antennas, RF cables (if the antenna(s) are not integrated into the same LRU as the receiver and transmitter), and input/output interfaces (which may include a display of altitude information as a visual output interface, either integrated or as a part of a separate display or indicator component).
D.16 Radio Altimeter Transceiver.
The subsystem or component of the RA system that generates and transmits the RF signal and receives, processes, and determines a measured altitude result from the RF signal reflected from the terrain. An RA will include one and only one RA transceiver.
D.17 RF Filter Subassembly (RFFSA).
A subassembly implemented within the RA transceiver LRU that selectively filters RF signals outside of the RA band. The RA transceiver could be implemented with an RFFSA at the transmitter output port, the receiver input port, or both.
D.18 Transceiver Subassembly.
A subassembly implemented within the RA transceiver LRU that performs all of the normal functions of the RA, with the exception of the selective filtering implemented in one or more RFFSAs.
D.19 Terrain Smoothness.
Ranging from smooth to rough (where rough terrains may be further characterized by the feature size and density of the surface roughness).
D.20 Terrain Flatness.
Ranging from flat to undulating (where undulating terrains may be further characterized by the depth and period of their undulations).
D.21 Terrain Inclination.
Ranging from level to sloped (where sloped terrains may be further characterized by the angle of the terrain slope).
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AC 20-199 Appendix D D.22 Terrain Surface Features.
Ranging from bare to densely featured. Terrains may be further characterized by the density of the surface features (e.g., sparsely or densely featured, as well as the size of the surface features).
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AC 20-199 Appendix E APPENDIX E. ACRONYMS Acronym Definition AC Advisory Circular ACAS Airborne Collision Avoidance System AFGCS Automatic Flight Guidance and Control System AFM Aircraft Flight Manual AMC Acceptable Means of Compliance ARP Aerospace Recommended Practice AWGN Additive White Gaussian Noise CS Certification Specification CW Continuous Waveform DH Decision Height EASA European Union Aviation Safety Agency EFIS Electronic Flight Instrument System EFVS Enhanced Flight Vision Systems EUROCAE European Organization for Civil Aviation Equipment FAA Federal Aviation Administration HAGL Height Above Ground Level HIRF High-Intensity Radiated Fields HTAWS Helicopter Terrain Awareness and Warning System ICAO International Civil Aviation Organization IM Installation Manual ITM Interference Tolerance Mask LRU Line Replaceable Unit MASPS Minimum Aviation System Performance Standards MFD Multifunction Display MOC Method of Compliance MOPS Minimum Operational Performance Standards NVG Night Vision Goggle PAPR Peak-to-Average Power Ratio PFD Power Flux-Density RA Radio Altimeter RF Radio Frequency RFFSA RF Filter Subassembly RFI Radio Frequency Interference RTCA Radio Technical Commission for Aeronautics RX Reverse Port SAE Society of Automotive Engineers SSA System Safety Assessment STC Supplemental Type Certificate TAWS Terrain Awareness and Warning System TC Type Certificate TCAS Traffic Alert and Collision Avoidance System E-1
AC 20-199 Appendix E Acronym Definition TSO Technical Standard Order TSOA Technical Standard Order Authorization UUT Unit Under Test E-2
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