Appendix C C-2 International Civil Aviation Organization (ICAO) Standards and Recommended Practices (SARP) for ACAS II. TCAS II V7.0 or V7.1 is mandated for carriage in Australia, India and certain European countries. V7.0 was mandated for carriage in 2003 by ICAO with V7.1 becoming mandatory by ICAO on January 2, 2014 for new aircraft and for existing aircraft by January 1, 2017. In addition, if you operate an aircraft that is equipped with TCAS II in RVSM airspace, it must be a TCAS II that meets TSO-C119b (V7.0) or a later version.
C.2.2 Investigation of operational problems resulted in changes to TCAS II V7.0. The changes resulting from that investigation resulted in TCAS II V7.1.
C.2.3 While developing corrective action for the operational problems, the Federal Aviation Administration (FAA), along with industry representatives, decided to develop performance standards for TCAS II Hybrid Surveillance. That work resulted in creation of RTCA/DO-300, Minimum Operational Performance Standards (MOPS) for Traffic Alert and Collision Avoidance System II (TCAS II) Hybrid Surveillance.
Investigation of operational problems reported after introduction of TCAS II units incorporating hybrid surveillance resulted in changes to TCAS II V7.1. Those changes are invoked by TSO-C119e. Change 2 to RTCA/DO-300 and Change 1 to RTCA/DO- 300A also incorporate these changes for TCAS II hybrid surveillance units designed to TSO-C119c and C119d, respectively.
C.2.4 As a result of a 2006 midair collision in Brazil, the FAA has determined that a need exists to strengthen requirements for crew alerting for loss of TCAS functionality.
Consistent with 14 CFR sections 25.1302, 25.1309(c), and 25.1322, we have incorporated those changes into this AC.
TSO-C119e classifies failure of the TCAS II to provide a reliable traffic alert and collision avoidance function as a Hazardous/Severe-Major failure condition.
However, previous revisions of this AC have only provided guidance for “incorrect RAs”, defined in the AC as an “RA occurring when a threat is present, but, because of a failure of the installed TCAS II, Mode S transponder, or associated sensors, commands a maneuver that reduces separation to the threat [emphasis added].” In some cases, this has resulted in design approval holders and ACO engineers incorrectly classifying failure to provide RA when a threat is present, or late provision of an RA, as simple loss of function and therefore minor (loss of TCAS II functionality is only minor if the loss of function is appropriately annunciated).
The FAA considers failure to provide an RA (or late provision of an RA) when a threat is present, without annunciation of loss of TCAS II functionality, to also be a Hazardous/Severe-Major failure of the function defined in paragraph 3.a of TSO- C119e (i.e., provide a reliable traffic alert and collision avoidance function).
Therefore, this AC clarifies TCAS failure classification and system safety assessment considerations by adding reference to a “Missing RA”, defined as “An RA that does not occur, or that occurs later than the CAS logic indicates is necessary, when a threat is present”, which is a Hazardous/Severe-Major failure condition. The System Safety
Appendix C C-3 Assessment section of this AC contains means of compliance for addressing missing RAs.
Since TCAS is a supplemental system to ATC separation services and the flight crew’s responsibility to see-and-avoid, the FAA considers that those two factors (ATC separation services and see-and-avoid responsibility) partially mitigate the normally assigned failure classification for TCAS, and allow the probability of incorrect RA and missing RA event(s) to be improbable (10-5) versus the 10-7 usually associated with a Hazardous/Severe-Major failure classification.
C.3 Accident history related to the development and evolution of TCAS.
C.3.1 This section provides links to online information on significant historical accidents that have played a role in the development and evolution of TCAS. This section does not provide a detailed narrative of those events, but rather enables interested readers to conduct further research into accidents that have influenced the development of TCAS by providing easy access to relevant information. The intent of providing links to this information is to capture historical lessons learned related to TCAS, in order to preserve key safety objectives for the system and facilitate its continued refinement.
C.3.2 PSA 727, San Diego and Aeromexico DC-9, Los Angeles, Midair Collisions with General Aviation Aircraft: Detailed information is available at the FAA’s Lessons Learned from Transport Airplane Accidents website at:
http://lessonslearned.faa.gov/ll_main.cfm?TabID=3&CategoryID=14&LLID=48 C.3.3 Boeing 757/Tupolev Tu-154 midair collison, Überlingen, Germany, July 1, 2002:
Further information is available at the Aviation Safety Network website at:
https://aviation-safety.net/database/record.php?id=20020701-1 (for the Boeing 757), and https://aviation-safety.net/database/record.php?id=20020701-0 (for the Tu-154).
The final report of the German Federal Bureau of Aircraft Accidents Investigation (BFU) is also available, in English, at: http://www.bfuweb.de/EN/Publications/Investigation%20Report/2002/Report_02_AX001-1- 2_Ueberlingen_Report.pdf?__blob=publicationFile . Appendices to the BFU final report are at: http://www.bfuweb.de/EN/Publications/Investigation%20Report/2002/Report_02_AX001-1- 2_Ueberlingen_Appendix_1-3.pdf?__blob=publicationFile C.3.4 Boeing 737-800/Embraer Legacy 600 midair collision, near Peixoto Azevedo, MT, Brazil, September 29, 2006: Further information is available at the Aviation Safety Network website at: https://aviation-safety.net/database/record.php?id=20060929-0 (for the Boeing 737-800), and https://aviationsafety.net/database/record.php?id=20060929-1 (for the Embraer Legacy 600).
Appendix D D-1 APPENDIX D. RELATED DOCUMENTS.
D.1 14 CFR Parts.
You can apply current portions of 14 CFR for the design, substantiation, certification and operational approval of TCAS II and Mode S transponders. Sections prescribing requirements for these types of systems are listed below. Order copies of 14 CFR Parts 21, 23, 25, 27, 29, 43, 91, 121, and 135 from the Superintendent of Documents, U.S. Government Publishing Office, P.O. Box 979050, St. Louis, MO 63197-9000, telephone (866) 512-1800, fax (202) 512-2104. You can also get copies from the Government Publishing Office (GPO), electronic CFR Internet website at http://www.ecfr.gov.
14 CFR § 25.301 Loads.
14 CFR § 25.303 Factor of safety.
14 CFR § 25.305 Strength and deformation.
14 CFR § 25.561 General.
14 CFR § 25.603 Materials.
14 CFR § 25.609 Protection of structure.
14 CFR § 25.629 Aeroelastic stability requirements.
14 CFR § 25.869 Fire protection: systems.
14 CFR § 25.1301 Function and installation.
14 CFR § 25.1302 Installed systems and equipment for use by the flightcrew.
14 CFR § 25.1303 Flight and navigation instruments.
14 CFR § 25.1307 Miscellaneous equipment.
14 CFR § 25.1309 Equipment, systems, and installations.
14 CFR § 25.1316 System Lightning Protection.
14 CFR § 25.1317 High-intensity Radiated Field (HIRF) Protection.
14 CFR § 25.1321 Arrangement and visibility.
14 CFR § 25.1322 Warning, caution, and advisory lights.
14 CFR § 25.1331 Instruments using a power supply.
14 CFR § 25.1333 Instrument systems.
14 CFR § 25.1335 Flight director systems.
14 CFR § 25.1351 Electrical Systems and Equipment: General.
14 CFR § 25.1353 Electrical equipment and installations.
14 CFR § 25.1355 Distribution system.
Appendix D D-2 14 CFR § 25.1357 Circuit protective devices.
14 CFR § 25.1381 Instrument lights.
14 CFR § 25.1431 Electronic equipment.
14 CFR § 25.1541 Markings and Placards: General.
14 CFR § 25.1581 Airplane Flight Manual: General.
14 CFR § 25.1585 Operating procedures.
Note: References to 14 CFR part 25 are appropriate when installing TCAS II on transport category airplanes. When TCAS II is to be certified for non-transport category airplanes, use the equivalents to the above 14 CFR part 25 sections in other parts of the regulations.
D.2 FAA ACs.
You will find a current list of ACs on the FAA Internet website at http://rgl.faa.gov.
AC 20-131A, Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II) and associated Mode S Transponders AC 20-115C, Airborne Software Assurance AC 20-165B, Airworthiness Approval of Automatic Dependent Surveillance - Broadcast OUT Systems AC 20-172B, Airworthiness Approval for ADS-B In Systems and Applications AC 25.1302-1, Installed Systems and Equipment for Use by the Flightcrew AC 25.1309-1A, System Design and Analysis AC 25.1322-1, Flightcrew Alerting AC 25.1329-1C, Approval of Flight Guidance Systems AC 25-11B, Electronic Flight Displays AC 120-55C, Air Carrier Operational Approval and Use of TCAS II D.3 FAA TSOs.
You will find a current list of TSOs on the FAA Internet website Regulatory and Guidance Library at http://rgl.faa.gov. You will also find the TSO Index of Articles at the same site.
TSO-C112e, Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne Equipment TSO-C119e, Traffic Alert and Collision Avoidance System (TCAS) Airborne Equipment, TCAS II With Hybrid Surveillance Functionality
Appendix D D-3 D.4 FAA Other.
You will find this related information on the FAA Internet website Regulatory and Guidance Library at http://rgl.faa.gov. The document is posted adjacent to the links for AC 20-151 and TSO-C119.
Introduction to TCAS II V7.1, February 28, 2011 D.5 RTCA Inc. Publications.
Order RTCA documents from RTCA, Inc., 1150 18th Street N.W. Suite 910, Washington D.C. 20036 or order online at www.rtca.org.
RTCA/DO-160G, Environmental Conditions and Test Procedures for Airborne Equipment, dated December 12, 2010.
RTCA/DO-178C, Software Considerations in Airborne Systems and Equipment Certifications, dated December 13, 2011.
RTCA/DO-181E, Minimum Operational Performance Standards for Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne Equipment, dated March 17, 2011.
RTCA/DO-185A, Minimum Operational Performance Standards for Traffic Alert and Collision Avoidance Systems II (TCAS II), dated December 16, 1997.
RTCA/DO-185B, Minimum Operational Performance Standards for Traffic Alert and Collision Avoidance Systems II (TCAS II), dated June 19, 2008; including Change 1 dated July 1, 2009, and Change 2 dated March 20, 2013.
RTCA/DO-300, Minimum Operational Performance Standards for Traffic Alert and Collision Avoidance System II (TCAS II) Hybrid Surveillance, dated December 13, 2006; including Change 1 dated July 1, 2009, and Change 2 dated December 15, 2015.
RTCA/DO-300A, Minimum Operational Performance Standards for Traffic Alert and Collision Avoidance System II (TCAS II) Hybrid Surveillance, dated March 20, 2013; including Change 1 dated December 15, 2015.
D.6 SAE International.
Order SAE documents from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096, telephone (724) 776-4841, fax (724) 776-0790. Also, you may order copies online at www.sae.org.
ARP 926B, Fault/Failure Analysis Procedure, dated June 11, 1997.
ARP 1834A, Fault/Failure Analysis for Digital Systems and Equipment, dated June 1, 1997.
ARP 4102/7, Electronic Displays, dated July 1, 1988.
ARP 4102/8A, Flight Deck Head-Up Displays, dated November 1, 1998.
Appendix D D-4 ARP 4754A, Guidelines for Development of Civil Aircraft and Systems, dated December 21, 2010.
ARP 4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment, dated December 1, 1996.
D.7 AERONAUTICAL RADIO, INC. (ARINC).
Publications are available from SAE-ITC, ARINC Industry Activities, 16701 Melford Blvd., Suite 120, Bowie, MD 20715, telephone (240) 334-2578 or online at http://store.aviation-ia.com/cf/store/customer_service.cfm.
ARINC 718( ), Mark 3 Air Traffic Control Transponder (ATCRBS/MODE S).
ARINC 735( ), Mark 2 Traffic Alert and Collision Avoidance System (TCAS).
D.8 International Civil Aviation Organization (ICAO).
Publications are available from ICAO, Attention: Customer Service unit, 999 University Street, Montreal, Quebec, Canada H3C5H7; telephone +1 514-954-8022, facsimile: 514-954-6769, sitatex YULCAYA, email: sales@icao.int or on line at http://www.icao.int.
Airborne Collision Avoidance System (ACAS) Manual document 9863, First Edition dated 2006.
D.9 JAA.
JAA documents transposed to publications of the European Aviation Safety Agency (EASA) are available on the EASA web site at https://www.easa.europa.eu/. JAA documents are also available on the EUROCONTROL site at http://www.eurocontrol.int/ .
JAA Temporary Guidance Leaflet (TGL) 13 Revision 1.
D.10 EASA.
Publications are available on the EASA web site at https://www.easa.europa.eu/.
AMC 20-13 Certification of Mode S Transponder Systems for Enhanced Surveillance.
EASA Certification Specification and Acceptable Means of Compliance – Airborne Communication Navigation and Surveillance, Book 1 and Book 2.
Appendix E E-1 APPENDIX E. DEFINITIONS AND ACRONYMS.
E.1 Definitions. - The following definitions are specific to this AC and may differ from definitions contained in other references.
Active surveillance. - Using TCAS interrogations and subsequent replies to update or acquire a TCAS track.
Advisory. - Message given to alert the flight crew of converging aircraft and/or a potential collision.
Air traffic control radar beacon system (ATCRBS). - Secondary surveillance radar system with ground based interrogators and airborne transponders capable of operation on Modes A and C.
Alert. - Indication (aural or visual) that informs the flight crew in a timely manner about converging aircraft or potential collision.
Automatic dependent surveillance broadcast (ADS-B). - A function on an aircraft or vehicle that automatically broadcasts its own aircraft's identity, state vector (horizontal and vertical position and velocity), associated quality and performance parameters (accuracy and integrity) and other information. Broadcast links include the 1090 MHz extended squitter (ES) and the universal access transceiver (UAT) broadcast on 978MHz.
Coast. - Condition which occurs when TCAS II does not receive a reply to an interrogation from an intruder for which it has established a track, resulting in the logic continuing the track based on previous track characteristics.
Comm-B. - A 112-bit Mode S reply containing a 56-bit MB message field containing the extracted transponder register.
Corrective resolution advisory. - Advises the pilot to either deviate from current vertical speed, such as CLIMB when the aircraft is level, or to maintain an existing climb or descent rate.
In TCAS II V7.0 and V7.1, a “Maintain Rate RA” is classified as a corrective RA solely to provide a green fly-to arc or zone on a vertical speed indicator.
Discrete. - Separate, complete and distinct signal.
Failure. - Inability of a system, subsystem, unit, or part to perform within previously specified limits.
False advisory (TA or RA). - Advisory caused by a false track or TCAS II malfunction.
Hybrid Surveillance. - Combined use of active and passive surveillance to update a TCAS track.
Incorrect resolution advisory. - RA occurring when a threat is present, but, because of a failure of the installed TCAS II, Mode S transponder, or associated sensors, commands a maneuver that reduces separation to the threat.
Appendix E E-2 Intruder. - Aircraft satisfying the TCAS II traffic advisory detection criteria.
Missing resolution advisory. - An RA that does not occur, or that occurs later than the CAS logic indicates is necessary, when a threat is present.
Mode A. - Type of secondary surveillance radar (SSR) equipment or mode of operation that replies by selected 4096 code (nonaltitude) when interrogated.
Mode C. - Type of secondary surveillance radar (SSR) equipment or mode of operation that replies with aircraft altitude information when interrogated.
Mode S. - Type of secondary surveillance radar (SSR) equipment that replies to Mode A and Mode C ground interrogations, a discrete address, and other aircraft information in response to interrogations from the ground or air.
Other traffic. - Aircraft more than ±1200 feet vertical or 6 nautical miles (NM) from own aircraft that are neither RA nor TA.
Passive surveillance. - The use of airborne position messages to update a TCAS track.
Preventive resolution advisory. - Requires a pilot to avoid certain deviations from current vertical rate (for example, a Do Not Climb RA when the aircraft is level).
Proximate traffic. - Aircraft within 6 NM in range and within ±1,200 feet vertically from own aircraft, but does not meet the TCAS II thresholds of a TA or RA.
Resolution advisory. - Aural voice and display information provided by TCAS II to a flight crew, advising that a particular maneuver should, or should not, be performed to attain or maintain minimum safe vertical separation from an intruder.
Resolution display. - Shows vertical guidance depicting areas to “fly to” and/or avoid above or below the TCAS II equipped aircraft.
Sense. - A direction that an RA may take (either Climb or Descend) relative to the existing flight path of own aircraft.
Threat. - An intruder that satisfies the threat detection logic and thus requires an RA.
Track. - Estimated position and velocity of a single aircraft based on correlated surveillance data reports.
Traffic. - Aircraft with an operating transponder capable of being tracked and displayed by a TCAS-equipped aircraft.
Traffic advisory (TA). - Aural voice and display information from TCAS II to a flight crew, identifying the location of nearby traffic meeting certain minimum separation criteria.
Traffic display. - Horizontal position of transponder-equipped aircraft relative to the TCAS II equipped aircraft.
Transponder register. - Transponder register means a transponder data buffer containing different pieces of information. It has 56 bits which are divided into different fields. The definition of the transponder registers can be found in ICAO Doc 9871 edition 2 and in RTCA/DO-181E, Minimum Operational Performance Standards for Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne
Appendix E E-3 Equipment. Transponder registers are numbered in hexadecimal (00 hex to FF hex).
The register number is also known as the BDS code (Comm-B data selector). In this documentation a register is named: register XY16 or register addressed by BDS code X,Y. Outside this document, it is also often referenced as just BDS X,Y.
E.2 Acronyms.
14 CFR Title 14 of the Code of Federal Regulations ACARS Aircraft communications addressing and reporting system ADS-B Automatic dependent surveillance - broadcast AFM Airplane flight manual AFMS Airplane flight manual supplement AGL Above ground level ASR Airport surveillance radar AMC Acceptable Means of Compliance ATA Air Transport Association ATC Air traffic control ATCRBS Air traffic control radar beacon system CAS Collision avoidance algorithm, or CAS logic CMC Central Maintenance Computer CRS CAS requirements specification dB Decibel EADI Electronic attitude display indicator EFIS Electronic flight instrument system EHS Enhanced Surveillance EHSI Electronic horizontal situation indicators ELS Elementary Surveillance EMC Electromagnetic compatibility FAA Federal Aviation Administration FD Flight director FHA Functional hazard assessment FL Flight level FMEA Failure modes and effects analysis FPM Feet Per Minute
Appendix E E-4 GPS Global positioning system GPWS/TAWS Ground proximity warning system/terrain awareness warning system HUD Heads-up device ICA Instructions for Continued Airworthiness ICAO International Civil Aviation Organization IVSI Instantaneous vertical speed indicator JAA Joint Aviation Authorities MHz Megahertz NAS National Airspace System ND Navigation display NM Nautical mile PFD Primary flight display RVSM Reduced Vertical Separation Minimum RA Resolution advisory SARP Standards and Recommended Practices STC Supplemental type certificate TA Traffic advisory TC Type certificate TCAS II Traffic alert and collision avoidance system TSO Technical standard order TTP TCAS transition program Vmo Maximum operating limit speed
Appendix F F-1 APPENDIX F. INTERFACING THE TRANSPONDER TO AIRCRAFT SYSTEMS TO
SUPPORT TRANSMISSION OF SHORT-TERM INTENT F.1 General.
F.1.1 Selected altitude information is intended for use by ATC to improve the controller tactical view by providing them with a digital indication of altitude clearance intent and for improving performance of conflict probe automation.
F.1.2 With respect to implementing short-term intent, the term “target altitude” is the next altitude at which the aircraft will level-off if in a climb or descent, or the aircraft current intended altitude if it is intending to hold its altitude.
F.1.3 A pilot may operate the aircraft in a manual mode or Flight Director/Autopilot mode where the level off altitude is not known by any aircraft system. Even when operating the aircraft in Flight Director/Autopilot mode, some legacy flight automation may have knowledge of the level off altitude, but not provide this information via an external interface. In either of these conditions, the BDS 4016 and BDS 6216 implementation must indicate that the target altitude is unknown.
F.1.4 Some legacy aircraft do not have selected altitude functionality, but do have a function that alerts the flight crew when a desired altitude is reached, commonly called an altitude alerter. In installations where an altitude alerter is present and the operator of the aircraft has operating guidance to require its use, the altitude alerter setting may be used to encode MCP/FCU selected altitude.
F.1.5 Note: If the flight crew does not use the altitude alerter, encoding this information will be misleading and the equipment should not be interfaced to the transponder.
F.1.6 In existing aircraft with federated avionics suites, it is typical to have a pilot interface to the autopilot implemented as separate self-contained unit which is wired to the rest of the systems in the aircraft as needed. This is commonly referred to as a Mode Control Panel (MCP) or Flight Control Unit (FCU). Historically, there was no connection between these control units and the transponder. In the following paragraphs, the guidance is written from the perspective of this type of federated architecture. In aircraft with more integrated avionics suites, the display and control of autopilot functions may be integrated with the display and control of several other aircraft functions. In this type of integrated architecture there is not a literal MCP or FCU. In these cases, the guidance still applies to the autopilot control function regardless of what hardware it is integrated into.
F.1.7 A similar case exists for the Flight Management System (FMS) function. Historically, the FMS was a self-contained unit wired to other aircraft systems as needed. In modern flight decks, the FMS function can be integrated in hardware with other aircraft systems. The following guidance is written as if the FMS is a federated unit.
The guidance still applies to the case where FMS functionality is integrated with other aircraft systems.
Appendix F F-2 F.2 F.2.1 F.2.2 F.2.3 F.2.4 F.2.5 F.2.5.1 F.2.5.2 F.2.5.3 F.2.5.4 Populating Selected Vertical Intention Register BDS 4016.
This section provides guidance for interfacing the transponder to aircraft systems for complying with the EU Enhanced Surveillance requirement for Selected Vertical Intent Register BDS 4016.
I f available on the aircraft, interface the MCP/FCU to the transponder and verify that the selected altitude information is reported correctly and marked as valid. If the data is either not available or invalid, verify that it is reported as invalid.
For installations with an FMS system, the installer should ensure the transponder is receiving valid selected altitude information. If the data is either not available or invalid, verify that it is reported as invalid.
The installer should ensure that the transponder receives the barometric pressure setting in use. In some installations, it is possible to override the barometric pressure setting and fly the aircraft to the uncorrected pressure altitude. In this case the reported correction should be zero. If the data is either not available or invalid, verify that it is reported as invalid.
The installer should verify all reserved fields are unused and set to zero.
For installations that do not have VNAV, LNAV, Autopilot Engaged, Altitude Hold, or Approach Mode information available, the installer should ensure the MCP/FCU Mode bits are marked invalid. If the transponder receives one or more of the mode parameters, the installer should verify the MCP/FCU Mode bits are set in accordance with the horizontal/vertical mode controlling the aircraft. The extent of these modes can vary significantly across different aircraft platforms. A description of each field follows, to clarify the intended use of these parameters by ATC. Refer to the example scenarios for a detailed description on setting the mode field.
Note: Altitude Hold Mode may be inhibited when the aircraft has c aptured the approach (e.g. capturing the glideslope).
F.2.5.5 Approach Mode indicates the pilot has armed the desired approach source (e.g.
VOR/LOC and G/S or LNAV and VNAV).
VNAV indicates when an aircraft is following vertical path guidance using information from the FMS. The pilot may arm this mode manually.
LNAV indicates when the aircraft is following lateral path guidance using information from the FMS. The pilot may arm this mode manually.
Autopilot Engaged indicates when the pilot has engaged the Autopilot system.
Altitude Hold Mode indicates that the aircraft will remain at its current altitude regardless of the current setting or a change to the MCP/FCU selected altitude or FMS selected altitude data.