Preface This booklet provides the background for a better understanding of the Traffic Alert and Collision Avoidance System (TCAS II) by personnel involved in the implementation and operation of TCAS II. This booklet is an update of the TCAS II Version 7.0 manual published in 2000 by the Federal Aviation Administration (FAA). It describes changes to the CAS logic introduced by Version 7.1 and updates the information on requirements for use of TCAS II and operational experience. Version 7.1 logic changes will improve TCAS Resolution Advisory (RA) sense reversal logic in vertical chase situations. In addition all “Adjust Vertical Speed, Adjust” RAs are converted to “Level-Off, Level-Off” RAs to make it more clear that a reduction in vertical rate is required. The Minimum Operational Performance Standards (MOPS) for TCAS II Version 7.1 were approved in June 2008 and Version 7.1 units are expected to be operating by 2010-2011. Version 6.04a and 7.0 units are also expected to continue operating for the foreseeable future where authorized. 2 Preface................................................................................................................................. 2 The TCAS Solution............................................................................................................. 5 Early Collision Avoidance Systems................................................................................ 5 TCAS II Development .................................................................................................... 6 Initial In-Service Evaluations ......................................................................................... 7 Version 6.0 / 6.04a Implementation................................................................................ 8 Version 7.0 Implementation............................................................................................ 8 Version 7.1 Implementation............................................................................................ 9 Requirements for World-Wide Carriage......................................................................... 9 RVSM Considerations .................................................................................................. 10 Standards and Guidance Material ................................................................................. 10 TCAS II Components ....................................................................................................... 11 TCAS Computer Unit ................................................................................................... 11 Mode S Transponder..................................................................................................... 11 Mode S/TCAS Control Panel........................................................................................ 11 Antennas ....................................................................................................................... 12 Cockpit Presentation ..................................................................................................... 12 Traffic Display.............................................................................................................. 12 Traffic Display Symbology........................................................................................... 13 Resolution Advisory (RA) Display............................................................................... 14 Target Surveillance ........................................................................................................... 17 Mode S Surveillance..................................................................................................... 17 Mode C Surveillance..................................................................................................... 17 Interference Limiting .................................................................................................... 20 Electromagnetic Compatibility ..................................................................................... 20 Hybrid Surveillance ...................................................................................................... 20 Collision Avoidance Concepts.......................................................................................... 22 Sensitivity Level ........................................................................................................... 22 Tau ................................................................................................................................ 23 Protected Volume.......................................................................................................... 26 CAS Logic Functions........................................................................................................ 26 Tracking ........................................................................................................................ 26 Traffic Advisory............................................................................................................ 28 Threat Detection............................................................................................................ 28 Resolution Advisory Selection ..................................................................................... 29 3 TCAS/TCAS Coordination........................................................................................... 34 Air/Ground Communications........................................................................................ 34 Traffic Advisory (TA) Display ..................................................................................... 35 Resolution Advisory (RA) Displays ............................................................................. 35 Aural Annunciations ..................................................................................................... 35 Performance Monitoring............................................................................................... 37 Requirements for Use ....................................................................................................... 37 Regulations and Operational Guidance ........................................................................ 37 Training Programs ........................................................................................................ 41 Operational Experience..................................................................................................... 42 Performance Monitoring Programs............................................................................... 42 Observed Performance.................................................................................................. 43 Summary........................................................................................................................... 46 Abbreviations.................................................................................................................... 47 Glossary ............................................................................................................................ 48 Bibliography ..................................................................................................................... 50 4 aircraft to operate with ATC’s ground-based The TCAS Solution radars. The level of protection provided by TCAS equipment depends on the type of transponder the target aircraft is carrying. After many years of extensive analysis, The level of protection is outlined in development, and flight evaluation by the Table 1. It should be noted that TCAS Federal Aviation Administration (FAA), provides no protection against aircraft other countries’ Civil Aviation Authorities that do not have an operating (CAAs), and the aviation industry, Traffic transponder. Alert and Collision Avoidance System or TCAS was developed to reduce the risk of Table 1. TCAS Levels of Protection mid-air collisions between aircraft. In the international arena, this system is known Own Aircraft Equipment as the Airborne Collision Avoidance TCAS I TCAS II System or ACAS. Mode A TA TA XPDR TCAS is a family of airborne devices that ONLY function independently of the ground-based Mode C TA TA and air traffic control (ATC) system, and or Mode S Vertical RA provide collision avoidance protection for a XPDR broad spectrum of aircraft types. All TCAS systems provide some degree of collision threat alerting, and a traffic display. TCAS I TCAS I TA TA and and II differ primarily by their alerting Vertical RA capability. Target Aircraft Target Equipment TCAS II TA TA and Coordinated TCAS I provides traffic advisories (TAs) to Vertical RA assist the pilot in the visual acquisition of intruder aircraft. TCAS I is mandated for use in the U.S. for turbine powered, Early Collision Avoidance passenger-carrying aircraft having more than Systems 10 and less than 31 seats. TCAS I is also installed on a number of general aviation The 1956 collision between two airliners fixed wing aircraft and helicopters. over the Grand Canyon spurred both the airlines and aviation authorities to initiate TCAS II provides TAs and resolution development of an effective collision advisories (RAs), i.e., recommended escape avoidance system that would act as a last maneuvers, in the vertical dimension to resort when there is a failure in the ATC- either increase or maintain the existing provided separation services. During the vertical separation between