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A traffic collision avoidance system or traffic alert and collision avoidance system (both abbreviated as TCAS, and pronounced tee-kas) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of mid-air collision (MAC). It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over or authorized to carry more than 19 passengers. CFR 14, Ch I, part 135 requires that TCAS I is installed for aircraft with 10-30 passengers and TCAS II for aircraft with more than 30 passengers. ACAS / TCAS is based on secondary surveillance radar (SSR) transponder signals, and operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft. In modern glass cockpit aircraft, the TCAS display may be integrated in the Navigation Display (ND) or Electronic Horizontal Situation Indicator (EHSI); in older glass cockpit aircraft and those with mechanical instrumentation, such an integrated TCAS display may replace the mechanical Vertical Speed Indicator (which indicates the rate with which the aircraft is descending or climbing). ==Impetus for a collision prevention system== Research into collision avoidance systems has been ongoing since at least the 1950s. ICAO and aviation authorities such as the Federal Aviation Administration were spurred into action by the Grand Canyon mid-air collision in 1956.〔(Introduction to TCAS II Version 7 )〕〔(Introduction to TCAS II Version 7.1 )〕 The implementation of TCAS added a safety barrier to help prevent mid-air collisions. However, further study, refinements, training and regulatory measures were still required, because the limitations and misuse of the system still resulted in other incidents and fatal accidents, which include: * The Japan Airlines near-miss incident in 2001; * The Überlingen mid-air collision, between a Boeing 757 and a Tupolev Tu-154 in 2002, where the Tupolev pilots declined to follow their TCAS resolution advisory (RA), instead following the directions of the air traffic controller, while the Boeing pilots followed their TCAS RA, having no ATC instruction. By the time the crews of the two planes actually saw each other, it was too late and the planes collided, killing 71; * The Gol Flight 1907 collision with an Embraer Legacy 600 in 2006; 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Traffic collision avoidance system」の詳細全文を読む スポンサード リンク
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