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Aholustomy (talk | contribs) →Impetus for a system and history: adding wiki link to ATCRBS |
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Research into collision avoidance systems has been ongoing since at least the 1950s, and the airline industry has been working with the [[Air Transport Association of America]] (ATA) since 1955 toward a collision avoidance system. [[ICAO]] and aviation authorities such as the [[Federal Aviation Administration]] were spurred into action by the [[1956 Grand Canyon mid-air collision]].<ref name=TCAS71>[http://www.faa.gov/documentLibrary/media/Advisory_Circular/TCAS%20II%20V7.1%20Intro%20booklet.pdf Introduction to TCAS II Version 7.1]</ref>
Although [[Air traffic control radar beacon system|ATCRBS]] airborne transponders were available, it wasn't until the mid-1970s that research focused on using their signals as the cooperative element for a collision avoidance system. This technical approach enabled an independent collision avoidance capability on the flight deck, separate from the ground system. In 1981, the FAA decided to implement the Traffic Alert and Collision Avoidance System (TCAS), which was developed based on industry and agency efforts in the field of beacon-based collision avoidance systems and air-to-air discrete address communication techniques that used Mode S airborne transponder message formats.<ref name="20-151B">{{citation|title=20-151B – Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II), Versions 7.0 & 7.1 and Associated Mode S Transponders|date=March 18, 2014|url=https://www.faa.gov/documentlibrary/media/advisory_circular/ac_20-151b.pdf|page=C1|publisher=faa.gov|access-date=October 13, 2018}}</ref>
A short time later, prototypes of TCAS II were installed on two [[Piedmont Airlines]] [[Boeing 727]] aircraft, and were flown on regularly scheduled flights. Although the displays were located outside the view of the flight crew and seen only by trained observers, these tests did provide valuable information on the frequency and circumstances of alerts and their potential for interaction with the [[Air traffic control|ATC]] system. On a follow-on phase II program, a later version of TCAS II was installed on a single Piedmont Airlines Boeing 727, and the system was [[Airworthiness certificate|certified]] in April 1986, then subsequently approved for operational evaluation in early 1987. Since the equipment was not developed to full standards, the system was only operated in [[visual meteorological conditions]] (VMC). Although the flight crew operated the system, the evaluation was primarily for the purpose of data collection and its correlation with flight crew and observer observation and response.<ref name="20-151B" />
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