Traffic collision avoidance system: Difference between revisions

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* [[1996 Charkhi Dadri mid-air collision]] accident over [[New Delhi]]
* 1999 Lambourne near-collision, involving a [[Boeing 737 Classic#737-300|Boeing 737-300]] and a [[Gulfstream IV]]. The airspace above [[Lambourne]] is the waiting zone for [[Heathrow Airport|Heathrow]]. The event is notable as both planes entered the zone from different directions leading to an imminent head-on collision (one o'clock position). The traffic advisory (amber mark) almost immediately turned into a resolution advisory (red mark) with a projected time for collision of less than 25 seconds.<ref>{{cite web|url=https://www.gov.uk/aaib-reports/boeing-737-300-d-abek-and-gulfstream-iv-n77sw-26-february-1999|title=Boeing 737-300, D-ABEK and Gulfstream IV, N77SW, 26 February 1999|publisher=[[Air Accidents Investigation Branch]]|archive-url=https://uploadweb.wikimediaarchive.org/wikipediaweb/commons20180807000000/0https:/07/Boeing_737www.gov.uk/aaib-reports/boeing-737-300%2C_D-ABEK_and_Gulfstream_IV%2C_N77SW%2C_26_February_1999.pdfd-abek-and-gulfstream-iv-n77sw-26-february-1999|url-status=live|archive-date=2018-08-07}} [https://upload.wikimedia.org/wikipedia/commons/0/07/Boeing_737-300%2C_D-ABEK_and_Gulfstream_IV%2C_N77SW%2C_26_February_1999.pdf Alt URL]</ref>
* [[2001 Japan Airlines mid-air incident]], in which the Captain of Japan Airlines Flight 907 (a [[Boeing 747-400]]), 40-year old Makoto Watanabe ({{langx|ja|渡辺 誠|translit=Watanabe Makoto|label=none}}), chose to descend, ordered by the air traffic controller, when TCAS told the flight crew to climb, nearly colliding with the descending JAL Flight 958 [[McDonnell Douglas DC-10|DC-10]] en route from [[Gimhae International Airport|Busan]] to Tokyo's [[Narita International Airport|Narita Airport]].
* [[2002 Überlingen mid-air collision]], between a [[Boeing 757]] and a [[Tupolev Tu-154]], 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.
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[[File:ACAS Protection Volumes Diagram.svg|TCAS Volume|center]]
 
{| class="wikitable"
|+ Symbols used to depict nearby traffic on cockpit displays
|-
| style="color: aqua" | ◇
| Distant traffic
|-
| style="color: aqua" | ◆
| Traffic within 6 NM horizontally and 1200 feet vertically
|-
| style="color: gold" | ●
| Traffic close enough to trigger TA, within 40 seconds of potential collision
|-
| style="color: red" | ■
| Traffic close enough to trigger RA, within 25 seconds of potential collision
|}
 
=== System components ===
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* TCAS is not fitted to many smaller aircraft mainly due to the high costs involved (between $25,000 and $150,000). Many smaller personal business jets for example, are currently not legally required to have TCAS installed, even though they fly in the same airspace as larger aircraft that are required to have proper TCAS equipment on board. The TCAS system can only perform at its true operational potential once all aircraft in any given airspace have a properly working TCAS unit on board.
* TCAS requires that both conflicting aircraft have transponders. If one aircraft doesn't have a transponder, then it will not alert TCAS as there is no information being transmitted.
* Military aircraft may not be using TCAS. They could be operating with their transponders off based on their mission requirements.
 
To overcome some of these limitations, the FAA is developing a new collision avoidance logic based on dynamic programming.
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|Europe ([[European Aviation Safety Agency|EASA]])
|All civil turbine-powered transport aircraft with more than 19 passenger seats (or MTOM above 5,700&nbsp;kg)<ref name="eurocontrol" />
|ACAS II (Effectively TCAS II Version 7.1)
|1 March 2012
|-
|Europe ([[European Aviation Safety Agency|EASA]])
|All civil turbine-powered transport aircraft with more than 19 passenger seats (or MTOM above 5,700&nbsp;kg)<ref name="eurocontrol" />
|ACAS Xa<ref>{{cite web|title=European legislation clears aircraft to fly with ACAS Xa collision-avoidance systems|url=https://www.flightglobal.com/safety/european-legislation-clears-aircraft-to-fly-with-acas-xa-collision-avoidance-systems/162070.article|date=2025-03-05|archiveurl=https://archive.today/20250305110955/https://www.flightglobal.com/safety/european-legislation-clears-aircraft-to-fly-with-acas-xa-collision-avoidance-systems/162070.article|archivedate = 2025-03-05}}</ref> or ACAS II (Effectively TCAS II Version 7.1)
|10 March 2025
|-
|Australia ([[Civil Aviation Safety Authority|CASA]])
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* [https://web.archive.org/web/20100421004001/http://www.eurocontrol.int/msa/public/standard_page/ACAS_Upcoming_Changes.html TCAS II Version 7.1]
* [http://www.allstar.fiu.edu/aero/TCAS.htm Discussion of TCAS] {{Webarchive|url=https://web.archive.org/web/20050831201200/http://www.allstar.fiu.edu/aero/TCAS.htm |date=2005-08-31 }}
* {{usurped|1=[https://web.archive.org/web/20070209222607/http://www.airsport-corp.com/adsb2.htm Critical discussion of TCAS using hypothetical abuse/exploit scenarios of TCAS usage]}}
* [http://www.faa.gov/documentLibrary/media/Advisory_Circular/TCAS%20II%20V7.1%20Intro%20booklet.pdf Introduction to TCAS II Version 7.1]
* [https://web.archive.org/web/20110612131435/http://www.eurocontrol.int/msa/gallery/content/public/documents/SIRE+_WP7_69D_v1.2.pdf Decision criteria for regulatory measures on TCAS II version 7.1]