Airborne collision avoidance system

The U.S. Air Force's F-16D Ground Collision Avoidance Technology (GCAT) aircraft.

An airborne collision avoidance system (ACAS, usually pronounced as ay-kas) operates independently of ground-based equipment and air traffic control in warning pilots of the presence of other aircraft that may present a threat of collision. If the risk of collision is imminent, the system recommends a maneuver that will reduce the risk of collision. ACAS standards and recommended practices are mainly defined in annex 10, volume IV, of the Convention on International Civil Aviation.[1] Much of the technology being applied to both military and general aviation today has been undergoing development by NASA and other partners since the 1980s.[2]

A distinction is increasingly being made between ACAS and ASAS (airborne separation assurance system). ACAS is being used to describe short-range systems intended to prevent actual metal-on-metal collisions. In contrast, ASAS is being used to describe longer-range systems used to maintain standard en route separation between aircraft (5 nautical miles (9.3 km) horizontal and 1,000 feet (300 m) vertical).[3]

  1. ^ "EUROCONTROL - ACAS II ICAO Provisions". Archived from the original on 2010-04-21. Retrieved 2010-04-18.
  2. ^ "NASA-Pioneered Automatic Ground-Collision Avoidance System Operational". NASA website. Retrieved 8 Oct 2014.
  3. ^ [Hoekstra, J.M. (2002). Free flight with airborne separation assurance. Report No. NLR-TP-2002-170. National Aerospace Laboratory NLR.]