It is a fundamental principle of flight that those involved in the management of a flight, especially pilots and air traffic controllers, shall take all necesary action to avoid collision.
Collision avoidance is achieved when the pilot(s) maneuver(s) the aircraft after becoming aware of conflicting traffic by one of the following means:
- Visual observation:
- The pilot takes visual avoiding action (application of the "See and Avoid" principle); or,
- Traffic information provided by Air Traffic Control:
- The pilot follows avoiding action instructed by the ATCO.
ICAO Annex 2: Rules of the Air, Chapter 3 establishes the following standard:
"An aircraft shall not be operated in such proximity to other aircraft as to create a collision hazard."
Annex 2, Chapter 3 Paragraph 3.2.2 then proceeds to enunciate the basic rules governing Right-of-way which are applied internationally.
Subsequent paragraphs deal with standards and recommended practices (SARPS) concerning collision avoidance, under the following headings:
- 3.2.3 Lights to be displayed by aircraft;
- 3.2.4 Simulated instrument flights;
- 3.2.5 Operation on and in the vicinity of an aerodrome; and,
Operating procedures for use of ACAS detailing the responsibilities of the pilot-in-command are contained in ICAO Doc 8168: PANS-OPS, Volume I, Part VIII, Chapter 3; and in EU-OPS 1.398.
Carriage requirements for ACAS equipment are addressed in ICAO Annex 6: Operation of Aircraft, Part I, Chapter 6 and Part II, Chapter 6; and in EU-OPS 1.668.