# Commission Regulation (EU) No 1332/2011 of 16 December 2011 laying down common airspace usage requirements and operating procedures for airborne collision avoidance (Text with EEA relevance), Article 2: Definitions

Extent: E+W+S+N.I.

For the purposes of this Regulation the following definitions shall apply:
(1) ‘airborne collision avoidance system (ACAS)’ means an aircraft system based on secondary surveillance radar (SSR) transponder signals which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with SSR transponders;
(2) ‘airborne collision avoidance system II (ACAS II)’ means an airborne collision avoidance system which provides vertical resolution advisories in addition to traffic advisories;
(3) ‘resolution advisory (RA) indication’ means an indication given to the flight crew recommending a manoeuvre intended to provide separation from all threats or a manoeuvre restriction intended to maintain existing separation;
(4) ‘traffic advisory (TA) indication’ means an indication given to the flight crew that the proximity of another aircraft is a potential threat.

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Source: https://www.legislation.gov.uk/eur/2011/1332/article/2 (the official version)
Page: https://openlegislation.uk/eu-regulation-2011-1332/article-2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.