Airborne Collision Avoidance System (ACAS) guide

This Airborne Collison Avoidance System (ACAS) Guide has been designed to support the understanding of the ACAS systems and the training of people involved in the operations of ACAS.

However, it is not, per se, designed for the complete training of controllers or pilots. For a deeper knowledge, the Reader is advised to refer to documentation listed in the bibliography section.

The Guide concentrates on operational principles as well as technical details of TCAS II version 7.1, as it is the version currently mandated and operated in Europe. The previous TCAS II versions 6.04a and 7.0, as well as TCAS I system, are also briefly described. Moreover, the forthcoming ACAS Xa/Xo system is extensively covered but it should be noted that, at the time of publication of this ACAS Guide, this system has not yet been approved for operations in European airspace. Other non-standardised traffic awareness systems, like FLARM, and Portable Collision Avoidance System (PCAS), intended for general aviation or military aircraft are not covered.

The information contained in this Guide, EUROCONTROL ACAS II Bulletins and training presentations is based on the ICAO provisions and other applicable regulations. The information is considered to be accurate at the time of publishing but is subject to change.


Airborne Collision Avoidance System (ACAS) guide - March 2022