RTF Phraseology associated with TCAS RAs

By its nature, a Airborne Collision Avoidance System (ACAS) RA is a warning of an immediate risk of collision. It is therefore essential that all activities connected with response to a TCAS RA should make a positive contribution to collision avoidance. For this reason, RTF phraseology associated with TCAS RAs must be clear, precise and unambiguous.

RTF phraseology has developed following the introduction of TCAS in response to emerging problems. This has resulted in extensive revision of procedures contained in ICAO Doc 4444: PANS-ATM and ICAO Doc 8168: PANS-OPS. The current phraseology is detailed below. (ICAO Doc 4444 PANS-ATM, Chapter 12, Para

After a flight starts to deviate from any ATC clearance or instruction to comply with a TCAS RA(callsign) TCAS RAROGER
After the response to a TCAS RA is completed and a return to the ATC clearance or instruction is initiatedCLEAR OF CONFLICT. RETURNING TO (assigned clearance)ROGER (or alternative instruction)
After the response to a TCAS RA is completed and the assigned ATC clearance or instruction has been resumedCLEAR OF CONFLICT (assigned clearance) RESUMEDROGER (or alternative instruction)
After an ATC clearance or instruction contradictory to the TCAS RA is received, the flight crew will follow the RA and inform ATC directlyUNABLE, TCAS RAROGER

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