FAA Aircraft Dispatcher (ADX)Navigation and ATCMedium
During an approach in IMC, a Part 121 crew's Traffic Alert and Collision Avoidance System (TCAS) issues a Resolution Advisory (RA) instructing a climb, while ATC simultaneously issues an instruction to descend. What is the correct crew action?
- AFollow the ATC descend instruction since ATC has separation authority
- BFollow the TCAS RA climb instruction and notify ATC as soon as practical
- CDisregard both instructions and continue the current approach profile
- DSplit the difference by maintaining level flight until the conflict resolves
Show answer & explanationAnswer & explanation
Correct answer: B. Follow the TCAS RA climb instruction and notify ATC as soon as practical
FAA guidance requires flight crews to follow a TCAS Resolution Advisory even if it conflicts with an ATC instruction, since the RA is based on the immediate traffic conflict information not available to the controller. The crew should comply with the RA and advise ATC of the deviation as soon as practical.
Why the other options are wrong
- A. ATC instructions do not override an active TCAS RA.
- C. Ignoring the RA defeats the collision avoidance protection it provides.
- D. Splitting the difference does not follow either instruction and increases collision risk.
TCAS Resolution Advisory Priority
When a TCAS Resolution Advisory conflicts with an ATC instruction, the flight crew must follow the RA and notify ATC of the deviation as soon as practical.
- TCAS RA takes priority over conflicting ATC instructions
- Crew must respond promptly and notify ATC after complying
- Traffic Advisories (TA) do not require evasive action, only increased vigilance
- TCAS uses transponder replies from nearby aircraft to compute closure rate
Memory trick: 'RA rules' — Resolution Advisory beats ATC every time