2-1-28. TCAS RESOLUTION ADVISORIES
When an aircraft under your control jurisdiction informs you that it is responding to a TCAS Resolution Advisory
(RA), do not issue control instructions that are contrary to the RA procedure that a crew member has advised you
that they are executing. Provide safety alerts regarding terrain or obstructions and traffic advisories for the
aircraft responding to the RA and all other aircraft under your control jurisdiction, as appropriate.
Unless advised by other aircraft that they are also responding to a TCAS RA, do not assume that other aircraft in
the proximity of the responding aircraft are involved in the RA maneuver or are aware of the responding aircraft's
intended maneuvers. Continue to provide control instructions, safety alerts, and traffic advisories as appropriate
to such aircraft.
NOTE: When notified by the pilot of an RA, the controller is not prohibited from issuing traffic advisories and
Once the responding aircraft has begun a maneuver in response to an RA, the controller is not responsible for
providing approved separation between the aircraft that is responding to an RA and any other aircraft, airspace,
terrain or obstructions. Responsibility for approved separation resumes when one of the following conditions is
- The responding aircraft has returned to its assigned altitude, or
A crew member informs you that the TCAS maneuver is completed and you observe that approved separation has
been reestablished, or
The responding aircraft has executed an alternate clearance and you observe that approved separation has been
NOTE: 1. AC 120-55, Air Carrier Operational Approval and Use of TCAS II, suggests pilots use the following
phraseology to notify controllers during TCAS events. When a TCAS RA may affect an ATC clearance, inform ATC when
beginning the maneuver, or as soon as workload permits.
- 1. “New York Center, United 321, TCAS RA.”
NOTE: 2. When the RA has been resolved, the flight crew should advise ATC they are returning to their previously
assigned clearance or subsequent amended clearance.
- 2. “New York Center, United 321, clear of conflict, returning to assigned altitude.”