SERA.11014 ACAS resolution advisory (RA)

(a) ACAS II shall be used during flight, except as provided in the minimum equipment list specified in Commission Regulation (EU) No 965/2012 in a mode that enables RA indications to be produced for the flight crew when undue proximity to another aircraft is detected. This shall not apply if inhibition of RA indication mode (using traffic advisory (TA) indication only or equivalent) is called for by an abnormal procedure or due to performance-limiting conditions.

(b) In the event of an ACAS RA, pilots shall:

(1)  respond immediately by following the RA, as indicated, unless doing so would jeopardise the safety of the aircraft;

(2)  follow the RA even if there is a conflict between the RA and an ATC instruction to manoeuvre;

(3)  not manoeuvre in the opposite sense to an RA;

(4)  as soon as possible, as permitted by flight crew workload, notify the appropriate ATC unit of any RA which requires a deviation from the current ATC instruction or clearance;

(5)  promptly comply with any modified RAs;

(6)  limit the alterations of the flight path to the minimum extent necessary to comply with the RAs;

(7)  promptly return to the terms of the ATC instruction or clearance when the conflict is resolved; and

(8)  notify ATC when returning to the current clearance.

(c) When a pilot reports an ACAS RA, the controller shall not attempt to modify the aircraft flight path until the pilot reports ‘CLEAR OF CONFLICT’.

(d) Once an aircraft departs from its ATC clearance or instruction in compliance with an RA, or a pilot reports an RA, the controller ceases to be responsible for providing separation between that aircraft and any other aircraft affected as a direct consequence of the manoeuvre induced by the RA. The controller shall resume responsibility for providing separation to all the affected aircraft when:

(1)  the controller acknowledges a report from the flight crew that the aircraft has resumed the current clearance; or

(2)  the controller acknowledges a report from the flight crew that the aircraft is resuming the current clearance and issues an alternative clearance which is acknowledged by the flight crew.