Your excellent editorial "Basic Instinct" (Flight International, 16-22 July) [referring to the DHL Boeing 756 and Bashkirian Airlines Tupolev Tu-154M collision on 1 July] correctly stresses the primary need for pilot training to reinforce the rule that an ACAS resolution advisory (RA) must take precedence over contradictory ATC instructions.
However, in considering the circumstances of the 1 July tragedy, I was struck by the obvious shortcoming of the current ACAS systems which do not include ATC in the loop.
While changes to pilot training can be introduced relatively quickly and should, if effective, remove the possibility of a recurrence of this accident, I would suggest that a longer-term, secondary objective should be to make the ACAS RA automatically available to the controller as soon as it is given to the pilot.
This could be achieved by adding the RA instruction to the transponder squawk, so that an appropriate symbol could appear on the controller's display. This would achieve two objectives.
Firstly, it will ensure that the controller's instructions reinforced, rather than countermanded, the ACAS response and secondly, it will alert the controller to the likely situation he/she will face after the conflict is resolved, ensuring that ATC regains control of both aircraft in a timely manner after the immediate danger has passed.
Brian M Matthews
West Sussex, UK
Source: Flight International
