Reporting the mid-air collision over Germany on 1 July this year, you state "if both crews had followed their RA [resolution advisory], the accident would have been avoided" (Flight International, 3-9 September).
However, the details of the report seem to indicate the same would be true if no aircraft had received and followed the traffic alert and collision avoidance system (TCAS) instruction.
The Russian aircraft seems to have been established in descent away from FL360, following air traffic control instruction, when the RA order to climb was issued.
Training in responding to TCAS is an issue. However, the basic problem lies in two conflict-avoidance systems being in conflict (ATC and ACAS), and so long as these systems are not co-ordinated, similar critical situations seem likely.
Jens Gjerlev
Bodo, Norway
Source: Flight International
