Originally Posted by
The Fat Controller
If only I had the luxury of concentrating on just 2 aircraft to separate
Comments as to how ATC worked 37+ years ago are not very helpful
This crossing scenario happens often and in this instance was identified, correct lateral avoiding action
WAS given and
IF the pilots had acted immediately and correctly, as the report states, separation
WOULD NOT have been eroded.
Granted, the confliction was not marked on the strips, but it could just have easily been missed using paper.
I am valid on the sector concerned.
The problem here is what is called open-loop instructions as compared to closed-loop instructions.
With open-loop instructions an aircraft is told (as in this case) turn right heading (sic) 050. Pilot then reaches forward and selects 050 on the FMS. The controller may have in his head what to do next but nobody else does, least of all the crew. Similarly as in this case the lower aircraft was cleared to climb flight level 340 - controller knows something needs to happen after that but its an open loop as he may not have thought ahead or if he has it is only shown by cocked strips - or electronic highlight and an interrupt like a stuck mic or a controller relief and all can go pear shaped rather rapidly.
The trajectory based control systems that are just starting to appear in European airspace are 'closed loop'. An aircraft isn't put onto a heading or told to climb to a level, the trajectory which runs all the way to destination is given constraints (level, position and time windows) that it has to pass through. In this case the controller giving the lower aircraft a level constraint of FL340 would have received an immediate medium term conflict alert with the other aircraft as the new trajectory would be in conflict, so the controller would then have put in a lateral constraint on the trajectory that would have cleared the conflict. So the aircraft would now received a trajectory amendment with a climb and a deconflicting lateral constraint- not unlike an oceanic routeclearance.
Closed loop control is the way of the future systems. It will move air traffic management from the known traffic environment to the known trajectory environment with FMCs sharing their trajectories with the ground systems. It will also enable more efficient 'business trajectories'.
Experience gained 30+ years ago in that airspace being used to create more efficient and probably safer systems for the future.