Originally Posted by Fat Controller
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 ...
But four pilots each with a brain supposedly plugged in to the radio transmissions of one ATC brain did NOT heed "the correct lateral avoiding action" which was "given". I think we might therefore be entitled to ask when is receipt / compliance with an ATC instruction a "given" (or not) ?
Is it for example:
(a) When a request to climb to a desired level is cleared without any cautionary condition attached about the new level having created a convergence problem ?
(b) When a sudden instruction to turn on the end of a busy series of transmissions to other aircraft is read back correctly ?
(c) When the aircraft addressed with the urgent instruction responds only with a transmission comprising just the digits of its callsign ?
(d) When the onscreen radar track appears to reflect the instruction given ?
(e) When the onscreen radar track appears to reflect the opposite of the instruction given ?
I don't think the report was particularly clear on all this beyond it being clear that the 5 brains involved in communicating and executing the instructions clearly were not ad idem (or was it 6 brains eventually including two ATCOs ?). At best it appears that at one point three pairs of brains were doing their own thing with each being unaware of what the other pairs were doing or expecting to be done.
I don't know if ATCO(1) realised it was a "given" when he ultimately cleared 747(2) to 340 or whether those posters reading the report have realised it, but once at the same level and using the data in the report it would appear that between 1252:00 and 1255:22 when low level STCA was triggered i.e. in 3.35 minutes the two aircraft had converged 14.5nm. That is a
closing speed of 260 knots. In the next 38 seconds the aircraft closed a further 3.2nm i.e. an
increased closing speed of 303 knots.
In the next 17 seconds before high level STCA alerted, a further 1.7nm separation was lost (that is a
further increased closing speed of 360 knots or 185 metres a second with just 9000m left to close or
just 48 seconds left until tracks cross).
Now when, as had already been seen in this incident, you factor in that the first attempt to instruct the aircraft to take avoiding action had taken almost a full minute to establish as not happening, we can begin to guess what colour pants ATCOs might favour for these frequent crossing scenarios. I am sure they are more aware of the hazards of the closing speeds involved than any civilian pilot. Question is, when they see one coming, how will they get the message across next time without the fail ?
I have to say, that "Resume own navigation" intruction that followed the first little fiasco was a little ironic (that's the fiasco up to about 1257 which warranted the description "airprox"). Own navigation seems largely to have been what was pervading from the moment 747(2) decided they wanted a better level and were given it!
Then,
love-a-duck, just when some of us may have stopped reading the report and breathed a sigh of relief that it obviously all turned out ok with thousands of metres to spare, we get another STCA alert at 1258:20 seemingly caused by 747(2) having drifted down out of their 340 level just a couple of minutes after the first STCA alert! Perhaps they'd decided 340 was feeling a bit crowded / own navigation is the better part of valour etc...
So then, Part 2 of this buggers muddle then also takes the best part of a minute to resolve including two new ATC avoiding action instructions, one of which this time is queried and cancelled when the aircraft seem to have straightened themselves out (TCAS
?).
Anyway, I really do hope this wasn't that typical "not newsworthy" day out some posters would have us believe it was.