Ultranomad wrote:
ove you, and TCAS suddenly says “Descend descend”. What shall you do? A TCAS RA in such a situation is fairly likely to be irrelevant – for example, this Eurocontrol study, albeit old, analysed 35 RAs in a hold and found 6 useful ones, 19 nuisance ones (i.e. dictated by TCAS logic but operationally unwarranted), 3 false ones, 4 RAs replicating ATC instructions already issued and 3 with insufficient data
I am not an airline pilot, does not operate aircraft with TCAS (only TAS), and I did not read the survey, but I understand 6 out of 35 were “useful ones”, so more than 17%.
If by “useful one” you can translate to “would have fd up a pilot day if the RA would not have been followed”, I think I would be better safe than sorry, and don’t care if I push adrenaline to my fellow colleague orbiting 1000 feet lower.
Snoopy wrote:
You simply can’t do that in a holding stack over London. Flying airliners, it just doesn’t work that way.
If @Peter’s anecdote about the NATS video is true, it would appear it does.
Just because there was a seminal accident doesn’t mean the issues raised with ELP and competence have gone away. I’m pretty sure some/most airline pilots don’t explicitly trust others in the stack to do the right thing, just as I don’t explicitly trust others in the circuit to do the right thing.
Graham wrote:
Personally I can totally understand why pilots would flee the hold laterally. In this scenario you have one job and that’s to avoid a collision – so it’s better to able to argue the toss afterwards. Of course mine were not airliner/TCAS situations, but I have been in one or two difficult situations with close-proximity traffic doing unexpected things and my philosophy (and the action I took) is to get the hell out of Dodge – I simply fly away from the problem into an area that I can see to be clear. I don’t care whether in doing so I’m breaking a rule, protocol or even a law – I will simply be glad that I’m alive to argue about it afterwards!
You simply can’t do that in a holding stack over London. Flying airliners, it just doesn’t work that way.
Graham wrote:
That’s fine so long as you trust other pilot(s) involved to do the same. I think that @Peter’s point is that, essentially, that may not be the case.
Since Ueberlingen it is the case.
Knowing both worlds and realizing the misconceptions I think it’s too bad jump rides aren’t a thing anymore. Would be a good experience for private pilots.
Snoopy wrote:
That’s the whole point of TCAS. You don’t react / trust humans, you strictly follow the TCAS‘ logic.
The worst you can do is being the 1 of a 2 party TCAS arrangement who comes up with another course of action.
That’s fine so long as you trust other pilot(s) involved to do the same. I think that @Peter’s point is that, essentially, that may not be the case.
I don’t think one can argue for exceptionalism for TCAS. It’s just another system for keeping aircraft apart (like ATC) and there are feasible scenarios where, principally because of the failings of others, it might not keep you alive.
Personally I can totally understand why pilots would flee the hold laterally. In this scenario you have one job and that’s to avoid a collision – so it’s better to able to argue the toss afterwards. Of course mine were not airliner/TCAS situations, but I have been in one or two difficult situations with close-proximity traffic doing unexpected things and my philosophy (and the action I took) is to get the hell out of Dodge – I simply fly away from the problem into an area that I can see to be clear. I don’t care whether in doing so I’m breaking a rule, protocol or even a law – I will simply be glad that I’m alive to argue about it afterwards!
That’s the whole point of TCAS. You don’t react / trust humans, you strictly follow the TCAS‘ logic.
The worst you can do is being the 1 of a 2 party TCAS arrangement who comes up with another course of action.
I don’t have time to scan the internet for other forums, generally 
I understand that SOPs are SOPs and you risk your job if you don’t follow them, but it would take balls of steel to follow the SOP when you know those above and below you are 3rd world airlines, right on the edge of their ELP perhaps, and perhaps not exactly the best trained button-pushers who wrote the answers in the 14 ATPL exams on the back of the Jeppesen chart and applied that philosophy throughout their subsequent career
Especially if your traffic display shows somebody actually getting really close. If I see traffic on my TAS heading for me, traffic which doesn’t exist officially, I am not gonna just sit there and watch it.
Peter wrote:
Yes, at a presentation in Swanwick, c. 10 years ago. The holding stack disintegrated, with planes doing orbits off to the outside of it. At Heathrow, IIRC. The radar display was shown.
As aptly mentioned on another forum, one thing has improved since then: starting from the version 7.1, TCAS II has a Level off, level off advisory, which would provide for 500 ft vertical separation and thus largely prevent a chain reaction of RAs along the holding stack. It may not prevent the pilots from fleeing the stack, but will at least make the whole situation less messy.
Yes, at a presentation in Swanwick, c. 10 years ago. The holding stack disintegrated, with planes doing orbits off to the outside of it. At Heathrow, IIRC. The radar display was shown.
@Peter, do you mean you’ve really seen it?
