Originally Posted by Frangible
Your first point. It may well have been a “rational choice”, but there is no evidence it is the one the Russians took,
Correct.
Originally Posted by Frangible
so you are only confusing matters by calling it “crucial”.
To date (five years), only a couple people have been confused.
Originally Posted by Frangible
Your second point. If the instructor searched in vain, it does not mean he or the crew were confused, especially as they did not discuss it.
He was the commander of the airplane. If he is looking for it, it means he thinks it might be there. If he thinks it might be there, it is reasonable to assume it will enter his decision-making (recall, he made the decision to continue to descend, against the query of the PF).
But you are right, and I emphasise again, that I am not attempting to *explain the actual decision*, merely to point out that it is a rational decision-theoretic choice.
Originally Posted by Frangible
You are introducing the possibility of confusion by fastening on a speculative case rather than the actual, accepted case.
I am analysing a specific scenario which is very, very close to the Überlingen scenario, if not identical with it.
This is exactly what hazard analysts do. This is what the laws of most countries require to be done before any piece of safety-related digital equipment such as TCAS is introduced into use.
If that introduces the "possibility of confusion", then so be it.
Originally Posted by Frangible
No TCAS design could possibly account for a factor completely extraneous to it, e.g. a controller getting on the horn and telling the crew to do the opposite of the TCAS instruction.
Now, you see, I don't believe that.
Hazard analysis *has to* account for factors completely extraneous to systems. That is what hazard analysis is.
Originally Posted by Frangible
It was the responsibility of the managers and regulators of air traffic control generally to demarcate the respective responsibilities of the controller and TCAS in all situations, and they failed to do that unambiguously.
Well, yes, but that is a separate issue. BTW, that demarcation is still ambiguous, and will remain so for the foreseeable future.
Originally Posted by Frangible
I somehow doubt, however, that the risks here are not understood and have been ignored.
On what basis do you doubt it?
Originally Posted by Frangible
I spoke of incidents only [rather than collisions].
I see. Maybe it wasn't clear to me what you were meaning to say. You said
Originally Posted by Frangible
.... incidents ...... where pilots thought their visual intepretation of a TCAS situation was better than the gizmo’s, and they were wrong every time.
You explain now:
Originally Posted by Frangible
I simply suggest that there have been rare cases where pilots thought they knew better than TCAS, and your remarks could encourage that tendency.
Well, you see, it is that "every time" that is problematic. There are a number of incidents in which the human interpretation was *in fact* better than that of TCAS.
Originally Posted by Frangible
you, incidentally, will acquire lots more credit if you drop the sarcasm.
Sorry you took it badly. I was trying to be humorous. I don't need the credit, thanks (or even the extra credit....).
Could you maybe actually answer the questions that the smileys were attached to? There is a reason I asked them.
PBL