I don't disagree with anything you have said. My phraseology was perhaps confusing. When I said "ultimate cause", I meant the last safety net which should have prevented this collision. My choice of words was misleading I think, I don't believe there was a single
cause for the accident. Certainly a whole chain of events led to this collision, TCAS was the final chain which should
have saved the day, that was my point.
Ignoring the events leading up to the TCAS conflict (which I fully appreciate as part of any aviation accident is impossible to do) it boiled down to no controller at a station, and 2 planes flying towards one another at right angles with the same relative bearing at the same height (= collision course).
The reason TCAS then didn't save the day was not the fault of the equipment, but the fault of the Russian flightcrew, who incorrectly responded to the controller's command rather than the (opposing) TCAS command. This has always been something I have been trained not to do. The TCAS must always
be followed in these circumstances.
I was amazed at discussions between pilots in the aftermath of this accident, some of whom really weren't certain of the correct action to take in this situation.
There is only one solution, FOLLOW TCAS! And it really is that simple.
Ok so in this case it wasn't that simple. There were several events which led to the TCAS RA
which should not have occurred. But if you take the final stages of the flights alone, following the procedure by the book would have saved all those lives.
After this collision, the UK CAA released a reminder to flightcrews of the procedures to follow in this scenario which (paraphrased) reads:
"...If pilots receive simultaneously an instruction to manoeuvre from ATC and an RA, and they conflict, the advice given by ACAS should be followed..."
It's a bit like those pilots over the years who have ignored GPWS warnings below MSA and happily flown their perfectly good airliners, many with hundreds of people on board, into the ground. The technology is there... and it works. If you let it.
I used to love the smell of Jet-A in the morning...