The problem is when you get conflicting advice from ATC and TCAS, particularly if in the order:
- ATC advice
- starting following ATC
- TCAS RA
Which I do not see you considering at all. You seem to be stuck in the scenario where ATC has in fact failed. But the premise that that has always happened at the time TCAS issues an RA does not hold.
From a pilot's POV I have to assume that there has been a failure of ATC when in receipt of an RA and act appropriately. Why? If I assume that ATC has not failed and carry on with their advice (possibly against an RA) and I am wrong in that assumption, I could be part of an accident. If I follow the RA, it will keep me clear of traffic, whether ATC are giving valid commands or not...
I one of my previous posts I said:
No, the controller carries on trying to separate the traffic. If, in extremis, there comes a point where there are conflicting instructions from ATC and TCAS, TCAS is followed.
and
If it gets to the point of an RA, then TCAS "controls the vertical" and ATC are informed ASAP of a deviation. Climb or descent instructions from ATC are ignored as their information is not as up-to-date as that possessed by the TCAS computers. (Amongst other reasons.)
I think that covers the conflict case?
Off flying across the Atlantic now with my trusty TCAS, EGPWS and sextant.