It is an invaluable tool with uses far beyond simple collision avoidance.
I'm more than a little interested in your thoughts on this. Just exactly what other uses do you believe exist aside from providing Traffic Advisories and, heaven forbid, Resolution Advisories if the parameters are met.
I believe (and I'm relying on my poor memory here) there was a trial a couple of years ago over the Atlantic where TCAS was being considered for climb through "separation" or something like that, but I didn't hear any more about it.
And to pick up a point that
4-3-3 has spoken about reference a request for level change and "obvious conflictions", the azimuth of TCAS is no where as accurate as the radar we use (hence the reason RAs are only given in the vertical), and what may be perceived as a conflict on the flight deck may not be at all (adhering to our separation standards). Or perhaps a cheeky little vector could be used. On the other side, I have had pilots request further climb/descent whe they are about to get a face full of opposite direction traffic.
If questioning ATC by relatively small number of pilots is a by product of TCAS (and I'm sure it is) then it will simply have to be accepted as is more than offset the positives TCAS offers
I do find this unacceptable. Yes, we all know a captain is ultimately responsible for his aircraft and all those on board. However, if ATC issue an instruction and a driver looks at his TCAS and doesn't agree simply because he/she is using it for something that it isn't designed for (ie where THEY think they are in the sequence) then that is folly indeed. And
Westy, I see you're still waving that "relatively small number of pilots" flag. With all due respect, I've spoken with quite a few guys I work with who have worked in various parts of the world, and more than a few have agreed "Yeah, that's happened to me", so the incidence of it isn't exactly insignificant. And it shouldn't "have" to be accepted.