Ouch GB!!. I agree with all your points here, Transponder altitude accuracy is PARAMOUNT. (I do miss having to test Mode A & C with the ATC 600. In the pre CMC days you got to test the transponder replies for real, checking P1, P2s etc. Ahh the nostalgia of it all).
Regarding what you said about the directional antennas, I seem to remember that one of the reasons for the lack of TCAS 3 implementation was the poor azimuth resolution of the TCAS " directional antennas.
On my previous fleet I remember that when we intitially fitted TCAS. MOST of my pilot friends were extremely sceptical about it's value. However, within weeks of finally going live, one of our aircraft was climbing FAST out of JFK on it's way back to LHR when we got an RA. A KC-10 with 2 F15s in tow was where it should not have been, and a certain near miss was avoided. (Within a few months of living with TCAS operation, none of our guys would ever want to be without it).
Last edited by M2dude; 2nd Feb 2010 at 13:24.