TCAS Question
I was flying with a captain recently and we discussed an incident in which another aircraft had been vectored to pass 500' over the top of his aircraft. The incident occurred in the US and the other aircraft was operating VFR. Aside from the legality of this clearance, what confused us was whether this would generate a TCAS RA given that both aircraft would pass each other flying straight and level.
Does TCAS only give RA's if there is an actual impending collision or does it give RAs if the clearance between you and the conflicting aircraft drops below a certain figure? If so, what is that minimum clearance?