Originally Posted by
BlueMoon
Just as a correction above...mode S transponders aren't required...TCAS works with Mode-C as well. The TCAS system figures out collision hazards and not the transponders. If one aircraft has TCAS and the other doesn't the aircraft with TCAS will still get an RA.
No, you need each aircraft to be equipped with TCAS II to get an RA, in all other cases, only a TA will be issued (the box cannot tell you which way to go unless it knows where the other guy is going...and can you imagine the lawsuit if TCAS told an aircraft to climb into the path of a non-TCAS Aircraft?).