When two conflicting traffics reach de RA threshold but one of them is in TA only, What does the TA/RA one do?
I guess it executes an RA, right?
and this RA has to take into account the lack of RA on the other traffic. Probably it assumes that the conflicting traffic will maintain path. If it changes, then RA will change, too.
I'm just guessin, but I think this is the key. Airplanes wihich performance is compromised should not execute RAs. The conflicting traffics will.
In Airbus fbw, the procedure is TA only when engine out.