Hi mikemal
Quick Reference Checklist (QRH), Airbus states "Do not manoeuvre based on a TA alone". We have similar wording in the Boeing manuals.
I would say that if you see the other traffic, and manoeuvring is required, then this is not on TA alone. If you can find space on the radio, (not always easy) you 'should' have 40 secs to enquire with ATC, ask for a hdg or what ever you deem to be neccessary.
From Memory, somewhere in my Boeing training, I was told performance is not taken into account for the TCAS command. That doesn't of course mean what was told is the actual truth.
Engine failures are rare events. RAs are rare events. I guess murphy says you can have a really bad day and combine them on one day. I wonder however if this is part of Boeing/Airbus risk assessment and management. Regulatory authorities do not consider compounding failures in some other areas.
What happens to the TCAS commands (other acft) if you decide during a manoeuver to switch from TARA to TA as you have run out of performance?
Still plan to follow the QRH
IBT