Originally Posted by
buzzc152
....
A) Does TCAS know what you can and can't achieve ?
Sometimes, yes.
AC20-131A provides guidance for approval of TCAS II systems. One of the requirements, in para (6), is that
The collision avoidance maneuvers posted as RAs by TCAS II assume an aircraft's ability to safely achieve them. If it is likely they are beyond the capability of the aircraft, then TCAS II must know beforehand so it can change its strategy and issue an alternative RA. These performance limits shall be provided to TCAS II from the aircraft interface and discretes relative to altitude and/or configuration. However, the need to inhibit TCAS II CLIMB or INCREASE CLIMB RAs should
Testing/analysis is conducted to determine a flight envelope within which RAs can be complied with safely, and the inhibit is outside that enveleope.
Note that the enevelope so defined is not exact, nor necessarily correct for the specific aircraft on a specific day, since any deterioration or excess performance on a given aircraft cannot be known. Also, there is a desire to not overly restrict the RA envelope by making excessively conservative assumptions, as this would deny useful RAs in many cases.
Thus there will be "edge of the envelope" RAs which some aircraft can achieve, but other cannot. But this design approach at least ensures that RAs which that type cannot comply with under any reasonable assumptions are excluded.