Let's try a different approach, then...
Let's say that you have left the switch in TA/RA. During your emergency descent, you get an RA.
Now, gents, please raise your hand if you would not follow said RA....
...anyone...???
Good, then - that should wrap it up
I know that TA only will modify the response of the other aircraft - but what would that response be, and would it be any different by you selecting TA only? Bear in mind, you are descending @ 4-5000 fpm on a steep profile (that alone reducing the likelihood of conflict, but lets leave that aside for now). If the other aircraft was climbing, cruising or descending on a normal profile - the easiest way to solve the puzzle would (geometrically speaking) be to issue the other aircraft with a climb command and you with a "Monitor vertical speed".
I'm fully aware that a lot of factors could cause the scenario to play out differently (i.e. you getting a climb command) - but it is a game of statistics in the first place. What if - as stated above - the other crew don't know how to deal with their end of the stick? What if you accidentially in the rush of an emerency descent select ALT on your transponder? What if the other a/c is for some reason or another also in TA ONLY mode? Or what if your SOP says nothing about selecting TA ONLY during an emergency descent?
As long as ICAO have not drafted any policies on the matter @ hand, my airline has not implemented the procedure i our SOP and nobody can find a QRH reference for such a drill - I'd be very tempted to get on with the emergency descend & leave the TCAS alone. You are not gonna die from a decompression - both the F/D & C/C are all on oxygen. Nor is a fire gonna kill you in the 1 minute it takes to resolve an RA (if you reacted quickly enough in the first place & initiated the descent & diversion ASAP i.s.o. waiting to find out that it - God forbid - is uncontrollable).
But hitting the other aircraft IS gonna kill you - no matter what your previous actions & subsequent plans!
Any thoughts? Best reagrds - and a merry Chistmas/Holiday to all
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