Re: TCAS on Emer Descent
LEM - I disagree that we always have to consider 'Murphy's Law' when planning for these sorts of scenarios. As with everything else in Aviation we have to always also consider probabilities, otherwise everything ends up being so over-engineered and doubly- triply-redundant that we can't fly in the first case.
There are some aircraft around without TCAS, though nowadays very few in UK/Central European airspace above FL100 (I have no experience of Oceanic flying so my comments cannot be extended to that arena). Additionally, I would hope that one is able to talk to ATC within the first 30 seconds of beginning an Emergency Descent (when one will have likely descended only 3-4000 from cruising level) who should then be able to provide assistance as well.
Or are we expected to always consider a depressurisation, comms failure AND non-TCAS traffic above FL100/MSA? This is where it seems our respective opinions diverge.
As I have said before, the 'answer' really depends on the personal judgement of the crew on the day, taking into account airspace, traffic levels, ATC service, terrain, and aircraft equipment, amongst other things. I am not brave enough to say ALWAYS do this, or NEVER do that in such circumstances; in certain situations I would probably take your advice (and may not have considered that scenario until you mentioned it here, so thank you), but my advice will remain as it has been, for those of us in busy controller airspace: select TA and let those other black boxes out there know you won't be doing anything except descend!
For info, an ADJUST VERTICAL SPEED can be more than just a level off - this summer over East Germany I was descended to FL270 from FL350 and turned into traffic climbing into me - my 2000fpm descent was eventually transformed by an ADJUST VERTICAL SPEED into a 1800fpm climb (though the scenario was resolved very shortly afterwards).
MrB - you ask an interesting question, I'd like to know the answer to that as well!