Originally Posted by
Discorde
'Turning out of the airway' might be impossible in some congested regions of airspace with many aircraft on direct routings, such as the NE or SW US or NW Europe.
An aircraft dropping through the levels at a very high rate of descent might trigger an avalanche of interreacting TCAS RAs in surrounding traffic which in turn might jeopardise safe separations.
Can modern ATC and TCAS systems adequately deal with such an event? (I ask as someone who retired from the business 14 years ago.)
The country's AIP will advise about remaining in, or turning out of an airway during an Emerg. Des, which is why I said 'usually' and is something you need to be aware of in advance.
As for TCAS, well that's why one of the PM memory actions for Emergency Descent is to select TCAS to TA only: Your own aircraft won't then be asked to react to conflicts, but any others around - who are more capable to respond - will be.