Originally Posted by
Easy Street
Are you proposing here that aircraft should remain at their cleared level while depressurised and communicate with ATC before initiating emergency descent, working from the idea that emergency oxygen will supposedly last 15 minutes or so? If so, have you considered that time of useful consciousness is measured in single-digit seconds at modern airliner cruise altitudes? It is doubtful IMHO that all passengers and cabin crew would succeed in donning masks, much less be able to report 100% success to the flight deck in any kind of meaningful timeframe, so the only course open to pilots wishing to maximise the chances of survival of anyone who's failed to don a mask is to descend immediately upon depressurisation. A depressurised cockpit is not a place for complex thinking, cross-monitoring, assessing the state of the cabin, or negotiating a descent clearance with ATC - all communication is difficult under emergency oxygen, and anyone who has undergone decompression training can attest to the shock inducing effect of sudden cold and hyperventilation, which is likely to persist until some time after emergency oxygen is established. What's needed in this situation is a simple, mechanical drill which addresses the immediate and otherwise-inescapable threat to life presented by high cabin altitude. By comparison, midair collision is only a possibility, and one which other parties (not suffering the immediate and certain threat of decompression) can do their part to avert with full mental capacity in relative warmth and comfort. The existence of TCAS surely makes this a much safer procedure than it was many years ago. Triggering multiple RAs should be the least of anyone's concerns in this situation because TCAS is very good at changing its instructions as required to deal with the highest threat, whether that is the descending emergency aircraft or another aircraft making an RA against it.
The hypoxia and other distressing effects you describe would clearly be less injurious to the overall physical wellbeing of passengers and crew than mid-air collision.
Perhaps positive pressure oxygen systems for passengers and cabin crew would help to mitigate hypoxia effects while the flight deck crew attempt to negotiate an emergency descent clearance with ATC.
Hopefully this headline will never appear in our newspapers:
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COLLISION AIRLINER DESCENDED WITHOUT PERMISSION AFTER CABIN AIR PRESSURE FAILURE