Roy Smith writes:

wrote:
This also explains why cabin depressurization above 30000 feet is an
emergency requiring (a) the immediate donning by the pilot(s) of a pressure
mask and (b) emergency descent to an altitude where the conventional
emergency masks used by passengers will be sufficient.

I believe that emergency descent capability is one of the factors that
limits allowable operating ceilings. Some aircraft could get higher than
their certified ceilings, but are not allowed to do so because getting down
to breathable air before the pax suffocated would involve tearing the wings
off (or some other overspeed disaster).

After that golfer bizjet case; I mentally speculated about an
autopilot altitude un-hold. When the cabin pressure failed, the
autopilot would decend to $FEET, that being a level humans would
revive at.

Of course, you COULD run into Mount Whatever, but you're surely
dead at altitude...

It's not clear to me what the survival time is those altitudes; I
thought it was several minutes...


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