Emergency Descet
 

after descending to the safe altitude/ 10000 ft the nncl calls to remove the oxygen masks. Is it 10000 ft pr alt or cabin altitude :confused:

If you are depressurised (and I'm assuming thats the reason for rapid descent) then your cabin altitude will be the same as your altimeter or slightly lagging behind it, so it won't really matter

But to be safe I'd go with cabin alt. if there is a difference

i think the nnc states cabin altitude, i know what i would use

typos
 

Greetings
I any case regulation talks about cabin altitude, so it is CABIN ALTITUDE, however to be pratical as our colleague wrote above is you are depressurized they should be very closes to one another.
So in the SIM look at your CABIN ALTITUDE, one crew removing its mask at a time (usually Captain ask FO to do it first :*)

Don't know whose procedures you might be referring to, but at my airline it is MSA or 10000ft altitude, not cabin altitude.

From a practical point of view, exactly how would you propose to fly your a/c type using cabin altitude as the reference? I very much doubt your pressurisation instruments are a certified flight instrument. Would certainly make for some hair-raising ATC controlling.

Greetings,
No body said that you fly your aircraft based on Cabin Altitude :ugh:, I said that Cabin altitude is the reference for regulatory authorities because it is what you are breathing :}
I am always amazed by the way people jump on things, without reading slowly and properly what is writen, I hope you dont do the same thing when you operate :hmm:
BTW, when the CABIN ALTITUDE warning extinguishes it simply means that you are below 10000 ft :O regardless of what you have on your altimeters :E

That really depends on your airplane.

It's possible to have a cabin above or below the indicated or pressure altitude, especially following a rapid descent. Your cabin altitude will generally be close to the indicated altitude, though it could lag by a considerable margin depending on how tight the cabin is, and the nature of the problem. If you happened to have an over pressurization event and shut off the pressurization as a result (and then descended), you may have a cabin below your level-off altitude.

So far as the use of oxygen, the aircraft altitude is irrelevant...the oxygen isn't for the airplane, it's for you, and all that's important to you is cabin altitude.

Descend to a safe altitude and continue on oxygen once the aircraft cabin is at or below that altitude, if the safe altitude is one at which you can get off the oxgyen. A safe altitude doesn't mean a safe cabin altitude however, as the MEA for that area may be too high to permit going off oxygen. There are spots around the world where rushing to 10,000 will hurt you and your crew, and you could very well arrive there even though it's a safe altitude and find the cabin lagging well behind. Descend to the safe altitude, and remove your oxygen mast when it's safe and advisable to do so. That isn't necessarily at the same time you arrive at your descent altitude.

Greetings,
Thanks:ok: