Cabin pressurization alarm

[Ralgh 43]

Also keep in mind that under FAR Part 91 in the US pilots are allowed to operate up to 12,500 with no supplemental oxygen and from 12,500 to 14,000 for 30 minutes with no supplemental oxygen for the pilots so at the 10,000 foot cabin altitude when the alarm goes off there shouldn't be a problem. 

 

Something to keep in mind in the OPs situation is that you should reinstate bleeds slowly. We had a flight where they forgot to turn on the bleeds after engine start and ended up getting a cabin altitude warning. They had done the memory item which included fully closing the outflow valve. When the FO discovered the bleeds were off he immediately turned them both on. The pressure increase was so significant some people had ruptured ear drums. 

[Fabo 213]

 

 

Something to keep in mind in the OPs situation is that you should reinstate bleeds slowly. We had a flight where they forgot to turn on the bleeds after engine start and ended up getting a cabin altitude warning. They had done the memory item which included fully closing the outflow valve. When the FO discovered the bleeds were off he immediately turned them both on. The pressure increase was so significant some people had ruptured ear drums. 

 

IIRC if you leave the control in AUTO it should maintain normal-ish rates.

 

 

 

To be more precise... The oxygen generators for passengers don't go off until someone actually pulls on the mask cord. There is one generator for every 3 masks or so (can't remember exactly), and pulling on any of those starts the generator.

 

Any moment a single mask is out, you should consider emergency oxygen to be depleted. I could see how you could block maybe one or two rows off in case of malfunction of the latches or some such, but at the same moment the jungle goes off, for all intents and purposes, you are flying without reserve oxygen (pax) and you may not continue. If for no other reason, then there would be no indication for passengers to pull on the cords should a real loss of pressure event occur.

Not even considering the fact that you are virtually guaranteed that at least one person per row will pull the cord the instant they see a mask in front of them.

[scandinavian13 5,192]

I'm with those noting the air pressure up around 10,000 being just fine.  I've been up higher than 10,000 with no oxygen and was just fine.  This was both while flying, and various ski trips (Monte Cristallo's lodge is pretty close to the peak of 10,500ish, and to be honest, most of us were pretty loaded when we were up there, which as any good pilot should know, only enhances the effects of hypoxia).  I've been a little higher, unpressurized in a plane, too, for about 5 hours (CKM-BCB in a 207...woooooo!).  No issues there.

 

The FAA makes note that you start feeling the effects around 6,500, and occasional medical references speak to 8,000 and above for the possibility for altitude sickness.  It's a graduated thing.  It's not like you're 100% fine below some altitude, and as soon as you cross it *BANG* you're 100% unconscious.  That's the danger of it all, really.  You could be up at FL180, unpressurized (though not legally), and be "fine" for a while, and slowly fade out over time, not even realizing it because your body doesn't have enough oxygen to recognize the issue.

 

Interesting video of a hypoxia situation:

[Captain Kevin 586]

I've been up higher than 10,000 with no oxygen and was just fine.  This was both while flying, and various ski trips (Monte Cristallo's lodge is pretty close to the peak of 10,500ish

Oh, that's nothing. I've driven up to 14,110 feet and made it just fine.   ^_^  :mellow:

[Ralgh 43]

IIRC if you leave the control in AUTO it should maintain normal-ish rates.

True. In the case I mentioned the pressurization would have been in manual if they did the memory item correctly. That being said when we do bleeds off takeoffs there is a noticeable pressurization bump when reinstating the engine bleeds one at a time so even in auto turning both bleeds on simultaneously would likely be uncomfortable. 

[Fabo 213]

 

 

True. In the case I mentioned the pressurization would have been in manual if they did the memory item correctly. That being said when we do bleeds off takeoffs there is a noticeable pressurization bump when reinstating the engine bleeds one at a time so even in auto turning both bleeds on simultaneously would likely be uncomfortable. 

 

Even auto can only open the valve so fast but it should be better than to blast the air in with closed valve.