Originally Posted by
V-Jet
There are multiple O2 bottles aside from the a/c built in supply.
None will work if you dont know you are incapacitated.
The question I still have is how long does it take to 'wake up' once the aircraft is below about 15,000'? I would have have thought that unless it was descending very fast there would be time to regain consciousness prior to impact.
Anyone know?
I can only quote from subjective experience way back when we were put in small groups into 'the chamber' to experience and watch each other get hypoxic. The chamber was 'climbed' to (I think) about 30,000ft equivalent.
We were given a simple maths test to work out - write down 500 now start subtracting 17 - then one in each pair had their oxygen switched off.
I became woozy and not with it relatively rapidly say 45 seconds or less but subjectively within 20 - 30 seconds was back up to speed when given 100% oxygen. My 'partner' seemed to be totally unaffected when his supply was shut off neatly writing sum after sum.... it was only when we looked after about 45 seconds we noted that although the writing was neat it was gibberish... he also recovered quite rapidly 20 - 30 seconds or so.
So what we learned was onset can be fast and obvious - or fast and not obvious, imagine the FO happily punching nonsense into the FMC. Recovery - on 100% oxygen was rapid. However, we had not spent a long time at height and were young and relatively fit. I expect as with all things biological YMMV.