Okay, I wasn't going to join in, but Jetguy has added an interesting post, on which I’d like to comment, so here goes.
FL600, you guess which aircraft type!
"...The big problem with those kinds of altitudes is if you loose the cabin you're dead - the time of useful consciousness is just to freaking short to allow any type of response...
I know you are also a very experienced pilot, but with respect, I find that statement rather misleading and a touch over-dramatic.
We need to keep a sense of proportion about the risks involved in operating aircraft at these altitudes. It certainly isn't something to be treated lightly, as you rightly imply, but as someone who was trained for (and until last week operated at) those sorts of altitudes, I do not believe the problems are as dangerous as you suggest.
If by "...loose the cabin..." you mean the cabin has completely depressurised to 51,000 ft, that the aircraft is still flying at 51,000 ft and the flight crew haven't donned their O2 masks, then I would agree with you. They would have minimal TUC, and their chances of surviving such an encounter would be negligible.
However, aircraft pressure hulls, other than when a catastrophic failure occurs, do not suddenly depressurise to ambient atmospheric pressure (even if it may feel like it to the occupants), they take time to depressurise.
In those rare cases of a catastrophic breach of the pressure hull, the altitude at which it occurs is largely irrelevant, as in all probability the aircraft will no airworthy - the early Comet accidents being a case in point.
For all the other depressurisations, whether due to pressurisation system failure, discharge valve failure, a small hull breach, a door or window blow-out, or just plain human error, the cabin will take time to climb, often a considerable amount of time.
It is this time which provides us with a safety margin, precious seconds, during which we must act positively.
Firstly to protect ourselves (pressurised O2 masks) next to analyse the situation (what warnings?, what cabin rate-of-climb?) then to rectify if possible (re-instate packs, select alternate systems, close errant valves manually) or if control of the cabin has been lost, initiate an emergency descent.
The cabin altitude on my aircraft would typically be at about 5,000 ft during cruise. In common with most commercial aircraft, various flight deck warnings will occur as the cabin altitude rises through 10,000 ft, and again passing 14,000 ft, to alert me to the problem, assuming my own eyes, ears, sinuses and lower intestine have not already done so!
There are many protection devices fitted that should ensure that the cabin altitude never exceeds 14,000 ft, but even if they all fail, and even if the cabin were climbing at 10,000 fpm, it would still take 18 seconds before it exceeded 8,000 ft and 55 seconds before it exceeded 14,000 ft.
Ample time for the crew to don their O2 masks, whilst still at normal cabin altitudes, and to initiate an emergency descent. The cabin altitude would never get near 60,000 ft in this scenario.
Even if the cabin were climbing at a much higher rate, say 30,000 fpm, a horrendous cabin rate of climb, it would still be 30 seconds before the cabin altitude exceeded 20,000 ft, plenty of time in which to don a mask, and well within the TUC available at that cabin altitude.
The point I would like to emphasise is that if we are to talk about TUC, then it should be the TUC for the cabin altitude by which the O2 mask is likely to be have been donned, not the TUC at the aircraft cruise altitude.
I believe that it is on this basis that the aviation authorities in the US, UK and France have all decided that high altitude commercial operations do not pose any undue risk to passengers or crew and have licensed them accordingly.
…All of you guys who are flying high performance aircraft…should get yourselves a ride in an altitude chamber...you'll walk away with a new found respect for your physical limitations…
My thoughts exactly, I totally agree. Such training should be mandatory.
The ability to recognise the onset of hypoxia can only really be learned in an altitude chamber, and likewise the experience of what hypoxia does is best learned by sitting in an altitude chamber opposite someone who is experiencing it - you won’t remember your own experience, even when shown it on video.
To those of you thinking of flying high performance aircraft, and especially for those of you who occasionally fly higher than you should without oxygen, this could be the best money you’ll ever spend on aviation training.
It will certainly change your views, it may one day save your life.
[Edited 2003-11-05 19:53:47]