Alexis wrote:
And what do you do if you have a failure? Descend into IMC in an emergency descent while trying to fix it? No thanks.
There was an article recently describing the importance of doing that, instead of dying while trying to disentangle the tubes.
I have enough experience with icing and how it impacts my aircraft to be able to draw that conclusion. I don’t know why it is like that.
That would be most unusual… to have no ice on the prop but have significant ice on the airframe.
the importance of doing that, instead of dying while trying to disentangle the tubes
For sure one needs to have a Plan B for oxygen system failure, but at FL250 you would not normally die right away. It’s an interesting Q whether there exists the piston GA equivalent of a quick donning mask. I’ve never seen such a thing.
Because it’s mentioned so often – does anyone know any statistic of actual accidents related to failure of oxygen-systems
No idea. As others have said, the perception of risk is very individual. Not many people fly regularly at those altitudes in unpressurised aircraft. If you do lose o2 at that altitude above weather, you’re in a tight spot. But even if weather is good below (in which case why were you up there in the first place?), you need to drop more than 10,000’ If you pass out in the process, you may have the autopilot capture altitude, but when leveling out will there be enough power to maintain altitude until you’re fit for fight?
Having a backup system you’re probably better off but you need to react quickly.
I just do not want to ever experience an oxygen failure at such an altitude. In my case the failure could be something trivial like the MH regulator running out of batteries. Reports have it that you get very little prior warning.
No, of course you don’t die “right away”, but with a TUC of three minutes the result will often be the same. That’s three minutes from the system failure … so it might be 30 seconds from the time you realize there’s a failure.
Alexis wrote:
No, of course you don’t die “right away”, but with a TUC of three minutes the result will often be the same. That’s three minutes from the system failure … so it might be 30 seconds from the time you realize there’s a failure.
I’m not so sure about that. Without wanting to trivialize a situation like this (it isn’t!), I believe you’ve got longer than that. I recently did an FAA high-altitude course where we had to sit in an O2 depletion chamber (IOW sea-level pressure, but O2 removed) that simulated 26k ft. Very, very interesting. The biggest takeaway was that hypoxia is extremely individual. On the two extremes, there was a 20-something CFI whom I happen to know and a 70+ guy. Guess who was happy as a pig in shit after 5 mins in there? Nope, not the young, fit, nonsmoking man. The old guy kept doing the puzzles we were given as if he was at sea level. The young chap nearly passed out….amazing. Which was also the point of this course – to get a better understanding of your personal limits. Btw, while of course no substitute for proper O2, the instructors said that the portable O2 bottles like this one may well save the day and also help to maintain blood O2. Tested that recently and they certainly give you a boost (which is what they are designed to do).
Well, the official tables used by the airlines say 3-6 minutes for FL250.
I have done that test too, and it was scary to fly the SR22 simulator like that.
The problem is you don’t realise the failure until you’re well on your way into hypoxia and there is high risk you don’t react accordingly and correctly. IOW your brain is like honey and you don’t process. Which means: of course ! ther is a high risk you die without ever realising it. Don’t forget that in these tests you know what’s coming. In a plane you won’t.
Last year, a TBM on its way from northern US to Florida reported problems with the pressure cabin and descended from FL 320 to 240 after having requested clearance to do so for some time. The last radio contact was at 240, after that: silence. The TBM proceeded south, and a military jet started to see what’s up. It reported frosted over inner cabin windows. The TBM later fell in the water close to Puerto Rico or Cuba, don’t remember. That pilot did have quick donning masks and they were of no help.
Hey why am I feeling sooooo tired is there something with the oxygen ahh I don’t know what are these tubes where is the plug I don’t get any oxygen and what’s going on I don’t know hey funny feeling so many lights and knobs funny place what’s my name I don’t know ohhhh cool clouds should I descend how is it done I don’t understand it so many instruments hahaha. And then: Blackness.
The idea that you a) realise the failure immediately after occurring, and b) act correctly are totally slim and these tests are futile.
EuroFlyer wrote:
and these tests are futile.
Here I disagree. These tests are not designed to make you feel overconfident, quite the contrary. They are designed to help you recognize the onset of hypoxia and then act accordingly. Does that always work? Probably not. Is it good to have another string to you bow? IMHO, yes. Btw, the classroom portion of this course put very strong emphasis on the insidious nature and the concomitant dangers of hypoxia.
Explosive decompression is in some ways easier. Noise, fogging atmosphere, ear pressure. The gradual decompression is the greater and more worrying problem. This is the case when you wouldn’t notice until you became impaired -assuming you notice then.
Jason, compared to our SEPs your plane is nothing less than a small airliner. TUC in FL400 is 15-20 seconds – but i’d trust that airplane and it’s systems much more than the toys i have on board.
