Flight above FL100
 

What is the hard and fast about unpressurised (or without supplemental oxygen) flight above FL100?

I understand that this is the normal limit of unpressurised flight, for good reasons, and I have searched and read quite a few threads about degraded ability at altitude etc etc.

Lets say the lower limit of an airway is FL110 and you would have to stick at this altitude for half an hour or so to use it... legal?

Cheers, CS

Pressurised flight, and using supplemental oxygen at ambient pressure are two different things :) What's legal depends on the regs. What's sensible depends on all sorts of things. 11000 ft is too high for some for any period of time, but easily doable for extended periods by others.

yes, it was the regulations I was after...

http://www.caa.co.uk/docs/224/Appendix%205a.pdf

just found it... apparently when the aircraft is unpressurised it is illegal for flightcrew to fly above FL100 without supplemental oxygen altogether...

Just love it, document says "Vertical displacement of the flying machine in relation to flight levels". How quaint.

Unless you're flying an 'N' on an FAA licence, where the lower limit for supplemental oxygen is 12,500ft amsl.

Anyone know how that N increases the oxygen concentration?

Are we sure we're not confusing CAT requirements and private requirements?

I'm not aware of any law that says private pilots need to be on oxygen above FL100 in the UK.

But please, don't let that stop the usual suspects :p :zzz:

It probably works along the same lines as US vs UK gallons: A US gallon being smaller than a UK one.

Working on the same ratio 12,500 US amsl equates to around 10400 UK amsl - so that's all right then :ok:

Or even 14500 (i think) for 30 minutes or less ;)

Seriously, 10,000' is not a problem, 12500' for 3 hours is not a problem in my experience......

It would be, if the Proposed amendment that you quoted had ever been incorporated. AFAIK, it has not been incorporated in the ANO 2005.

The simple solution, requiring no certification, is a portable oxygen kit.

I use O2 at 10k+ if I am up there for more than an hour or two, and especially prior to landing.

The only drawback is getting the bottle refilled. Facilities for this don't generally exist. I rent a huge bottle from BOC - about 1/10 of what I used to pay.

I read a very interesting article recently, and I can't remember where it was. I'm pretty sure it was one of the magazines.

The pilot concerned was a very experienced ATPL, who was carrying out a high level flight in a glider. He had an oxygen system, but hadn't begun to use it yet. He was keeping a check on his mental state by regularly counting backwards from 100 to ensure he wasn't suffering from hypoxia.

He goes on to explain how he made a series of mistakes throughout the flight, which although he didn't realise at the time, were caused by hypoxia. He had been regularly counting backwards, but towards the end of the flight he'd become increasingly bored with the counting, and had gone from 100 to 50, or from 100 to 80. He'd considered that he wasn't suffering from hypoxia because he was able to count backwards - he had assumed that hypoxia would show as an inability to count backwards, not as a lack of enthusiasm for it.....

Maybe someone else will remember the article and be able to point us to it, because it's very relevant to the thread?

FFF
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Anoxia v. dangerous and pernicious, so one should always be careful.

But anyone like me brought up on First World War memoirs - 'Sagittarius Rising', etc., must puzzle of the high altitude flights and fights claimed by those heroes. Did their altimeters under-read, or was their endurance sufficiently short that pilots usually got away with it?

Anyone know?

No chance of me emulating them! Strictly below FL10 or plenty of o2 for me!

FFF,

That report that you're talking about was in the most recent CHIRP circular.

Here's a link to the online version. :ok:


HTH,

B73

Trouble with Hypoxia is that even using a method to check like counting backwards it creeps up on you. You may in fact think you are counting backwards fine when in reality you are spouting a load of drivel! The only way to do it is to get on O2 before you need it.:uhoh:

IO540 what is the point in using an oxygen bottle "...prior to landing". Unless you are landing at an airfield around 10,000ft amsl then fair enough. Otherwise surely your blood stream would have been replenished with oxygen in the decent below 10,000ft.

I used to fly for about 3hrs at FL120 in an unpressurised aircraft and it was fine really. Been up to FL130 a few times but only for about 20 mins. Wouldn't advise going that high without a gasp of o2

Sorry, I should have clarified.

Unless you carry a kevlar-reinforced bottle with 6000psi of O2 and weighing enough to seriously affect your W&B :O there is always an issue of O2 consumption, because refills are so hard to arrange.

One could argue that typical GA flights are only an hour or two and while that itself would make this a non-issue (4 pax at FL180 for 2hrs is OK from a reasonably small bottle) the problem is that the infrastructure for non-pressurised O2 refilling just doesn't exist around Europe. Occassionally one can get a refill from a bizjet maintenance facility, but one has to carry a range of adaptors and a lot will refuse to refill a portable bottle because "their insurance won't cover it". It's always pricey, at 50-100 quid a time. Plus the long wait, huge hassle if abroad.

So, on a typical away flight, one tries to make do with one initial fill, done back home at a friendly scuba shop (and a lot of those are staffed by anally retentive idiots who won't do it, which is why I got my own bottle in the end).

So one may have to be a bit economical with the stuff. With 2 people total, one can do a number of hours at FL140 with a normal sized bottle and cannulas. At FL140 I would use it all the time. But at say FL100, in perfect VMC, there is a case for either turning the stuff down (to say an "8000ft" flow rate) or not using it at all and turning it back on for the last hour or two to freshen up.

The thing is that FL140/160 is needed only over mountains, so that is another aspect of flight planning. There is just no way to do 10hrs with 4 POB at FL140 with anything that's remotely portable. Unless, perhaps, one spends $1000s on the new electronic control kit.

Only the most unfit people, or smokers, will have trouble at FL100. Above that it varies a great deal. One has to carry an O2 monitor; the thing you stick a finger into :O

I'm surprised no one has mentioned a pulse oximeter. Not cheap (£260) but I wouldn't fly at > FL100 without one. Sure beats counting!

I have; I called it an O2 monitor :O

I use the Nonin one too. Not sure if it is the best though. It's good for passing around between people, less good for more continuous monitoring.

Counting is no use at all. I can count fine straight up to FL150 but would be completely knackered very quickly up there.

Or $245 from http://portablenebs.com/nonin9500.htm

I find it's only when you put the oxygen on and you start to feel much sharper that you realise the effect the lack of oxygen has been having on you. On a flight I did a couple of weeks ago, with the climb and vectors through the London TMA, I didn't get a chance to don the oxygen until FL110 (N-reg). Even at that level, as soon as I got the oxygen on, I really noticed a difference.

I also feel a lot less drained after long flights if I've been on oxygen. Long exposure to even moderately high altitudes can have a significant effect.

It's also worth noting that (in my experience) your oxygen level isn't just a factor of the altitude you fly at. Additional factors, such as starting early and missing breakfast, also have a physical effect on your oxygen saturation readings.

Or to remain above a band of icing.

There's no need to go to that expense. Just turn the passengers' oxygen flow right down ;)