Hypoxia

[Rocket_Bird]

I was just wondering.  I know mostly unpressurized aircraft wouldnt fly above 10,000 ft, but what is about the maximum altitude that you can fly without needing supplimental oxygen?

[JerryO]

Well, it

[eno]

With proper acclimatisation its possible to climb Everest without oxygen. However the symptoms of altitude sickness can begin round about 5000ft. The Deathzone begins at around 17,000ft at this point there isn't enough oxygen to sustain human life properly and the body begins to die slowly.

[Hagar]

Interesting. I raised this question once before when I heard accounts of WWI pilots in combat at anything up to 20,000 feet, in open cockpits & presumably without oxygen. I can't remember what the general opinion was now but I'm sure this would be possible. Assuming the aircraft were capable of operating at that altitude I imagine the rate of climb would be slow enough to allow the pilot to become acclimatised. I can't see that the energy required to fly an aircraft could be compared with climbing Everest (which as Eno points out has been done without oxygen) - although this might be different in combat. It might also be different with modern aircraft with a much higher performance & rate of clmb.

I'm currently reading "Spitfire into Battle" by Group Captain W.G.G Duncan Smiith DSO DFC * (WWII fighter pilot & father of Iain, the former Tory party leader).

[Boss_BlueAngels]

If you fly over 12,500 feet for more than 30 minutes you are requred to have suplimental oxygen as flight crew.  


Having undergone high altitude training recently, I lasted about 7 minutes at 25,000 before I had to use the mask. (one of the safety officers in the "chamber" actually had to tap me on the shoulder and help put it on.  Apperantly they were talking to me trying to get my attention for about 2  minutes)  Although, my time of useful conciousness was only about 4 at the most.  After the 4 minutes I had no idea what I was doing.  

[JerryO]

I raised this question once before when I heard accounts of WWI pilots in combat at anything up to 20,000 feet, in open cockpits & presumably without oxygen.

I did some research on WWI airplanes and found out that quite a few of them could fly up to 20 000 feet, and even higher. The best British plane in that sense was the Airco D.H.4, it

[Poseidon]

With proper acclimatisation its possible to climb Everest without oxygen.

I don't think this is correct. Someone can survive on top of Everest without an oxygene mask but not climb . In fact soemone can feel quite well while sitting but most probably would be unable even to stand up.

[Hagar]

I don't think this is correct. Someone can survive on top of Everest without an oxygene mask but not climb . In fact soemone can feel quite well while sitting but most probably would be unable even to stand up.

Read this. http://www.pbs.org/wgbh/nova/everest/history/firstwoo2.html It's been done several times since.

Sometime between 1 and 2 in the afternoon on May 8, 1978, Messner and Habeler achieved what was believed to be impossible -- the first ascent of Mt. Everest without oxygen.

Messner and Habeler's success puzzled the medical community, and caused a re-evaluation of high-altitude physiology. Messner would return to Mt. Everest in 1980 to successfully complete a solo ascent -- again without supplemental oxygen.

Italy's Reinhold Messner has climbed Everest twice without oxygen, once in four days.

[flightmedic]

[quote]If you fly over 12,500 feet for more than 30 minutes you are requred to have suplimental oxygen as flight crew.

[Hagar]

I'm sure that these limits are only guidelines & might vary depending on the country, time & situation. I think 10,000 feet is the general limit for civil aviation nowadays. Not sure about the military. It might be the same or higher & this might well be raised in wartime. The quote in my earlier reply is from a reliable source & it clearly states that 16,500 feet was the limit for RAF pilots & aircrew in 1940, the early days of WWII. I have no idea whether this was changed as the war progressed. The limit in WWI, if there was one, would have been much higher as not so much was known about the effects of hypoxia at the time. I suspect that not too many aircraft of the period could operate at the altitudes we're discussing so an altitude limit on the pilots might not have been necessary.

[flightmedic]

Very good points there Hagar. 16.5 !!! in a SPIT ......
......Ok...where do I stop drooling.......

I'm sure you hit the nail with the fact that not much was known back then about Hypoxia. It just seems funny how low the regs are to be safe nowa days
Hmmm..........I wonder.....if possibly some of those "unkown" air loses from all sides was perhaps in some way affected by Hypoxia.

Now all we need is a time machine so we could fine out for ourselves...

[Boss_BlueAngels]

Well, not only do the effects of high altitude flying vary with individuals, but it also depends upon exposure (ie 30 minute rule) for a single flight, and whether someone has physiologically adapted to the lower pressure.  I have spoken with many pilots who have experienced hypoxia at 8,000 and 9000 feet.  And they were perfectly healthy people... now add in the people who smoke (which can give an additional 8,000 feet to one's physiological altitude)  and its naturally insideous onset and you've got one really scarry problem on your hands.  That is, if you're not aware of the risks.  To which I recommend EVERY civilian pilot do whatever they can to take the ground portion of high-altitude training.  It WILL save your life.

And yes, what I mentioned are US regs.  Also, for ANY portion of a flight above 14,000 feet all required flight crew must use supplimental oxygen.

[Hai Perso Coyone?]

16,000ft as this man found out:

(1982, California) Larry Walters of Los Angeles is one of the few to contend for the Darwin Awards and live to tell the tale. "I have fulfilled my 20-year dream," said Walters, a former truck driver for a company that makes TV commercials. "I'm staying on the ground. I've proved the thing works."

Larry's boyhood dream was to fly. But fates conspired to keep him from his dream. He joined the Air Force, but his poor eyesight disqualified him from the job of pilot. After he was discharged from the military, he sat in his backyard watching jets fly overhead.

He hatched his weather balloon scheme while sitting outside in his "extremely comfortable" Sears lawnchair. He purchased 45 weather balloons from an Army-Navy surplus store, tied them to his tethered lawnchair dubbed the Inspiration I, and filled the 4' diameter balloons with helium. Then he strapped himself into his lawnchair with some sandwiches, Miller Lite, and a pellet gun. He figured he would pop a few of the many balloons when it was time to descend.

Larry's plan was to sever the anchor and lazily float up to a height of about 30 feet above his back yard, where he would enjoy a few hours of flight before coming back down. But things didn't work out quite as Larry planned.

When his friends cut the cord anchoring the lawnchair to his Jeep, he did not float lazily up to 30 feet. Instead, he streaked into the LA sky as if shot from a cannon, pulled by the lift of 42 helium balloons holding 33 cubic feet of helium each. He didn't level off at 100 feet, nor did he level off at 1000 feet. After climbing and climbing, he leveled off at 16,000 feet.

At that height he felt he couldn't risk shooting any of the balloons, lest he unbalance the load and really find himself in trouble. So he stayed there, drifting cold and frightened with his beer and sandwiches, for more than 14 hours. He crossed the primary approach corridor of LAX, where Trans World Airlines and Delta Airlines pilots radioed in reports of the strange sight.

Eventually he gathered the nerve to shoot a few balloons, and slowly descended. The hanging tethers tangled and caught in a power line, blacking out a Long Beach neighborhood for 20 minutes. Larry climbed to safety, where he was arrested by waiting members of the LAPD. As he was led away in handcuffs, a reporter dispatched to cover the daring rescue asked him why he had done it. Larry replied nonchalantly, "A man can't just sit around."

The Federal Aviation Administration was not amused. Safety Inspector Neal Savoy said, "We know he broke some part of the Federal Aviation Act, and as soon as we decide which part it is, a charge will be filed."

cheers,
ashar