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Hypoxia
Hypoxia occurs when the brain does not get enough oxygen. At sea level, the air is pushing down on someone with enough pressure that oxygen can easily get in and out of healthy lungs. But as altitude increases, there is less air pressure because there are fewer air molecules, meaning it becomes harder to get enough oxygen into the lungs. When someone reaches a point when the atmospheric air pressure is not sufficient to push enough oxygen into the lungs and circulate the bloodstream, symptoms of oxygen deprivation will begin.
For most people, this occurs around 10,000 feet above sea level. The first symptoms are tingling in fingers and toes, followed by light-headedness and mild euphoria. Left unchecked, this can rapidly lead to confusion and eventually loss of consciousness. For fighter pilots in particular, confusion can make taking simple steps such as recalling emergency training, checking the oxygen supply or dropping to a lower atmospheric level, hard to think through. This means that, for single seat aircraft hypoxia’s final symptom, loss of consciousness, can be deadly.
AV-8B pilot having oxygen problem on a low-level through the Virginia mountains
Pete Bowen, former US Marine Corps AV-8B Harrier II pilot, recalls on Quora;
‘“Bingo fuel, knock it off” the AV-8B Harrier student pilot said. We were a two-ship, student leading me (instructor) as we flew at 450kts and 200′ on a low-level through the Virginia mountains.
‘I expected him to immediately pull his nose up to 40d and start a maximum climb at full power. We were at bingo fuel and had to get to 25,000ft as quickly as possible so we had enough gas to get back home. He wasn’t doing that. I gave it a couple of seconds and called him on the radio to remind him.
‘“I think I have vertigo” came his reply. That’s not good in a single seat aircraft. Vertigo means he his disoriented. Vertigo at low-level and high speed means he has a high probability of hitting the ground.
‘“Get on your instruments,” I said so he could re-orient himself. I added power and joined up on him.
‘“I can’t see my instruments” he said. Now we’ve entered very-not-good territory. If he can’t control his vertigo and aircraft, he is going to have to eject.
‘He was flying blind. “OK” I said. “Pull back on your throttle. Right wing down…. Stop. Pull your nose up…. Stop.” I was giving him instructions from my aircraft on what to do in his aircraft to get us away from the ground, wings level, and to slow down. We weren’t going to be flying back to MCAS Cherry Point. We didn’t have enough gas. We were going to be doing an emergency divert to another airport. If he couldn’t regain control of his aircraft, he would be doing a controlled ejection somewhere over an open area in central North Carolina.
Call-sign “Toxin”
‘I suspected he might have an oxygen problem. The text-book emergency procedure for an oxygen issue is to pull an emergency oxygen tab to get reserve O2. If his oxygen was bad, then pulling reserve O2 might fix it. If it was something else in that system going bad, it would still be bad. If he passed out while we worked through procedures, he would be unable to eject.
‘We were at low altitude, however. At low altitude I knew the outside air was good. So, I told him to go to ram (outside) air and take off his mask. That wasn’t in accordance with the published emergency procedures, but in naval aviation you are permitted to use good judgment. Ten seconds later, he said he could see his instruments. I took the lead, and we made the local news doing an emergency divert into Raleigh-Durham airport.
‘Maintenance did a thorough check of his aircraft and flight equipment, and found some residue in his O2 mask or tubing. I never heard whether it was lubricant or something else. He instantly picked up the call-sign “Toxin”, graduated Harrier training, and went to a combat/gun squadron.’
Bowen concludes;
‘Unfortunately, a few months later, Toxin died when his Harrier hit the water while flying a low-level over Pamlico Sound. Good man. Good Marine. RIP George.’
Photo credit: Cpl. Gregory Moore / U.S. Marine Corps
