What Hypoxia Sounds Like

Listen to this and you’ll understand why hypoxia makes you stupid.

Since this seems to be the season for discussing hypoxia and the threat it presents to GA pilots, I was reminded that we published this dramatic audio on AVweb five years ago. I had forgotten about it, which isn't a good thing given what an incredible lesson it is.

The incident occurred in July 2008 and in addition to the podcast, there's a video with better audio here. I'm not clear on the exact date because the incident doesn't seem to appear in the NTSB records. We published it as a consequence of the National Air Traffic Controller's Association awarding the controllers involved an Archie League award for a flight save.

When I blogged about the recent TBM accident on Monday, I posed the somewhat rhetorical question of why didn't the pilot declare an emergency and not just ask for lower, but proceed rapidly lower on his own. The answer may be evident in this tape. The aircraft is a Kalitta Flying Service Lear 25 enroute from Manassas, Virginia to Ypsilanti, Michigan. When the pilot checks in on the frequency, he's already deeply hypoxic and slurring his words, but he declares an emergency then, oddly, doesn't ask for or descend to a lower altitude on his own. This is a stunning example of how tunnel-visioned hypoxia can render you. Salvation is 20,000 feet lower, but the pilot is focused on getting vectors to his destination. Although he's declared an emergency, he declines vectors to a closer airport. Interestingly, there are at least four people involved in some way on the frequency, yet despite the pilot's obvious incapacitation, the word hypoxia isn't heard until 3:24. That's a long time to be oxygen deprived.

The controllers deserved the Archie for this incident. Although they did well, they didn't do as well as they might have had they been trained to quickly recognize a hypoxic pilot, who might not be capable of even formulating intentions, much less saying them. But they figured it out soon enough to make the save and that's what counts. The tape is now used as a classroom training aid in Oklahoma City and I daresay it's an effective one.

In its citation for the award, NATCA said the First Officer's arm was moving violently and contacting the controls, keeping the autopilot offline. Convulsions are the truly dark side of hypoxia and aren't always listed in the garden variety symptoms. When I did my first chamber ride around 1992, one of the participants convulsed and it was terrifying. As per the training doctrine, at 25,000 feet, half the students remove their masks, the other half keep them on. You're invited to stay off oxygen as long as you can stand it.

I was in the group with masks on when I noticed another guy in my row going into the funky chicken. I thought he was clowning around but the instructor got a mask on him fast and turned it to emergency flow. He came back around in a few seconds and the dance stopped, although he was still twitching for a few minutes afterward. After the fact, he was completely unaware of what had happened. When we finished our training, I asked the instructor how often that happens. Kinda rare, he said, but it does happen.

Which reminds me to mention another kind of hypoxia training that Flight Safety does. I went through that course a few years ago. Rather than a chamber ride, they have a system that mimics high altitude by having the pilot breath through a mask in which the oxygen partial pressure is reduced. It's called ROB, for reduced oxygen breathing. The gist of the training is to teach you to recognize your own hypoxic symptoms while you're still able to make judgments and act. It's all done in the simulator, with actual emergency descents from high altitude. I learned, for instance, that my early onset symptoms are lightheadedness and sweating. Other people may react differently. But better to find that out down here than up there.

Monday A.M. addition: The FSI course seems to have been dropped, which is too bad. It's another way to train hypoxia awareness without going to the chamber. This company, however, does offer the equipment for ROB training.

Join the conversation.
Read others' comments and add your own.