My Experience with Hypoxia

I thought you might be interested in my experience with hypoxia. This was some time ago—1955 or 1956. I was flying a T-33 en route to Malmstrom AFB, where I would stage as a target aircraft for an exercise.

The T-33, usually called the “T-Bird” by pilots, was a first-generation USAF jet trainer. It used a centrifugal-flow engine that looked remarkably like Whittle’s original design. The airplane would cruise nicely at altitude at nearly 300 knots and had almost neutral stability in all axes. That characteristic has some relevance to this story: if you let go of the controls, the airplane won’t stay straight and level for long.

I was cruising at 30,000 feet on a clear night—probably IFR, on top. This was well before RVSM. After leveling off, I could see the glow of the port-side flashing navigation light out of the corner of my eye. The starboard green light wasn’t bright enough to show the same effect.

It’s worth noting that while the T-33 had cockpit pressurization, it wasn’t anything like a modern airliner. At 30,000 feet, the cockpit altitude would have been around 19,000 feet.

About an hour into the flight, I noticed something: I could no longer see the red flashing light.

Hmm… why is that?

Around this time, my thought processes began to slow—but I didn’t recognize it.

My first thought was:

T h a t i s j u s t l i k e I h a v e h y p o x i a . . .

Then:

O h… m a y b e… I d o h a v e h y p o x i a…

And finally:

W e l l… w h a t a r e y o u g o i n g t o d o a b o u t i t ?

All of that took more than 60 seconds in real time.

The A-14 oxygen regulator in the T-33 was located beside and below the seat on the left side of the cockpit. On the inboard side was a lever to select either 100% oxygen or “normal” (mixed with cockpit air). On top was a rotating dial to select pressure delivery for very high altitudes.

I had two options: select 100% oxygen or increase pressure. Fortunately, it was easier to twist the top dial than to find the lever. Soon, the cockpit was being flooded with oxygen from the regulator—some of which I was breathing.

My brain started trending back toward normal. Trending—not there yet.

Then I had another thought: Why don’t I feel pressure in the mask?

I looked down and saw that my mask hose was disconnected from the supply hose.

At this point, some of you may be wondering about the warning indicator on the panel—the “blinker.” Didn’t I see it?

As you’ve probably guessed by now, this was not my finest hour. I didn’t notice it until I had fully recovered.

As noted earlier, this happened a long time ago. Modern oxygen mask systems now include a spring-loaded valve in the hose that makes it difficult to breathe if disconnected—an immediate and effective warning.

Takeaways

If I had not gone through altitude chamber training, I might not have recognized the symptoms of hypoxia—even if I was a little slow to act.

If I had not corrected the problem, I have no doubt I wouldn’t be here today. The T-33, left unattended, would have quickly entered a dive or spiral and passed through 10,000 feet in no time.

I strongly recommend altitude chamber training for any pilot who flies above 10,000 feet.

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Gennaro Avolio

Gennaro (Bill) Avolio was born and raised in Portland, Oregon, and took his first flight lesson on January 13, 1946. He worked as a mechanic (including time as a crew chief on P-51s) and was in the Oregon Air National Guard for 24 years. He spent time as an instructor pilot in the T-33, F-94B, F-89 and F-102, and even performed atomic cloud sampling. A commercial pilot, flight instructor and A&P, he holds the Wright Brothers Master Pilot Award.

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