When studying for the first pilot certificate we learned that neither engines nor pilots perform well without oxygen. Human oxygen needs are as variable as shoe size, and individual response may vary dramatically from the FAA’s absolute rules.
A fit, young nonsmoking/nonvaping person will perform well at much higher altitudes than an older out-of-shape wheezer. Folks who live in the high country develop greater lung capacity to stay oxygenated to much higher than flatlanders but at some point, a pulse oximeter will show when it’s time to get supplemental. When O2 drops below about 94 percent, a gradual degradation of performance, vision, and general cognition occurs. It gets progressively worse faster, the lower our oxygenation. The insidious part is that when on the downhill slide, we don’t care.
High fliers who clearly suffer hypoxia typically go until fuel is exhausted. They are unconscious, or worse, and the autopilot dutifully carries on until combustion ceases. But an undefined number of events show pilots making one or a series of bad decisions. Hypoxic? We’ll never know.
The FAA grants considerable flexibility to Part 91 pilots by not requiring O2 except when above 12,500 feet for more than 30 minutes. The idea was to allow us to zip across a ridge without having to get hooked up. But what’s legal isn’t always smart.
As a young pilot, I had a trip from Phoenix, Arizona, to Wichita, Kansas, in an unoxygenated Beechcraft Sierra. It was solid VFR the whole way with considerable unforgiving terrain until crossing the high ground east of Albuquerque. That would occur at twilight and then I’d be over the high plains when it got dark and could slip down to lower altitudes.
I landed at ABQ right on schedule, refueled, and with IFR clearance in hand, taxied out. The engine had been running just fine, but the runup revealed a rough magneto. Drat! No amount of leaning to clear a possibly fouled plug would improve things. Reluctantly, I taxied back to the maintenance hangar. The shop was working two shifts and yes, they could accommodate me right then. Three hours and a new mag later, the problem was solved.
It was about eight o’clock mountain time and had already been a long day when I made the imprudent decision to fly. An overnight stay would have been a much better choice, but it was only three hours to home and the weather was perfect. The only real obstacle was the Sandia peak. The initial IFR altitude along the airway was 11,000 feet eastbound.
I launched into the inky blackness that is the Intermountain West after dark and climbed. And climbed. And climbed. The 11,000-foot minimum en route altitude lasted for about 100 miles to clear the Front Range and then dropped rather quickly to a more breathable level. At that point I asked ATC for lower. The controller granted pilot’s discretion to 8,000 feet, wrong altitude for eastbound, but the lower altitudes were empty. The night was calm and the co*ckpit warm. After about 10 minutes the controller asked, “Sierra Two Four Lima Delta did you want to descend or remain at 11,000?” Huh? Oh, right! We’re out of 11,000 now! Hypoxia and fatigue had struck, and I was oblivious. Classic!
That had never happened before and I’m pleased to say, or again, at least that I can remember. I carry a $30 pulse oximeter, which is as essential as a headset. Once level, it’s time to check the corpuscles to see how they’re doing. Nowadays, once getting to about 7,000 feet msl, it’s time to slip on a cannula when my oxygen level drops below 94 percent. Your level may be different.
Part 135 requires pilots to wear oxygen above 10,000 feet when there for longer than 30 minutes. It seems that the paying customer deserves a fully functional person up front.
Cannulas work fine below FL180, and now there’s a boom cannula that quickly clamps onto a headset and is much more convenient than the usual over-the-head kind (an uncompensated endorsem*nt.) If oxygen is easy to use, you’ll be much more likely to use it and it doesn’t interfere with the boom mic, eating, or drinking. Additionally, it’s long past time for the FAA to drop its guidance to only use aviator’s breathing oxygen, which is a holdover from World War II. O2 is O2. Aviation maintenance shops like to charge $100 for a refill while using the same welder’s oxygen that they use for repairs.
More of us should be using this essential brain maintainer at much lower altitudes. Make it easy to acquire, easy to use, leading to better brain function. What’s not to like? 
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Bruce Landsberg is the past vice chairman of the National Transportation Safety Board and former president of the AOPA Foundation and AOPA Air Safety Institute.
