In our FAA ground school I had to show students a slide reminding them that FAR 91.211 requires oxygen for a pilot exposed to cabin altitudes above 14,000′ (and when flying between 12,500′ and 14,000′ after 30 minutes). They’ll be tested on that. From experience, however, I know that I feel more alert if I keep the (typically shorter) Cirrus flights to 7,500′ and the (sometimes long) Pilatus PC-12 flights to cabin altitude of no more than 5,000′.
“A Medical Look at Hypoxia” by Kevin Ware, a physician and ATP/CFI is an interesting article from a recent Twin&Turbine. The doc/pilot notes that the narrowing of arteries that comes with aging (and an American diet!) makes it tougher for the brain to get sufficient oxygen when starved due to altitude:
In summary, when a pressurized piston or turboprop aircraft is in the high 20 flight levels and operating just as it was designed (cabin altitude of 10,000–12,000 feet), the pilot’s body is only being supplied with half the oxygen available at sea level. This, in turn, triggers the Bohr effect, further decreasing the amount of oxygen available to the brain and heart, which if the pilot is of mature age, are already compromised due to the narrowing of blood vessels. … Given this physiologic reality, is it really safe for pilots with grey hair and some common health issues such as elevated cholesterol, high blood pressure, and possible arterial narrowing, to operate pressurized aircraft at their highest legal altitudes with cabin altitudes? The answer is probably not. But, if the pilot is willing, some steps can be taken to lower the physiologic risk to a more acceptable level, and it involves the use of supplemental oxygen.
Supplemental oxygen is something that needs to be used before hypoxia is present because its effect on the brain is very insidious and makes such recognition of what is occurring, and the logical solutions that would follow, nearly impossible. The best solution to recognizing the gradual onset of hypoxia is to wear a pulse oximeter anytime the cabin altitude is above 5,000 feet and watch the numbers on the dial.
Worth a read if you’re trying to decide if it makes sense to climb up another
4,000′ in a turboprop to save 15 gallons of fuel. Also if you’re trying to decide on whether to pay up for a pressurized plane or rely on supplemental oxygen. The author of this article implies that the typical buyer of a high-performance turbocharged, but not pressurized, piston airplane should be breathing supplemental oxygen for 95 percent of the flights.
How hard is it to fly a plane with a pulse oximeter attached to one of your fingers?
I guess the good thing at least is the lowest task load for the pilot is in the cruise phase where the chance of being oxygen deprived is greatest.
I was a sensor operator in the back of a Twin-Otter when I was in my late forties, and we carried supplemental oxygen and a cannula for the times when the controller put us in the stack above 12,500. We wore a pulse-oximeter to verify our SO2 was > 96%. I can say in my case though, that my ability to perform complicated tasks diminished quite a bit even at the lower altitudes when oxygen wasn’t used. So I would have to agree – older pilots should be more conservative and use supplemental O2 below regulatory required altitudes.
I wonder how many stateside FBO’s have the ability to replenish O2 canisters for those going on longer cross-country flights under conditions where carrying more or larger canisters is impractical?
Tony: It is easy to watch the autopilot fly while wearing a pulse ox!
Craig: Any FBO that deals with jets should have oxygen. It tends to be cheaper/simpler to get them to fill a portable bottle at the airports near the Rockies and Sierra.
How does the cost of 15 gallons of fuel compare with the amount of supplemental oxygen you would need for that flight?
I know that people who rely on oxygen at sea level have home oxygen concentrators – I don’t know how the cost of one of those devices would compare with buying oxygen.
“to operate pressurized aircraft at their highest legal altitudes with cabin altitudes? ” surely they mean UNpressurised?
Federico: I think that they wrote what they meant. A PC-12 at 30,000′, for example, subjects occupants to a cabin altitude of 10,000′. Turbojets typically have a cabin altitude of 8,000′ at their highest certified altitude. The latest and great business jets offer higher pressure differentials and therefore can maintain lower cabin altitudes for a given cruising altitude.