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training wherein the oxygen masks are never used unless there is an emergency caused by an abrupt depressurization event. The other explanation is that the typical pressurized piston aircraft has a limited inbuilt oxygen supply which is frequently difficult and expensive for the pilot to have re-filled, and therefore needs to be “saved” or at least used very conservatively. The resupply problem can be a real one, but a very convenient way around this is a portable oxygen bottle that can be filled by any local medi- cal oxygen supplier at minimal cost. One rumored concern about using medical oxygen is that it is not “dry” enough and as a result, moisture could form in the supply tubes which can clog them shut. This concern originated in WWII when bomber crews were flying in non-pres- surized and non-heated cabins in freezing temperatures in the high flight levels, but is not applicable to the heated and pres- surized general aviation aircraft we have today. A portable medical oxygen tank and its supply lines will almost always work just fine in a heated aircraft cabin.
Pressurization makes a significant contribution to the potential safety of flight because it enables the aircraft to overf ly otherwise bad weather, and as long as the aircraft’s altitude does not exceed far above FL180, the cabin alti- tudes are as physiologically safe that of an airliner or newer executive jet. Above that altitude, however, the tradeoff starts to shift the other way depending to a large extent upon the pilot’s age, medi- cal history, and physical condition. The older the pilot, the higher the risk, par- ticularly if he or she has some adverse health history such as known coronary artery disease, high cholesterol, diabetes, or high blood pressure. But for nearly everyone, using supplemental oxygen whenever the pressurized piston aircraft goes above about FL180 will convert the physiologic risk to that of driving across most mountain passes in the western United States.
Now, all this discussion about physi- ologic risks, oximeters, and the use of supplemental oxygen may sound like a needless hassle. But if you feel that way,
have your spouse or close relative read this Twin & Turbine article. It would be wise to follow the advice that I am sure will follow. Be safe out there.
Kevin Ware
is an ATP who also holds CFI, MEII and heli- copter ratings, has more than 10,000 hours
and is typed in several differ- ent business jets. He has been flying for a living on and off since he was 20, and currently works as a contract pilot for vari- ous corporations in the Seattle area. When not working as a pilot he is employed part time as an emergency and urgent care physician. He can be reached at kevin.ware2@aol.com.
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28 • TWIN & TURBINE
December 2018