Pilot Counsel:

Supplemental oxygen

October 1, 2011

John YodiceRule FAR 91.211 requires supplemental oxygen for general aviation (noncommercial) operations (airliners and some other commercial operations and aircraft have stricter requirements). I present this review at this time because gradually, over the years, more and more GA aircraft are operating at higher altitudes where the rule kicks in. I can simplify this review for the reader by focusing on the requirements that apply to the particular aircraft that one flies. So, let’s differentiate aircraft as either (1) an unpressurized aircraft that does not carry supplemental oxygen, or (2) an unpressurized aircraft that has supplemental oxygen, and (3) a pressurized aircraft.

  • Unpressurized aircraft; no oxygen. For anyone operating an unpressurized aircraft that does not carry supplemental oxygen, which still constitute the majority of the GA fleet, the rule is simple. The key altitude is 12,500 feet msl. There is no regulatory requirement for supplemental oxygen at or below that key altitude (although there could be good physiological reasons why a pilot would want to use oxygen below that altitude). The regulation contains some leeway, just in case we need a little time above that key altitude; for example, to get over some weather or to maintain VFR cloud clearance. It provides that an aircraft may be operated above 12,500 feet msl for up to 30 minutes, free of any supplemental oxygen requirement. However, that is a very limited exception, and any part of the flight of more than 30 minutes duration above that key altitude triggers the requirement for supplemental oxygen.
  • Unpressurized aircraft; oxygen. Above the key altitude of 12,500 feet msl in an unpressurized aircraft with supplemental oxygen (installed or portable), we can, of course, utilize the oxygen to meet the requirements. The requirements above this altitude vary depending on whether a person is a required flight crewmember or merely another occupant. And, they vary depending on other key altitudes, i.e., “above 14,000 feet msl” and “above 15,000 feet msl.” A person who is a “required minimum flight crew” member—the pilot in command of a typical GA aircraft—must have available and use supplemental oxygen for any part of the flight above 12,500 feet msl that is longer than 30 minutes. Above 14,000 feet msl, we lose the 30-minute grace period. There, the “required minimum flight crew” must have available and use supplemental oxygen during the entire flight time above the key altitude of 14,000 feet msl.

What about occupants of the aircraft who are not required flight crewmembers? Passengers? At or below 15,000 feet msl, the PIC need not assure that occupants, other than the required flight crew, have supplemental oxygen available to them. Above 15,000 feet msl each occupant of the aircraft must be provided with supplemental oxygen. Notice that the PIC is responsible to assure that supplemental oxygen is available to the other occupants, but the PIC is not responsible for assuring that the occupants use the oxygen.

  • Pressurized cabin aircraft. Pressurized aircraft have both special requirements related specifically to pressurized cabin aircraft, and, in addition, have the above requirements that relate both to pressurized and unpressurized aircraft. The key altitudes related to the special requirements for pressurized aircraft only, are “above flight level 250” and “above flight level 350.”But, before we get to the special requirements for pressurized aircraft only, in a pressurized aircraft, the above requirements that apply to unpressurized aircraft still apply, depending on the pressure altitude of the cabin. If the aircraft is able to maintain cabin altitudes at or below the appropriate key altitudes mentioned above, there is no additional requirement for the availability or use of supplemental oxygen by the flight crew or other occupants. However, in a pressurized-cabin aircraft, if the cabin pressure is above an altitude of 12,500 feet msl, the minimum flight crew must have available and use supplemental oxygen (with the same exception for any portion of the flight of 30 minutes or less, at or below 14,000 feet msl.)

Now to the special requirements specifically for pressurized aircraft that are operated above the key altitudes of FL250 and FL350. At flight altitudes above FL250 there must be a least a 10-minute supply of supplemental oxygen available for each occupant of the aircraft, including flight crewmembers. This reserve is required in the event of a descent due to a loss of cabin pressurization. This minimum supply is in addition to the oxygen that may be necessary to meet the above requirements common to both pressurized and unpressurized aircraft.Aircraft operating at flight altitudes above FL350 are usually certificated to require more than one pilot. However, we are seeing more aircraft certificated for single-pilot operation. At flight altitudes above FL350, one pilot (maybe the only required pilot) at the controls is required to wear and use an oxygen mask at all times above that altitude. The mask must be secured and sealed.

If there are two pilots at the controls and each has a quick-donning type of oxygen mask available, neither pilot need wear the oxygen mask. This exception does not apply when one pilot leaves the controls of the aircraft for any reason. Then, when operating at the flight altitudes above FL350, the remaining pilot at the controls must put on and use an oxygen mask until the other pilot has returned to that crewmember’s station.

Happy landings!

John S. Yodice owns and pilots a Cessna 310.

John S. Yodice