"fred" wrote in message
...

So what the devil is "91.211"?


FAR 91.211, applicable to the US.


§ 91.211 Supplemental oxygen.

(a) General. No person may operate a civil aircraft of U.S. registry-

(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including
14,000 feet (MSL) unless the required minimum flight crew is provided with
and uses supplemental oxygen for that part of the flight at those altitudes
that is of more than 30 minutes duration;

(2) At cabin pressure altitudes above 14,000 feet (MSL) unless the required
minimum flight crew is provided with and uses supplemental oxygen during the
entire flight time at those altitudes; and

(3) At cabin pressure altitudes above 15,000 feet (MSL) unless each occupant
of the aircraft is provided with supplemental oxygen.

(b) Pressurized cabin aircraft. (1) No person may operate a civil aircraft
of U.S. registry with a pressurized cabin-

(i) At flight altitudes above flight level 250 unless at least a 10-minute
supply of supplemental oxygen, in addition to any oxygen required to satisfy
paragraph (a) of this section, is available for each occupant of the
aircraft for use in the event that a descent is necessitated by loss of
cabin pressurization; and

(ii) At flight altitudes above flight level 350 unless one pilot at the
controls of the airplane is wearing and using an oxygen mask that is secured
and sealed and that either supplies oxygen at all times or automatically
supplies oxygen whenever the cabin pressure altitude of the airplane exceeds
14,000 feet (MSL), except that the one pilot need not wear and use an oxygen
mask while at or below flight level 410 if there are two pilots at the
controls and each pilot has a quick-donning type of oxygen mask that can be
placed on the face with one hand from the ready position within 5 seconds,
supplying oxygen and properly secured and sealed.

(2) Notwithstanding paragraph (b)(1)(ii) of this section, if for any reason
at any time it is necessary for one pilot to leave the controls of the
aircraft when operating at flight altitudes above flight level 350, the
remaining pilot at the controls shall put on and use an oxygen mask until
the other pilot has returned to that crewmember's station.