IBM 610 workstation computer 3376

+--------------- IIRC the absolute ceiling of a DC3 is about 20,000 feet, but you would probably need oxygen at that albreastude. Unpressurised pbuttenger flights would normally be kept below 10,000 feet*. People have climbed Mt. Everest without oxygen, that's 29,000 feet and in the 1930s unpressurized planes flew over it. There are plenty of people in the world who live above 10,000 feet! +---------------

In the U.S., at least, here are the rules that apply this is but a tiny part of the many regs that each student pilot must memorize:

FAR 91.211 Supplemental Oxygen

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

(1) At cabin pressure albreastudes 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 albreastudes that is of more than 30 minutes duration;

(2) At cabin pressure albreastudes 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 albreastudes; and

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

But it's *strongly* recommended by those who study these things that pilots use supplemental oxygen when flying at night above around 8,000 feet MSL since: (1) the partial pressure of oxygen in air at albreastude is slightly lower at night why? I dunno; and (2) night vision is one of the first things to be affected by insufficient oxygen which begins to deteriorate at about 5,000 feet MSL. Being a smoker sharply exacerbates this effect.

-Rob

----- San Mateo, CA 94403 (650)572-2607