Re: Cabin Depressurization

Date:         10 Feb 2000 05:03:27 
From:         rdd@netcom.sucks.com
Organization: NETCOM / MindSpring Enterprises, Inc.
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In article <airliners.2000.12@ohare.Chicago.COM>,
GLPILOTSRV <glpilotsrv@aol.com> wrote:
>This is the reason that above 25,000 feet, if one crew member leaves the
>flight deck, the remaining crew member is required to use supplemental
>oxygen. Above 35,000 feet, regardless of number of crew members on the
>flight deck, one crew member must utilize supplemental oxygen.

Not exactly.

http://www.faa.gov/avr/AFS/FARS/far-121.txt

(2) When operating at flight altitudes above flight level 250, one pilot
at the controls of the airplane shall at all times wear and use an oxygen
mask secured, sealed, and supplying oxygen, in accordance with the following:

(i) The one pilot need not wear and use an oxygen mask at or below the
following flight levels if each flight crewmember on flight deck duty
has a quick-donning type of oxygen mask that the certificate holder has shown
can be placed on the face from its ready position, properly secured, sealed,
and supplying oxygen upon demand, with one hand and within five seconds:

(A) For airplanes having a passenger seat configuration of more than 30
seats, excluding any required crewmember seat, or a payload capacity of
more than 7,500 pounds, at or below flight level 410.

(B) For airplanes having a passenger seat configuration of less than 31
seats, excluding any required crewmember seat, and a payload capacity of
7,500 pounds or less, at or below flight level 350.

And:

http://www.faa.gov/avr/AFS/FARS/far-91.txt

 Sec. 91.211  Supplemental oxygen.
(a) General. No person may operate a civil aircraft of U.S.  registry--

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

(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.

To wit:

1.  Don't need to wear oxygen under FL410 if you have quick-donning masks.

2.  If anyone leaves the cockpit above FL350, a remaining pilot needs to
go on oxygen.

Full text at the URLs.  Yes, the rules are real, and yes, crews tend to
obey them.  So when you note the captain stretching his legs halfway through
a flight, feel confident that the first officer is on oxygen.

--
Robert Dorsett                         Moderator, sci.aeronautics.simulation
rdd@netcom.com                         aero-simulation@cactus.org

           "Bother," said Pooh when his engine quit on take-off.