Re: Cabin pressure controls

From: (TriStar500)
Organization: America Online, Inc. (1-800-827-6364)
Date:         12 Sep 95 02:44:29 
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>valve position.  Something still needs to regulate the amount of
>air bled from the engines.

>On designs I've examined, there really isn't anything.

The pack valves do control the amount of air flowing into the pack - the
proper terminology is actually 'pack flow control valve'. I'll have to
check the books, but I believe that a 727 pack valve allows flow on the
order of 60-70 lbs per minute.

The 757/767 pack valve (probably on other newer airplanes) actually have a
low-flow and a hi-flow mode which is what allows a single pack 757/767 to
cruise at normal altitudes. An older airplane like a 727/737 is limited to
about 25,000' on one pack.