Re: Cabin pressure controls

From: (Robert Dorsett)
Organization: Netcom Online Communications Services (408-241-9760 login: guest)
Date:         12 Sep 95 20:18:55 
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In article <airliners.1995.1453@ohare.Chicago.COM> (TriStar500) writes:
>>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.

I'm sure there must be relief mechanisms to control flow within parts of the
distribution manifolds.  But I would argue that such mechanisms are not part
of the pressurization system per se: they're just flow limiters, and are
static in nature.

I'm also not clear what the purpose of a 60-70 ppm limit would be: from my
information, pack airflow can exceed 140 lbs/minute.  Based on SAE ARP 1270,
I do not think it would be possible to maintain pressurization controller
authority on 60-70 ppm/pack.

I hope I'm not arguing semantics here...

Robert Dorsett                         Moderator, sci.aeronautics.simulation