Re: Cabin pressure

From: (Ted Gallop)
Organization: Curtin University of Technology
Date:         01 Jun 95 05:00:58 
References:   1
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In article <airliners.1995.686@ohare.Chicago.COM> (Wayne Dockery) writes:

>If the cabin in a commercial passenger aircraft is
>pressurized, how is it possible to exhange fresh
>air from the outside since I would assume the aircraft
>is somewhat airtight?  Also, is the pressure managed
>by a air-compressor or is it simply "scooped" from the
>outside via some sort of duct-work into the cabin thereby
>generating the pressure?

The cabin air is bled from the engine compressors. (Older aircraft like
the 707 had separate turbochargers on the top of each engine because it was
feared that engine bleed air may get "contaminated") Although it may be -60
degrees C outside, the compressed air is Hot so it is fed through
airconditioners to cool it to the required temp before entering the cabin.

Pressure is maintained by regulating the size of the exit valve opening. The
air is fed in from the duct via the airconditioning packs and permitted to
escape at a controlled rate. Simple.