Re: Passenger cabin pressurization

Date:         17 Sep 97 02:49:16 
From:         jf mezei <"[non-spam]jfmezei">
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Some kind soul did explain to me by e-mail how it all worked and pointed
me to a table on the internet which shows pressure (amongst other
things) related to altitude. (table at )

I made some quick calculations and with an 8.5psi differential,
a plane flying at 33k feet would be able to provide a cabin pressure
equivalent to approx 5000feet.

Flying at 40k feet, that plane would be able to provide cabin pressure
equivalent to roughly 7000 feet.

Based on my current understanding, providing an 8000feet cabin pressure,
in an aircraft with an 0.58 atm (8.5psi) cabin pressure differential
would mean that outside cabin pressure would be at 0.16 atm and this
represents somewhere between 42 and 43k feet.

So back to my original question (with additions):

-For a given model, how much control do airlines have on how
 much the cabin is pressurised ? How much is pilot vs maintenance
 control ?

-Do airline generally allow the pressure to rise to the FAA limit or
 do they pressurise the cabin to the designed 8.5psi to maintain
 a cabin pressure as close to sea level as possible ?

 In other words, if a plane is designed to keep to 8000ft when flying at
 its maximum altitude of 43k feet, will the cabin pressure also be
 8000ft when flying at 33k feet (with lower than 8.5psi difference) or
 will it be at 5000ft with presure difference of 8.5psi ?