Why aren't air cabins pressurised to 1 atmosphere?

Date:         18 Apr 98 00:49:26 
From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
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>I've a vague recollection of reading that aircraft cabins are
>pressurised to 0.5 atmosphere.

They're pressurized to the equivalent of an altitude of about 8,000 ft
above MSL.  I'm not sure what that works out to in atmospheres offhand,
but I'd guess it would be more than 0.5.

>Presumably it would be simple enough to hold it at 1 atmosphere in which
>case all this ear ache stuff at takeoff/landing would be eliminated?
>OK so where's the flaw in this?

First, the greater pressure differential (assuming the same cruise
altitude) would require a considerably stronger fuselage structure,
which implies more weight.  Weight is anathema to airliner design.

Second, it requires energy to pressurize the cabin, and more energy
would be needed to sustain higher pressurization.

Avoiding the minor annoyance of everyone's ears "popping" on ascent
and descent isn't worth the tremendous cost.

Karl Swartz	|Home	kls@chicago.com
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