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From: "F. Barry Knotts" <bknotts@buckeye-express.com>
Pete, Bill, Carl
I did a little research and the math. Here's cabin altitude plots based
upon the "Naval Aviators Standard Day" in Excel format. There is some
error in this due to the lack of temperature correction on the estimates
of the final cabin altitude. I used 3, 4, 4.3 and 5 psi differentials.
The 4.3 psi differential is what I am familiar with. On a good day
(when the turbos and pressure bottle are working well) I see a cabin of
10,000 at about 22,000-23,000 ft. with a 4.3 psi differential. Looks
like with 5 psi differential a 10,000 ft. cabin should be maintained up
to 40,000+ ft. The altitude of a cabin in space with 4.5 psi is 30,000
ft. Seems like there's enough headroom to back the pressure
differential down just a little. Or use the max differential only at the
times when you really need it. Cruising at 18,000 ft should allow a
much lower pressure differential if the cabin is allowed to climb to the
8,000 ft range. (3.7 psi differential)
Somebody check my math.
Barry Knotts
LIV-P, Conti TSIO 550, Toledo, Ohio, 20%
ps The 5 psi curve has been corrected. Still, there seems to be a fair
amount of headroom to reduce the differential. (Just not quite as
much.)
[ xls converted to pdf for net readablity -Rob ]
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