"Mike Rapoport" wrote in message
hlink.net...

"Ralph Nesbitt" wrote in message
gy.com...

"Mike Rapoport" wrote in message
hlink.net...

"Ralph Nesbitt" wrote in message
m...
Hopefully all realize when referring to "Air Pressure" at altitude
this
is
an "absolute" pressure value inside the fuselage irrespective of
ambient.
When referring to air pressures at ground level the pressure reading
is
above unadjusted ambient barometric pressure.

This is incorrect, pressurization is the differential between ambient
and
cabin preasure.

Mike
MU-2

Please reconsider your statement above as it applies to pressurization
of
A/C cabins at altitude.

At altitude A/C cabins are like a pressure vessel. A/C cabins are
pressurized to maintain ~ 12 PSI Gauge, ~ the same as normal atmospheric
pressure @ 11,000' ASL, in the cabin irrespective of altitude above
11,000'
ASL.
Ralph Nesbitt
Professional FD/CFR/ARFF Type

No, the cabin is not at a constant preasure above 11,000' (and the number
that you are looking for is 8,000') unless the rate controller is set to a
rate greater than the climb rate of the aircraft (which is never done).
If
what you say were true then the cabin altitude would not climb with the
airplane above 11,000' (8,000') which it clearly does. If you doubt this,
go buy an altimeter watch and see for yourself. Or you could buy a
pressurized airplane.

OK, I'll bite.

Just how does the psia in the cabin track the psia "ambient."