"Robert Moore" wrote in message
...
"Ralph Nesbitt" wrote

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.

In the Boeing aircraft that I flew (B-727,B-707,B-720) there were two
gages on the FE's panel. One was a simple altimeter that indicated the
cabin altitude at all times and the other, a differential pressure gage
that indicated the difference in pressure between outside and inside.
The maximum differential for those aircraft was around 8.6 psi. The only
way to determine the absolute pressure inside the aircraft would be to use
a graph to convert the altimeter indication to pressure.

Bob Moore

The protocols you reiterate above will translate to a ~ constant pressure of
12 PSI Gauge inside the cabin as the A/C moves through it's flight profile
above ~ 11,000'.
Ralph Nesbitt
Professional FD/CFR/ARFF Type