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

"Ralph Nesbitt" wrote in message
m...

"Jeff Franks" wrote in message
...

Witnessed the result of "Port Hole Window" on the starboard side of a
C-5
blowing out during "Initial Factory Pressure checks" on a new C-5". The
window itself went through the side of a "Tin Sided Building" ~ 200'
from
where the window/port hole came from. A substantial number of the
insulation/batting blankets were torn from their normal place in the
cargo
bay & piled on the cargo bay floor near the opening. A large number of
the
insulation blankets/bats, along with seat cushions from the upper aft
troop
compartment were piled around the entrance to the stairs from the troop
compartment down to the cargo bay, plus scattered along the cargo bay
floor
in the direction of the failed port hole/window. Seat cushions,
mattresses
from bunks, & insulation bats/blankets from the upper front area were
piled
against the exit stairs from the upper from lobe & along the cargo bay
floor
toward the failed port hole/window. A few of the insulation
bats/blankets
were blown out the failed port hole/window.

A/C being tested were instrumented to record/document test protocols as
appropriate. According to instrumentation on the A/C, at time of port
hole/window failure the air pressure dropped from 14.5 lbs to 0 in .003
seconds.

Factory Pressure Check on C-5's was 15 pounds, slightly over 1
atmosphere.
This was worked up to in stages. This incident occurred.
Ralph Nesbitt
Professional FD/CFR/ARFF Type


This is not the same situation. First the preasurization was set to twice
what it will be in flight. Second the preasure dropped because the
engines
were not pumping air in. Take a bicycle tire pump it up to 8psi (almost
flat) and then let the air out. This it the same preasure differential.

Mike
MU-2

Agreed.

The purpose of the pressure test in question is to assure structural
pressure integrity to 1 atmosphere above AGSL.

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.

A/C pressure systems are set to operate from departure point. If set
manually from info provided by ATC this is "Unadjusted Barometric Presser"
read from an instrument at the base of the Tower, a specified height above
the ramp. Most modern commercial A/C are equipped with automatic systems
that capture relevant data upon command/that is reset for each flight.
Ralph Nesbitt
Professional FD/CFR/ARFF Type