Gee, I never thought of that!
I knew that cabin doors were designed so that the cabin pressure keeps them closed, but that raises another question: in the 727, how in the word did they keep that enormous door for the rear stair closed against cabin pressure when at high altitude? The door was much bigger than a typical cabin door, and it was obviously openable in flight, as proven by ol' D.B.
I wonder how they managed that? Must have been some pretty clever mechanical engineering.
Rear ramp on a 727 has hydraulics to raise and lower.
Now have db cooper locks. Plane under power no workie
There was a more conventional door at the back of the cabin that maintained cabin pressure and that would have to be opened first. The air stair was in an unpressurized area of the fuselage beyond that. From what I recall, D.B. Cooper had the pilot descend to an altitude at which the cabin could be depressurized, permitting him to exit via the rear airstair.
After the D.B. Cooper incident, airlines were required to install small vanes on the exterior of the airstair that generated a vortex and made it impossible to open that door in flight as well.
There is a pressurized door at the top of the Rear Stairway on a 727.
The compartment the stairs fold up into is not pressurized.
The plane was below 10K and depressurized. Also slowed to 200 knots
The access door to the stairwell was similar to a regular cabin door, it opened inward.
Well, not so much. The engineers first used suicide doors like on the old Lincolns, but they figgered that one out real quick! :-p