aviatorhi states...
On a more serious note I remembered the DB Cooper incident when I was reading through the replies, while the door in the aft bulkhead on a 727 is a plug type door it opens inward only. From my point of view (I go in and out of it often enough) and from a purely functional stanpoint it's near identical to the L-1 door (well duh, it's a door)
aviatorhi asks
but I'm wondering how much pressure, if any, DB Cooper was dealing with when he went to do that. I doubt it was 8.6 DPSI, but I bet someone knows the exact figure.
The answer aviatorhi's question is 0 PSI Diff. as the aircraft was depressurized. The DB Cooper switch was installed in 1972 after a few incidents to prevent the ventral stairs from being lowered in flight. The DB Cooper Switch is a spring loaded vane that rotates 90 degrees.
On the ground the plate which is attached to the vane is out of the way of the ventral stairs for normal operation. A preflight item is to ensure that the spring in the vane operates as it should. As airflow hits the vane, it rotates about 90 degrees so that a plate will cover the ventral stairs to prevent operation during flight.
All doors, including cargo doors on the 727 are plug type doors.