I was reading the description of an old hijacking which has this snippet of interesting information:
After takeoff Cooper told Mucklow to join the rest of the crew in the cockpit and remain there with the door closed..... At approximately 8:00 pm a warning light flashed in the cockpit, indicating that the aft airstair apparatus had been activated.... The crew soon noticed a subjective change of air pressure, indicating that the aft door was open. At approximately 8:13 pm the aircraft's tail section sustained a sudden upward movement, significant enough to require trimming to bring the plane back to level flight. At approximately 10:15 pm Scott and Rataczak landed the 727, with the aft airstair still deployed, at Reno Airport....an armed search quickly confirmed that he was gone.
Would a 90 kg man jumping off the aft stairs of a B-727 in flight create a detectable "sudden upward moment". Not just a slight one but "significant enough to require re-trimming"?
Doesn't sound like a fluke or the product of a vivid imagination because we further know that:
An experimental re-creation was conducted using the same aircraft hijacked by Cooper in the same flight configuration, piloted by Scott. FBI agents, pushing a 200-pound (91 kg) sled out of the open airstair, were able to reproduce the upward motion of the tail section described by the flight crew at 8:13 pm.
The full story is here:
I'm estimating the mass of a fully-fueled B-727 as about 60,000 kg. A detectable perturbation by a 90 kg ejected body sounded a tad unlikely.
But I'd love to see a more accurate calculation. I suppose the center of gravity and the long lever arm for the aft stairs location will matter?
PS. It seems far more plausible to me that the movement detected was actually due to the aerodynamic forces on aft stairs and not the effect of the ejected 90 kg mass. The only reason I was rejecting this explanation was that the timing seems off if we are to believe the flight crew report:
They seem to have detected two events: A pressure change and later this reported sudden movement. So the movement does not seem correlated in time with the aft stair deployment.