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Persistent pesky questions about them stairs and the oscillations and bump...

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...going down a couple of steps past that hinge point is going to lower the stairs enough to create pressure changes in the cabin that would be noticeable in the cockpit cabin altitude instrument...     ...this time, he goes way down the steps as far as he can, perhaps to the very end of the stairs, and jumps.  Cooper's weight on the stairs will not lower them to the same degree as they are lowered on the ground.  But when Cooper steps off those stairs they slam up into their closed position but don't lock there...     

In that clip from the Treat Williams movie, when the stunt guy jumps off the stairs, they retract very slightly and slowly. They certainly don't 'slam' shut, even momentarily. I would imagine the pilot could feel a bit of change on the pitch influence, but I don't see it re-sealing the cabin momentarily and causing a pressure event. For the stairs to behave in the way described, I would guess that Cooper would have to have pulled the emergency release, which should disconnect them from the hydraulic system and allow them to free-float. But I'm told that did not happen, that he did not pull the emergency release. So would there be that much variable from plane to plane, how much the stair door would be able to move while still connected to (dampened by) the hydraulic system?  ...??

I don't have a good answer for that either. I have heard different things - the stairs hydraulics were not deployed and the stairs were freefloating and vice versa. Regardless, it seems that the pressure bump was simulated during the drop test in January 1972.

Here is what I do know:  the cabin rate of climb and descent gauge uses a sensor in the cabin to measure cabin pressure altitude. During an unpressurized flight - like the Cooper hijacking for example - it will read approximately the altitude that the aircraft is at. It will respond just like the flight altimeter - going up and down with the aircraft.

I propose that the 727 was experiencing what's known as a phugoid.

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If the plane was experiencing a phugoid, that would be reflected as oscillations in the cabin rate of climb indicator. I think the slow extension of the airstairs by Cooper caused phugoid oscillations in the aircraft that the crew noticed on the gauges. When Cooper jumped, the crew experienced a pressure bump - a rather well-known phenomenon in aviation when the pressure of the cabin increases dramatically - that usually causes your ears to "pop". When that happened, the airstairs were no longer descending and the aircraft stabilized from its phugoid.

Thus, while both phenomena - the phugoid oscillations and the pressure bump - were caused by Cooper's behavior on the airstairs, they were distinct things. Whether the crew, the airline flight ops, or the FBI understood the difference when it happened or immediately after is the question.

Chaucer, as an aeronautical engineer my main time was in flight dynamics which included aircraft performance and stability and control.  Longitudinal aircraft stability involves a short period mode and a longer mode called the phugoid.

The short period mode is typically completely damped out within a couple of seconds and is not generally noticeable to the pilot.  I have never noticed anything that I could identify as the short period mode in flying powered general aviation aircraft and unpowered sailplanes.

I have more than 1000 hours of flying time in unpowered sailplanes which spend about 90 percent or more of their time in maneuvering flight.  Consequently, for sailplanes, it is desired that the longitudinal stability be essentially zero.  This means that when the pilot takes his hand off the stick the sailplane will diverge longitudinal as well as about the other two axes.  Longitudinally, this divergence is the phugoid and it will never dampen itself out.  Without corrections by the pilot the sailplane will end up in a spiral and if it stalls it will spin.  Long flights in sailplanes can be very tiring.  My longest flight sailplane flight was about 7 hours and 20 minutes.  After landing, it took me at least 5 minutes to get out of the cockpit and stand up and I felt lousy the next day.

Powered aircraft, even fighter aircraft, generally spend about 90 percent or more of their time in straight and level flight.  Again, the short period mode dampens out in only a few seconds.  But the phugoid mode may take 4, 5, 6, or more minutes, repeat minutes, to dampen out naturally if it ever does so.  Hand flying early jet airliners at high altitudes was particularly tiring for the pilots due to the phugoid.  Consequently, the autopilots were typically activated as soon as possible after takeoff and stayed on until the descent for landing.

Flying a sailplane sounds like fun. Too bad I'm a nervous flyer. Go figure.

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But the phugoid simply cannot explain the cabin pressure altitude oscillations or the bump when the stairs hit the fuselage when Cooper jumped.  It is just not possible.

First, in my post I said that the phugoid would explain the cabin pressure oscillations, but NOT the bump. The bump, I think as has been clearly shown, is caused by the door swinging back up after Cooper jumped.

Second, since this would appear to be your area of expertise, I would hope you could explain why a phugoid mode can't explain the oscillations in the cabin pressure rate of climb. I may be wrong about it, and I only offered it up as a possibility. At its face, it appears to make sense. Rather than simply tell me it's not possible, tell me why.

Simple.  The autopilot or the pilot hand flying the aircraft would cancel out the phugoid and it would not be a factor in the cabin pressure oscillations.

This is not an insult.

I certainly think if the autopilot was on, then a phugoid would be easily dampened. I don't think the autopilot was on.

With that said, would flying unpressurized at night through clouds with little frame of reference, impact the ability of the pilot to detect a phugoid and thereby react to it? Rataczak obviously had a lot of other things to be distracted about.

I'm not arguing strongly in favor of a phugoid. I'm sincerely asking. If it's not possible, then it's not possible.

It's not possible.  Again, the phugoid was never a factor.

Flying at night through clouds and unpressurized doesn't mean anything.  The gyroscopic instruments on their instrument panel was all they needed for reference.

In 1971, in addition to an FAA Pilot's Certificate, I also held an FAA Ground Instructor Certificate that permitted me to teach pilots Basic, Advanced, and Instrument Flying.  While I never had a pilot's certificate for instrument flying, I have quite a few hours of flying under a hood with a safety pilot on board and this included ILS and other instrument approaches.  Some of that flying was done in two-place sailplanes with the only gyroscopic instrument being a "needle and ball" which predates today's "turn coordinators".

The above is not an insult.   

Hayden provided the two backpack parachutes that were given to Cooper and he said they were identical.  The surviving backpack is now on display at the WSHM in Tacoma, WA.  The pictures of that backpack indicate that it was put together from a collection of parts that came from different designs and did not itself have a formal designation.

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I'll leave an explanation of the aft stairs hydraulic system to others, but the drop tests prove the point about the bump and cabin pressure oscillations.

I don't need an explanation of hydraulic systems, I know how they work. What I'm saying is that there is something in all this that doesn't make sense. Things attached to hydraulic systems don't move all that freely, as their movement is restricted and dampened by the systems, as evidenced in the footage of the Treat Williams movie jump. The pilots did note the pressure bump, both in Cooper's jump and in the subsequent test. Flyjack has posted evidence that Cooper did not pull the emergency release, I don't think I've heard one way or the other about the test. I just have a hard time seeing the door rebound to the point of momentarily slamming shut while it's connected to the hydraulics, again as evidenced by the movie footage.

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In 1971, in addition to an FAA Pilot's Certificate, I also held an FAA Ground Instructor Certificate that permitted me to teach pilots Basic, Advanced, and Instrument Flying.  While I never had a pilot's certificate for instrument flying...

You were not instrument rated as a pilot, yet you were rated to teach instrument flying as an instructor? How does that work?

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The pictures of that backpack (Hayden's parachute) indicate that it was put together from a collection of parts that came from different designs and did not itself have a formal designation.

Please detail that for me. Please.

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It's not possible.  Again, the phugoid was never a factor.

Flying at night through clouds and unpressurized doesn't mean anything.  The gyroscopic instruments on their instrument panel were all they needed for reference.

In 1971, in addition to an FAA Pilot's Certificate, I also held an FAA Ground Instructor Certificate that permitted me to teach pilots Basic, Advanced, and Instrument Flying.  While I never had a pilot's certificate for instrument flying, I have quite a few hours of flying under a hood with a safety pilot on board and this included ILS and other instrument approaches.  Some of that flying was done in two-place sailplanes with the only gyroscopic instrument being a "needle and ball" which predates today's "turn coordinators".

The above is not an insult.   

What specific instruments on the Boeing 727 would the crew used to identify a phugoid?

No instruments exist for identifying a phugoid except the pilot's posterior.  And again, the phugoid was not a factor in the Cooper hijacking.