Wind loads are tricky. on the ground you have a vast amount of variations in determining wind loads. testing is based on 150 mph winds with a 3 second gust. if not mistaken 100 lbs per square foot was applied the the back of the stairs at 170 knots. that's several thousand lbs pushing against the stairs. on the ground you have positive and negative loads. you can actually watch a window breath in a major hurricane. the only + or - would be pressure inside the aircraft.

I had posted the weight of an aft stair replacement on DZ.com at one point. A maintenance guy wrote about how he had the brainstorm of having them packaged and available rather than waiting for them to be shipped, if a replacement as needed.

In any case, what's interesting to me is the comparison of body+money weight to the massive wind loads you mention. Since body+weight can cause the stair to deflect, it shows that it's an unstable configuration where small changes can cause or not cause deflection.

So it would be easy for small changes in plane velocity and attitude, and maybe outside air velocity, to change behaviors dramatically.

Witness in the transcripts where they had to slow down to help Cooper get the door open?

Also, depending on the engle of the airplane, things would change around. (like if you were ascending rapidly) ??

lots of variables.

One fbi test doesn't convince me of much.

The fabric would slowly deteriorate. it wouldn't come off in one piece. if not mistaken the stuntman said they did something like 10 takes..don't quote me on that, but it's what I recall..

I'm just going from the Parachutist article. Once someone jumps, they're not going to do another shot until they get the jumper again.

Unless they did multiple jumpers. At DZ.com, it was claimed Jerry Meyers was the jumper (Cooper). But unclear if he was always the jumper. I wonder if the closeups during freefall were of Jerry Meyers.

I'm assuming "two loads" means two flights, therefore 2 jumps.

And if a videographer jumped too (on the 2nd load)..then you probably need him too.

They said they had 3 cameramen. (apparently they were jumpers and probably had parachutes, just in case).
Don't know if that includes the camera in the Lear jet.

"Donnelly and Cottingham chose four others for their basic crew: Boenish, Dean Westgaard, Bill Edwards and Jerry Meyers. It was an experienced group of jumpers; Donnelly estimated that the average number of jumps was about 3,000. Boenish was chosen as a third photographer to insure high-quality footage. All three photographers carried both 35mm film cameras and 35mm still cameras...

But the big expense was renting the 727 as a jump platform. Total cost for two loads came to $65,000"

(note: I had thought it was $60,000 a load. Apparently it was only $65,000 for both loads.
Total shoot cost (budget) was $140,000. Maybe that included painting the plane!)

The Parachutist article page I posted, detailed how a 10 foot section of fabric came off and knocked  Donnelly off his feet while standing on the stairs spotting the DZ. (over Yosemite Park)

so the fabric apparently doesn't always come off in small pieces

Quote

So it would be easy for small changes in plane velocity and attitude, and maybe outside air velocity, to change behaviors dramatically.

Yes, impact windows are no different. each size of a window will have different pressures applied. 150 vs 170 can make a big difference in actions..

The force goes up as the square of wind velocity.

F = 1/2 p * (v**2) * A

the p is density of air.
A is area exposed to the wind
v = wind speed
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That would be with him on the bottom of the stairs? one would think not much damage would occur with the stairs only dropping a couple feet prior to getting on the stairs.

It's hard to say. a lot more damaged occurred with 305 vs testing..only one side was affected during the testing..

was reading this theory (Gregory Hall, Sept 2016)

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pressure bump vs pressure dip

He talks about how the cabin pressurization system was not documented to have been turned off?

since the system was automated, pressurization would have occured depending on whether the door to the aft stairs was open or closed?

he talks about how the pressure might have dipped due to the door being closed, some cabin pressurization, then opened.
If so, maybe the pressure bump was the first time the door was opened? The lever for the stairs is on the left of the door. so activating it doesn't require door open? See attached from 727 manual

He also claims "For most people it is difficult to determine if air pressure change in their ears is the result of high pressure (bump) or low pressure (dip)..both feel essentially the same"

background on Greg Hall

Retired Investigator had a 27 year career in law enforcement. Three years were as a "street cop" (Deputy Sheriff) and 24 years as an FBI Special Agent. Prior to law enforcement, Retired Investigator served in the US Army during the tail-end of the Vietnam war. He was a paratrooper in the 82nd Airborne Division, serving in the Airborne Infantry, attaining the NCO rank of E-5. After college, he entered the US Air Force, Officer Training School (OTS) and received an Officer's commission. He received additional training in the USAF Security Police (now Security Forces) career field. During the 1980's, he received an appointment to the FBI as a Special Agent. He spent approximately half his career investigating criminal matters and the other half involved in National Security. During 2017, his "DB Cooper" theory was portrayed in an episode of EXPEDITION UNKNOWN, hosted by Josh Gates on television's TRAVEL CHANNEL and the DISCOVERY CHANNEL.

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The link should take you to all my Cooper pics sent to me by WSHS

Shutter, do you know if there were any NWA mechanics or other personnel onboard for the FBI tests to do the actual lowering of the stairs?