The Boeing airstair tests and DB Cooper

dfs346

dfs346

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DFS346
For the first time in the public domain, the FBI has released one of the technical reports on the Boeing Company’s tests of the Boeing 727 with the air stairs down in flight. The report in question is numbered and titled D6-7771: “Flight Characteristics with Aft Airstair Down – B”. The airplane used was the second prototype, tail number N72700. The tests described were conducted on March 13 and 19, 1964.

For anyone interested, the FBI release is at https://vault.fbi.gov/D-B-Cooper /d.-b.-cooper-part-71-of-71/view. The Boeing report is on pages 333-356.

I extracted the following key passages: “Purpose of Conditions Performed: Simulate a failure of the aft airstair up-latch in flight, evaluating the characteristics of the extended airstair and the effect on airplane performance and handling. The airstair was extended both by allowing it to freefall and by utilizing normal hydraulic power. These extensions were made with the airplane trimmed for level flight at 125 knots and flaps at 25 degrees. The airstair extended a nominal 8.5 degrees when allowed to free-fall and it required only approximately one-tenth unit of nose-down trim to compensate for the stair. The stair extended a nominal 13.5 degrees with hydraulic power and this caused approximately a three-tenths unit nose-down trim change."

On November 24, 1971, the hijacker of Flight 305 departed the airplane via the aft airstair, at an indicated air speed of between 160 and 170 knots. Would it be reasonable to conclude that via the control lever, with or without hydraulic power, he would have been unable to lower the stairs by more than 13.5 degrees?

Alternatively, did the Flight 305 airplane (model 727-51, tail number N467US) have a different control system for the aft airstair, or a more powerful hydraulic system than the prototype N72700, such that the airstair could be fully extended in flight? Documents in the public domain indicate that the 727 hydraulic system generally had an operating pressure range of 2800-3100 psi, but I have not found documents specific to the prototypes or the 727-51 model.
 
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I’m surprised the pitch-down effect was so small.

Fortunate for everyone who remained aboard.
 
NoHeat said:
I’m surprised the pitch-down effect was so small.
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Pitch up. It required nose-down trim to compensate.

I don't understand the point of these tests though, being conducted after the flight has already happened. They knew the plane could fly fine. Wasn't the only question whether someone could survive the egress?
 
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Lindberg said:
Pitch up. It required nose-down trim to compensate.

I don't understand the point of these tests though, being conducted after the flight has already happened. They knew the plane could fly fine. Wasn't the only question whether someone could survive the egress?
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Test was done in 1964. DB Cooper was 1971
 
dfs346 said:
Would it be reasonable to conclude that on November 24, 1971, the hijacker of Flight 305 encountered the same situation?
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I’m confused, what situation are we talking about? I’m just seeing some data about flight characteristics by lowering the air stairs with and without hydraulic power.
 
Lindberg said:
Pitch up. It required nose-down trim to compensate.

I don't understand the point of these tests though, being conducted after the flight has already happened. They knew the plane could fly fine. Wasn't the only question whether someone could survive the egress?
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Given the era, I wouldn't be surprised if the tests were done on behalf of a certain northern VA agency who sometimes enters countries through the back door and simply attributed to another org/entity.
 
Sounds like a flight test of the 727 for "what if" a latch failed and the stairs dropped. Not related to the FBI or the DB Cooper case.
 
Didn't some skydiving club do a DB Cooper run where they jumped out of the rear door of the 727. It may have been one with the stairs removed however.

Here's some video on 727 stair deployment. It would appear you don't need much depoyment (just pretty much in trail) to have enough room to get out. There's plenty of head room, you just have to fit through the opening at the end.
 
Wearing loafers and a business suit he jumped out in -7 degrees into either a snowstorm or a freezing rain storm. He jumped at 10,000’ at night with no visibility to the ground as the ceiling was 5,000’. And he experienced a wind blast of 150 kts.

The club that duplicated the 727 jump hopefully only duplicated the part about 10,000 feet and a 727.
 
That and knowing the leadership at NWA, I think there's a good chance he didn't have a viable parachute.
 
flyingron said:
That and knowing the leadership at NWA, I think there's a good chance he didn't have a viable parachute.
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Conflicted between “that’s horrible” and “hah!”
 
Found a link for the video of the "DB Cooper" jump. It appears from the video that the airstairs and perhaps even the rear door were removed prior to the flight.

 
They used to do this nearly every year at the skydiving event in Quincy.
 
That’s assuming he ran the stairs all the way down, Maybe he didn’t need too to exit the plane
 
He probably needed to go all of the stairs. There's not much room on the sides because there are automatically deploying handrails plus the two large arms that actuate the moveable part. The first six steps or so are part of the fuselage, then you have ten on the hinging part. The hard part is clearing the top of the rear opening in the fuselage. If the stairs were sticking straight out behind the plane in the stripstream, that'd still give you like two feet to crawl over the end.
 
dfs346 said:
For the first time in the public domain, the FBI has released one of the technical reports on the Boeing Company’s tests of the Boeing 727 with the air stairs down in flight. The report in question is numbered and titled D6-7771: “Flight Characteristics with Aft Airstair Down – B”. The airplane used was the second prototype, tail number N72700. The tests described were conducted on March 13 and 19, 1964.
The airstair extended a nominal 8.5 degrees when allowed to free-fall and it required only approximately one-tenth unit of nose-down trim to compensate for the stair. The stair extended a nominal 13.5 degrees with hydraulic power and this caused approximately a three-tenths unit nose-down trim change."
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I don't understand how the lowered air stair would cause a nose up condition requiring "nose-down trim". The lowered air stair would certainly produce a lot of drag, and the center of pressure of this drag would be below the trimmed level flight center of drag ... causing a nose down condition. Right? Wrong? Maybe? Maybe not?

There are many things in life which I fail to understand ... this could be one of 'em.
 
Simply created a low pressure under it, pivoting the nose up a bit...

I’m nearly certain it had normal hyd pressure and just extended all the way. There’s a valve you can kick with your foot in to free fall it, which requires more training than just using the controls.

They double as a tail stand, normally fully powered down. I doubt the pitch change would be very significant.

Seems a test not very relevant to the Cooper event, but I can see what they were possibly checking.
 
Not mentioned here is that after DB Coopers jump a simple spring loaded rotating wind vane was added to all the 727’s in passenger service. As the aircraft accelerates on takeoff the slipstream rotates the vane and locks the air stair closed in flight. There is no override. This insures that if you have a armed hijacker on board who wants to exit the aircraft he can’t leave. Not really sure I liked the concept!
 
Jeff767 said:
Not mentioned here is that after DB Coopers jump a simple rotating wind vane was added to all the 727’s in passenger service. As the aircraft accelerates on takeoff the slipstream rotates the vane and locks the air stair closed in flight. There is no override. This insures that if you have a armed hijacker on board who wants to exit the aircraft he can’t leave. Not really sure I liked the concept!
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...and it's called the "Cooper vane". :cool:

Nauga,
blowin' in the wind
 

In 2012 a 727 was intentionally crashed in the desert as an experiment. The plane was rigged with remote controls flown by a pilot in the spotter plane, but it actually took off with a crew, who bailed through the air stairs after turning the control of the plane over to the remote pilot.

I can't find the full documentary, but it's out there, and it's pretty interesting.

Edit: Found it.

 
Sac Arrow said:

In 2012 a 727 was intentionally crashed in the desert as an experiment. The plane was rigged with remote controls flown by a pilot in the spotter plane, but it actually took off with a crew, who bailed through the air stairs after turning the control of the plane over to the remote pilot.

I can't find the full documentary, but it's out there, and it's pretty interesting.

Edit: Found it.

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I would say that is pretty good indication that ol’ DB probably survived the exit. Whether or not he survived the jump is still unknown.
 
He was probably in critical hypothermia before he hit the ground.
 
Sac Arrow said:

In 2012 a 727 was intentionally crashed in the desert as an experiment. The plane was rigged with remote controls flown by a pilot in the spotter plane, but it actually took off with a crew, who bailed through the air stairs after turning the control of the plane over to the remote pilot.

I can't find the full documentary, but it's out there, and it's pretty interesting.

Edit: Found it.

Click to expand...
Red bull guys are jealous
 
flyingron said:
Found a link for the video of the "DB Cooper" jump. It appears from the video that the airstairs and perhaps even the rear door were removed prior to the flight.

Click to expand...

Also known as the ''DB Cooper Skydiving School''...
 
MBDiagMan said:
I would say that is pretty good indication that ol’ DB probably survived the exit. Whether or not he survived the jump is still unknown.
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Unknown? I thought DG solved this. He made a YT vid about it, so it has to be true.
 
I believe that a quantity of the money from the D B Cooper stash was found many years later, scattered in the forest. None of the recorded serial numbers have surfaced any where else.

If he came down in the area where the money was found, the terrain was extremely inhospitable to a parachute arrival. Successfully cutting loose from a parachute high in mature trees of the PNW is a very difficult task, requiring tools and equipment. Doubtful he had such with him, since he was in a business suit.
 
The area originally targeted and searched is drained by the Lewis river. The money that was found was in a sand bar in the Columbia River, upstream of where the Lewis enters, meaning that DB Cooper must have come down much further to the east, in the Washougal river watershed.

Regardless, his chance of survival had to have been slim to none. Somewhere up in a Douglass Fir there’s probably a skeleton hanging in the remains of a business suit and parachute harness.
 
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