robert edwards commentary on the details of the boeing air stairs tests is reasonable, and here:
with discussion about hydraulics
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Loginalso a later update
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Loginthis second post has images showing oscillations in airplane altitude. I think he made the graphs from the data in the fbi files?
Edwards makes an interesting point:
"If on Flight 305 the autopilot was engaged (as the FBI assures us was the case) and "altitude hold" was switched on (which I think probable), it would compensate for the pitch-up without any intervention by the pilot, and would return the airplane to the desired angle of attack and to the desired altitude. There would surely have been some oscillations in the airplane's altitude, in the cabin's equivalent altitude, and in the cabin rate-of-climb (rate of change of cabin pressure), as there were in Boeing Test 100-1, summarized in the graphs below.]"
also:
"[I believe that there were at least three relevant differences between the Boeing tests and Flight 305.
* In the Boeing tests, the landing gear was up. On Flight 305, the gear was down.
* In the Boeing tests, according to my correspondent, the autopilot was probably disengaged. On Flight 305, according to two statements to the FBI by Northwest's Director of Flight Operations (Technical), the autopilot was engaged throughout most of the segment between Seattle and Reno. A former senior FBI agent advised me that the FBI had no reason to question these statements.
* In Boeing Test 100-1, all the interior panels in the stairwell were removed. to avoid possible damage. I do not know what the aerodynamic effects might have been, but I suspect that this condition would have created more turbulence in the stairwell. In Boeing Test 100-3, the panels were re-installed. On Flight 305, all the panels were in place."
He has a nice pic of N727000 doing a test drop over the Pacific with the stairs removed. Interestingly, the payload and parachute descend at a more vertical angle from the plane, then I've seen in other test drops. (in other tests)
interestingly Edwards said
"Back on March 5, 2020, I had submitted a FOIA request for all reports relating to the Boeing test flights. The FBI replied on July 6, 2020, to the effect that they had searched for the reports and found nothing."
and then the FBI released the files with the detailed test reports.
Weird.