Re:I was there when the DC-8 went supersonic
by throwthere on Sunday August 22, 2021 @08:41AM
(#28264993)
Autopilot malfunction is too charitable to the pilots. From wiki, "Investigators believed that 727 pilots (in general, and this flight specifically) were setting the trailing edge flaps to two degrees during high altitude cruise, while at the same time pulling the circuit breaker for the slats so that they would not activate."
The captain denied that, but who can believe him? He erased 21 minutes out of 30 minutes recorded from the cockpit voice recorder.
Re:I was there when the DC-8 went supersonic
by LeonM on Sunday August 22, 2021 @09:03AM
(#28265143)
> He erased 21 minutes out of 30 minutes recorded from the cockpit voice recorder.
The investigation never concluded this.
In a deposition taken by the Safety Board, the captain stated that he usually activates the bulk-erase feature on the CVR at the conclusion of each flight to preclude inappropriate use of recorded conversations. However, in this instance, he could not recall having done so.
Re:I was there when the DC-8 went supersonic
by throwthere on Sunday August 22, 2021 @09:09AM
(#28265180)
Are we talking about the same investigation?
The NTSB made the following statement in the accident report:
We believe the captain's erasure of the CVR is a factor we cannot ignore and cannot sanction.
Re:I was there when the DC-8 went supersonic
by WalterBright on Sunday August 22, 2021 @02:26PM
(#28268074)
Airplane accident causes are often complicated. I was told the story by my lead in helping me to understand separation. The reason for the dive was not germane, he just said autopilot malfunction.
Probably the funnest part about working in engineering at Boeing was hearing all the war stories from the previous generation.
If you're not careful with a jetliner, it can go into "mach tuck" if you're in a shallow dive, where (again) the separation of flow over the stabilizer makes it ineffective. In one incident on a 707, the pilots weren't paying attention and it went into a shallow dive, and mach tuck. The elevator was ineffective, and the stab trim system wasn't functioning (I don't recall why, but likely it was overloaded). So the copilot got down on his needs and cranked the manual stab trim wheel, and got control back just in time.
(The 707 and 737's had a manual stab trim wheel, as does the 737MAX.)
Edit: Well, well, another poster linked to a wikipedia article about the 727 incident https://en.wikipedia.org/wiki/TWA_Flight_841_(1979) so it seems my memory was accurate.