Originally Posted by
zzuf
That is not a question I asked.
Stick pushers are only fitted when the actual stall characteristics are non-compliant, not for stability issues approaching the stall. Not heard any issues about the 737 MAX stall characteristics which would mandate fitting a stick pusher.
The 737 can go vertical nose-up at the stall, due to engine thrust/lift moments. As was amply demonstrated at Bournemouth, when a stalling -300 series pitched 44 degrees nose up, as speed continued to reduce to 82 kts. Now that is an adverse stall characteristic, if ever there was one. And remember that the NG and Max have a greater engine thrust/lift nose up moments at the stall, and are much more likely to go vertical.
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Originally Posted by
Mad (Flt) Scientist
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Regarding why no "nudger" was fitted and MCAS adopted instead: A "nudger" would operate on the elevator, not the stab. If the issue is insufficient elevator authority/power to dependably recover from a stall under worst case conditions, nudging the stick will achieve nothing.
As you said in your preable to this, you set the stick-pusher to operate at a speed when the elevator still has some authority. And you might also limit engine thrust too, to reduce pitch up moments. And the reason you stick-push, rather than trim-push, is so that you are not completely out of trim when you pull out of the ensuing dive.
As you say, a stick-pusher has been used to great and reliable effect on many aircraft types that have similar stabiliser-elevator configuatations to the 737, so why try to re-invent this particular wheel? The stick-push wheel is perfectly circular, while the trim-push system has proven to be hexagonal or octagonal.
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Originally Posted by
patplan
, the BIG ONE- the stick shaker, their failure to mention it, in the log or to the MX, is likely to become one of the major focus for the investigation.
I am left wondering what the new crew knew, before they departed.
There would have been no open ADD-HIL, as the fault was signed off. Did the new crew see the previous tech-log entry, or did they get going in a hurry? Did they fully understand the previous entry, if they even saw it? Did they know this was a recurrent problem, that had happened the previous week? Did the engineer on the flight brief them, or was he just flying out so that there would be maintenance cover at the out-station (ie, was the mechanic asleep down the back...?).
This is speculation, but if the new crew had been fully briefed on
all the events of the prievious flight, perhaps they may have handled the situation better. This is the problem with signing off and clearing entries in the tech-log, instead of leaving an open ADD-HIL. Artificially cleared tech-logs keep management and lawyers happy, but are of no use to pilots.
(A clean tech-log does not mean a serviceable aircraft - never has, never will. As this aircraft amply demonstrated. So why not be honest, and keep an ADD-HIL entry open about this fault, so the next crew can read about it...?)
Silver.