Originally Posted by
Lyman
Infrequentflyer789
NO. The a/c did not respond immediately to PF's back stick, read the report. The a/c did not start upward until the PITCH UP reached ten degrees, read the report.
I have, I guess I just don't see what you see in the traces.
I have been looking at the graphs with expanded timescale - which show the time we are interested in. P29-31 of the report has useful graphs but without gridlines so it is difficult to be precise, P42 is the best for that - it doesn't have pilot input, but we know from P29 that this begins at 02:10:07.
From graph on P42 I reckon at 02:10:07 we have pitch = 2, THS -2.8, VS maybe -300. Then at 02:10:10, pitch = 4, THS -3 (started to move), and VS maybe +300 (ie. started to climb). Pitch 10 degrees is not till a bit after 02:10:16 by which time VS is already +5000.
Hence my comment that the THS seemed unavailable from a/p drop, until just prior to the STALL.
It looks to me to be moving to follow elevator trend, with a delay, a rate limit and a stop, not much more complex than that. At some point I might try and digitize the traces and try and extract the rule, but it looks right. It also matches the sim results (see P41).
It also counters the myth that he pulled the a/c up immediately, HE DID NOT. The report shows a pilot with measured pull, and interrupted, waiting for response.
Page 29 - A/P drops 02:10:05, "I have controls" at 02:10:06, stick goes back 02:10:07, 2secs delay. I don't see the stick going back to pitch neutral awaiting response either.
Further, the response tracks simulation, so the a/c was responding as PF
should have expected. If we ascribe his actions to
unexpected a/c response, then we are back to the question of why doesn't PF know what to expect from his a/c, are we not ? [and is it PFs fault if he's never actually flown (been allowed to fly) his a/c in cruise ? - no]
Their is NO determination of Iced Pitots. It is a guess, for all we know it may have been wind shear that bolluxed up ADRS. And that is a reason for TOGA and high Pitch, in its own right.
If there's a windshear procedure that calls for 15deg pitch and TOGA
in cruise (at max alt) then I would respectfully suggest that it is a recipe for another disaster. No ?
On the pitots, I think I almost agree. There is some evidence (audio ascribed to icing), and there is the experience of all the other flights - but not totally conclusive.
The worrying thing to me is that I can't see anything that connects the PF actions (cause of stall) with pitot failure specifically, or even uAS specifically. If he climbs to arrest a (real or perceived) altitude loss, or inadverdently while focused on roll, then pitot failure is not a required cause, and fixing the pitots will
not prevent a recurrence. UAS may make the
recovery less likely - but speeds were actually valid again by the time they stalled, and stalling a big jet is big trouble regardless.
If the triggers for the PF climbing his a/c into a stall were
only: A/P drop out, Alt Law, and turbulence (maybe), then we have a big problem, because Alt Law / A/P drop could have lots of causes, and is an
expected condition at 1 in 10k flight hours (I think). That is more than a little worrying.