Mr Cheese
First, there is that AND word, which an earlier poster suggested, ' . . . AND, and etc., etc.'

Again, wording is so critical. But your main point: while the extent of the trim via the mini-corrections IS variable, (i.e. Mach), for the most part the repeated blips are very similar on the graphs available to us. Although the Mach modification is very small, it does get me wondering what it was doing during the fatal dive.

Rounded estimate of the status of the identification process based on public information - and excluding empty seats:
About 50% of those in front rows have been identified.
About 25% of those in the back rows have been identified.
The cabin apparently had seatrows numbered 1-34 but probably excluded rows 13 and 14 (in spite of 1 passenger mentioned to be in 13).
Standout is seat column F which has the largest percentage missing.

From the data it is not possible to estimate where the 3+3 cabin crew were seated. A guess is that at least 1 in a front folding seat, and 2 at the back galley, with the 3 trainees in row 1 seats DEF.

It suggests a nose down impact and right hand roll (more than 90 degrees would not surprise me).

.
FCeng84, could this statement be also interpreted as fixing a non-linearity in control response at high AOA? Is that the type of improvement in handling characteristics being created?

The ratchet effect exists - and is very apparent from the post of the FDR permalink here to post

https://cimg1.ibsrv.net/gimg/pprune....6b67acda9b.jpg



Regardless of wordings in spec, the pitch trim position can be seen to 'ratchet' down in 3 full steps without correction back by the PF who just blips the trim. From the scale on the left of the image the stab trim reached max nose down.

Something I'd not noticed before on that FDR data - not sure it's been remarked on. At the VERY end of the trace, the stab is seen to apparently move a long way back towards to trim state. Given the compressed scale, it's not possible to see if that is a "final instant" artifact and not "real" or if there's an actual slope to the stab trace. If it's "real" it indicates that the stab remained under the potential for crew control throughout the flight to the very end, and that the ratcheting prior to that was not "uncorrectable".

The graph in the report shows a number of the parameters end in vertical lines like that.

To address your question I think it is important to be very clear with regard to your phrase "non-linearity in control response". The FAR in question speaks to the progression of column pull force required to command increased AOA. Well behaved stability characteristics would involve the need for the pilot to apply ever increasing column pull to command ever increasing AOA. Not having that desired characteristic could be a result of either the pitching moment vs. AOA (Cm-alpha) characteristic of the overall airplane or the pitching moment vs. column (Cm-column or similarly Cm-elevator) generated via deflection of the column. The net effect that the FARs speak to is how these two sources of pitching moment (AOA vs column) balance one against the other.

The issue that MCAS addresses is non-linearity of Cm-alpha stability derivative. The pitching moment generated by the elevator (and thus the column) is much more linear. As I have mentioned in previous posts, it is not a matter of the pilot having insufficient ability to generate pitching moment via the column. The issue is that as AOA increases into a range higher than normal operation (near and beyond the AOA for stick shaker activation), the amount of nose down pitching moment generated by additional increase in AOA is not sufficient to require the FAR mandated increase in column pull to balance.

CT with all due respect... I don't see anyone disputing that Boeing's MCAS system ran the nose down and crashed the jet killing 189 people, but it is noteworthy that two switches may have prevented this tragedy.

What remains to be seen is how ambiguity in the QRH, distraction, lack of training, a flying spanner, CRM, or perhaps even crew competency factor in as possible contributing causes.

"We study and discuss accidents so we don't become the subject of a thread on PPRuNe."

Or, come to that (with 20/20 hindsight), simply grabbing and holding the trim wheel.

N.B. No criticism of the crew intended.

I am with gums on this one, in terms of "if something moves the flight control surfaces, the pilots need to be aware that it exists and how it helps them, and thus some training/education is required." Also needed for safe operations is "what turns it on or off" if it moves the flight control surfaces.
That quoted "executive" needs a talking to from the pilot's union.
Anything that is built can break, anything with computer code or electricity involved can malfunction.

Question on the MEL: is one AoA sensor INOP a downing discrepancy? I'd assume so, but I've been surprised before.

Regardless of the fault or cause, one does wonder after all those trim corrections, or whatever fault that caused the trim to run counter to where they wanted it , at what stage would the crew have used those switches.

B-737-8/9 MMEL on FAA website (rev 1, Jan 2018) only mentions AOA heater as related MMEL option; AOA sensor itself does not appear on MMEL. (Based on a few search terms)

from this SLF- when ONE faulty sensor input allows " hal " to override manual control AFTER correction by the pilots without warning or deliberate reset, without notice, or mention, the " chain of command" which allowed/approved/designed such a process to be incorporated needs to be held responsible.

Well yes, but the majority of the thread is leaning towards the stabilizer not being disabled. Something is nagging away in the back of my mind. Stabilizer runaway memory actions are so fundamental that the thread's detective logic changed quickly to looking at the ~5 second delay adding to the confusion of an already chaotic flight-deck - causing a radical diversion from old established SOPs.

The relatively calm ATC and the prolonged period of approximate hight holding, coupled with the huge handful of power in the last moments, is leaving me with a mind that's wide open.

There seems to be a significant amount of hindsight bias regarding the specific term "runaway". A lot of the discussion is now anchored to what has been revealed about MCAS and the behavior of this aircraft. If you survey every single poster in this thread before this incident and asked them to describe what "runaway stabilizer" looks like, I imagine the answers would be quite different than what you would get in a poll with hindsight of this incident. For an example of a 2016 reference guide description of runaway stabilizer, google: The Ultimate B737 NG Technical Handbook STABILISER TRIM SYSTEM AND RUNAWAY STABILISER

It's not even clear that the previous crew diagnosed a "runaway" and followed the NNC. They may have gone directly to the cutout switches as a way to isolate an unknown electrical trim problem- they later reported that they believed it was STS operating in reverse due to IAS issues. This may even have been a conclusion/guess they reached later in the flight rather than a contemporaneous diagnosis.

EDIT: climber314 pointed out that the preliminary report says they followed the Runaway Stabilizer NNC. Hopefully we get more specifics on this later.

The JT43 crew ran the R/S NNC and cut out Stab Trim. I posted this shortly after the report was released.
https://cimg5.ibsrv.net/gimg/pprune....20e61039fb.png

I think it's a fair distinction to raise but feel this presentation is disengenous.

As far as we can tell, MCAS is intended to provide a more consistent and predictable handling response in incipient stall conditions.

How does an intermittent and unadvertised control input, of complex algorithmic intensity, every 5 seconds, provide that?

Sure enough. Is that statement based on interview with the crew?

My assumption is they were debriefed. The whole flight is described in detail in a little over one page - 18.1 PK-LQP Previous Flight.