Dunno about you but MY runaway stabiliser checklist says, and I quote, "Uncommanded stabilizer trim movement occurs continuously".

​​​​​​Yes, since Lion Air, we know carrying out this checklist would have solved the problem .

Apparent test flight now . . .

https://flightaware.com/live/flight/BOE302

https://cimg6.ibsrv.net/gimg/pprune....89f72619c2.png

Salute!

Previous rant continued:

At least one of the Chuck Yeager wannabes here pointed out lack of previous flight writeups that likely had MCAS activation prior to the 610 crash. WRONG!!! We went thru the acatual writeups and maintenance actions right here on pPrune.
- IAS disagree - alt disagree - feel difference
The FDR traces clearly showed the same things that 610 experienced at the onset, as well as the "corrective action". It showed what they did. You know, the Luke Skywalker/Yeager procedure -turn off stuff and go "manual". It worked, but they forgot to writeup the constant stick shaker. Hmmmmmmmmmm. Would that have helped the 610 crew?
The traces show that crew had instant shaker, likely GPWS warning when they did their dive just as flaps retracted, and so forth - exactly what the 610 crew experienced.

The FAA Airworthiness Directive mentioned all of the above possible indications plus stick shaker indicating that something was awry, and recommended the "runaway trim" procedure ( basically, "O.K. R2, let's go manual!")

The recognition of inadvertant AoA-related MCAS activation upon takeoff must be pre-thought and actions rehearsed, as many things are happening. WoW and shaker starts. Flaps up and nose goes down, maybe get GPWS alert, several caution indicator lights come on and trim goes nose down again a few seconds after trimming up. and so forth. To make things worse, 610 crew put flaps down and the MCAS behaved itself. uh huh. Step 2 or 3 or "x" in the stick shaker/stall warning proedure, right? Flaps back up and MCAS starts again. Are you confused now?
So I cut the 610 crew some slack, especially since the intermittent trim was not what one would expect from the tradional runawy trim emergency.

Dunno why 302 crew didn't recognize the problem, but it may have been caused by something else and may be yet another undocumented "feature" of the MAX.

Gums sends...

That is just the point.
I would have expected a large number of 737 pilots to start quoting what happened when they get an AoA mismatch and unreliable airspeed. There is no large number - despite everyone piling on (with some justification) that reliance on a single AoA was not good engineering. It would appear that AoA subsystem failures in the earlier variants of the 737 are rare enough to be considered highly improbable and that would be added to the 'in any case a repeatedly running MCAS can be handled as with any other trim runaway'.
So the question remains what is different about the Max AOA subsystem that makes it less reliable that the earlier 737s?

if Norwegian have a lot of grounded MAX8s, and are already short of cash, is this extended grounding their death knell? I doubt Boeing are paying any compensation on a day by day basis, it could be years after a lot of litigation which is not much use for cashflow...

G

DOT memo
 

It's official -- DOT will audit FAA certification of 737Max.

It's an error they type is grounded... that kind of thing doesn't "slip through"

The thing I'm having a hard time understanding is why the MCAS finally wins. Did the pilots simply give up? If you feel the aircraft becoming nose heavy, what do you do? You apply counteracting nose up trim. MCAS trims the nose down, and you, in turn, trim nose up. Over and over and over. It should be a draw. (Of course this doesn't take into account the myriad of conflicting and confusing warnings that you are also trying to deal with). It would appear that the issue that eventually lead to both crew's demise was excessive airspeed. Although airspeed is life, in these instances it may have been just the opposite. The higher the airspeed, the more authority the stabilizer has over the elevator until you reach the point where control is impossible. But, if you continue to trim, shouldn't you be able to maintain some semblance of controlled flight? However, when you add in extremely high airspeed, pitch sensitivity becomes a huge issue.

CNBC

Transportation Department seeks audit of FAA’s certification of Boeing 737 Max 8

https://www.cnbc.com/2019/03/19/transportation-secretary-asks-departments-inspector-general-to-audit-faas-certification-of-boeing-737-max.html

memorandum-secretary-audit-certification-boeing-737-max8-2012-2017.pdf

But did they notice that there is a new (and decent) nominee as head of the FAA?

Did they notice that international certification bodies may not be as compliant accepting US airworthiness certification as they have been in the past?
Have they considered that they may have a backlash from the flying public to contend with?

How can they make such a prediction anyway unless the ET incident has been properly investigated and a cause found that excludes MCAS?
And if it excludes MCAS, then what about the alternate cause of that incident?

And now loop back to the "flying public".

From Boeing statement So Lion air only. But the ET aftermath is not yet be known, so until it is made known to certification authorities and then unless it shows the exact same issue as Lion air , I do not think independent authorities like EASA or Canada are going to lift the ban..

Pilot trim via yoke mounted thumb switches stops MCAS stab command and runs stab in direction of pilot trim input. On the other hand, non-MCAS runaway stab may or may not continue to run if opposed by thumb switch trim or column cutout (i.e., large column in opposite direction). Nature of runaway depends on where in the system the error that is the cause is located. In the worst case, non-MCAS runaway can only be stopped by stab cutout switch activation. It is for that reason that timely identification and shutdown via stab cutout switches of a runaway that cannot be arrested by other means is critical.

Timeliness of stab cutout shutdown of misbehaving MCAS is not as critical as long as the crew continues to oppose it via pilot trim inputs to keep close to pitch trim while diagnosis of need for stab cutout switch activation is made. Lion Air pilot on accident flight was able to manage pitch control for many minutes in presence of MCAS responding to errant AOA with repeated airplane nose down trim commands that had to be walked back to trim via thumb switch commands. It was only after control was transferred to the right seat and the F/O failed to provide sufficient airplane nose up trim to fully counter each MCAS increment of airplane nose down trim that the stabilizer move progressively more airplane nose down to the point where full aft column was not sufficient to keep the nose up. As has been noted in earlier posts, increasing airspeed once in the dive made the situation worse as elevator authority was reduced due to actuation blowback.

yanrair
Perhaps not so dangerous, since it is a well practised memory item and should be contained in a moment. What is proving to be the real danger is the timing of the symptoms. With the added problems of other chaotic items, the MCAS's progress is insidious - "proceeding in a gradual, subtle way, but with very harmful effects".

Just the word for this situation.



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I may be "picking nits" here, but my (limited) understanding of the 737 NG trim system is that the manual trim wheels are mechanically connected to the jack screw gearbox which rotates the jackscrew, resulting in linear (vertical in this case) movement of the jack screw nut. I guess it could be said that the trim wheels are linked to the jack screw nut, but that link is via the jackscrew itself (that's sorta nit-picking on my part right there). Anyway, my understanding (again limited) of the process is that the jack screw nut is attached to the structure of the horizontal stabilizer resulting in up/down movement of the stabilizer leading edge. Am I correct in my understanding that an electric motor(s) can drive the jackscrew gearbox via yoke-mounted trim switches?

I tried to attach, for comment, a diagram of the 737 NG trim system I had found on line, but was unable to do so, and when I attempted to post a link to the diagram I was informed that I don't yet have the required 10 posts to allow me to post links. Anyway, the name of the site with the diagram is "Satcom Guru".

All absolutely true, at least when the American system is shaken into high-alert status. It is definitely in that status, now, WRT the MAX and its certification and apparent defects. Given that, it seems rather a stretch to expect that Boeing's pending MCAS software patch will result in the airplanes returning to service in the immediate future.

Among any number of other issues, it seems likely that the insurance carriers that issue the policies required under 14 CFR 205 are paying close attention and communicating forcefully with the airlines.

Bloomberg reports that dead-heading pilot on penultimate Lion Air flight diagnosed the problem:

BREAKING: An off-duty pilot who happened to be riding in the cockpit saved a diving Boeing 737 Max 8. The next day, the same Lion Air jet crashed into the Java Sea, killing all 189 aboard

capngrog - you are not picking nits, you caught a mistake that I made. Thanks for pointing that out. I have corrected that entry. The jack screw is turned by the motor or cables and the nut attached to the stabilizer is raised or lowered. Sorry for the confusion and again thanks for catching it and point out my error.