Ethiopian airliner down in Africa

[Ian W]

Originally Posted by PEI_3721

Ian W, # 2076, patplan # 2071,
Take care when attempting to compare failure reports with supposed accident scenarios; local investigation or narratives might not have the same level of expertise or understanding.
Furthermore, it would be unwise to make direct comparison with recent accidents, because without knowledge of the source of failure (where did the erroneous AoA originate), everything else is assumption.

My reading of the other events cannot identify any connection with AoA or any other parameter associated with MACS.

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?

[groundbum]

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

[Zeffy]

DOT memo

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

[Livesinafield]

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

[runner1021]

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.

[Longtimer]

CNBC

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

Published 2 hours ago | Updated Moments Ago

Leslie Josephs@lesliejosephs

Christine Wang@christiiineeee

Key Points

• Transportation Secretary Elaine Chao has asked for a formal audit of the FAA’s approval of Boeing 737 Max 8 planes.
• Two of the planes have been involved in fatal crashes in less than five months.
• Chao asked the agency’s inspector general to audit the FAA’s process.

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

[acad_l]

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

[WingNut60]

Originally Posted by acad_l

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".

[ATC Watcher]

From Boeing statement

Soon we'll release a software update and related pilot training for the 737 MAX that will address concerns discovered in the aftermath of the Lion Air Flight 610 accident.

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..

[yanrair]

On previous models opposing stab movement with yoke automatically jammed the stab and stopped it moving. Consider... Much more dangerous than MACS is a fault called runaway stabiliser where the STAB runs out of control until it hits the stops and we all say the Lord’s Prayer and goodbye.Except that this is not what happens. Pilot sees /senses/feels/ hears (it’s loud) stab runaway and counteracts initially with control yoke , THUS STOPPING THE STAB , MOVING. Then , applies opposite stab trim , and finally if none of this succeeds, STAB OFF switches. And from years of watching pilots do this NNP procedure they usually get it stopped PDQ. And if it runs a long way out of trim, they trim it back manually. It’s never been a problem. Are you now saying that the trim was permitted due to a tech issue to run so far forward nose down as to result in a vertical dive - AND THERE WAS NOTHING WE COULD DO ABOUT IT? That’s what I’m getting from a lot of this feedback. Have I misunderstood. Because I’ve heard nothing from any source so far to suggest that this plane was unfliable.
Talk tomorrow. It’s late here.
Yanrair

[FCeng84]

Originally Posted by yanrair

On previous models opposing stab movement with yoke automatically jammed the stab and stopped it moving. Consider... Much more dangerous than MACS is a fault called runaway stabiliser where the STAB runs out of control until it hits the stops and we all say the Lord’s Prayer and goodbye.Except that this is not what happens. Pilot sees /senses/feels/ hears (it’s loud) stab runaway and counteracts initially with control yoke , THUS STOPPING THE STAB , MOVING. Then , applies opposite stab trim , and finally if none of this succeeds, STAB OFF switches. And from years of watching pilots do this NNP procedure they usually get it stopped PDQ. And if it runs a long way out of trim, they trim it back manually. It’s never been a problem. Are you now saying that the trim was permitted due to a tech issue to run so far forward nose down as to result in a vertical dive - AND THERE WAS NOTHING WE COULD DO ABOUT IT? That’s what I’m getting from a lot of this feedback. Have I misunderstood. Because I’ve heard nothing from any source so far to suggest that this plane was unfliable.
Talk tomorrow. It’s late here.
Yanrair

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.

[Loose rivets]

yanrair

"... Much more dangerous than MACS is a fault called runaway stabiliser where the STAB runs out of control until it hits the stops and we all say the Lord’s Prayer and goodbye . . ."

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.



.
.

[capngrog]

Originally Posted by FCeng84

The 737 stabilizer trim wheel (actually two, one on each side of the aislestand with mechanical connection between) is a basic part of all 737 flight decks. As it is mechanically linked to the stabilizer jack screw nut, it moves to reflect any motion of the jack screw nut. Any extension or retraction of the jack screw requires that the jack screw nut rotate thus will be observable on the flight deck in the form or trim wheel rotation. The flight deck also has a readout showing the position of the horizontal stabilizer.

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".

[krismiler]

The whole process of certifying the Max will be gone through with a fine tooth comb by government experts. Senior people are going to be appearing before committees and grilled under oath, a whole can of worms is going to be opened up. Lawyers, investigative journalists and top experts in various fields are going to be running at full speed.

The American system is unmatched when it comes to digging up the real story and laying it out in public.

[OldnGrounded]

Originally Posted by krismiler

The whole process of certifying the Max will be gone through with a fine tooth comb by government experts. Senior people are going to be appearing before committees and grilled under oath, a whole can of worms is going to be opened up. Lawyers, investigative journalists and top experts in various fields are going to be running at full speed.

The American system is unmatched when it comes to digging up the real story and laying it out in public.

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.

[GroundGeek]

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

As the Lion Air crew fought to control their diving Boeing Co. 737 Max 8, they got help from an unexpected source: an off-duty pilot who happened to be riding in the cockpit.
That extra pilot, who was seated in the cockpit jumpseat, correctly diagnosed the problem and told the crew how to disable a malfunctioning flight-control system and save the plane, according to two people familiar with Indonesia’s investigation. The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.

[FCeng84]

Originally Posted by capngrog

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".

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.

[Airbubba]

A Bloomberg article credits a jumpseat rider with saving the plane on the Lion air flight prior to the JT610 accident.

Pilot Who Hitched a Ride Saved Lion Air 737 Day Before Deadly Crash

By Alan Levin and Harry Suhartono
March 19, 2019, 7:33 PM EDT

As the Lion Air crew fought to control their diving Boeing Co. 737 Max 8, they got help from an unexpected source: an off-duty pilot who happened to be riding in the cockpit.

That extra pilot, who was seated in the cockpit jumpseat, correctly diagnosed the problem and told the crew how to disable a malfunctioning flight-control system and save the plane, according to two people familiar with Indonesia’s investigation.

The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.

Rescuers recover the wheels of flight JT610 on Nov. 4.
Photographer: Fauzy Chaniago/EPA-EFE

The previously undisclosed detail on the earlier Lion Air flight represents a new clue in the mystery of how some 737 Max pilots faced with the malfunction have been able to avert disaster while the others lost control of their planes and crashed. The presence of a third pilot in the cockpit wasn’t contained in Indonesia’s National Transportation Safety Committee’s Nov. 28 report on the crash and hasn’t previously been reported.

The so-called dead-head pilot on the earlier flight from Bali to Jakarta told the crew to cut power to the motor driving the nose down, according to the people familiar, part of a checklist that all pilots are required to memorize.

“All the data and information that we have on the flight and the aircraft have been submitted to the Indonesian NTSC. We can’t provide additional comment at this stage due the ongoing investigation on the accident,” Lion Air spokesman Danang Prihantoro said by phone.

The Indonesia safety committee report said the plane had had multiple failures on previous flights and hadn’t been properly repaired.

Representatives for Boeing and the Indonesian safety committee declined to comment on the earlier flight.

The safety system, designed to keep planes from climbing too steeply and stalling, has come under scrutiny by investigators of the crash as well as a subsequent one less than five months later in Ethiopia. A malfunctioning sensor is believed to have tricked the Lion Air plane’s computers into thinking it needed to automatically bring the nose down to avoid a stall.

Boeing’s 737 Max was grounded March 13 by U.S. regulators after similarities to the Oct. 29 Lion Air crash emerged in the investigation of the March 10 crash of Ethiopian Airlines Flight 302. In the wake of the two accidents, questions have emerged about how Boeing’s design of the new 737 model were approved. The Transportation Department’s inspector general is conducting a review of how the plane was certified to fly and a grand jury under the U.S. Justice Department is also seeking records in a possible criminal probe of the plane’s certification.

The FAA last week said it planned to mandate changes in the system to make it less likely to activate when there is no emergency. The agency and Boeing said they are also going to require additional training and references to it in flight manuals.

“We will fully cooperate in the review in the Department of Transportation’s audit,” Boeing spokesman Charles Bickers said in an email. The company has declined to comment on the criminal probe.

Earlier: Boeing-FAA Scrutiny Is Stepped Up as U.S. Reviews Max’s Approval

After the Lion Air crash, two U.S. pilots’ unions said the potential risks of the system, known as the Maneuvering Characteristics Augmentation System, or MCAS, hadn’t been sufficiently spelled out in their manuals or training. None of the documentation for the Max aircraft included an explanation, the union leaders said.

“We don’t like that we weren’t notified,’’ Jon Weaks, president of the Southwest Airlines Pilots Association, said in November. “It makes us question, ‘Is that everything, guys?’ I would hope there are no more surprises out there.’’

The Allied Pilots Association union at American Airlines Group Inc. also said details about the system weren’t included in the documentation about the plane.

Following the Lion Air crash, the FAA required Boeing to notify airlines about the system and Boeing sent a bulletin to all customers flying the Max reminding them how to disable it in an emergency.

Authorities have released few details about Ethiopian Airlines Flight 302 other than it flew a “very similar” track as the Lion Air planes and then dove sharply into the ground. There have been no reports of maintenance issues with the Ethiopian Airlines plane before its crash.

If the same issue is also found to have helped bring down Ethiopian Airlines Flight 302, one of the most vexing questions crash investigators and aviation safety consultants are asking is why the pilots on that flight didn’t perform the checklist that disables the system.

“After this horrific Lion Air accident, you’d think that everyone flying this airplane would know that’s how you turn this off,” said Steve Wallace, the former director of the U.S. Federal Aviation Administration’s accident investigation branch.

The combination of factors required to bring down a plane in these circumstances suggests other issues may also have occurred in the Ethiopia crash, said Jeffrey Guzzetti, who also directed accident investigations at FAA and is now a consultant.

“It’s simply implausible that this MCAS deficiency by itself can down a modern jetliner with a trained crew,” Guzzetti said.

MCAS is driven by a single sensor near the nose that measures the so-called angle of attack, or whether air is flowing parallel to the length of the fuselage or at an angle. On the Lion Air flights, the angle-of-attack sensor had failed and was sending erroneous readings indicating the plane’s nose was pointed dangerously upward.

[GarageYears]

Soon we'll release a software update and related pilot training for the 737 MAX that will address concerns discovered in the aftermath of the Lion Air Flight 610 accident.

What if Boeing have seen the FDR and this accident isn’t related to Lion Air? All this talk of MCAS, but no hard evidence. Assumptions. The crew did NOT report unreliable airspeed which I believe was one of the first Lion Air calls to ATC.

-GY

[runner1021]

I would assume an operational MCAS system is required for flight and not deferrable. Is there a means to test it during preflight?