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Ethiopian Airlines flight’s stall-prevention software was active at crash, CEO says

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The chief executive of Ethiopian Airlines told the Wall Street Journal in an interview published today that he had reason to believe that software intended to prevent Boeing 737 MAX aircraft from stalling in flight had been activated aboard Ethiopian Airlines Flight 302 shortly before its crash. CEO Tewolde Gebremariam said that “to the best of our knowledge,” the Maneuvering Characteristics Augmentation System (MCAS) for stall prevention was active at the time of the crash. ( Mais...

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Tom Zaidman 5
In the aircraft manual of the 737 Max stated by a Canadian aviation lawyer there is no mention on how to turn off the MCAS since it never mentions that it exists and how it works. Boeing hid this from the pilots at least in Canada. At night a plane suddenly starts to dive is quite a complicated situation if you are not expecting it. I am sure all piloits agree.
Gary Bain 1
I do not agree.
rapidwolve 3
You don't agree that unexpected major trim, with nose down attitude, can be overwhelming if you don't anticipate or expect it?
Abe Snossis 3
It’s easy to say you don’t agree when you have never been in that exact situation. He is an idiot that probably thinks he can handle anything!!
Tom Ellis 2
How did the crews know they were fighting trim? Did each know the MCAS was on the plane and moving the horizontal stabilizer? Did the MCAS movement mimick runaway trim?
clarify 3
There are two wheels mounted on the center console, one each for the left and right seat pilots, that turn when the trim is changing. They are a dark color with white markings, so one can visually see it turning. They turn when either pilot uses the thumb switch to adjust trim and when an automated system adjusts trim. Furthermore, when electric trim is shut off with two switches, each wheel has a handle that can be popped out, and those wheels can be turned manually to adjust trim.

See this video that includes time in a 737 simulator to see them in action (specifically watch starting around 4:20):
chalet 0
My understanding is that there are two switches to cut off MCAS both located together at the central control panel (near the throttles) so that captain and FO can access them very easily.
Ben Thurston 3
It didn't so much as mimic runaway trim, it WAS runaway trim in every respect; and there's a known procedure for dealing with runaway trim.
lecompte2 2
On previous models if the pilot moved the control column in the opposite direction of the trim movement there was a break to immediately stop the trim from moving. Why has this brake been removed on the MAX ?
jmt123 2
To those that know more than me...It SEEMS as though MCAS used stab trim to push the nose down and pilot responded with elevator to bring the nose up. This stab trim down with elevator countering repeated many times. Pretty soon the plane was so out of trim there wasn't enough control surface travel left to fly level.

Does that make sense?
lecompte2 2
exactly, worst of all the control surface moved by MCAS is twice the size of the one operated by the pilot, guess who wins.
jthyland 3
According to sources,(from Rueters, 3 un-named that listened to the CVR) the stick shaker and stall warning were blaring on the Lion CVR. Most difficult to fly especially at night.
Manufacturers are deferring more and more flying duties to the flight computer. STOP. Pilots, know your systems (AOA) and how to fly the airplane.
David Beattie 3
DAMMIT JIM! If there were just a way to turn it off! Oh, there IS a way. It’s called the “Trim Cut Out Switch”!
brent young 2
when an airline puts a 200 hour FO in the plane, that’s a big indicator of problems besides an MCAS system.
Enrique Silva 2
There’s a huge difference between being active and causing the crash. It’s very convenient for airline CEO’s to blame Boeing and hide a potential mess. LionAir aloowed a plane with a known problem to fly and pilots did not apply the proper memory items, why isn’t anyone talking about this?
Bill Babis 1
Not really news. I'm sure it had a false signal and was just waiting for gear retraction, flap retraction, or whatever to let it start doing its thing and moving the stab. The question the airline needs to answer is why the crew did not take the simple steps to disable it. When you're fighting the trim for whatever reason, you disable the trim. It was two switches either pilot could have moved.
Christos Psarras 6
Plus, based on this, "In flight simulations designed to recreate the problems from a doomed Boeing 737 Max airliner, pilots found that they had less than 40 seconds to override a controversial automated system and prevent a crash, according to The New York Times", that's an awfully short time to figure out what the heck is going on... it is possible they just run out of time before they could realize what was happening.
Bill Babis 2
That report is very suspect. Lion Air flew for 12+ minutes and Ethiopian Air for 6+ minutes. The FDR in the Lion Air accident has been read and shows the crew fought the problem for much longer than 40 seconds and could have established control at any time with manual trim.
clarify 1
According to the NYTimes article, it was 40 seconds *unless* the crew engaged the thumb switch on the yoke to stop MCAS and adjust the trim bring the nose up. Engaging the thumb switch would reset MCAS, and then it could start another round.

rapidwolve 3
I agree to a point Bill, but who is to say they didn't? I know it's easy for us to point fingers, but best if we wait for full report.
I do, however, wonder why it is, that if the system was getting false readings, it did not deactivate itself. Or did it? Or why the system is even active at such low altitude. Questions hopefully answered in due time and investigation.
jbermo 2
"why the crew did not take the simple steps to disable it" .... There has to be more to this than fixed by a few simple steps (engaging stab cutout switches), else why overreact by parking entire fleets of $$ airplanes?
Bill Babis 0
You read too much into my post. The cutout switches stop the problem and save the flight. It does not fix the underlying issue. That is what the grounding is about.
rapidwolve 2
The thing is, and we have not heard official full reports on either crash so just speculation...what if they did hit the switches? And I would love to see the report on where flaps were sitting, in either crash.
Bill Babis 1
The flaps were up otherwise MCAS would have been inhibited. With an erroneous signal from the AoA it was flap retraction that probably started both accident sequences when MCAS started trimming nose down. Wreckage from both accidents also showed the stabs significantly nose down at impact. The DFDR from the Lion Air flight showed the crew fighting the nose down with elevator pull and intermittent CW trim which only served to reset the MCAS and allowed more nose down trim. Using the cutout switches would have stopped any movement of the stab through MCAS or the CW switches. Manual trim with the trim wheels would have to be used to relieve yoke pressure. They didn’t do it and ultimately were overcome. As we learn more about The Ethiopia Air crash I believe we’ll see similar findings.

My main question is why both these crews seemed to not include manual trim use in their troubleshooting.
Abe Snossis 1
I don’t think the trim wheels could be moved with the AP engaged. I could be wrong
jbermo 0
"My main question is why both these crews seemed to not include manual trim use in their troubleshooting." - Systems knowledge, a human factor . . .No doubt they would have found their way - eventually.
John Wilson 1
Blame the automation, blame the crew, just like in politics people pick a side and go all in, reality be damned. These accidents are entirely typical real-world aviation accidents....the cause was a confluence of factors. The automation folks should have thought a little deeper into the “what if” tree and the crew should have been able to recognize runaway trim (howcome those big wheels next to my leg are spinning like that?).

What makes this one so riveting are the ancillary factors, particularly the Lion Air. How could the crew have been seemingly unaware of the problem after all the publicity over the first one and the fact the aircraft they were flying was known to have not only experienced the problem on its last flight bur it’s crew on that run was saved from the same fate only because a deadheading jump seater said something like “Ah, why don’t you turn off the trim so it will stop doing that?”
Rex Bentley 1
People been trying to build idiot proof airplanes since the Wright brothers. You learn about stalls from day one of flight training. Flying Rube Goldberg machines aren't the answer. Practice practice practice is. Just like how you get to Carnegie Hall.
lecompte2 0
Boeing must explain why the 737 Max cannot be certified without the MCAS system or I will never board it. This system is either required or not, if it is required to prevent a stall and you weaken it now does it mean that aircraft will be allowed to stall, this is getting confusing.
David Beattie 3
You will have to get off of most commercial airplanes. They are all certified with systems that enhance flight characteristics and which attempt to prevent pilots from losing control of the aircraft. Every jet in existence has had systems such as these. The 707 had a Yaw damper to prevent pilots from losing control due to “Dutch Roll”. The DC-9/MD80 and most T-tailed airplanes had hydraulic boost to prevent deep stalls and all have stick shakers and/or pushers to prevent stalls and stick PULLERS to prevent “Mach Tuck”. But there is no system to protect against really stupid pilots determined to stall an airplane. There’s fool proof but nothing’s PILOT proof. Asiana and Colgan Air proved that.
lecompte2 2
I have flown most of the airplanes you mention and many more, there is a difference between a yaw damper, stick shaker or pusher and a 737 Max that has a computer operated control system that has more authority than the pilot. MCAS actuates a larger control surface (horizontal stabilizer) than the pilot uses (elevator), to control the nose up or down. As we have seen twice now for whatever reason the MCAS system decides to push the nose down there is nothing the pilot can do except disengage it. The stabilizer brake from previous models has been removed for some unknown reason and makes it more difficult for the pilot to intervene. As said previously if such a system is required for an airplane to be in the air it shows a poor design that makes it vulnerable to stall, and failure of the very system that is there to help can be catastrophic. The design and need for this MCAS should be re-certified from scratch.
This is a major problem with todays aircraft as they have to much automation. They have multiple computers and multiple software options and pilots have to be taught to shut them off and fly these planes manually. I remember all the problems with the A320's back when they were falling out of the sky quite frequently.
Christos Psarras 2
"A320's back when they were falling out of the sky quite frequently" ???

What are you talking about? Falling out of the sky quite frequently?? Where did you find this info?? Besides the well-known Air France crash in the late 80s that was due to automation error, what other A320 (plus 318-319-321) crashes flights do you know that were due to bad automation?

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