It's true there were aggravating factors, like the inability to manually rectify trim, which (would seem to me) would be a aerodynamic or design issue.

The point still stands, the root cause was MCAS, without it this would never have happened. MCAS would not have pitched them into a dive, and even if they were pitched into a dive by some non MCAS system, they would have been able to turn on electric trim and recover. MCAS both caused the situation, and made fixing it impossible, so it was the root cause of the crash.

> The point still stands, the root cause was MCAS

Agreed. One could argue that the AoA reading mismatch was the root cause, but the plane alerted the pilots to the discrepancy just as it was meant to (through stick shake and panel readouts).

They were aware of the issue, took measures to mitigate them, and MCAS still drove the plane into the ground.

> It's true there were aggravating factors, like the inability to manually rectify trim, which (would seem to me) would be a aerodynamic or design issue.

I don't see in the report that the pilots attempted to both operate the manual trim wheel at the same time. I'm not sure if its explicit in the training, but in the manual its made clear that pilots may need to work together to move the trim out of extreme positions when the electric system is not available, and that doing so will not break the manual trim system.

I don't think they were concerned about snapping the cable, but based on a simulation run last week by a Swedish pilot (who needed both arms locked around the column to keep it held back, towards the end), and the reports' notes of the pilot repeatedly instructing the co-pilot to help him trim up, the forces on the column were such that the pilot couldn't assist in cranking AND continue to pull back on the column at the same time.

Releasing the stick to assist with the wheel would have meant allowing the plane to nose-dive. This might have allowed them to crank in the stabilizer in time to recover, but they only had 7,000 feet above the ground to work with.

Likewise had Boeing designed a control surfaces system such that the pilot always has more control authority than the trim this also would not have happened.

I didn't say that MCAS wasn't the lions share root cause here. It's just not as simple as the "hurr durr, MCAS bad" that a lot of people keep trying to portray the more nuanced statements of various regulatory agencies as being equivalent to. MCAS might be bad but on an aircraft with a different trim system it wouldn't be "hurr durr" levels of bad.

Are there any airliners from any manufacturer where the pilot always has enough authority to override full trim?

Airbus just gives you a joystick with no force feedback at all. So yes ... but an entirely different philosophy. You tell the aircraft what you want it to do and it figures out how to do it. I suppose these recent events could be used as an argument against the idea of doing essentially fly by wire but then putting in a whole lot of extra stuff to make it seem that you are not doing fly by wire.

No, on Airbus the joystick still only moves the elevator, which has less control authority than the stabilizer, which is what trim controls.

It normally moves both as required. A good explanation here:

* https://aviation.stackexchange.com/questions/15268/how-does-...

Even if things degrade all the way down to "direct law" the pilot does not feel any aerodynamic force caused by the trim position.

We are talking about two different interpretations of the word "authority". In the case of the incidents, the pilots were physically unable to overcome the simulated force for an extended time.

Thanks for the correction! Reading about this brought me to:

https://en.m.wikipedia.org/wiki/XL_Airways_Germany_Flight_88...

with some similarities to the Ethiopian crash

I doubt this is possible. If it was it would be a certification requirement because it would make any trim runaway incident trivial.

MCAS issues nose-down, speed increases and nose pitches down. Nose never pitches back up. Plane crashes.

Sure, maybe some complex combination of maneuvers could have helped them out of this but there's really everything pointing the blame at this one system. Pilots did what the boeing manual suggested (even included at the end of this report).

MCAS forced the trim to a point where (because of aerodynamics) it was impossible to manually change the trim even after disabling MCAS, and was designed in such a way that it was impossible to engage the electrical trim controls (which could have saved the plane in this case) without also reenabling MCAS.

Flaps out supposedly would have kept MCAS off but the pilots weren't expected to know that.

Maybe, when they started thinking about a plan B, they were anyway already much too fast to use flaps?

I guess that there is a max speed for flaps (maybe the computer even actively refuses to extend them if the airspeed is higher than X to avoid that wings are destroyed).

Post Lion Air, they should have known that.

Why exactly? if Boeing did not updated the manuals and checklists how would pilots know that? from internet forums? Should a pilots ignore the checklists and try steps he read on the internet ?

I could not find if Boeing updated their manuals/checklists after the first crash.

Yes, Boeing issued this service bulletin after Lion Air:

http://www.avioesemusicas.com/wp-content/uploads/2018/10/TBC...

And the FAA made it an emergency airworthiness directive in response.

The steps on it were broadly followed by the Ethiopian flight.

Am I missing it because I don't see flaps mentioned anywhere in that link.

You're not missing it. The pilots followed the instructions, and the instructions do not mention flaps.

This bulletin notes that electric stabilizer can be used to neutralize the control column prior to STAB CUTOUT, which it appears the Ethiopian crew did not do.

They did so repeatedly.

The bulletin completely fails to note that if you don't time the STAB CUTOUT immediately after you use manual electronic control but instead the MCAS acts again before you cutout, you're left trying to manually trim the stabilizers in a situation where the elevators are putting so much force on the jackscrew that manual stabilizer trim may be impossible.

That's what got this flight.

Appears? Where are you reading this to come to that conclusion?

Page 11 of the preliminary report, 05:40:35 "stab trim cut-out".

Page 26, five manual trim up inputs before that time. Manual trim is electric trim instigated with yoke toggle switch.

What is not certain (to me) is if continuous nose up toggle for sure would have inhibited the automatic nose down from MCAS shown at 05:40:45. It really looks like pitch trim still needed to come up more in order to relieve the control column force to bring it back to neutral.

Why didn't they continue to manually trim (electric) after 05:40:35 to relieve yoke back pressure and also to improve climb rate and also reduce speed? I suspect they actually got ahead of themselves, setting trim stab cutoff too soon, not realizing how much more insideous the MCAS upset case is compared to runaway stabilizer trim.

And that is the problem with no training. They had no way to iterate various scenarios of working and failed MCAS behaviors.

It seems the "yo-yo manoeuvre" required to manually trim when severely mistrimmed with deflected elevator stopped being taught or mentioned in Boeing manuals decades ago.

Pilots should have known that MCAS is inactive with flaps extended, per information from Boeing.

Nope.

The Boeing/FAA directive re: MCAS does not instruct them to extend flaps.

Further, there's other things going on in the cockpit due to the malfunctioning AoA sensor that's the root of all this.

Specifically one of the effects is that they get an Unreliable Airspeed Indication, and run that checklist. That checklists memory items include maintaining the current flap configuration (in this case, flaps up).

The Boeing/FAA directive does not instruct them to deviate from this and extend flaps. They have a checklist memory item instructing them to in fact do the exact opposite, and not touch flaps.

You're correct that the AD and runaway trim procedure does not instruct them to extend flaps. What I was addressing was the statement upthread that "Flaps out supposedly would have kept MCAS off but the pilots weren't expected to know that."

If I'm a 737 MAX pilot, after the Lion Air crash I'm learning absolutely everything I can about MCAS. And from information Boeing provided I would learn that it operates with autopilot off, flaps up, at high indicated AoA.

You mention unreliable airspeed, that was actually their first problem. Flaps were extended at that point, as according to the narrative they were not retracted until after the AoA disagree, stick shaker, and airspeed disagree. In fact it almost reads like they were intending to continue the flight, engage autopilot, and climb to 32,000 ft with the stick shaker going the whole time. That seems very odd to me.

>If I'm a 737 MAX pilot, after the Lion Air crash I'm learning absolutely everything I can about MCAS. And from information Boeing provided I would learn that it operates with autopilot off, flaps up, at high indicated AoA.

And in a crisis situation you skip the checklists and think fast and apply your instincts because you read something on a forum? Sure if you have a lot of time you can try thinking but this is not debugging a bug where you have hours to observe the issue, try different inputs, observe again, Google some questions etc..

We don't want pilots to be creative. Air safety is so good because pilots learn memory items and checklists and actually follow them instead of making stuff up.

If the checklist doesn't mention flaps and the plane crashes if you keep the flaps up, that's on Boeing.

They were already too fast for that.

Sadly, it looks like those millions of man hours of incremental safety refinement also created a false sense of security. That (and management overriding engineering concerns) are the only explanations I have for how MCAS was implemented: because it had to be able to correct the pitch-up tendency of the 737 MAX and stay "invisible", so additional training could be avoided, Boeing apparently chose to use only one AOA sensor as "single source of truth" - because using both would have increased the chance of the system having to deactivate itself, which would probably have made the FAA mandate the additional training that Boeing wanted to avoid. This is just my personal theory however...

> Why is everyone so wedded to the narrative that this is the fault of MCAS and nothing else?

Because the other factors don't single this flight out, and the plane wouldn't have crashed without MCAS misbehaving, or more fundamentally, without the flawed plane design that required such a system in the first place.