[msbarnett]

My (non-expert) reading is that the co-pilot couldn't move the wheel, while the pilot was engaged in fighting to to keep the stick pulled back (a Swedish pilot tried this scenario in a simulator last week and literally had to keep both arms locked around the stick towards the end).

Counter-intuitively, letting go of the stick in brief increments might have been the correct move. Letting the nose pitch down would take force off the jackscrew and let both pilots crank hard on the stabilizer. Boeing manuals once covered this, but apparently they haven't since the 1980s, and their directive after the Lion Air accident made no mention of the necessity of such a procedure. Also they were only 7,000 feet above the ground so whether or not they'd have recovered in time is hard to say. Quite possibly the MCAS had already doomed the flight.

[cjbprime]

> they were only 7,000 feet above the ground

No, it's worse: the origin airport is at 7000ft elevation. They only had around 1000ft height AGL for all of the flight. So I agree that releasing the elevator at all seems surely suicidal.

[msbarnett]

They're at 12,000-14,000 feet altitude at 05:43ish, when the co-pilot reports the non-functional manual trim. So ~6,000-7,000 height.

Still damn close to the ground to be comfortable letting the plane dive.

[cjbprime]

Oh! I think this is new information in the report -- the FlightRadar24 ADS-B data never shows them above 8500ft altitude, ~1000ft AGL. FlightRadar24 must have missed the final few minutes?

https://www.flightradar24.com/blog/flightradar24-data-regard...

[treis]

But high enough to re-enable a system you know is malfunctioning?

I guess we will have to wait for the final report but the pilot's actions are perplexing here. Even if we accept that they can't trim with the wheel, why enable electric trim and then not use it? Why not enable it, trim to where you want, and then use the cut out switch again?

[msbarnett]

> But high enough to re-enable a system you know is malfunctioning?

They couldn't land with the stabilizers mis-trimmed. If the wheel wouldn't budge, re-enabling it and trimming electronically was the only option likely to occur to them, since the only other possible option (release the column, let the plane nose down so that the forces on the screw ease and they can trim manually) is completely counter-intuitive and was removed from Boeing's documentation and simulator training 30-40 years ago and was not covered in the FAA/Boeing MCAS directive.

> Even if we accept that they can't trim with the wheel, why enable electric trim and then not use it?

They did use it after re-enabling it. They just didn't re-disable it within 5 seconds of their last input manual electronic trim command, so the MCAS ran again a final time.

Whether that's because they just didn't get to the switches in time, weren't aware they had such a short window to do so (the FAA/Boeing bulletin does a piss poor job of communicating this), or were just so thoroughly overwhelemed by everything that was going on is hard to say at this point.

[treis]

>They couldn't land with the stabilizers mis-trimmed. If the wheel wouldn't budge, re-enabling it and trimming electronically was the only option likely to occur to them, since the only other possible option (release the column, let the plane nose down so that the forces on the screw ease and they can trim manually) is completely counter-intuitive and was removed from Boeing's documentation and simulator training 30-40 years ago and was not covered in the FAA/Boeing MCAS directive.

They could have just kept flying. They weren't in any immediate danger and had time to reach out for help. Worst case scenario, you fly straight for the next 30 minutes while ascending to 20-30k until you figure out what's going on.

>They did use it after re-enabling it.

Not really. The barely blipped it. Not what I would expect if they had a clear intention to re-enable electric trim in order to get the trim to where they wanted it.

[msbarnett]

> They could have just kept flying. They weren't in any immediate danger and had time to reach out for help. Worst case scenario, you fly straight for the next 30 minutes while ascending to 20-30k until you figure out what's going on.

The stabilizer's trimmed down. The pilot is repeatedly requesting the co-pilot's assistance in maintaining elevator trim up, and says to the co-pilot at 05:43:04 that the pitch is not enough to keep the plane level. They're well above Vmo at this point.

Per the Seattle Times coverage, a Swedish pilot simulation of the conditions could barely control the column to stay level: https://www.seattletimes.com/business/boeing-aerospace/boein...

> In the test, the two European pilots in the 737 simulator set up a situation reflecting what happens when the pre-software fix MCAS is activated: They moved the stabilizer to push the nose down. They set the indicators to show disagreement over the air speed and followed normal procedures to address that, which increases airspeed.

> They then followed the instructions Boeing recommended and, as airspeed increases, the forces on the control column and on the stabilizer wheel become increasingly strong.

> After just a few minutes, with the plane still nose down, the Swedish 737 training pilot is exerting all his might to hold the control column, locking his upper arms around it. Meanwhile, on his right, the first officer tries vainly to turn the stabilizer wheel, barely able to budge it by the end.

They're absolutely not climbing 14,000 feet in that condition. The control forces on the column in this situation are absurd. Their arms couldn't have held them level for more than a few minutes max.

Retracting the stabilizer was their only option.