The idea that a pilot would knowingly leave thrust at climb power while in modestly level flight at low altitude and expect not to overspeed is very strange to me, checklist or no checklist.
I think they were too busy fighting the controls to worry about that.
Note IAS DISAGREE alert:
"In the event of an uncommanded horizontal stabilizer trim movement, combined with any of the following potential effects or indications resulting from an erroneous Angle of Attack (AOA) input, the flight crew must comply with the Runaway Stabilizer procedure in the Operating Procedures chapter of this manual:
- Continuous or intermittent stick shaker on the affected side only.
- Minimum speed bar (red and black) on the affected side only.
- Increasing nose down control forces.
- IAS DISAGREE alert.
- ALT DISAGREE alert.
- AOA DISAGREE alert (if the option is installed)"
About which was written here:
https://leehamnews.com/2019/04/03/et302-used-the-cut-out-swi...
"the high speeds observed" ... "were logical. It’s a consequence of following the Emergency checklist for “IAS disagree” (IAS is Indicated Airspeed, i.e. the dynamic air pressure experienced by the aircraft) after takeoff."
In short, seeing that Boeing indeed wrote about the IAS alert being activated when the sensor fails, and MCAS gets activated, I can only conclude that Boeing indeed knew that the pilots would make the plane uncontrollable if they followed Boeing's instructions. It seems they just gambled on the chance that the second crash won't happen so soon after the first.
Either that, or we'd have to believe that what a single pilot manage to do for his Youtube video a company which is to deliver the planes in worth of hundreds of billions (!) of USD wasn't able to do.
Why? Because your instruments disagree about your airspeed. You want to have a large margin to keep your speed high enough that you won’t accidentally stall while you try to establish what’s reliable.
You can't point at a memory item and treat it like the pilots can only apply what's in there in exclusion to everything else. The structural limits of the aircraft are there for a reason.
Aside from anything else the pilots were trying to maintain altitude by their communication with ATC.
Not that I'm blaming them. I think they had too much going on to even consider moving the throttles, and thats 100% on Beoing, but it probably didn't help their chances of recovery.
But aerodynamic forces can conspire to make it very hard or physically impossible for human force to rotate it if the elevator is being used to combat the stabilizer at high speeds. See here for more discussion of the physics behind it: https://www.satcom.guru/2019/04/stabilizer-trim-loads-and-ra...
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.
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.
Still damn close to the ground to be comfortable letting the plane dive.
https://www.flightradar24.com/blog/flightradar24-data-regard...
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?
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.
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.
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.
If I'm reading the charts right it took them about a minute to go from 5,000 to 7,000 feet. So even if they hold on for just a few minutes more they're almost to 14,000 feet.
And you're taking speculation based on assumed facts too seriously. If they were struggling to keep the plane level then their simulation was different. In reality the plane was climbing all the way up until they enabled the electric trim and MCAS kicked in.
So must be manual trim wheel movements.
I believe that's correct given that they had an Unreliable Airspeed Indicator warning (due to the malfunctioning AoA sensor), per the memory items on the UAI checklist.
It makes the forces on the trim wheel much worse, which explains why they couldn't turn it, but it's the correct checklist response to the conditions observed, and the Boeing/FAA directive completely failed to take the impact of this response into account.