[inferiorhuman]

I know, sounds too simple to be true. But it is

No, it's not.

So here's some context. Boeing installed known not-to-spec structural components on the NG. Boeing installed known to fail prematurely slat tracks on the NG and 737 MAX. Boeing installed (probably known) not-to-spec pickle forks in the NG and 737 MAX. Boeing falsified repair documentation for an Air Canada 787. Oh, and of course, Boeing hid any mention of MCAS. Point being Boeing doesn't have a lot of credibility left.

With that in mind:

Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT.

As the Ethiopian crew found out: it can't. The larger instruments of the NG required the hand cranks to shrink while the stabilizer itself grew. With the resulting lower mechanical advantage and increase in force required to move the stab itself the wheels became unusable. Sure, the Ethiopian crew went over the "maximum" speed but they were still under the max diving speed (Vd). That means the cranks were supposed to work.

It works because the first incident of MCAS failure (Lion Air) was safely dealt with by doing just this.

It worked because the first crew got lucky and had a third set of eyes that was free to dig through everything in search of a best guess.

[WalterBright]

> As the Ethiopian crew found out: it can't.

Whatever you read about that is simply wrong. (I've seen a LOT of misinformation in popular print about this.) You're correct that the hand cranks were unusable. But the electric thumb switches WERE usable and were pointed out in the AD.

Note that the crews of BOTH the LA and EA crashes had already used the thumb switches to restore normal trim, the LA crew did so 25 times.

> best guess

No guessing required. Follow the training, which is supposed to be a "memory item", meaning they weren't supposed to need to consult a checklist nor dig through anything nor guess.

I am not a pilot, but I would not consider myself fit to fly unless I knew by memory what every single switch in the cockpit does, ESPECIALLY the ones prominently located within easy reach. You can bet it's not the infotainment system.

For damn sure I would read every Emergency Airworthiness Directive for the airplane I'm the pilot of, most especially one issued in response to a crash.

[inferiorhuman]

Whatever you read about that is simply wrong. (I've seen a LOT of misinformation in popular print about this.) You're correct that the hand cranks were unusable. But the electric thumb switches WERE usable and were pointed out in the AD.

And if you enable the electric trim switches on a 737 MAX you get MCAS activation. MCAS, of course, trims faster than the switches. Using the electric switches is fighting a losing battle (look at the graphs of trim input vs output). How are you supposed to fly the plane when you can't trim the stabilizer?

Look at the graphs from the Indonesian report. The pilots were countering with trim up button presses and MCAS still managed to take the trim to a severe AND position.

Look at the graphs from the Ethiopian report. You'll see a long gap where the electric trim was disabled (leaving the pilots with no way to trim the stabilizer). Outside that gap you'll see an automatic (MCAS) AND command with no change in trim and a couple ANU clicks from the pilots with no resulting change in trim.

No guessing required. Follow the training, which is supposed to be a "memory item", meaning they weren't supposed to need to consult a checklist nor dig through anything nor guess.

And what memory items were they supposed to have in mind? Keeping in mind MCAS presented counter to how Boeing defines runaway trim.

[WalterBright]

> And if you enable the electric trim switches on a 737 MAX you get MCAS activation.

The electric trim switches override MCAS. That is why the steps are:

1. use the electric trim switches to set the trim to normal

2. cut off the electric trim

That's all there is to it.

> MCAS presented counter to how Boeing defines runaway trim.

That's simply false. (And runaway trim does not need definition, Boeing does not define it.)

[inferiorhuman]

The electric trim switches override MCAS.

They pause MCAS but do not disable or override it it. The trim switches move the stabilizer slower than MCAS activation thus as seen by the Ethiopian and Lion Air crews using the electric trim switches is tantamount to fighting a losing batle.

1. use the electric trim switches to set the trim to normal

What happens when the electric trim switches don't work? They didn't in the Ethiopian crash.

runaway trim does not need definition, Boeing does not define it.

Sure they do, it's in the QRH plain as day.

Condition: Uncommanded stabilizer trim movement occurs continuously.

MCAS activation isn't continuous, especially not if you're pausing it with the trim switches.