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Comment by js2 | Hacker News Reader

> There is no absolute reference on the position of the stabilizer.

There’s an indicator right next to the wheel:

https://qph.fs.quoracdn.net/main-qimg-1dc99dbe662c71d7c470cf...

And the pilots must have recognized it was a trim issue because they countered it multiple times. Why they didn’t flip the stab trim cut off switch is a mystery.

An earlier crew was able to fly the plane. I agree the pilots should have been made aware of MCAS (though either the Ethiopian pilot was shockingly not aware of it or being aware didn’t help him). But at the end of the day the pilots are there to fly the plane, not manage automation:

https://vimeo.com/159496346

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The earlier crew faced an identical issue the day before, and it was only the deadhead pilot onboard who recognized the issue and suggested flipping the stab trim cut off. Out of 5 pilots (7 if we count the other crash), only one suggested the correct fix.

> Why they didn’t flip the stab trim cut off switch is a mystery.

Not really. In the previous incarnations of the 737, a hard pull on the yolk by a pilot disengaged the automatic trim system. In the 737 MAX, the yolk pull method to disengaged the trim was disabled. What the pilots did would have worked on the previous version of the plane, but not on the MAX.

Boeing really tried to claim that the MAX was just like the previous version, and that pilots didn't need new training to fly it. I think the data shows that more pilot training is appropriate for this plane.

> The earlier crew faced an identical issue the day before, and it was only the deadhead pilot onboard who recognized the issue and suggested flipping the stab trim cut off. Out of 5 pilots (7 if we count the other crash), only one suggested the correct fix.

And there are two ways to look at that. One is to say "obviously this means that this failure mode is too hard to diagnose". Another is to say "holy shit Lion Air pilots are fucking incompetent, I'm never going to fly any sort of third world budget airline if any of them are like this".

The truth is probably somewhere in the middle, of course.

> What the pilots did would have worked on the previous version of the plane, but not on the MAX.

And yet the checklist continues past that point, because guess what? The "control inputs disengage trim" component can also fail, and Boeing planned for that.

I believe you're right that the truth is in the middle. It really points to the pilots being inadequately trained on this aircraft. Boeing strongly pushed to avoid requiring new pilot training for the MAX airplane. They claimed that MAX was similar enough to the previous version of the 737 that if a pilot were checked out on the previous plane they were good to go. What we're seeing now is that assessment was wrong. More training should have been required.

Boeing fucked up big time on this one. FAA also fucked up. Pilots were inadequately trained, and some delivered info was false (Boeing said MCAS could only bring the nose down 0.6 degrees, in fact, it was unbounded)

The MCAS system was designated "hazardous" by Boeing in their own safety assessment. A system that is labeled hazardous can not be reliant on a single system failure. MCAS is reliant on a single sensor. That's already a major error in the safety analyses. As we can clearly see from two accidents, MCAS system should have been designated "catastrophic", one step more dangerous in that scale, with even more stringent redundancy requirements.

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