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Comment by mc32 | Hacker News Reader

I'm not in aeronautics obviously and I overstated the case, but my understanding is that the MAX series have different flight characteristics (behaves differently) due to bigger engines which also were moved forward both of which resulted in altering the aerodynamics and flight characteristics --making it different to non MAX 737s... so far, so good. They fly different and you have to treat them differently. But in order to make the pre MAX 737 pilots pre-crosstrained for the new MAXes they installed MCAS systems that made the controls feel like they would respond in a pre MAX 737. In other words computerized compensation. But due to the new flight characteristics you could not exactly fly it like a ore MAX 737 and so if you did bad things could happen if you were not being attentive.

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Wrong again.

The design goal for the software was to make it fly like other 737s. The software did not actually do that, but did "something" that inspectors allowed was just enough different from without to certify. And, in case of equipment failure, or various other circumstances, the software failed completely, because it was just really badly designed. If you knew about the system, you could turn it off in case of trouble, and then the plane would fly fine, just not enough like a real 737 that you could completely ignore the difference.

Then they made it hard to know that the system was there. People who knew how to turn it off could prevent disaster.

Correct, switch it off and the plane can fly fine.

Thing is though the pilots of the second MAX crash took all the right steps. Just too slow.

There was like 10 seconds to turn off mcas, after that a crash was inevitable.

This isn’t correct. There’s one portion of the flight regime where the new engines result in different characteristics. To counter that, the MAX has an automated stick pusher. What’s the alleged fix? Pull the breaker on the overhead panel.

There’s a similar failure mode in pre-MAX 737s called “runaway trim”. The giant trim wheels on the center pedestal spin in a loud and attention-getting fashion. The fix? Pull the breaker on the overhead panel.

> To counter that, the MAX has an automated stick pusher.

The MAX does not have a stick pusher. MCAS works on the position (trim) of the stabilizer. The elevator feel system (which the NGs have as well) works by creating additional resistance at the yoke (which is hydraulically assisted). Neither are stick pushers.

> There’s a similar failure mode in pre-MAX 737s called “runaway trim”.

That's a thing that can happen on any plane with a similar horizontal stabilizer setup. I'm sure even a plane with a flying stabilizer (e.g. L-1011) has similar failure modes.

> The giant trim wheels on the center pedestal spin in a loud and attention-getting fashion.

The "giant" trim wheels were reduced in size on the NG (and MAX?) reducing their leverage.

> The fix? Pull the breaker on the overhead panel.

There are two switches (whose function was subtly changed with the MAX) that control the trim motors and they're located behind/below the thrust levers.

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