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Comment by WalterBright | Hacker News Reader

> Sorry, but this is a naive understanding of aviation safety.

Very few aviation crashes are the result of a single failure. Usually, they are a combination of failures, all of which were required to produce the crash.

These crashes are no different:

1. the design shortcomings of MCAS

2. the refurbished AOA sensor on the LA airplane was not calibrated properly

3. LA put the plane back in service despite the failed AOA sensor

4. The crew of the LA flight were not informed of the failed AOA sensor

5. The flight crews did not follow the memory runaway trim procedure

All of these had to happen. A typical NTSB crash report dispassionately identifies all the contributing factors to an accident and issues corrective action recommendations for each of them.

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I was curious about point 3; was lion air responsible for detecting the failed AOA sensor or someone else?

I can't exactly say but a quick read comes up with some relevant points:

"According to the reports presented to the Indonesian parliament, a Florida-based aerospace company performed the repair of the faulty AOA sensor."

https://airlinerwatch.com/broken-aoa-sensor-in-lion-air-737-... [from april 2019]

So possibly it's not LA's fault, however

"On Nov. 5, CNN published an update on the crash investigation from Capt. Nurcahyo Utomo of Indonesia's National Transportation Safety Committee (KNKT) noting that the FDR review also concluded that the aircraft's airspeed indicator had been malfunctioning on four consecutive flights prior to the crash. Utomo also indicated the pilots should have recognized the malfunction when it occurred on flight JT610."

https://www.aviationtoday.com/2018/11/07/faa-issues-boeing-7... [from nov 2018]

There's no excuse for LA putting the airplane back in service after the first crew had to cut off the stab trim, or even bothering to inform the next crew of the issue.

That was my point (edit: and Nurcahyo Utomo's point). I was backing you up on this.

I know, I was just concurring. Thanks for lending a hand here :-)

@WalterBright: “These crashes are no different” ..

“1. the design shortcomings of MCAS”

“5. The flight crews did not follow the memory runaway trim procedure”

How would the pilots have switched off MCAS if they didn't know it was there?

They throw the switch that turns off automatic trim. That the automatic trim system is going nuts due to some new system (MCAS) they don't know about as opposed to it going nuts for one of the reasons it might do so on earlier planes doesn't matter.

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