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Ethiopian 737 Max 8 crash and Fallout

flychrisfly

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This event really does show that a failure to understand all possible failure modes and their outcomes is a dangerous situation.
It seems they (Boeing) barely understood any failure modes. I would have thought it was obvious to test a system (MCAS) for a situation when its key input (AOA vane or sensor) might fail. Maybe they did, and declared the test as passed after a single simple recovery without seeing it through to the bitter end.
 

NM

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It seems they (Boeing) barely understood any failure modes. I would have thought it was obvious to test a system (MCAS) for a situation when its key input (AOA vane or sensor) might fail. Maybe they did, and declared the test as passed after a single simple recovery without seeing it through to the bitter end.
Indeed, with hind-sight it is very obvious now. Unfortunately those involved with the design, development, testing, analyses and certification seemed to have missed the devastating implications of what we now see as an obvious, to-be-expected, and somewhat predictable failure mode. And this leaves me wondering what other situations have not been predicted, anticipated, tested, properly evaluated? But this also highlights the way the aircraft industry improves safety as the causes of accidents and incidents are thoroughly investigated and changes implemented to minimise the risk of future similar events. The fact that this was the second accident with the same causal effects is disappointing. In this Ethiopian case, it appears the holes in the Swiss cheese aligned in a slight different manner, resulting in MCAS events at a much lower altitude, contributing to the outcome as the pilots had much less time/space to remedy the inappropriate control inputs from the automation systems.
 

Quickstatus

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FAA declares MCAS V2 to be “operationally suitable”. I’m not sure what that means.
 

woodborer

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But this also highlights the way the aircraft industry improves safety as the causes of accidents and incidents are thoroughly investigated and changes implemented to minimise the risk of future similar events.
Although in the MCAS case, it seems they ignored 50 years of learnings about fault tolerant systems in giving it only one sensor.
 

Moody

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Call me an idiot if you like, but couldn't this all have been solved better by :-

1. Informing pilots of the performance changes and MCAS protections in the new MAX variant
2. Only triggering MCAS when BOTH AoA sensors agree there is a danger of stalling

Of course ideally there would have been updates of and compulsory certification on simulators, but the primary need is to let the pilots have the knowledge needed to let them fly the aircraft.
 

jb747

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Call me an idiot if you like, but couldn't this all have been solved better by :-

1. Informing pilots of the performance changes and MCAS protections in the new MAX variant
Boeing were desperate to ensure that they could claim that little to no training was necessary prior to flying the MAX. Keeping MCAS hidden was largely part of this ploy.

2. Only triggering MCAS when BOTH AoA sensors agree there is a danger of stalling
You mean designing it properly. Not only should in never trigger with any form of instrument disagreement (and I’ll bet that all the aircraft weren’t even checking for that), but the idea of it triggering continually is outright stupid. They simply did not think it through, and it was a kludge, to correct an aerodynamic weakness that cannot be properly engineered out of the aircraft.

I would not be surprised if some of the foreign authorities refuse to certify the aircraft now....not because of MCAS, but because it is needed.

The cockpit is totally different to previous models of the aircraft, and it should not have a common endorsement.

Of course ideally there would have been updates of and compulsory certification on simulators, but the primary need is to let the pilots have the knowledge needed to let them fly the aircraft.
No...the primary need is to sell the aircraft, using the ‘it will not happen’ school of engineering and marketing. This system, as designed, was so dangerous that it’s hard to believe anyone thought it would be a good idea.

The upshot, is that this system has almost certainly killed more people than it ever might have saved, if it had actually worked.
 

coriander

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How do I "like", "agree" and vote "informative" on jb's post above. Excellent, succinct, accurate.
 

Berlin

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The upshot, is that this system has almost certainly killed more people than it ever might have saved, if it had actually worked.
Wow, this is all just mind-boggling. And they still haven’t learnt at all but are simply tinkering with their software to get an aircraft off the ground that should never have been built in the first place. Maybe they should finally seriously listen to proper pilots like you!
 

stm1sydney

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The upshot, is that this system has almost certainly killed more people than it ever might have saved, if it had actually worked.
Not necessarily. We don't really know how many lives MCAS has saved / will save - that is probably the most interesting/worrying thing. To what extent is it needed to keep the MAX in the air?

You alluded to this earlier in your post:
"I would not be surprised if some of the foreign authorities refuse to certify the aircraft now....not because of MCAS, but because it is needed."
 

oz_mark

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Ansett

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Even though the aircraft handle completely differently and that, from what I have read, the cockpit layout is also not the same?
 

jb747

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Not necessarily. We don't really know how many lives MCAS has saved / will save - that is probably the most interesting/worrying thing. To what extent is it needed to keep the MAX in the air?

You alluded to this earlier in your post:
"I would not be surprised if some of the foreign authorities refuse to certify the aircraft now....not because of MCAS, but because it is needed."
It’s needed for some regulatory requirements regarding the stall behaviour. It may well be that these have more to do with the idea that it’s just the same as all other 737s as a real instability that needs to be protected.

In any event, this system has cost over 300 lives. Aircraft are very rarely stalled, with most instances actually being stall warnings, not actual stalls. So, how many uncorrected fully developed stalls will occur over the life of the aircraft, that MCAS might otherwise stop. I’d expect the answer is very few.
 

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