How Safe is the Boeing 737 Max's MCAS System?

[PeterDonis]

If they had followed the correct procedure

Which a number of US flight crews did during similar incidents that got reported to the FAA but never resulted in any casualties so never triggered a detailed review of what was going on. I think I mentioned in a much earlier post in this thread that lack of proper pilot training and competence appears to have been a contributing factor to the MCAS incidents that did result in casualties.

However, that does not change the fact that Boeing hid the very existence of MCAS from flight crews, and made a number of egregiously wrong design decisions in its original design (for example, no comparison of at least two AoA sensors, no detection of a faulty AoA sensor, too much control authority allowed to MCAS).

 

[hutchphd]

The Lion Air Captain did exactly that through 21 MCAS activations.

21 activations ! Yessir that's the system want on all my equipment. Wow I hope you do not do critical design...

 

[russ_watters]

It's fair to say that better training can lead to better outcomes in an emergency situation. But this [pretty severe, as these things go] emergency situation was caused by the faulty design and the lack of training was caused in part by the faulty documentation/roll-out of the change, so it is pretty harsh to judge the pilots' as bearing much of the responsibility for these crashes.

 

[FactChecker]

made a number of egregiously wrong design decisions in its original design (for example, no comparison of at least two AoA sensors, no detection of a faulty AoA sensor, too much control authority allowed to MCAS).

This is a good summary of the design issues. These are the major design deficiencies that we immediately recognized, and it was not just our opinion. -- These are also the problems that Boeing engineers have now corrected and are the first things Boeing mentioned in their recent release.
IMHO, one other issue is in an even more serious category. Boeing had removed the AOA miscompare indication from the standard displays so that they could make it optional and start charging to have it added. That seems almost criminal.

 

[russ_watters]

FYI, just last month Boeing acknowledged full legal responsibility for the crashes*. So, there's not much value in further debate of the point:
https://www.seattletimes.com/business/boeing-aerospace/boeing-accepts-liability-for-737-max-accidents-wins-agreement-that-avoids-punitive-damages/

Boeing’s lawyers filed a joint court motion Wednesday with the lawyers for the families of the 157 people who died in the 737 MAX crash in Ethiopia, accepting sole liability for the fatal accident and laying out a process to settle almost all the claims.

“The defendant, Boeing, has admitted that it produced an airplane that had an unsafe condition that was a proximate cause of Plaintiff’s compensatory damages caused by the Ethiopian Airlines Flight 302 accident,” the filing states.

Boeing explicitly agreed that the pilots were not at fault.

It also exonerated two MAX suppliers: the company that built the jet’s angle of attack sensor and the one that produced, to Boeing’s specification, the aircraft’s faulty flight control software.

*caveat: the title says full responsibility for both, but the body seems to be about a legal filing for only one of them.

 

[artis]

IMHO, one other issue is in an even more serious category. Boeing had removed the AOA miscompare indication from the standard displays so that they could make it optional and start charging to have it added. That seems almost criminal.

This reminds me of the TV add style offers that were so popular around the early 2000's , where they sold you a "super duper" heater but the power cable comes as an extra option for extra money.
I mean who doesn't love a heater without a power cable.

FYI, just last month Boeing acknowledged full legal responsibility for the crashes*. So, there's not much value in further debate of the point:

Nice to see there is still some justice in the world , sadly this could have been easily avoided.
Pretty much an engineered problem.

 

[EAG711]

21 activations ! Yessir that's the system want on all my equipment. Wow I hope you do not do critical design...

You realize the same amount of activations can occur on any 737, right? before the Max, a runaway trim would be caused by an electrical failure, and a loose wire making intermittent contact with a ground could do exactly that.

In all reality, Boeing has accepted responsibility and admitted change, unlike the two airlines who have not made any safety changes whatsoever, and are practically fine with pilots who can't even recognize a runaway trim, which is a memory item that's solved by flipping a switch, which happens to be right next to the trim wheel itself. Boeings role in JT610 was probably less than 10%.

 

[PeterDonis]

before the Max, a runaway trim would be caused by an electrical failure, and a loose wire making intermittent contact with a ground could do exactly that.

From the data we have, it seems like a loose wire making intermittent contact with a ground is a much, much rarer event than a faulty AoA sensor. So even if a runaway trim could occur before MCAS, the poor design decisions of MCAS made runaway trim a much less rare event. And the mechanisms provided to pilots for dealing with runaway trim were predicated on it being an extremely rare event like a loose wire, not a much more common event like a faulty AoA sensor.

the two airlines who have not made any safety changes whatsoever

Neither of those two airlines are US airlines (or European airlines, since Europe has much the same regulatory attitude as the US), and the regulatory requirements they have to meet are very different, reflecting a very different viewpoint on tradeoffs between risk mitigation and cost saving from the viewpoint that drives US regulations. You might not like that, but you are perfectly free to not fly on those airlines.

Also, part of what drives the very different viewpoint on tradeoffs that regulates those non-US, non-European airlines is a belief, which up until these incidents was mostly justified, that airliners from big name suppliers like Boeing and Airbus are designed to not require a high level of competence from pilots to be able to operate at the risk level that they deemed to be justifiable. And Boeing told everyone that the 737 MAX would be just like previous 737s, which those same airlines had operated for decades at that tolerable level of risk. As it turned out, Boeing's claim was egregiously wrong: the 737 MAX was not just like previous 737s, and it was not just like them in a way that drastically changed where the 737 MAX sat on the spectrum of tradeoffs between pilot competence and risk. It's not realistic to expect the regulators that have oversight of those non-US, non-European airlines to spot that, when the US and Europe had already accepted Boeing's claims and approved the 737 MAX on the theory that pilots would see no difference between it and previous 737s.

It's possible that all this will lead the regulators who have oversight of those non-US, non-European airlines to re-evaluate their risk tradeoff and start requiring a much higher level of pilot competence. But I wouldn't bet on it. I think a much more likely outcome is less market share for Boeing and more for Airbus in those markets because of a reduced level of trust in Boeing and in US regulators.

 

[hutchphd]

You realize the same amount of activations can occur on any 737, right?

Golly that's a revelation. Can that axact same number really occur?

I will cease kicking this dead horse. It is a true moral tragedy.