[nonamechicken]

Common! This gets brought up all the time when the topic is Boeing. Max's issue had nothing to do with the outsourced software. Netflix has a documentary called 'Downfall' which talks about what all went wrong. AirBus also outsources, they haven't crashed right?

[amarka]

Not sure if the last sentence is in jest or not, but here's a list of crashes for just one of their plane models:

https://en.wikipedia.org/wiki/List_of_accidents_and_incident...

[nonamechicken]

When I mentioned AirBus, I was thinking of this - that the Max crash is clearly due to corporate greed. I am not aware of any such scenario with AirBus. Not only that, according to the Netflix documentary, Boeing was trying to blame the pilots of the Indonesian and Ethiopian airlines initially. Then in turns out that the Indonesian pilot was an Indian who was trained in US, and the Ethiopian pilots followed Boeing's guidelines on MCAS failure properly.

I am looking at these blames on outsourcing from that perspective - that Boeing is trying to blame others to hide their greed.

[WalterBright]

> the Ethiopian pilots followed Boeing's guidelines on MCAS failure properly.

The Ethiopian pilots did not follow the procedure in the Emergency Airworthiness Directive distributed to all MAX pilots that says:

"Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."

https://theaircurrent.com/wp-content/uploads/2018/11/B737-MA...

You might want to also read the report:

2018 - 035 - PK-LQP Final Report http://knkt.dephub.go.id/knkt/ntsc_aviation/baru/2018%20-%20...

And note that the first incident of MCAS failure was overcome by the pilots and the airplane landed safely.

[nonamechicken]

Thanks for the links. I am not trying to refute what you said above. But I don’t want anyone to think that I am spreading misinformation here. So I checked the Netflix Downfall documentary again. It says at 34:30 that the pilots did what Boeing instructed them to do.

The documentary talks about the Ethiopian crash from 32:00 onwards. The below excerpt is from 34:30 onwards. Name of the person talking is in '[]' brackets.

[Pasztor] Soon after the hearings got underway, we managed to get more information about what actually happened in the cockpit of the Ethiopian aircraft. We got the information from the FAA within hours after they received it from the Ethiopian investigators. It was very late at night, and we tried to put together the most comprehensive story we could. When it came out, this was the first story that revealed that the crew, in fact, realized that MCAS had kicked off. And they did what Boeing instructed them to do.

[Tajer] When the MCAS kicks in, it runs for ten seconds and pushes the airplane very powerfully nose-down. Runs for ten, off for five. Runs for ten, off for five.

[Cox] They’ve got this cacophony of stick shaker, master cautions, airspeed disagree, altitude disagree. All of these…these warnings going off. The captain, who’s flying the airplane, is trying to figure out what’s gone wrong.

[Tajer] The first officer called out, “Stab trim cutout switches, Captain.” I think he said it twice. He did what Boeing said. He turned off the MCAS system. I remember reading that, and I said, “Man, the kid got it right. The kid got it right”.

[Cox] The problem now is that the airplane is going too fast. And because of the force on the tail itself, they cannot manually trim the airplane to be able to recover.

[WalterBright]

That is not following the instructions in the Emergency Airworthiness Directive issued to all MAX pilots:

"Initially, higher control forces may be needed to overcome any stabilizer nose down trim already applied. Electric stabilizer trim can be used to neutralize control column pitch forces before moving the STAB TRIM CUTOUT switches to CUTOUT. Manual stabilizer trim can be used before and after the STAB TRIM CUTOUT switches are moved to CUTOUT."

https://theaircurrent.com/wp-content/uploads/2018/11/B737-MA...

They didn't follow the first part, which was to restore normal trim with the thumb trim switches, which override MCAS.

[WalterBright]

> the Max crash is clearly due to corporate greed

Is it? The single path weakness in the MCAS design was not a cost saving measure. I've never seen an explanation for why this mistake was made.

[atoav]

The airframe was changed significantly, creating the need for the whole MCAS solution — why? Because this was seen as a solution to avoid a recertification of the airframe, which would mean pilots had to re-train, which would mean airlines wouldn't buy, which means money would not flow.

Avoiding this recertification was the only reason MCAS was chosen instead of designing an airframe in such ways the now bigger engines actually have their center of gravity where it is expected to be.

This was ultimately a cost saving measure. Boeing could not be bothered to recertify the airframe purely for comercial reasons, not because it objectively made sense.

[WalterBright]

There is nothing wrong with making an airplane behave like the previous version. In fact, it enhances safety, as pilots can and do make errors when under stress they do the right thing for the wrong airplane. Making airplanes predictable and consistent with existing training is a safety enhancing practice.

I worked on the 757 design, which was designed concurrently with the 767. A lot of effort was made to make them behave in a common manner, even though they were quite different airplanes. This makes perfect sense.

It's the same reason the steering wheel and pedals on your car are laid out the same and do the same things across nearly all very diverse cars. And yes, carmakers adjust the handling characteristics to be predictable and not need the drivers to have additional training.

[kayfox]

Boeing had originally proposed a new small aircraft (with carbon fiber), but the airlines did not want this as it would have higher operations costs to have two different types of aircraft, so Boeing had to come up with a new 737, and the MAX was it.

[salawat]

It was made because implementing a dual path system would have required simulator training. Boeing wanted to avoid that at all costs as a value pitch.

[WalterBright]

A dual path (along with the other changes made to the MCAS implementation) would not have required simulator training.

(With dual path, MCAS would have simply turned itself off if the two inputs disagreed.)

[salawat]

That was not my understanding, but the source I heard about the reasoning from was the 60 minutes expose.

https://m.youtube.com/watch?v=QytfYyHmxtc

Between 35-36m-ish. 35:30 I think.

Boeing was claimed to have "known the FAA would not certify a dual sensor system without Level D simulator training".

This was from an insider at the time, and admittedly, I've not heard of an identity being put to them, but that signal was claimed to have been there.

There is also corroborating evidence that the Chief Technical Pilot actively dissuaded customers who asked for simulator time anyway, characterizing it as unnecessary. I don't have those at my fingertips right now, and unfortunately, my memory is failing me as to whether or not an "oh shit" moment was had at some point as to whether the Chief Technical Pilot had mischaracterized the system to regulators.

I just remember I thought it was awful convenient at the yime that this Chief Technical Pilot had all the hallmarks of a scapegoat for management to start piling blame on, and being glad he got independent counsel instead of relying on Boeing's General Counsel.

[mannykannot]

That, of course, immediately raises the question of why, then, this was not done.

There is a proximate answer that still does not get us to root causes: An MCAS failure was rated as a Major condition as opposed to Hazardous, in which case the regulations allowed (but did not, of course, require) a single source of input.

This rating was arguably justifiable for the 737 MCAS in its original form, but its power had to be increased significantly after flight testing revealed the original version to be inadequate.

As it happens, the 737 MAX airframe was not the first use of MCAS: the KC-46 also has it. Despite the fact that this system is less powerful than that which was fitted to the initial production 737 MAXs, it uses two AofA sensors. There is clearly a strong and obvious engineering case for doing so, so simply observing that Boeing did not have to do so does not exhaust the questions that should be asked.

I have seen it stated in several places that using two AofA sensors would have required a warning in the case of their being in disagreement, which in turn would require it to be mentioned in the AFM, which might have prompted a reevaluation of the no-training decision, either directly or through a reevaluation of the risk classification. Unless a smoking gun has been found, Boeing can stonewall on whether the training concern suppressed a full and objective evaluation of the risks posed by MCAS (especially after its strengthening), and thereby improperly influenced design decisions (among other issues), but the concern is obvious to everyone except those who want to avoid considering it.