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Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

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Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#171

Post by peteretep »

massysett wrote: post #46
djsumdog wrote: post #28

What is the endgame now for 737 MAX planes? Every airline using them has had several weeks to totally reorganize to deal with these huge missing parts of their fleets. Boeing keeps talking about fixing them and putting them back in the air, but I dunno. At this point, it should be agreed the fundamental design flaws are serious, and Boeing should have simply made a brand new plane, with much more modern controls and…

These planes cost at least $100 million each. They will fix them and get them flying again.

Any other answer here is insane. They’re too expensive to write off.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#172

Post by Aeolun »

skybrian wrote: post #99
nikofeyn wrote: post #52

Earlier quoted context omitted.

it’s not just pr reasons. they tried to hot patch this airplane design with software, and now they are hot patching that fix. it seems it is a fundamentally flawed design that they tried to hide and get away with rather than doing the right thing. i know i don’t want to fly on a 737 max ever, and this whole ordeal with boeing and the faa has made me less confident in the airline industry as a whole. your parenthetica…

The fix taking a while to get right is not evidence for "fundamentally flawed". You have a strange idea about how to assess risk. It's like faults are somehow contagious.

> It’s like faults are somehow contagious.

They are. If 737 MAX was rushed to market and this is the first issue we become aware of, how many more are hidden?

If Boeing makes a habit of rushing planes to market without certification, how many more ticking time-bombs are flying around?

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#173

Post by Aeolun »

dsfyu404ed wrote: post #50
skybrian wrote: post #49

Earlier quoted context omitted.

It's rather weird to ask a huge number of mostly-good airplanes to be thrown away for PR reasons, rather than fixing them. (Not to mention that these planes have never crashed in most countries, even with an admittedly serious bug.)

>It's rather weird to ask a huge number of mostly-good airplanes to be thrown away for PR reasons Welcome to the internet where other people's money doesn't matter.

I don’t know about you, but in my real-life other people’s money doesn’t matter either.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#174

Post by TomVDB »

jschwartzi wrote: post #153
skybrian wrote: post #99

Earlier quoted context omitted.

The fix taking a while to get right is not evidence for "fundamentally flawed". You have a strange idea about how to assess risk. It's like faults are somehow contagious.

The notion that you can fix an aerodynamic stability problem in software by making a software program mimic the flight characteristics of an older plane is fundamentally flawed. And the notion that we can just patch the system later if it turns out you did it wrong is dangerous. You're betting with human lives that this time you've got it right.

Why is it fundamentally flawed?

There’s no question that Boeing’s implementation had major issues, but there is IMO a higher burden of argument(?) to declare that a fundamental inevitability.

This could simply be a case of Boeing incompetent/reckless/...

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#175

Post by Aeolun »

staunch wrote: post #47
djsumdog wrote: post #28

What is the endgame now for 737 MAX planes? Every airline using them has had several weeks to totally reorganize to deal with these huge missing parts of their fleets. Boeing keeps talking about fixing them and putting them back in the air, but I dunno. At this point, it should be agreed the fundamental design flaws are serious, and Boeing should have simply made a brand new plane, with much more modern controls and…

Now imagine if Boeing had created a brand new design instead of the 737 MAX and it had some mysterious fatal flaw as well? Second System Syndrome is something every engineer should understand. There's just no good reason to suspect a brand new design would've been bug free or easier to debug than the 737 MAX. The 787s or A320neos could start dropping out of the sky at any minute. Maybe their carbon fiber panels start…

Well, for one thing, a new design would have to be recertified.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#176

Post by Xixi »

CydeWeys wrote: post #102
joe_the_user wrote: post #64

Earlier quoted context omitted.

I'm not an engineer but what about: A) Adding two more angle-of-attack sensors so a pilot can be reasonably sure of auto-adjust will work. Retrofitting those would be expensive, of course. B) Put the two buttons back the way they were and add a "light" indicator an angle-of-attack sensor failure. C) More pilot simulator training so pilots know what to expect in the unusual situation that the system fails. I suspect t…

You need three redundant sensors for safety-critical systems, so that if one fails you know which one is failing. Airbus has three AoA sensors (and three of others as well) on their planes for this reason. And it's worth pointing out that 737s already have two of these sensors, but don't use them both for MCAS (?!?!).

The A350 has 4 AoA sensors: I suspect it is a lesson learned from an A320 that had 2 AoA sensors froze in the same position, outvoting the only AoA sensor that was still working. In other words: failures are not always independent.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#177

Post by mannykannot »

Scaevolus wrote: post #141
Obi_Juan_Kenobi wrote: post #130

Earlier quoted context omitted.

> These engines moving made the plane more vulnerable to a stall situation. I don't think this is correct. A lot is being made about the engine move with regard to aerodynamic behavior, but it doesn't seem at all outside of the bounds of what is considered standard. Pilots report that a similar 'light stick feel' at high AoA is already present in aircraft like the 757. It's not that the aerodynamic change was worse o…

> MCAS was there to satisfy the type rating. MCAS is not anti-stall. MCAS's only observable intervention is to push the nose down to prevent stall, which means it is by definition anti-stall. Boeing says MCAS is an acronym for "Maneuvering Characteristics Augmentation System", but a better name for MCAS is "Machine Controlled Anti Stall". https://en.wikipedia.org/wiki/Maneuvering_Characteristics_Au...

While the effect of pushing the nose down is an all-too observable effect, that its purpose is stall prevention is not directly observable.

According to this article[1], the intended purpose was to restore the back-force needed to put the airplane in a stall, as the effect of the new engines was to make the control feel lighter at high AofA. The article also discusses the certification requirements with regard to acceptable handling characteristics.

FWIW, Boeing CEO Dennis Muilenburg is quoted in [2] as saying that "When you take a look at the original design of the MCAS system. I think in some cases, in the media, it has been reported or described as an anti-stall system, which it is not. It's a system that's designed to provide handling qualities for the pilot that meet pilot preferences.

"We want the airplane to behave in the air similar to the previous generation of 737s. That's the preferred pilot feel for the airplane, and MCAS is designed to provide those kinds of handling qualities at a high angle of attack."

Of course, the elephant in the room not being mentioned here is whether Boeing's primary motive for replicating the handling characteristics of earlier versions of 737s was an overriding concern with avoiding pilot training.

[1] https://leehamnews.com/2019/02/15/bjorns-corner-pitch-stabil...

[2] https://www.businessinsider.com/boeings-ceo-on-why-737-max-p...

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#178

Post by Aeolun »

erichocean wrote: post #149
dd36 wrote: post #6

Earlier quoted context omitted.

Gotta love deregulation. How many institutions are left? Any? CFPB, EPA, HUD, Interior are all run by people that don’t believe in their missions. It’s all about undermining from inside. Who protects the public when private rights of collective action are forbidden by arbitration agreements and the government has been captured by private interests?

> Gotta love deregulation. I dunno, I see it as the opposite: regulation (apparently) made it impossible to just train pilots on this one new feature, instead requiring a full recertification of both the airframe and the pilots, which is incredibly expensive and unnecessary relative to what was actually required to save lives. So one way of looking at is is: regulation caused perverse incentives that ultimately got p…

That’s such a roundabout way of thinking that I’m not sure whether you believe it yourself.

You’re basically saying that because shitty people don’t want to follow safety regulations we shouldn’t have them.

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#179

Post by rasz »

cjbprime wrote: post #154
cyberferret wrote: post #140

Wait, what? Reading this is turns out that flipping both switches on the centre panel not only deactivates MCAS, but also deactivates the thumb switch on the control wheel that the pilots routinely use to change the elevator trim. So, MCAS trims the plan to a dangerous attitude, then when pilots follow Boeing's SOP to disable, they lose the ability to re-trim the way they have done it a million times before? I can se…

Yes, exactly. The MAX "stab trim cutout" simply disabled the trim motor altogether. Everything you describe appears to have happened in the Ethiopian flight report. A 737 pilot also tried to run the same flight in simulator and had his arms wrapped around the control column trying to hold level while the copilot failed to move the trim wheel.

>737 pilot also tried to run the same flight in simulator

https://news.ycombinator.com/item?id=19627660#19627755 That video was removed :(

Re: Boeing altered key switches in 737 MAX cockpit limiting ability to shut off MCAS

#180

Post by TomVDB »

erichocean wrote: post #149
dd36 wrote: post #6

Earlier quoted context omitted.

Gotta love deregulation. How many institutions are left? Any? CFPB, EPA, HUD, Interior are all run by people that don’t believe in their missions. It’s all about undermining from inside. Who protects the public when private rights of collective action are forbidden by arbitration agreements and the government has been captured by private interests?

> Gotta love deregulation. I dunno, I see it as the opposite: regulation (apparently) made it impossible to just train pilots on this one new feature, instead requiring a full recertification of both the airframe and the pilots, which is incredibly expensive and unnecessary relative to what was actually required to save lives. So one way of looking at is is: regulation caused perverse incentives that ultimately got p…

A different way to look at this is: does this particular perverse incentive justify reduced regulation so that it can’t happen anymore.

Even if your assessment is valid, you’d likely be throwing away the baby with the bath water if you’d cut regulation to avoid it.

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