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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

#201

Post by simion314 »

manigandham wrote: post #80
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…

There's no fundamental design flaw, the aircraft is sound. The problem came from using software systems to artificially make the plane behave like older designs to avoid entirely new training and certifications. Even that would've been acceptable and similar systems are already in use in other planes but it was the inadequate info, redundancy, warnings and controls to disable the system that created the problem. It's…

>There's no fundamental design flaw, the aircraft is sound.

You can claim this because now all the FAA approvals for this planes, all tests need to be redone by somebody that we can trust. Sure they but larger engines, did they improved the supports, the bolts ,FAA "checked" this updates but can you trust them? the idea that MCAS is the only subsystem that must be fixed and checked is flawed, everything needs to be tested.

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

#202

Post by __m »

Xixi wrote: post #176
CydeWeys wrote: post #102

Earlier quoted context omitted.

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.

Wouldn’t they eventually all freeze at roughly the same position when the AoA doesn’t change for a while? Can’t they be heated?

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

#203

Post by rurban »

__m wrote: post #202
Xixi wrote: post #176

Earlier quoted context omitted.

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.

Wouldn’t they eventually all freeze at roughly the same position when the AoA doesn’t change for a while? Can’t they be heated?

They are heated now, after the Air France loss. This incident was also the reason for the MCAS system in the first hand: "Don't trust the pilot, regulate it into safety by your own".

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

#204

Post by manigandham »

JudgeWapner wrote: post #111
jhayward wrote: post #87

Earlier quoted context omitted.

> The engines are mounted incorrectly, so much so that Boeing believed pilots need the assistance of MCAS on take-off now. This overstates the issue. The engine mounting changes the flight characteristics enough that the MAX 8 needs to be flown differently in certain corners of the flight envelope. The MCAS was added to avoid having to re-train pilots or trigger a new type certification. The engine mounting certainly…

> The engine mounting certainly does not make the plane unsafe. I don't think this is a very...'precise' statement. what is "safe" in the context of aviation? If you had no MCAS, then this plane has a very bad propensity to stall . I hope we can both agree that's an unsafe airplane. You can't just say "don't do that [pull up too much] and then you're fine". The aircraft "wants" to pitch up too high and stall, which p…

The aircraft flies fine. MCAS is a stability control system that applies in certain cases (full power, high angle of attack) where the nose pitches up. It may lead to a stall but that's not what it's correcting for and it doesn't just happen during level flight. If the MCAS system was disabled then pilots handle it manually. Trim is not an exotic concept and just takes training and understanding of the operating characteristics.

Airliners are very safe. They're not in dynamic stability like jet fighters and don't need active measures at all times to stay airborne. Having sensors and systems that coordinate to keep the aircraft flying optimally to remove pilot load and increase safety margins is a good thing and has been in use for decades.

The problem here was a badly implemented system without redundancies and without enough training so that pilots were actually aware of the flight profile and MCAS. Also aircraft do not have millions of flight hours, they wouldn't reach a million even if they flew 24 hours a day for 100 years.

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

#205

Post by michaelmrose »

kuzehanka wrote: post #182
kortilla wrote: post #138

Earlier quoted context omitted.

No, it did not “have a bad propensity to stall”. That’s a very imprecise statement in the first place but if you take it to mean, it would try to stall during normal flight conditions, it’s definitely false. Airbus aircraft are “safe” despite the fact that dual conflicting pilot input is averaged without stick feedback (see the Airfrance flight from Brazil). If electronics being used to fly the aircraft upsets you, y…

So much ignorance and misinformation about this issue even on HN. The parent comment and entire thread is 100% correct. There is nothing inherently unstable or unsafe about the MAX 8. It has a pitch-up characteristic that's mild compared to some other commercial jets like the 757. The only reason MCAS was put on that plane was to allow the MAX 8 to share a type rating with the rest of the 737 family, to make it so th…

Nobody who isn't an engineer wants is terribly interested in the argument that a model of plane that has killed 2 planes full of people recently is in anyone's opinion safe.

Personally I won't fly on one in my lifetime.

I'll leave the analysis of why to others to figure out why I fly on other airplanes.

Incidentally I have seen pilots argue that the max is inherently unsafe on this forum which is probably why people are reiterating it.

What is your area of expertise and what is your opinion?

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

#206

Post by michaelmrose »

manigandham wrote: post #80
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…

There's no fundamental design flaw, the aircraft is sound. The problem came from using software systems to artificially make the plane behave like older designs to avoid entirely new training and certifications. Even that would've been acceptable and similar systems are already in use in other planes but it was the inadequate info, redundancy, warnings and controls to disable the system that created the problem. It's…

Citation needed

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

#207

Post by madarcho »

__m wrote: post #202
Xixi wrote: post #176

Earlier quoted context omitted.

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.

Wouldn’t they eventually all freeze at roughly the same position when the AoA doesn’t change for a while? Can’t they be heated?

They definitely are now. If you want to see what they look like, the channel AvE on YouTube tears one down (Search for BOLTR AoA) and discusses the mechanics. You can see what they suspect to be small cables for heating go up into the element.

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

#208

Post by manigandham »

simion314 wrote: post #201
manigandham wrote: post #80

Earlier quoted context omitted.

There's no fundamental design flaw, the aircraft is sound. The problem came from using software systems to artificially make the plane behave like older designs to avoid entirely new training and certifications. Even that would've been acceptable and similar systems are already in use in other planes but it was the inadequate info, redundancy, warnings and controls to disable the system that created the problem. It's…

>There's no fundamental design flaw, the aircraft is sound. You can claim this because now all the FAA approvals for this planes, all tests need to be redone by somebody that we can trust. Sure they but larger engines, did they improved the supports, the bolts ,FAA "checked" this updates but can you trust them? the idea that MCAS is the only subsystem that must be fixed and checked is flawed, everything needs to be t…

The fault here is complex and involves the architecture of the system, the sensors, and how the behavior mimicked the older designed which reduced the training required which meant pilots were not as aware of both the changed flight characteristics and the MCAS itself.

Sure the FAA definitely needs to be questioned as to how they let this through without enough redundancy and pilot awareness but the engines are not the problem and certainly not the supports and bolts. Those are things that are well-tested before it even gets to the FAA and having extreme paranoia about the industry doesn't help.

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

#209

Post by michaelmrose »

bushido wrote: post #112
skellera wrote: post #76

Earlier quoted context omitted.

Most people don’t even think about the plane they’re flying in. It will not be that big of an issue to continue using them unless some group actively tries to warn passengers about flying in those specific planes.

It seems like this is becoming a concern now - per: https://www.cnbc.com/2019/05/07/barclays-downgrades-boeing-s... The primary reason for the downgrade being: Barclays’ survey of airline passengers says many people will avoid the 737 Max “for an extended period” once the aircraft is flying again.

Wherein an extended period of time is effectively forever.

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

#210

Post by manigandham »

michaelmrose wrote: post #205
kuzehanka wrote: post #182

Earlier quoted context omitted.

So much ignorance and misinformation about this issue even on HN. The parent comment and entire thread is 100% correct. There is nothing inherently unstable or unsafe about the MAX 8. It has a pitch-up characteristic that's mild compared to some other commercial jets like the 757. The only reason MCAS was put on that plane was to allow the MAX 8 to share a type rating with the rest of the 737 family, to make it so th…

Nobody who isn't an engineer wants is terribly interested in the argument that a model of plane that has killed 2 planes full of people recently is in anyone's opinion safe. Personally I won't fly on one in my lifetime. I'll leave the analysis of why to others to figure out why I fly on other airplanes. Incidentally I have seen pilots argue that the max is inherently unsafe on this forum which is probably why people…

Actual engineers do care about the "why" since that's what matters. Otherwise don't bother flying on any aircraft since all models have crashed at some point.
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