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

seattletimes.com

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

#191

Post by ummonk »

cesarb wrote: post #125
mcsoft wrote: post #44

Earlier quoted context omitted.

They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff. And it was unstable because larger CFM engines could not fit under the wing anymore so they had to put it further forward and a bit up. This increased the pitch up moment when a full power is applied. Also, can't really see how the height of the fuselage above the ground affects fuel efficiency.

> They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff. Forgive me if I'm missing something, but isn't MCAS disabled while the flaps are extended, which is the case during takeoff and landing?

Yup. The real danger was during climb I believe. And it wasn’t unstable, just had a backwards feel at high angle of attacks which could lead to pilots inadvertently stalling it.

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

#192

Post by smadurange »

staunch wrote: post #68
blattimwind wrote: post #56

Earlier quoted context omitted.

> 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. A brand new design actually supporting the engines used would not have aerodynamic issues that place the airframe outside the limits set forth by regulations.

What regulations are you referring to? Yes, it's true that it would be have been free from this specific MCAS issue. But what other issues would a new design have had? It's impossible to know. It's also true that if Boeing had done a better job of implementing the MCAS design it would have been viewed as a triumph of software solving hardware problems. Air France 447 crashed in large part because the pilot flying was…

Airbus uses software to enhance safety. MCAS is trying to fix a very specific and a potentially dangerous issue while keeping it from the pilots. So, I'm not sure if there's a good analogy there.

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

#193

Post by v8engine »

jsjohnst wrote: post #75
peteradio wrote: post #60

Earlier quoted context omitted.

What was the reasoning?

The linked article says why, but to paraphrase, the training has always said to flip both switches. Previously the only time you’d need to flip the switches was due to an electric motor being stuck-on. It’s only with the MAX that there was an actual useful reason to flip one vs the other, but the training was always to flip both and Boeing decided to simplify it. My personal guess is that it was internally totally di…

Just to spare others from the search:

Before 2004, those Boeing technical employees who worked safety on behalf of the FAA were called “Designated Engineering Representatives,” or DERs. Though paid by Boeing, they were appointed by the FAA and reported directly to their technical counterparts at the FAA.

What changed since 2004 is that safety engineers, now called Authorized Representatives, are appointed by and report to Boeing managers.

The opaque bureaucratic name for this new structure — Organization Designation Authorization (ODA) — masks the significant change: Instead of having individual Boeing employees authorized as FAA reps, Boeing now has an entire organization within the company so authorized. The individual FAA Authorized Reps — Boeing engineers — report up the chain to their Boeing managers, not the FAA.

source: https://www.seattletimes.com/business/boeing-aerospace/engin... Interesting read.

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

#194

Post by cozzyd »

logjammin wrote: post #184
old-gregg wrote: post #65

Earlier quoted context omitted.

> The bugs will be addressed and they'll still fly. The engines are mounted incorrectly, so much so that Boeing believed pilots need the assistance of MCAS on take-off now. The bug isn't with its algorithms, rather the need for MCAS to begin with. They can't "address" it. That's why I'll be very careful not to ever book a flight on a 737 Max, probably easier to simply stick to Airbus-only airlines: Jetblue, Alaska/Vi…

Alaska was, before they bought Virgin, famously a Boeing-only airline! (And a 737-only airline at that!)

I was gonna say... How could a Seattle-based airline be all Airbus?

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

#195

Post by chaboud »

TomVDB wrote: post #168
bushido wrote: post #112

Earlier quoted context omitted.

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.

Here’s my thought experiment on that: if I booked a flight to my vacation destination and, at the last moment, I discovered that I’d be flying in a 737 MAX, would I cancel my trip or pay a considerable amount of moment to get all our tickets changed? I very likely would not. Would you? Would others? It’s one thing to answer a question of a pollster, it’s another to take concrete action.

For a year after it is reinstated, my answer will be "yes, I'm changing my flight". Doubly so if my wife and child are on the plane.

Why? Because I'd be so unbelievably pissed at myself if the plane nosed itself into the ground, at least for the time it took to impact.

I also vote with my money.

Simple answer? I won't be flying airlines that use the 737 Max. Stick to the NG or pick up some 320's. Between work and personal travel for our family, that's over $50k of gross revenue per year (we both travel a lot for work). Maybe nobody else cares? I'm betting there are more people like me and my wife.

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

#196

Post by cornellwright »

jussij wrote: post #157
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. From what I have read, the new aircraft design had a habit of raising it's nose when engine power was applied, which put the plane into a situation where it might stall. The MCAS was added to automatically detect this behaviour and stop the nose lifting. So basically, without the MCAS, under certain scenarios the plane had a tendency to want to stall. That…

Lots of airplanes do weird undesirable things at certain points in the flight envelope. Airplane design is all about tradeoffs. There is nothing fundamentally wrong with the aerodynamic design of the Max.

There are serious flaws with a safety system (MCAS) which was added to prevent the need for more training and a new type rating for pilots who are already rated to fly the 737. This needs to be fixed.

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

#197

Post by chaboud »

Aeolun wrote: post #167
bushido wrote: post #112

Earlier quoted context omitted.

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.

Yeah, they say that, but when they get their non-refundable ticket and see it is in an 737 MAX. How many do you think will sue their airline claiming a refund?

The airframe is listed at purchase. I won't be suing. I just won't be buying.

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

#198

Post by cm2187 »

hirowan wrote: post #98
cm2187 wrote: post #94

Earlier quoted context omitted.

A brand new design would probably introduce more serious flaws than an interation of a mature design, so I am not sure it would be safer. In term of public perception, it is a PR disaster but not unprecedented. The DC-10 went through a similar rocky start where passengers just wouldn't want to board it. But after the flaws were fixed it turned out to be quite reliable.

> A brand new design would probably introduce more serious flaws than an interation of a mature design As evidenced by the ever-crashing 787s and A350s.

I rather had the exploding engines of the A380 in mind, the flaming batteries of the B787, but we can also talk earlier B737 (rudder, rivets on early models), DC-10 (cargo door), C-5 (door lock), A340 (freezing pitot tubes) etc.

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

#199

Post by sjwright »

CydeWeys wrote: post #146
dmix wrote: post #143

Earlier quoted context omitted.

How hard would it be to add two more sensors to every plane? I'd imagine insanely expensive but this is clearly the ideal solution in addition to whatever patches they can do via software and existing hardware/controls in the whole plane.

These planes cost nearly $100M each; how can adding another AoA sensor the size of your hand be that much in the grand scheme of things? https://i.kinja-img.com/gawker-media/image/upload/t_original... Note that the 737 already has two such sensors, but only consults one at a time for MCAS, so there'd be a software change required in addition to adding a new sensor.

Surely they can predict the expected/likely value of an AoA sensor with all of the other telemetry available to an aircraft computer. Surely in combination with software fixes to ensure that both sensors are factored in, they could augment with that computed value to pick a sensor in the case of disagree.

If the needed telemetry is already exposed to MCAS, it could all be fixed in software.

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

#200

Post by elpatinante »

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…

That's not quite correct. When the aerodynamics of a plane was not designed to push forward the mounting of the engines, you have more reinforcement. That alone causes an uneven distribution for lift not accounted in the design itself. THIS is what causes the plane to nose up. But that doesn't mean stress is not put on the frame itself and mechanical parts that will be, on a daily basis, "abused" to the point of metal fatigue. You see, when it comes to aerodynamics, it's easy to test it on a simulator. And it seems boeing's 737 max passed with flying colors. Then, it had to fly. That's the moment when test pilots came to a conclusion that the design will not work. Boeing's solution was a software "fix" and it needed to relay on 1 sensor to pass certification.

So, what do you have? NO TRAINING on this airplane, a bugged software system, poor aerodynamics, poor design choice, stress on elevator, etc. The ethiopian airlines plane had such force that pilots were not able to manually turn the trim control wheel. Do you know how much force that plane had to have that the jack screw couldn't be operated manually? THAT is a severe design flaw. THAT is what is being investigated. Who is investigating Boeing? Boeing is investigating Boeing. Boeing on 5/7/19 admits it knew they had a severe problem but it can still be fixed. Who certified the fix? Boeing. But now the FAA is investigating that fix which was promised by April. Again, this is a severe design flaw with still many unknowns yet to be found.

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