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Boeing MAX production cut signals long grounding

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Re: Boeing MAX production cut signals long grounding

#141

Post by ulfw »

cryptonector wrote: post #138
DuskStar wrote: post #102

Earlier quoted context omitted.

What about it isn't fixable? Redundant (and thus more reliable) AOA sensors + a less aggressive MCAS system that at maximum displacement can't override the yoke would be more than enough of a fix for me.

No need to make MCAS less aggressive. Training + an alarm should be sufficient. Even now, with no other changes at all, training might well be sufficient, though I'd much rather they make the system more robust and add an alarm.

No training in the world will help if this system malfunctions and puts the nose down at 1000ft already. You can't react fast enough to not hit the ground.

Also I don't want to fly in a plane where 'trained' pilots have to fearfully watched every feet they climb to quickly overturn a system that malfunctions.

Re: Boeing MAX production cut signals long grounding

#142

Post by darkpuma »

tropo wrote: post #131
darkpuma wrote: post #48

Earlier quoted context omitted.

You can't compensate because you don't know which one is wrong. However you can make MCAS inactive whenever the two sensors are disagreeing with each other.

A good rule would be to keep MCAS active, choosing to use the sensor that produces the less-extreme adjustment.

Eh, that kind of makes a certain amount of sense, but I don't think that's quite right. Determining which of the two sensors is less-extreme supposes knowledge about the airframe's current state. If he aircraft is currently in a very high angle of attack low speed stall, then the sensor that says everything is A-Okay is the extreme sensor.

I understand that's not what you mean, that the sensor indicating a situation closes to nominal flight should be chosen, but I think the sticky part is that MCAS isn't a system meant for normal flight conditions. MCAS is only supposed to be active when the aircraft is in an extreme scenario. So in fact if the sensor with "less-extreme adjustment" is preferred, in a way that actually means the system functions as I suggested: MCAS is disabled if the sensors disagree. But not quite. In your scheme if both the sensors are extreme but disagree, MCAS would be active to the lesser extent. But in my scheme, if both sensors are extreme but disagree, MCAS would be totally inactive (while leaving the pilot with electronic stabilizer trim control of course, allowing the pilot to manually do anything MCAS would be capable of doing.)

Re: Boeing MAX production cut signals long grounding

#143

Post by matt-attack »

thechao wrote: post #14
tibbydudeza wrote: post #9

Like the Toyota unintended acceleration issue we need third parties to look at the flight control software and engineering decisions taken for the MAX line and give a an independent report. Certainly not the FAA who delegated their oversight to Boeing. 346 people died because of their ineptitude.

Toyota never had an “unintended acceleration issue”—that was purely human error. A Toyota engine can’t overpower its brakes, unless there was gross negligence in the care of the brakes, i.e., they were totally inoperative. Just to make sure we’re clear on the braking thing: if you were to accelerate a Toyota sedan (any of them) to 70mph, then stomp on the brakes while holding the accelerator to the floor, the car wil…

I agree with your first statement that it's clearly human error but I disagree with the argument about burn outs. Static friction is an entirely different mechanism than kinetic friction. The force needed to stop the car in your first scenario is kinetic friction. Burn outs work by static friction. In general, static friction is the higher of the two.

Re: Boeing MAX production cut signals long grounding

#144

Post by matt-attack »

Zak wrote: post #122
iforgotpassword wrote: post #80

Earlier quoted context omitted.

This doesn't mention the horrible spaghetti code NASA found when reviewing the code. 250k lines of C with thousands of global variables. It leaves a pretty bad taste. Then again, I still wouldn't be surprised if most people were just too perplexed if their car suddenly accelerated like crazy and not stay calm and hit the brakes as hard as possible right away. It might take you a second or two to get what's going on,…

I can't speak to what most people would do, but I've experienced unintended acceleration before. The throttle stuck all the way open while I was driving a friend's car because he routed the throttle cable improperly after installing a larger carburetor for more power. I had intended to give it full throttle, but only briefly. I stood on the brakes and didn't let up. He reached over and shut off the key, which locked…

Doesn't the steering column only lock when you remove the key?

Re: Boeing MAX production cut signals long grounding

#145

Post by selimthegrim »

bilbo0s wrote: post #78
tus87 wrote: post #5

I wonder how high the scandal goes. I mean does the CEO have to sign off on design decisions like the engine misplacement on the MAX?

I'm pretty familiar with how all this works on the FDA side with medical devices/software. If it's the same general setup as on the medical side with the FDA, then it's a virtual certainty that liability will fall with some compliance and QA types, as well as any engineers or engineering managers who signed the relevant documents. Those signatures are all legally binding, and represent to everyone up the chain that t…

Good luck with the medical software industry - I was told things like “HIPAA audits never ask about hashing passwords so why should we care”

Re: Boeing MAX production cut signals long grounding

#146

Post by matt-attack »

Obi_Juan_Kenobi wrote: post #116
HarryHirsch wrote: post #96

Earlier quoted context omitted.

MCAS trimmed it so much that the pilots were unable to bring it back manually. Not only that, MCAS controlled an electric motor which turned the trim wheel and which could apply more torque than a human turning it manually. The only way to disable MCAS was to cut power to that motor. MCAS pointed the aircraft at the ground, and it was impossible to trim the aircraft to achieve level flight again. Mind, MCAS was suppo…

The electric trim adjustment is obviously going to be more powerful, that's just the reality of large planes. That's not the issue. The issue from the Ethiopian crash was that, in the extreme trim angle, there was simply too much force on the screw to turn manually. This condition is trained for, and the solution is to let the plan angle down to relieve the aerodynamic pressure on the control surface. That gives you…

Are you suggesting with the auto-trim disabled, the two pilots working together, with those handles extended on the trim wheel, were not strong enough to crank the trim wheel?

Re: Boeing MAX production cut signals long grounding

#147

Post by Zak »

matt-attack wrote: post #144
Zak wrote: post #122

Earlier quoted context omitted.

I can't speak to what most people would do, but I've experienced unintended acceleration before. The throttle stuck all the way open while I was driving a friend's car because he routed the throttle cable improperly after installing a larger carburetor for more power. I had intended to give it full throttle, but only briefly. I stood on the brakes and didn't let up. He reached over and shut off the key, which locked…

Doesn't the steering column only lock when you remove the key?

No, and I haven't driven a car with that behavior. Most US market cars have a sequence of lock, off, accessory power, on, start as the key is turned farther clockwise. Some cars require manipulation of a lever near the key to reach the lock position.

Very new cars with an entirely radio-based "key" might behave something like that.

Re: Boeing MAX production cut signals long grounding

#148

Post by kazinator »

diminoten wrote: post #104
lisper wrote: post #100

Earlier quoted context omitted.

Then you don't understand irony. Which is itself ironic. I was using the word in this sense: "Irony: a literary technique, originally used in Greek tragedy, by which the full significance of a character's words or actions are clear to the audience or reader although unknown to the character."

This isn't a story, and I am not a character. If that's what you were using it like, you are wrong. It'd make at least some sense if you incorrectly meant "irony" in the sense that fucking with the FAA, which I said was bad, is how the MAX was made so poorly. Your fake choice of definition is even worse than what you actually meant.

It is possible to see irony in real world statements, actions and situations; "irony" is not strictly the name of several literary or dramatic devices.

Re: Boeing MAX production cut signals long grounding

#149

Post by mrpippy »

fanf2 wrote: post #126
mrpippy wrote: post #44

Earlier quoted context omitted.

No 737 has 3 AoA vanes, and it’s extremely unlikely they’ll ever change the design to accommodate that. Every MAX will have an indicator to show if they disagree though.

The AOA disagree indicator was an optional extra that was missing on the planes that crashed - https://arstechnica.com/information-technology/2019/04/boein...

Correct, and the AoA disagree indicator will be added to every plane (for free) as part of the MCAS software fix.

Re: Boeing MAX production cut signals long grounding

#150

Post by fulafel »

Someone1234 wrote: post #114
Innominate wrote: post #105

Earlier quoted context omitted.

I would be perfectly comfortable flying on the 737 Max right now even without the software fixes.

That's an irrational position. After the Ethiopian Airlines initial report was released pilots were discussing refusing to fly them even for ferry flights (i.e. no passengers). The Ethiopian airlines crew followed Boeing's post-Lion Air safety bulletin and still crashed. There's no safe way to operate a 737 Max in its current state. The hypothetical recovery techniques (e.g. point nose down to release pressure on the…

Flying at all, given currently unfolding climate catastrophe, does reflect tolerance (or even disregard) for putting life at risk. Actually this change in the risk appetite of the average future air travelers might have impact on how safety is emphasized in the future.
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