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American Airlines Is Quietly Bringing Back the 737Max

zdnet.com

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Re: American Airlines Is Quietly Bringing Back the 737Max

#161

Post by getpost »

stouset wrote: post #157
getpost wrote: post #114

Earlier quoted context omitted.

The advantages of fly-by-wire are too good to pass up, so that leaves the question of how to design an FBW system. A high school teacher of mine in the 1970s predicted an accident like AF447. He framed it this way: the 'American' approach is to implement FBW to always do what the pilot inputs indicate, whereas the 'French' approach is to do the right thing, and override the pilot if the FBW 'knows' better. That's an…

None of this is relevant to the actual issue raised by the GP: the yokes of the pilot and co-pilot are not mechanically linked. They can be mechanically linked even with a FBW system. And personally, as someone with a bit of flying experience myself, I can't comprehend why you'd want them to not be mechanically linked. The opportunity for confusion with conflicting inputs is too damn high.

Mechanically linking is heavier than fbw/electrical/fiber optic linking, and what's the point if there's no mechanical linkage to the control surfaces?

With the fbw system, the software makes the choice on how to interpret the control movement, use one or both? If one, which one?

EDIT: Maybe you mean that a mechanical linkage would provide a feedback mechanism, so that one pilot would know if the other pilot was attempting an input? I don't know if there's force feedback on Airbus flight controls.

Re: American Airlines Is Quietly Bringing Back the 737Max

#162

Post by acqq »

Obi_Juan_Kenobi wrote: post #123
wycy wrote: post #67

I still don't think I'd trust it. While it's probably true that they fixed the software to never again produce this kind of error, I don't like the idea of software being used to correct the fundamental physics that the airframe is dynamically unstable. While the software probably does a good job of correcting it under a wide range of normal operating conditions, can it deal with evolving or abnormal operating condit…

737MAX is not nor never has been dynamically/aerodynamically unstable. Full stop. No airliner is permitted to be unstable by FAA regulations. At no point in the flight envelope will the aircraft pitch up into a stall without pitch-up inputs, thus it is not unstable. MCAS was used to augment flight stick characteristics, namely to simulate a linear relationship between flight-stick input force and pitch-up/AoA. This w…

Wait, wasn't MCAS used to fix two completely different flying issues, and weren't the changes introduced in the MCAS software twice, for two different points in the flight? Wasn't at least one crash caused by MCAS activation in the phase of the flight that was not even described in most of MCAS explanations initially (which reflected the decision behind the initial introduction of MCAS, not the later modifications)?

Therefore I believe the interpretation that MCAS "just augments" is too simplified from what it really was supposed to do. And the current "fixes" as they are implemented (still as to keep the "water not wet" there) could still leave plane as not behaving as it should, neither with MCAS active, nor when it is not active when it was supposed to be.

Re: American Airlines Is Quietly Bringing Back the 737Max

#163

Post by throwaheyy »

addicted wrote: post #37
tuna-piano wrote: post #12

737Max is certainly tainted now. But will that last forever? And do non-HN-aviation-geek consumers really care enough to check the model of the plane they'll be flying on, let alone make a flight decision based on the model? Certainly another crash could be devastating to the model. But was the 737Max a poorly designed death trap rushed to production or a super safe airplane with a single fatal flaw? Time will tell..…

In my experience the non aviation geeks are also worried about 737 Max’s. That’s validated by the fact that the involved companies are referring to it as the 737-8 instead, which will not fool anyone who knows anything about aviation and is geared entirely towards ordinary people.

Referring to it as the 737-8 is consistent with their current branding lineup. See other numerous examples 747-8, 787-9 or 777-9.

Similarly the 737-800 is widely just referred to as the 737-800 and not the 737 Next Generation 800.

Re: American Airlines Is Quietly Bringing Back the 737Max

#164

Post by schoolornot »

ravi-delia wrote: post #155
ProAm wrote: post #146

Earlier quoted context omitted.

> it's extremely unlikely that you'll die flying It's usually the not-flying that kills you

Given airplane safety statistics, you actually probably are more likely to die flying than not flying as long as you're in a plane.

What about the statistic of dying while flying on a Max?

Re: American Airlines Is Quietly Bringing Back the 737Max

#165

Post by stouset »

getpost wrote: post #161
stouset wrote: post #157

Earlier quoted context omitted.

None of this is relevant to the actual issue raised by the GP: the yokes of the pilot and co-pilot are not mechanically linked. They can be mechanically linked even with a FBW system. And personally, as someone with a bit of flying experience myself, I can't comprehend why you'd want them to not be mechanically linked. The opportunity for confusion with conflicting inputs is too damn high.

Mechanically linking is heavier than fbw/electrical/fiber optic linking, and what's the point if there's no mechanical linkage to the control surfaces? With the fbw system, the software makes the choice on how to interpret the control movement, use one or both? If one, which one? EDIT: Maybe you mean that a mechanical linkage would provide a feedback mechanism, so that one pilot would know if the other pilot was atte…

> what's the point if there's no mechanical linkage to the control surfaces?

In this case, the pilot would have realized the junior copilot was issuing control inputs and (likely) prevented a plane from crashing, saving the lives of all aboard.

Seems like a pretty decent point to me.

> EDIT: Maybe you mean that a mechanical linkage would provide a feedback mechanism, so that one pilot would know if the other pilot was attempting an input? I don't know if there's force feedback on Airbus flight controls.

Yes, that's what I meant. And no, there isn't. At least, not one that would indicate conflicting inputs from the other pilot.

Re: American Airlines Is Quietly Bringing Back the 737Max

#166

Post by js2 »

ravi-delia wrote: post #155
ProAm wrote: post #146

Earlier quoted context omitted.

> it's extremely unlikely that you'll die flying It's usually the not-flying that kills you

Given airplane safety statistics, you actually probably are more likely to die flying than not flying as long as you're in a plane.

> you actually probably are more likely to die flying than not flying as long as you're in a plane

You're more likely to die from natural causes on a plane than from the plane crashing.

Some quick googling:

"287 fatalities on commercial aircraft in 2019." [1]

"Deaths on board are far rarer: one for every 7.74 million passengers." [2]

4543 million passengers globally in 2019. [3]

4543 / 7.74 = 516.

516 > 287. And 2019 had relatively high deaths from crashes (down from 561 in 2018, but higher than the 59 in 2017.)

(Of course, natural cause deaths depend upon your demographic. Planes don't care who is on them when they crash.)

[1] https://www.forbes.com/sites/michaelgoldstein/2020/01/02/avi...

[2] https://www.nytimes.com/2019/10/18/well/live/death-airplane-...

[3] https://www.statista.com/statistics/564717/airline-industry-...

Re: American Airlines Is Quietly Bringing Back the 737Max

#167

Post by gnu8 »

ravi-delia wrote: post #155
ProAm wrote: post #146

Earlier quoted context omitted.

> it's extremely unlikely that you'll die flying It's usually the not-flying that kills you

Given airplane safety statistics, you actually probably are more likely to die flying than not flying as long as you're in a plane.

I guess it depends on exactly what point we consider the state of flying to have ended during a crash. The second the plane first makes contact with the ground, or after all of the fragments stop moving?

Re: American Airlines Is Quietly Bringing Back the 737Max

#168

Post by salawat »

Obi_Juan_Kenobi wrote: post #123
wycy wrote: post #67

I still don't think I'd trust it. While it's probably true that they fixed the software to never again produce this kind of error, I don't like the idea of software being used to correct the fundamental physics that the airframe is dynamically unstable. While the software probably does a good job of correcting it under a wide range of normal operating conditions, can it deal with evolving or abnormal operating condit…

737MAX is not nor never has been dynamically/aerodynamically unstable. Full stop. No airliner is permitted to be unstable by FAA regulations. At no point in the flight envelope will the aircraft pitch up into a stall without pitch-up inputs, thus it is not unstable. MCAS was used to augment flight stick characteristics, namely to simulate a linear relationship between flight-stick input force and pitch-up/AoA. This w…

>737MAX is not nor never has been dynamically/aerodynamically unstable. Full stop.

Correct in the jargonic sense. Incorrect in the colloquial. MCAS was necessary because the MAX was not compliant with Stick force response curves in high AoA flight regimes, and would experience a reversal in the pressures required to bring the plane up to a stall.

So yes, it was not aerodynamically unstable, but in the layman sense there is an instability or undesired quirk being compensated for.

I know we're all pedants here, but lets be productively pedantic.

Re: American Airlines Is Quietly Bringing Back the 737Max

#169

Post by Schiendelman »

aphextron wrote: post #56
Schiendelman wrote: post #44

Earlier quoted context omitted.

It’s not clear that’s true. Flying doesn’t appear to be causing covid to spread.

>It’s not clear that’s true. Flying doesn’t appear to be causing covid to spread. Come on now. Just because we don't have peer reviewed scientific studies confirming the fact doesn't mean common sense can't apply. You're sitting in an enclosed terminal with thousands of other people from all over the world who may or may not even be masked, waiting in multiple lines with no social distancing, and touching an endless…

I understand why common sense wants you to make that last statement, but we would be hearing that in the news. So far, I haven't run across stories asserting spread in airports.

Re: American Airlines Is Quietly Bringing Back the 737Max

#170

Post by AniseAbyss »

NikolaeVarius wrote: post #130
knaq wrote: post #115

Earlier quoted context omitted.

It sure looks defective to me: It was controlled more by pressure than movement, using joysticks instead of the traditional huge yoke. When one person was screwing up, the other could not observe this. On a Boeing, each person would feel the other person's force because the controls are physically linked. The stall warning was designed for mild stalls, not severe stalls, and would turn off if the stall was really bad…

Notice how 5/6 reasons the accident report contains are "crew screwed up"

Because humans screw up all the time. They are the weakest link. You can have the best damn plane and it only takes one guy or gal to drive it into the ground.
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