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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

#61

Post by hotsauceror »

techslave wrote: post #27
mcsoft wrote: post #20

It strikes me how a seemingly insignificant decision at the time - to position fuselage slightly higher above the ground - gave Airbus a strategic advantage 50 years later. It forced the competitor into a services of unexplainable and reckless decisions that break basic principles of reliable engineering. Which in turn led to a very visible disastrous business consequences: Boeing had to silently reduce 737 MAX produ…

basic principles? i think that’s a bit far. the plane isn’t inherently unstable is it? i thought it’s just the black box of MCAS that is the problem and MCAS is there to avoid a lengthy type certification. it’s completely explainable. and it wasn’t seemingly insignificant. it was for fuel efficiency. it was significant and they knew what they were doing.

Seems to me that redundancy in mission critical systems where failure means loss of several hundred lives is a basic engineering principle. MCAS apparently relied on a single AOA sensor's input. The system had no way to validate the data or handle a mismatch, and the only recourse was to light up an (optional) disagreement indicator - but still relied on just the one sensor to apply control forces.

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

#62

Post by jeremyjh »

CamperBob2 wrote: post #55
jeremyjh wrote: post #42

Earlier quoted context omitted.

When a culture becomes this defective, the top people need to end their careers in disgrace. This provides the necessary context, clearance and incentives for others to pick up the pieces and make substantial reforms.

Actually what it provides is the necessary context for fear-based decisionmaking, misallocation of resources, metastatic bureaucracy, R&D stagnation, and ultimately departure of talent. There is a reason why the aviation industry focuses on fixing the problem rather than the blame. A witch hunt makes everybody feel better in the short term but provides no guarantee of actual forward progress.

The problem here is corporate greed and willfully blind governance. It’s not a technical issue.

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

#63

Post by hotsauceror »

mcsoft wrote: post #44
techslave wrote: post #27

Earlier quoted context omitted.

basic principles? i think that’s a bit far. the plane isn’t inherently unstable is it? i thought it’s just the black box of MCAS that is the problem and MCAS is there to avoid a lengthy type certification. it’s completely explainable. and it wasn’t seemingly insignificant. it was for fuel efficiency. it was significant and they knew what they were doing.

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.

"Also, can't really see how the height of the fuselage above the ground affects fuel efficiency."

It doesn't. They wanted to use a larger, more fuel-efficient engine but the 737's ground clearance couldn't accomodate it. So they moved the engine forward.

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

#64

Post by joe_the_user »

erentz wrote: post #43
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…

> What is the endgame now for 737 MAX planes? The bugs will be addressed and they'll still fly. Airlines have no choice, there's a limited capacity in the world for airplane construction, several thousands of orders on the books for the 737 and 320 waiting to be filled. What can an airline do? They can cut back some orders but not all orders. > I'd honestly like to see the 737 MAX taken out of service and Boeing simp…

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 the answer would be: "Even now we're not willing to bite the bullet and pay all the expenses we were dodging before".

Searching, it seems Southwest already did something like this (after the first crash, in fact). The problem might be that if Boeing does this on their dime then Boeing would be essentially giving every one of their "bargain" customers the features of their "luxury" customers, which I would speculate might be a vastly expensive proposition especially if it sets precedent going forward.

https://theaircurrent.com/aviation-safety/southwest-airlines...

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

#65

Post by old-gregg »

erentz wrote: post #43
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…

> What is the endgame now for 737 MAX planes? The bugs will be addressed and they'll still fly. Airlines have no choice, there's a limited capacity in the world for airplane construction, several thousands of orders on the books for the 737 and 320 waiting to be filled. What can an airline do? They can cut back some orders but not all orders. > I'd honestly like to see the 737 MAX taken out of service and Boeing simp…

> 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/Virgin, etc.

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

#66

Post by davewasthere »

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.

Yeah, but who is going to want to fly in one again? Even working in aviation in the past and knowing that they've probably nailed the issue, I'd still be less than keen.

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

#67

Post by rdl »

old-gregg wrote: post #65
erentz wrote: post #43

Earlier quoted context omitted.

> What is the endgame now for 737 MAX planes? The bugs will be addressed and they'll still fly. Airlines have no choice, there's a limited capacity in the world for airplane construction, several thousands of orders on the books for the 737 and 320 waiting to be filled. What can an airline do? They can cut back some orders but not all orders. > I'd honestly like to see the 737 MAX taken out of service and Boeing simp…

> 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 is Boeing, Virgin is Airbus, Alaska/Virgin is primarily Boeing...

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

#68

Post by staunch »

blattimwind wrote: post #56
staunch wrote: post #47

Earlier quoted context omitted.

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…

> 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 incapable of handling the aircraft at cruise speeds without software assisting him. He thought the plane would stop him from doing something stupid but it didn't because the software failed in a somewhat similar way to the MCAS failures (sensor failure).

Airbus hasn't done anything to make their planes easier to fly at cruises speeds without software because software assisting pilots with complex flight characteristics is a fundamentally sound idea. The important thing is that the software actually works. Clearly the first version MCAS did not work reliably but there is no reason to believe that it couldn't work reliably.

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

#69

Post by addicted »

rootusrootus wrote: post #45
bumby wrote: post #29

Earlier quoted context omitted.

True, but this seems to sound like, "if we just hire the right people none of these safety procedures would be necessary". If we only had ethical people we wouldn't need laws. Its more important to focus on the processes rather than the individual people, especially because even great people can have off days.

My point was that we should figure out why one aircrew worked it out, and one did not. If we want to fix the process, we have to consider the humans. I get the impression from this whole debacle that one significant contributor to the accidents was that Boeing's idea of what the procedures should be and what pilots actually do is different enough to be catastrophic. Putting everything else aside for a moment, this ha…

It’s like seeing someone make a half court shot in basketball at the buzzer and wondering why other players don’t do the same. You could adjust the probability to it being a 3 pt shot, dunk, or free throw.

The failures in the Boeing 737 introduced a significant probability of unrecoverable failure. The fact that a few pilots managed to recover does not mean that the ones who didn’t recover did something wrong.

On the other hand, the fact that 2 crews with over decades of safely flying planes were unable to recover from the same plane indicates it had a lot to do with the issues in the plane.

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

#70

Post by Farradfahren »

skybrian wrote: post #49
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…

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.)

Thats a perfectly fine diesel-plane - we can rebuild it, we had the technology.
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