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A comment on Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max.

Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by Invictus0 on Saturday March 23, 2019 @09:12PM (#19473423)
I can't really see any decision point where an engineer might have stood up and said "this plane isn't safe," like Allan McDonald did with the Challenger. The article tries to hang blame on the decision not to upgrade the cockpit info displays, but there was nothing wrong with the old display systems. It's still not clear if the plane is actually aerodynamically flawed or if the MCAS was simply programmed poorly. Even the business decision was fine; from the perspective of a non-technical executive, "add newer engines but change as little else as possible" seems like a pretty reasonable directive and not likely to cause safety issues. Engineers could have complained about the pace of work but I think it was made clear to them that they were fighting for their jobs: Boeing has had numerous 10,000+ workers layoffs in the past. With everything we know now, I can't see any criminal charges being filed in relation with this disaster.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by frostburg on Saturday March 23, 2019 @09:15PM (#19473437)
Not having three AoA sensors seems either insane or criminally negligent.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by arcticbull on Saturday March 23, 2019 @09:21PM (#19473470)
Yep, there’s going to be a lot of hand wringing, finger pointing and hot air expended over the next few years and this is basically it. Boeing had two options:

(1) 3 sensors plus majority voter.

(2) A mandatory AoA disagree indication plus some training on how to react to it.

They chose option (3): Neither. Frankly when I heard there were just two sensors and no disagree indication, my first thought was well that’s just as good as one sensor and hoping for the best, isn’t it? The “challenger moment” would have been after the meeting they decided on this.

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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by cjbprime on Saturday March 23, 2019 @11:57PM (#19474202)
It's more literally "just one sensor" than you say, I think. MCAS doesn't average or anything: it just picks one sensor at a time arbitrarily and uses it. (This will change in next month's software fix.)

(2) sounds like it could be airworthy, but I think Boeing might instead find that it has to add that third sensor. Airbus has three, and any rationale that Boeing only needs two because the disagreement consequences are not severe seems atop quicksand at this point.

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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by Animats on Saturday March 23, 2019 @11:06PM (#19473954)
That's what really amazes me. Especially since AoA vanes are known to be troublesome.[1] In most aircraft they just trigger the stall warning horn and stick shaker; they don't directly affect aircraft control.

[1] https://mooneyspace.com/topic/19801-stall-warningaoa-failure...

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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by cjbprime on Saturday March 23, 2019 @11:58PM (#19474204)
I think Airbus will disable the autopilot in case of AoA sensor failure, which is why it has three of them instead of two.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by D_Alex on Sunday March 24, 2019 @12:40AM (#19474357)
Option (4): input from other sensors (altitude, climb rate, gyroscope/artificial horizon, pilot actions etc) for a sense check...?
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by arcticbull on Sunday March 24, 2019 @01:21AM (#19474514)
My gut tells me aerospace errs on the side of simplicity and reproducibility. It could work, though ideally system errors wouldn’t interfere with other systems.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by 7952 on Sunday March 24, 2019 @07:12AM (#19475670)
And the engine stats should be a good source of data.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by 7952 on Sunday March 24, 2019 @07:09AM (#19475659)
It is worth pointing out that an AOA sensor should not be critical for normal flight. If a sensor is faulty then why not simply stop using angle of attack as a data point. It should still be perfectly possible to fly safely and using a configuration that will avoid a stall. Pilots should be able to fly on a minimum set of instruments.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by cmurf on Sunday March 24, 2019 @01:26AM (#19474537)
As a pilot myself, that doesn't strike me as disqualifying. The minor problem I have is that it has has no self-verification/disqualification mechanism; even in the face of having two sensors available! The far bigger problem I have is, the automation discounts pilot input as if it's the pilots who are wrong. That's obscene. And it strikes me as a violation of CRM.

I do not accept that pilots must have disabled auto trim in order to prove they are the more valid input source, compared to a single alpha vane sensor. That's perverse. Pilots have to flip switches to prove they are working correctly? Yet the sensors don't have to have self-verification/disqualification, or cross check with an available second sensor?

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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by Osiris on Saturday March 23, 2019 @09:51PM (#19473614)
They could have also used inputs from other systems as a sanity check such as altitude, air speed, pilot input, etc. I'm really surprised the software didn't take any other available data into consideration.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by function_seven on Saturday March 23, 2019 @10:18PM (#19473740)
The horizon indicator alone should serve as a check. If you (the computer) think the plane is about to stall, it makes sense to nose it down to compensate. Ok, cool. But if you think it's stalling, and you see that you're at a negative attitude, then it's much more likely that trimming the horizontal stab is a bad idea.

I'm sure there are other checks as well. Also not sure if I'm missing something with this armchair analysis.

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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by ozmaverick72 on Saturday March 23, 2019 @09:20PM (#19473467)
I'm with you on that. It also seems completely against the Boeing ethos of when the auto pilot is off you should be hand flying the plane and your control inputs dictate the movement of the flight surfaces. That has been a perceived difference in philosophy between Boeing and Airbus. MCAS sounds like a hastly thrown together work around and a disaster waiting to happen.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by Invictus0 on Saturday March 23, 2019 @09:43PM (#19473578)
Has it been established that the AoA sensor malfunctioned?
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by cjbprime on Saturday March 23, 2019 @10:19PM (#19473744)
I believe the Lion Air investigators have made public that there was a 20 degree differential between the two AoA sensors even when they were sitting on the runway before flight. (I don't have a source easily accessible.)
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by newacct77 on Sunday March 24, 2019 @12:00AM (#19474209)
That's almost like saying two compasses should agree while standing on the north pole. These sensors need airflow to operate and provide meaningful indication.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by cjbprime on Sunday March 24, 2019 @12:19AM (#19474286)
It was during taxi for takeoff: https://theaircurrent.com/aviation-safety/the-world-pulls-th...
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by inferiorhuman on Sunday March 24, 2019 @01:22AM (#19474519)
Sure, but they maintained their twenty degree difference for the duration of the flight. That's why the one stick shaker started going off shortly after rotation, why autopilot wouldn't engage, and why MCAS was going nuts.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by dgritsko on Sunday March 24, 2019 @12:45AM (#19474383)
Is that necessarily true? Based on this article (https://www.flyingmag.com/how-it-works-angle-attack-indicato...) it seems like they should be accurate regardless.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by pintxo on Sunday March 24, 2019 @05:25AM (#19475342)
Why should an AoA sensor require airflow? And if we are talking about airflow, we are talking about measuring pressur differentialsm right? How to do calculate an angle using a pressure differential?
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by danaliv on Sunday March 24, 2019 @05:48AM (#19475404)
It’s literally just a metal plate that rotates with the oncoming air.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by pintxo on Sunday March 24, 2019 @09:42AM (#19476282)
Ok, makes sense.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by crumpets on Saturday March 23, 2019 @09:54PM (#19473626)
Not if the engineers were assured the pilots would be trained to quickly recognize trim issues and flip off the MCAS when it started misbehaving.
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by frostburg on Saturday March 23, 2019 @10:38PM (#19473825)
No, it's still obvious fail-deadly insanity. Having to say that the pilots would need to quickly notice issue is even worse (have you seen how you disable the system? It's not a button that you push).

The point of the plane variant was to not perform any additional training, too.

Anyone saying that to the engineers should be considered a criminal. There is probably a whole incentive structure that lead to this and that should be upended completely.

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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by dboreham on Saturday March 23, 2019 @11:19PM (#19474013)
"Oh darn! The pesky flight control system decided to go into crash the plane mode again. Let me reset it before I take another sip of my latte".
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Re:Boeing Was ‘Go, Go, Go’ to Beat Airbus with the 737 Max by caprese on Sunday March 24, 2019 @12:05AM (#19474227)
Plane tilts down due to erroneous inputs.

Pilot solution:

A) turn off autopilot

B) learn how to play MCAS override, current high score 6 minutes.

Plane maker solution: Get rid of MCAS and deal with the fallout that will broadcast, and stop trying to ONLY blame pilots.

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