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Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

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Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#111

Post by Aromasin »

jordache wrote: post #109
crocal wrote: post #61

I am a designer and implementor of vital speed and distance measurement systems, with triply modular redundancy, used in mass transit application. I cannot even imagine what the designers of this thing are going through now. It must be terrible. To make it worse, it's a confusing topic. There are two pillars to the design of such system. 1. Faulty sensor must be detected with a very high probability. The typical way…

>I cannot even imagine what the designers of this thing are going through now. It must be terrible. Their poor decisions led to this. Single sensor as input to autopilot to augment the nose!?

The turn-over of employees in aerospace is often quite quick. It's very likely that most of the people that designed this system are long gone, and the current design team are the ones picking up the pieces.

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#112

Post by havkom »

I have no idea of the facts in this case, but based on how organizations function in general, one possibility is that the redundancy issues of MCAS were raised internally by some engineers without result.

In that case, the engineers were probably not thanked internally back then and are probably not thanked now either.

If their potential concerns would had led to changes on the MCAS design they would probably not have been thanked either, but rather seen as the people who unnecessarily made the project more expensive or less profitable.

In conclusion, people who avert or try to avert risk are seldom proportionally thanked in organizations in general.

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#113

Post by Cacti »

crocal wrote: post #61

I am a designer and implementor of vital speed and distance measurement systems, with triply modular redundancy, used in mass transit application. I cannot even imagine what the designers of this thing are going through now. It must be terrible. To make it worse, it's a confusing topic. There are two pillars to the design of such system. 1. Faulty sensor must be detected with a very high probability. The typical way…

My understanding is that the recovery scenario wasn’t supposed to be complicated at all, because in the event of a MCAS failure, it would always manifest as a runaway trim scenario, and that pilots are trained heavily on recognizing as correcting for that scenario, and that by following the standard runaway trim solution/checklist/process that this would necessarily involve disabling MCAS whether the pilots were aware of it or not. So the question is, did they, and if so did this fail, and if not, why didn’t they? Is this actually a direct problem with MCAS or is it closer to an issue of basic pilot training that only happened to involve MCAS? I suspect as the investigations unfold that our understanding of the accidents is only going to get more complex and nuanced.

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#114

Post by gameswithgo »

FabHK wrote: post #102

The crux of the matter: > if the group had built the MCAS in a way that would depend on two sensors, and would shut the system off if one fails, he thinks the company would have needed to install an alert in the cockpit to make the pilots aware that the safety system was off. > And if that happens, Ludtke said, the pilots would potentially need training on the new alert and the underlying system. That could mean simu…

even before that: the plane is a bad design because making a new plane that works properly with the bigger engines was also off the table. so hundreds of people die.

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#115

Post by jordache »

Aromasin wrote: post #111
jordache wrote: post #109

Earlier quoted context omitted.

>I cannot even imagine what the designers of this thing are going through now. It must be terrible. Their poor decisions led to this. Single sensor as input to autopilot to augment the nose!?

The turn-over of employees in aerospace is often quite quick. It's very likely that most of the people that designed this system are long gone, and the current design team are the ones picking up the pieces.

Then they shouldn't have any personal guilt..

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#116

Post by carlmr »

magduf wrote: post #108
carlmr wrote: post #100

Earlier quoted context omitted.

Which is also the correct thing to do. Despite our president and some NYTimes columnists being scared of automation (apparently they only agree when they're wrong), automation has saved so many lives that a failure like this doesn't affect the big picture. Yes, mistakes were made, yes, we should find ways to avoid this happening in the future, no, automation isn't the enemy. Without automation in flying at the curren…

Automation is definitely not the enemy. However, automation that is designed in a criminally negligent manner is. People who create such designs should be put in prison, and we should not be using products from them ever again.

Have fun using any product. If your company gets big enough the probability that one of its products was faulty because of negligence slowly approaches 100%.

Any big company has a scandal, learns from it, the people that learned the lesson leave at some point, a new generation of employees makes a similar mistake again, wash rinse, repeat.

You probably can't fly any airplanes if you will not use any airplanes from a company that had a scandal like this.

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#117

Post by baddox »

jordache wrote: post #115
Aromasin wrote: post #111

Earlier quoted context omitted.

The turn-over of employees in aerospace is often quite quick. It's very likely that most of the people that designed this system are long gone, and the current design team are the ones picking up the pieces.

Then they shouldn't have any personal guilt..

Guilt isn’t the only emotion that can be described as terrible.

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#118

Post by sixothree »

crocal wrote: post #61

I am a designer and implementor of vital speed and distance measurement systems, with triply modular redundancy, used in mass transit application. I cannot even imagine what the designers of this thing are going through now. It must be terrible. To make it worse, it's a confusing topic. There are two pillars to the design of such system. 1. Faulty sensor must be detected with a very high probability. The typical way…

Are AOA sensors really so prone to failure that they caused the downing of two airplanes?

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#119

Post by iSnow »

golergka wrote: post #95
dsego wrote: post #92

Earlier quoted context omitted.

Didn't they "vote with their wallets"?

They certainly voted with their wallets for a plane that doesn't require additional training. But they sure as hell did not vote with their wallets for a plane that does that on expense of crashing. And, to reiterate my point, I think that managers who pushed for trade-offs between different objectives did not push for this particular trade-off either.

Well, that's the law of unintended consequences. Customers wanted so not pay for retraining, Boeing wanted to get to the market faster and not wait for re-certification, managers wanted a physical problem fixed in software - and in the end the envelope got pushed too far.

I am sure the company operating the Titanic didn't exactly strive to have a shipwreck either.

Re: Lack of redundancies on Boeing 737 MAX baffles some involved in developing it

#120

Post by ncallaway »

Cacti wrote: post #113
crocal wrote: post #61

I am a designer and implementor of vital speed and distance measurement systems, with triply modular redundancy, used in mass transit application. I cannot even imagine what the designers of this thing are going through now. It must be terrible. To make it worse, it's a confusing topic. There are two pillars to the design of such system. 1. Faulty sensor must be detected with a very high probability. The typical way…

My understanding is that the recovery scenario wasn’t supposed to be complicated at all, because in the event of a MCAS failure, it would always manifest as a runaway trim scenario, and that pilots are trained heavily on recognizing as correcting for that scenario, and that by following the standard runaway trim solution/checklist/process that this would necessarily involve disabling MCAS whether the pilots were awar…

One significant problem as I understand it was the assumption that a failing MCAS would present as runaway stabilizer trim.

When, in actuality, it may not have looked much like runaway stabilizer trim to the pilots.

My understanding is in a runaway stabilizer trim situation the trim wheel (a medium sized wheel near the pilot and co-pilots knees) spins continuously and makes a loud clacking noise as part of the spinning.

This makes runaway stabilizer trim easy to identify. The wheel is spinning (for no identifiable reason) and making noise.

The MCAS failure, however applies trim discretely with intervals of 10-20s. This means it might be very hard to spot the adjustments to the trim wheel if you glance down briefly.

A pilot might notice the control column is heavy, glance down to see if it's runaway trim see the wheel not moving, rule out that scenario and move on to other diagnostic steps.

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