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“I worked at Boeing for about 1.5 years in the 2008-9 time period”

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Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#301

Post by pas »

mannykannot wrote: post #97
Scarblac wrote: post #75

Earlier quoted context omitted.

It's worse than having one sensor, the chance that one of two breaks is larger than that just a single one breaks. And by alternating you ensure that the broken sensor will be used.

A broken AofA sensor has other consequences, such as the differing pressure altitude and airspeed on the left and right panels, so I would guess that it is expected that the problem would be found and fixed after the flight it occurred on (though this did not happen in the Lion Air case.)

They replaced "something", but probably haven't confirmed that, and haven't coordinated with the incoming crew to watch out for that, etc.

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#302

Post by pas »

foldr wrote: post #206
salawat wrote: post #156

Earlier quoted context omitted.

Yes conceptually, no because of signage error. If you were in a position MCAS would have to kick in, you were at positive AoA, reduced thrust would impart a negative AoA moment.

> you were at positive AoA, reduced thrust would impart a negative AoA moment I don't think that is correct. I think you're still thinking of the angle of the plane with respect to the horizon, not the AoA. If reducing thrust reduced AoA, then you could recover from a stall by reducing thrust. In reality, the opposite is the case. The only way to recover from a stall by manipulating engine thrust is to increase it (t…

AFAIAK the procedure is to not increase thrust, quite the opposite (disable the autothrust thingie), get the nose below the "horizon" (which is of course wind dependent), gain airspeed, and then start to increase thrust (which will automatically start to up the nose a bit), then climb back to whatever altitude you should be at.

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#303

Post by pas »

magduf wrote: post #270
linuxftw wrote: post #117

Earlier quoted context omitted.

> 1. Use inputs from both AOA sensors, if they disagree by 5.5 degrees, disable MCAS This can only mean that MCAS is disabled even more frequently. This is a terrible idea. This is like RAID0. The failure mode will increase greatly in complexity. MCAS might cut in and out, the plane might behave erratically. What the need to do is add a damn switch for 'disable MCAS' and tell people how and when to use the damn thing…

No, they can't do that, because then they'd have to retrain the pilots, or maybe even have a different type rating, which would make them uncompetitive against the Airbus and Bombardier planes. Remember, profits are more important than passengers' lives.

> because then they'd have to retrain the pilots,

I think that ship has sailed already.

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#304

Post by pas »

garaetjjte wrote: post #133
spectramax wrote: post #2

Btw, the new "fix" for the MCAS has just been announced and discussed by a 40-year experienced pilot [1]. Turns out that while we shouldn't be doing armchair analysis and assuming the worst of the engineering, management and executive team; the software fix released appears to be rather elementary and MCAS should have been designed with these safety checks in the first place. Why it wasn't is a huge concern and we wo…

>Furthermore, electric trim with the yoke switch will override MCAS. Does that mean it didn't override MCAS before? Really?

The point was, that they "just" put that shadow system there which will perfectly encapsulate the 737MAX to match the old 737 "interface".

Now, they completely fucked that up. They did a so mindblowingly bad job, that anyone involved at the FAA who should have known about this should be in jail. Either for incompetence (negligence) or worse.

They designed a system that relied on one input, operated periodically, told no one, documented nowhere, made it too powerful, always on, and un-turn-off-able, and spent the rest of the day corrupting/pleasing the FAA, then made the AoA input mismatch light an upsell feature, and finally called it a day.

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#305

Post by pas »

morpheuskafka wrote: post #168
spectramax wrote: post #2

Btw, the new "fix" for the MCAS has just been announced and discussed by a 40-year experienced pilot [1]. Turns out that while we shouldn't be doing armchair analysis and assuming the worst of the engineering, management and executive team; the software fix released appears to be rather elementary and MCAS should have been designed with these safety checks in the first place. Why it wasn't is a huge concern and we wo…

I know very little about aircraft, but wouldn't making the MCAS less powerful increase the risk of a stall? How do we know that there would be a net decrease in crashes?

We know nothing about how many times MCAS got engaged, maybe Boeing does. Who knows.*

Furthermore, the problem seems to be that there is no explicit feedback about this from the pilots, because some of them did not even know about this. Consequently there was no widespread beta test in simulators, meaning there was not much data to base the fine tuning on.

* actually, since MCAS activates only when the plane is over the critical angle (according to the AoA sensor), and there are other warnings, probably those can be counted.

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#306

Post by foldr »

pas wrote: post #302
foldr wrote: post #206

Earlier quoted context omitted.

> you were at positive AoA, reduced thrust would impart a negative AoA moment I don't think that is correct. I think you're still thinking of the angle of the plane with respect to the horizon, not the AoA. If reducing thrust reduced AoA, then you could recover from a stall by reducing thrust. In reality, the opposite is the case. The only way to recover from a stall by manipulating engine thrust is to increase it (t…

AFAIAK the procedure is to not increase thrust, quite the opposite (disable the autothrust thingie), get the nose below the "horizon" (which is of course wind dependent), gain airspeed, and then start to increase thrust (which will automatically start to up the nose a bit), then climb back to whatever altitude you should be at.

I don't mean to say that increasing thrust is the standard stall recovery procedure in most aircraft, or that all stalls could be recovered from merely by increasing thrust. But if one could only manipulate thrust, one would increase thrust to recover from a stall, not decrease it.

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#307

Post by pas »

rzimmerman wrote: post #248
rajbot wrote: post #190

Earlier quoted context omitted.

I’m surprised there wasn’t a push to standardize units after this incident: https://en.wikipedia.org/wiki/Mars_Climate_Orbiter

I dislike using MCO as an example of why engineers should standardize units/use metric. This was one of the first NASA projects to be done using metric units with this exact goal in mind. The more interesting part about MCO is that it's actually a pretty compelling story about engineering culture interacting with management and how risks and problems are handled. It's not as simple as "NASA messed up metric" at all a…

Is there a tl;dr on those relevant parts?

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#308

Post by pas »

starpilot wrote: post #203

In his other comments, he walks back on his remarks: > Also, in all fairness to my hated former employer, air travel is still by far the safest form of travel. Even with the shitshow at Boeing, Boeing planes manage to be incredibly safe. I'm really not sure how, but they are. > And it might be because I grew up around Boeing, but I'd still fly Boeing over Airbus, to be perfectly honest. Airbus makes good planes, but…

> You probably have nothing to worry about with air travel.

Well, the conclusion is already made in the statistics, and air travel is the safest, yes, but it's worrying that it's safe despite the enormous fallacies, despite the insane pressure of market forces.

A very eye-opening thing is to watch what the pilots should have done: https://www.youtube.com/watch?v=xixM_cwSLcQ&t=16m55s

Runaway stabilizer scenario has associated memory items (meaning the pilot must have the checklist committed to memory). There are big wheels that turn, with noise and a big visibility marking.

This was Boeing's initial defense too, that the pilots fucked up, because disabling any electronics works the same way. (There's a cutoff switch.) So if something is doing something, shut off the power, rotate the wheels manually.

And in this regard Boeing is right. Pilots decisionmaking was suboptimal. However, it is Boeing's fault that they opted for a no-training-required strategy.

A similar WTF is that pilots don't keep up with the aviation industry news. How - the fuck - can you pilot a plane that you know nothing about (except that your license is valid for it)!?

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#309

Post by starpilot »

pas wrote: post #308
starpilot wrote: post #203

In his other comments, he walks back on his remarks: > Also, in all fairness to my hated former employer, air travel is still by far the safest form of travel. Even with the shitshow at Boeing, Boeing planes manage to be incredibly safe. I'm really not sure how, but they are. > And it might be because I grew up around Boeing, but I'd still fly Boeing over Airbus, to be perfectly honest. Airbus makes good planes, but…

> You probably have nothing to worry about with air travel. Well, the conclusion is already made in the statistics, and air travel is the safest, yes, but it's worrying that it's safe despite the enormous fallacies, despite the insane pressure of market forces. A very eye-opening thing is to watch what the pilots should have done: https://www.youtube.com/watch?v=xixM_cwSLcQ&t=16m55s Runaway stabilizer scenario has as…

Commercial pilots these days are glorified bus drivers. Pay is similar too.

Re: “I worked at Boeing for about 1.5 years in the 2008-9 time period”

#310

Post by Mauricio_ »

puranjay wrote: post #123
basetop wrote: post #100

Earlier quoted context omitted.

You can thank their redesign. Try using "old.reddit.com" while it last. And stop using reddit once that gets taken down. Reddit was once a great site. Now it's a corporatized, censored mess that sold its soul for short-term cashout in their 2020 IPO.

I have never seen a more incompetent redesign in my life, especially for a "unicorn". That new redesign completely falls apart on Chrome on my mobile (a OnePlus 5T). Comment threads get squished together so much that by the 5th comment in a thread, all words are basically vertically arranged. If I switch to "desktop site" on Chrome, any text I enter gets automatically erased after hitting a certain number of characte…

I suspect it's bad on purpose to force people to install the app.
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