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Boeing 787 Suffers Rare Dual Engine Failure on Landing

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Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#171

Post by arkades »

ricardobeat wrote: post #120
maxxxxx wrote: post #112

Earlier quoted context omitted.

I always love it when you have worked on something for months and someone new comes by and says "Why don't you just X?".

They are right more often than you’d expect. Irrational escalation, loss aversion, confirmation bias, etc play their part everywhere causing senseless projects to be pushed to completion.

> They are right more often than you’d expect.

When the "they" is at least another expert in the same field and not a total stranger completely ignorant of pretty much every relevant detail, and the "you'd expect" part starts at a baseline of nearly 0% for people walking in out of the street unfamiliar with the specific problem at hand, then yes, "they" are right more often than I'd "expect."

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#172

Post by joezydeco »

DoofusOfDeath wrote: post #38
code4tee wrote: post #19

Boeing’s answer seems to say if you accidentally pull the thrust reverser lever before the aircraft is on the ground it just force shuts down the engines. That sounds like an odd safety override. Surely a better solution would be to just not activate reverse thrust. Unlike car engines a jet engine can’t just be quickly restarted if it accidentally shuts down. It typically takes 30-60 seconds to get going. This and ea…

Is that true even if the turbines are still spinning very fast?

A thrust reverser isn't like the reverse gear on your car.

It's a vent that opens to blow exhaust gases to the front instead of behind.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#173

Post by danielvf »

t0mas88 wrote: post #167
danielvf wrote: post #162

Earlier quoted context omitted.

Embraer 190? There are no non-electrical trim controls in the cockpit. http://www.smartcockpit.com/docs/Embraer_190-Flight_Controls... Whereas a 737 has physical cables connected from wheels in the cockpit to the stabilizer jackscrew.

I've never flown an E190, but if you Google the basic systems description you'll find that it has two sets of trim controls and on top of that separate override controls. Both circuits are electric, but they are separate systems on separate power busses to ensure you always have control.

Thanks!

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#174

Post by xadhominemx »

vpribish wrote: post #151
alliecat wrote: post #88

Earlier quoted context omitted.

"Sucking" doesn't actually generate any thrust - In highschool, my physics teacher did a demo with a T-shaped pipe with a fan in the middle, suspended from some string. Without the T, the pipe moved as you'd expect. With the T directing the airflow in equal proportions perpendicular to the axis of the pipe, the pipe stayed still as if the fan wasn't on at all.

physics says no. There was something wrong with that demo if this was the conclusion.

Nah the demo was right. The impulse from the sucking (ie air molecules bouncing off the inside of the fan blade) is countered by the impulse from the air molecules bouncing off the inside off the back T-pipe. Different at a low Reynolds number with a reversible flow.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#175

Post by marcinzm »

stephenr wrote: post #94

Did anyone else find it odd that it took 40 minutes to get the plane towed back to the terminal?

The article is a bit ambiguous to me about whether it was 40 minutes after landing or 40 minutes after they failed to restart the engines. The former is sensible to me since it'd take time for them to try to restart the engines and make sure the plane is otherwise safe (probably some kind of checklist to do as well). Some other articles on this explicitly say it was 40 minutes after landing.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#176

Post by Glawen »

JBReefer wrote: post #149
Rooster61 wrote: post #145

Earlier quoted context omitted.

Oddly enough, your comment makes me think that you are writing it from the perspective of a member of the very group of programmers you decry. Companies that write high-risk, life-critical systems don't just let any ole J. Random Hacker work on such critical systems, and I don't think anyone who has worked in such a field would realistically think that these "brogrammers" as you say would be seriously considered for…

Aren't almost all of the software engineers on those projects writing tests and formally verifying software?

Nope, not on safety critical software, the norms tells you that you need independence between the development team and the validation team.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#177

Post by t0mas88 »

cm2187 wrote: post #164
t0mas88 wrote: post #133

Earlier quoted context omitted.

Switching off is much safer than a turbine overspeed past certain limits. Because an engine failure (one engine) is a situation all pilots are trained for and it has an almost certain safe outcome. Airplanes fly and land just fine on a single engine. We all train for engine failures all the time. On the other hand, a runaway engine fire or uncontained turbine failure is much much more likely to cause a crash. So almo…

But why not throttling instead of switching off then?

Good question, you could theoretically throttle a runaway engine by reducing fuel flow (unlike a piston engine where you can limit air intake). But in 9 out of 10 cases you've already done that by pulling back the power levers. The next step is to cut off the fuel, because the throttles didn't get it under control.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#178

Post by jiveturkey »

maxxxxx wrote: post #152
ergothus wrote: post #116

Earlier quoted context omitted.

It's worse when they are right though. I wish I could say that had not happened to me.

I am fine with that. In most cases they aren't though. Or they don't understand the whole environment.

My experience is about 50/50, both with my own mistakes and with others.

Generally when one is very close to the problem, one sees the environment as immutable. Because, well you spent very many hours building that environment, for very good reasons. And your complex solution "has to" work within the constraints of that complex environment.

Whereas, the "mind of a child" that doesn't grok the environment, also doesn't have a fixed notion of it. This is anecdotal of course, but maybe half the time what I see happen is that it's easier/better to change the environment and this can only be seen with fresh eyes.

It's not the spoon that bends, and it's not you that bends around the spoon. There is no spoon.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#179

Post by koonsolo »

maxxxxx wrote: post #112
nck4222 wrote: post #110

Earlier quoted context omitted.

Do you have experience with aircraft engine design, or landing protocols, or insight in to the meetings when the engines were designed? If so, I'll take back my words but considering the manufacturer doesn't know exactly why this happened, and the engineers on the ground said it seems like a "software bug", it seems a bit presumptuous and frankly a bit comical to start saying things like: "Surely a better solution wo…

I always love it when you have worked on something for months and someone new comes by and says "Why don't you just X?".

The best part is when your project is running late or having issues, and the non-technical manager plans a meeting with all the other dead-weight people. "Explain the problem to us, and since we know absolutely nothing about it, our stupid questions might give you new insights". Facepalm.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#180

Post by SomeHacker44 »

ChuckMcM wrote: post #132
nck4222 wrote: post #110

Earlier quoted context omitted.

Do you have experience with aircraft engine design, or landing protocols, or insight in to the meetings when the engines were designed? If so, I'll take back my words but considering the manufacturer doesn't know exactly why this happened, and the engineers on the ground said it seems like a "software bug", it seems a bit presumptuous and frankly a bit comical to start saying things like: "Surely a better solution wo…

Reminds me of the quote, "For every complex problem there is an answer that is clear, simple, and wrong." -- H.L. Mencken One of the things I have experienced in my career is the mind boggling complexity of the software in systems that are capable of killing people. The more people it can kill the more complex the software. As a result when I read articles like the one posted I find it tantalizing to speculate about…

Yes, Boeing still puts the RAT - ram-air turbine - electrical backup system on their planes.
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