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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

#241

Post by gugagore »

a1369209993 wrote: post #231
gugagore wrote: post #208

Earlier quoted context omitted.

Thanks for bringing more precision to the conversation (really). What would you like to call the factor? 3? Call me a weasel, but I was hoping "roughly speaking an order of magnitude" would go down to 3. I suspected it was comfortably above 2. Am I right about that?

> I was hoping "roughly speaking an order of magnitude" would go down to 3. I'd call that half a order of magnitude, considering log₁₀(3) is around 0.477. So you're off by more than a factor of two.

You know, I considered saying that the "roughly" buys me a factor of two in log space. I didn't want to be that person, but I'm glad you were ;).

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#243

Post by bunderbunder »

weaksauce wrote: post #230
bunderbunder wrote: post #223

Earlier quoted context omitted.

Cutting power to all engines in response to an event that is most likely to happen while the aircraft is operating close to, but not actually on, the ground is not failing safe.

I am not sure there is a perfect solution here. you have competing issues that you need to resolve. If it gets pulled in normal flight you would lose both engines but that's fine because you can glide and restart the engines. if the altitude sensor/ground sensor was broken and you want to override the reverse thrusters you have a conflicting goal there. If you accidentally pull it during the approach you lose your en…

Well, I thought that the design was that they would not engage if it gets pulled in normal flight.

If it's on the approach, I'd be worried. I imagine that that, at an airport like ORD, that might result in more risk than anyone really wants of the plane unexpectedly touching down on an interstate highway or something like that.

If it's like what Boeing described in the bulletin, where the engines only get shut down after the wheels are on the ground, that's maybe not super worrisome, but I can still see some room for concern. My reconsidered but still totally uninformed reading on the situation is that it takes some time for all the aircraft's systems to get the memo on whether the plane is on the ground, and that what's really going on here is that the order in which they get the memo isn't quite right. So the question of whether or not to allow a Lauda Air type situation isn't really at play here, but perhaps a related glitch to the one that caused this event could interfere with something like aborting a landing at the last minute.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#244

Post by stephenr »

marcinzm wrote: post #175
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.

I wouldn't call it ambiguous:

> The pilots followed their checklists and worked with maintenance personnel via phone to troubleshoot, but were unable to get the engines to relight. This left the aircraft stranded and led to the closure of the runway. A tow truck arrived some 40 minutes later to tow the aircraft off the runway.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#245

Post by stephenr »

goodcanadian wrote: post #213
stephenr wrote: post #94

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

No, not really. It's not an emergency response. They probably did not request it right away as they expected to restart the engines. Once it was requested, they had to find someone available to operate it who had to go get it, perhaps check the fuel and fluids, et cetera, et cetera. Depending on the details, 40 minutes could actually be considered quite quick.

The article indicates it took 40 minutes from after they'd tried to re-start the engines, etc.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#246

Post by noir_lord »

AnimalMuppet wrote: post #229
noir_lord wrote: post #163

Earlier quoted context omitted.

It's quite possible that software creates new failure modes (as programmers I'm sure we all feel that to be true some days) while at the same time preventing more. When the software fails (if it did) we assume the software makes it more dangerous because we have a concrete example of what happened but not what could have happened in it's absence. This is what may eventually stall self driving cars for many years, the…

Statistically? I don't know. But I have a friend who's an airline pilot. He was telling me about hitting windshear while coming in for a landing. The plane has software that not only tells him that he hit windshear, but also tells him what angle to put the nose at for best results. (The problem is airspeed. So you go to full power, but pitching the nose down also helps you gain airspeed. But the ground is down there,…

Aye, Things like that the G3000 (Garmin avionics suite for light aircraft) that now do real time 3D terrain generation so that less experienced pilots can avoid controlled flight into terrain (literally the way they describe when a pilot in control smashes into a mountain).

My suspicion is that modern computerised avionics are on balance a life saver but I'd love to know by how much.

I ended up watching videos of modern avionics in light aircraft on youtube a while back (as you do) and I find that kind of programming fascinating, couldn't find much out about the actual hardware/software side of things though I did gather it runs a custom OS.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#247

Post by subhro »

focom wrote: post #200
esemor wrote: post #189

I think the auto shutdown of engines in flight, in case it senses reverse thrust, is a great design. The 787 is a replacement for my 767 (currently a pilot on the aircraft) and in 1991 a Lauda Air 767 suffered a failure in one of its thrust reverser and it became activated during cruise. The aircraft was destroyed in flight. The thrust reversers should not activate during flight (a air/ground sensors prevents that) b…

There is Airplane pilot on HN? I am surprised, did you make a career switch from IT?

Airplane pilot checking in. There are multiple. :)

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#248

Post by tlb »

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.

Feynman says yes, except at very low speeds. https://en.wikipedia.org/wiki/Feynman_sprinkler

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#249

Post by philjohn »

jshap70 wrote: post #202
esemor wrote: post #189

I think the auto shutdown of engines in flight, in case it senses reverse thrust, is a great design. The 787 is a replacement for my 767 (currently a pilot on the aircraft) and in 1991 a Lauda Air 767 suffered a failure in one of its thrust reverser and it became activated during cruise. The aircraft was destroyed in flight. The thrust reversers should not activate during flight (a air/ground sensors prevents that) b…

there's a really interesting story around Lauda Air flight 004 where Boeing attempted to write it off as pilot error but Niki Lauda basically threatened to go fly one himself and recreate the conditions as proof it was not. Eventually Boeing conceded and he didn't have to actually risk himself or another of his planes, but still an interesting anecdote.

That's just the kind of person Lauda is.

He was severely burned in a Formula 1 race at the Nurburgring, and despite still suffering badly scarred lungs and weeping wounds he was back in the seat before the end of the season and only lost the championship that year because he refused to go out in the pouring rain to race the Japanese Grand Prix as he decided it would have been foolhardy.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#250

Post by newnewpdro »

bobowzki wrote: post #216
focom wrote: post #200

Earlier quoted context omitted.

There is Airplane pilot on HN? I am surprised, did you make a career switch from IT?

I'm always amazed how diverse the people on HN are. Not everyone is an IT professional but we share a passion for technology.

'Passionate' is not the adjective I would use to describe my feelings towards technology.
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