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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

#351

Post by l33tman »

esemor wrote: post #338
zepearl wrote: post #304

Earlier quoted context omitted.

Summarized, I understand that you mean that a malfunction in the "reverse-thrust-detector" (which switches off automatically the involved engine(s) when the reverse-thrust is not operating within its envelope => referenced as "feature" below) is more desirable than not to have it? (because if, when having a mulfunction of the detector's "feature" in mid-air the engines switch off you still have some time to fix/overr…

Yes, no engines is bad but thrust reverser in flight is a instant killer.

Apparently it's bad if done at cruise (due to the small margins in thin air) but if done in mid-air it's controllable.

See this episode of Mentour Pilot:

https://youtu.be/OguKthkuaT4

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#352

Post by dnate »

camtarn wrote: post #295
stevehawk wrote: post #278

Earlier quoted context omitted.

No, but for as long as I've been driving manual cars they've had gates to prevent that very action. (1995)

Not mine (Honda Jazz). But you physically can't do it, as the reverse gear has no synchro and won't mesh unless stationary.

it should make a loud grinding noise though,

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#353

Post by ric2b »

flyinglizard wrote: post #347
alexbanks wrote: post #307

Earlier quoted context omitted.

I am very scared of flying (although I still do it, although it's not fun). Any advice/rationalism you can convey? I am a person that became sweaty and anxious reading your post.

I advise you to forget statistics. They are very hard to relate to (we're not good visualizing large numbers anyway). Instead, think of the pilots who know these things inside and out and still choose to happily board each and every day. They raise families and eventually retire uneventfully. If they know the risks and still choose to go to work, surely you can board a flight.

That's a bad argument, every dangerous profession also has lots of experienced people that still choose to work there.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#354

Post by philjohn »

mav3rick wrote: post #262
philjohn wrote: post #249

Earlier quoted context omitted.

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.

He lost the championship by one point. The movie Rush on this story is also amazing.

Indeed - you can tell Ron Howard is a genuine fan of the sport - he's often at races.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#355

Post by Rooster61 »

kondro wrote: post #340
Rooster61 wrote: post #140

The second high-profile potentially deadly software caused failure related to automated safety features in as many years (if that ends up being the cause, of course). Very glad the touchdown went nominally. Had they pushed the point of touchdown just a bit further down the tarmac, they'd have skittered right off the pavement.

Skittered right into the arrestor bed: https://en.wikipedia.org/wiki/Engineered_materials_arrestor_...

If that particular tarmac is equipped with such a countermeasure, yes.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#356

Post by soheil »

marvin wrote: post #348
soheil wrote: post #328

Earlier quoted context omitted.

An accident during flight is pretty much a binary event when it comes down to whether you live or not, but with cars there is a whole slew of different types of accidents and vast majority of them don't cause instant death preceded by 45 seconds of absolute terror. Before you downvote what I said in no way discounts the statistics. It is much safer to fly of course than to drive, but when we think of accidents which…

Aircraft accidents aren't binary at all. Many crashes have few or some casualties, e.g. landing gear failure, running off the runway or hitting another aircraft on the ground. Ditto with in-flight failures that don't impact the flight (there's only one major thing that fails, picked up by the redundancies), engine failures that lead to emergency landings, extreme unexpected turbulence or ditchings etc. that might cau…

How can you argue against what I said, it takes profound willingness to ignore precise words to accomplish that. I did not say all accidents I said majority are. If you consider a mosquito hitting the windshield of an airplane when it's parked on the ground and no passenger in it an accident that's your problem. Of course I meant an accident that happens during flight as that's the vast majority of the time that people are in an airplane and when they're worrying about dying.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#357

Post by [deleted] »

outworlder wrote: post #254
weaksauce wrote: post #222

Earlier quoted context omitted.

it's a great fail safe but not if you lose your engines in flight and can't relight them like in the article.

> it's a great fail safe but not if you lose your engines in flight and can't relight them like in the article. It is still better to lose all engines than to have thruster reversers deploy in unsafe situations. You may stall without an engine at low altitude in a landing configuration, but you should still be able to glide for some time. Deploy reversers (or even a single reverser) and you fall like a brick very qui…

[deleted]

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#358

Post by marvin »

soheil wrote: post #356
marvin wrote: post #348

Earlier quoted context omitted.

Aircraft accidents aren't binary at all. Many crashes have few or some casualties, e.g. landing gear failure, running off the runway or hitting another aircraft on the ground. Ditto with in-flight failures that don't impact the flight (there's only one major thing that fails, picked up by the redundancies), engine failures that lead to emergency landings, extreme unexpected turbulence or ditchings etc. that might cau…

How can you argue against what I said, it takes profound willingness to ignore precise words to accomplish that. I did not say all accidents I said majority are. If you consider a mosquito hitting the windshield of an airplane when it's parked on the ground and no passenger in it an accident that's your problem. Of course I meant an accident that happens during flight as that's the vast majority of the time that peop…

I don't think that's a super fair assessment of my comment. If we're just disagreeing on the definition of an in-flight accident, or what percentage between 30% and 90% of accidents constitute a vast majority, we should probably leave it at that, because that's not really disagreement :)

My point is, there's plenty of accidents caused by things that happened while the plane was in the air, that has many survivors or just some injuries. The news article at [0] has some examples, and it's possible to search for more. Granted, if you exclude the cases where the injuries or casualties were caused during an attempted landing or a forced landing due to malfunction, the picture would probably look much more bleak, but then you would also have ruled out a large portion of the accidents that happened.

It's thankfully _extremely_ rare that it's been impossible to make an honest attempt at a controlled landing or ditching during an accident, and in a large part of the cases where this was possible, things turned out okay for most passengers.

[0]: https://www.nbcnews.com/news/us-news/after-air-accidents-sur...

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#359

Post by vpribish »

tlb wrote: post #331
vpribish wrote: post #284

Earlier quoted context omitted.

that's very interesting! but it's about angular momentum and I'm not confident that I can take the lesson over to linear momentum. Here's my caveman f=ma thought experiment: 1. make it 2-d. 2. replace the fan with a person sitting on a chair on a frictionless surface. 3. instead of air it's an endless field cinder blocks ahead of him. the person reaches out, and pulls in a cinder block. f=ma says they each move towar…

You have to look for the equal and opposite reaction. A normal jet creates a stream of fast air behind it. There's no such thing for a reverse jet that sucks air in. With your concrete block example, as I start pulling the block towards me I experience an impulse forward. But when it approaches my body I slow it down to zero speed, creating an opposite impulse. So although I might have moved forward a few inches duri…

thanks for following up. I think this is one of those conversations that works better in front of a white board - it's surprisingly tricky to express in words.

if the demo was mainly to show that it's the jet of air expelled out the back that's providing thrust, then, fine it does that and its a valuable lesson. I guess I'm hung up on the technicality that there is actually a real movement of air mass even without that rearward jet and that has to be felt by the apparatus - I guess it's just unnoticeably small in the real world demo.

anyhow, my confidence in physics intuition has been shaken. thanks bunches.

Re: Boeing 787 Suffers Rare Dual Engine Failure on Landing

#360

Post by sandworm101 »

esemor wrote: post #339
sandworm101 wrote: post #310

Earlier quoted context omitted.

Fyi, military pilot here, there are a handful of mil aircraft that can reverse thrust in flight. A great too for dropping down fast to avoid low/slow flight over hostile areas. There might be a relationship between that ability and this problem.

Lucky bastards, get all the fun features...

It can be crazy dangerous. Once a big plane is dropping like a rock, getting back into a climb is very difficult.
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