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Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

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Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#71

Post by hueving »

WalterBright wrote: post #61
ajarmst wrote: post #57

Earlier quoted context omitted.

Agreed. When I saw the amount of damage, but little on the wing edge (there may be damage on the underside), I assumed the engine maintained confinement long enough to dissipate a lot of energy. If the cowl was damaged during this, then it may have then come off due to aerodymic stress. Either that or they were very lucky. From the photo I saw, it looks like they lost the forward cowl, fan and maybe a compressor stag…

> I assumed the engine maintained confinement long enough to dissipate a lot of energy. Not unless the cowling was armored, which it wasn't at least back in the 80's. That thin sheet of aluminum won't even be noticed by the high strength fan spinning at tremendous speeds.

I suggest you watch the blade separation test videos. The entire point of the cowling is to contain fan blade loss.

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#72

Post by nielsbot »

inferiorhuman wrote: post #44
hexane360 wrote: post #33

Earlier quoted context omitted.

*For what a failing fan disk could do to a DC-10 built in 1973. Since this accident, hydraulic fuses and backup electronic actuators have become standard.

Uncontained engine failures can still cause a significant amount of damage: https://en.wikipedia.org/wiki/Qantas_Flight_32

amazing that such a tiny manufacturing error could lead to complete engine failure, associated damage, and near catastrophe.

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#73

Post by WalterBright »

hueving wrote: post #71
WalterBright wrote: post #61

Earlier quoted context omitted.

> I assumed the engine maintained confinement long enough to dissipate a lot of energy. Not unless the cowling was armored, which it wasn't at least back in the 80's. That thin sheet of aluminum won't even be noticed by the high strength fan spinning at tremendous speeds.

I suggest you watch the blade separation test videos. The entire point of the cowling is to contain fan blade loss.

The main purpose of the cowling is to improve the efficiency of the fan by preventing the air from being slung off radially.

https://en.wikipedia.org/wiki/Ducted_fan

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#74

Post by WalterBright »

InternetOfStuff wrote: post #70
WalterBright wrote: post #61

Earlier quoted context omitted.

> I assumed the engine maintained confinement long enough to dissipate a lot of energy. Not unless the cowling was armored, which it wasn't at least back in the 80's. That thin sheet of aluminum won't even be noticed by the high strength fan spinning at tremendous speeds.

> Not unless the cowling was armored, which it wasn't at least back in the 80's. AFAIK part of engine qualification is proving that the nacelle will retain a fan blade breaking off at full throttle. There are remarkable youtube videos of these qualification tests. The entire fan is another matter though. I assume the nacelle will offer some resistance, but not contain it entirely. And the turbines as well, they don't…

> qualification tests

When did that become a requirement?

> And the turbines as well, they don't even attempt to retain those.

I knew about the turbine blades, I just assumed the fan blades were as uncontainable. I think my information is out of date. Thanks for the correction.

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#75

Post by boulos »

hueving wrote: post #71
WalterBright wrote: post #61

Earlier quoted context omitted.

> I assumed the engine maintained confinement long enough to dissipate a lot of energy. Not unless the cowling was armored, which it wasn't at least back in the 80's. That thin sheet of aluminum won't even be noticed by the high strength fan spinning at tremendous speeds.

I suggest you watch the blade separation test videos. The entire point of the cowling is to contain fan blade loss.

Indeed. https://youtu.be/736O4Hz4Nk4 is a bit long, but they detonate some charges on a blade, watch it take out all the others and keep it all inside.

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#76

Post by KGIII »

CydeWeys wrote: post #54
inamberclad wrote: post #53

Earlier quoted context omitted.

It's not really coasting. A transport category aircraft is required to have enough power to continue climbing if it loses an engine, so it must also have enough power to maintain level flight indefinitely (barring fuel consumption, oil leaks, or mechanical damage from an engine failure)

I meant to say "cruise", if that makes more sense.

If it is any consolation, I knew what you meant. Otherwise, you'd probably have said something like glide and the glide ratio of the big planes isn't very good.

Out of curiosity, I just checked for the A380 and the best guess is 15:1, so it does glide better than I expected, but still not that far.

Google tells me that it'd glide ~130 miles if it had a starting altitude of 45,000'. That's better than I expected.

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#77

Post by WalterBright »

WalterBright wrote: post #74
InternetOfStuff wrote: post #70

Earlier quoted context omitted.

> Not unless the cowling was armored, which it wasn't at least back in the 80's. AFAIK part of engine qualification is proving that the nacelle will retain a fan blade breaking off at full throttle. There are remarkable youtube videos of these qualification tests. The entire fan is another matter though. I assume the nacelle will offer some resistance, but not contain it entirely. And the turbines as well, they don't…

> qualification tests When did that become a requirement? > And the turbines as well, they don't even attempt to retain those. I knew about the turbine blades, I just assumed the fan blades were as uncontainable. I think my information is out of date. Thanks for the correction.

I found it:

http://federal.elaws.us/cfr/title14.part33.section33.94

Looks like it became a requirement in 1984, after I left Boeing. So that's why I didn't know about it.

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#78

Post by KGIII »

cialowicz wrote: post #65
WalterBright wrote: post #60

Earlier quoted context omitted.

> There's no other part of the airplane behind the engines either, so nothing to be hit by debris. The fans spin very fast, and will fly out radially, not just fall back. They'll slice right through anything they contact. The Airbus flight was very, very lucky.

The engines are designed so that a detached fan blade stays contained within the cowling. Here's a video of a fan blade containment test on a Rolls Royce Trent 500: https://youtu.be/RIOWjhjC1jM

I guess they use really, really precise timing and explosives to knock one blade loose in order to do the containment tests. They want it to come loose at a specific point in the revolution.

The documentary didn't say why they wanted it to be at such a specific place, only that they did. I've long since forgotten the margin of error, but it was very small.

You probably noticed that the individual blade is painted a different color and is different colors. My recollection is that they use the multiple colors because they do very high definition recording and the colors are all in different areas of the spectrum, so they can observe it better as the thing tends to be quickly obscured by fire and smoke.

I probably do watch too many documentaries.

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#79

Post by katastic »

KGIII wrote: post #76
CydeWeys wrote: post #54

Earlier quoted context omitted.

I meant to say "cruise", if that makes more sense.

If it is any consolation, I knew what you meant. Otherwise, you'd probably have said something like glide and the glide ratio of the big planes isn't very good. Out of curiosity, I just checked for the A380 and the best guess is 15:1, so it does glide better than I expected, but still not that far. Google tells me that it'd glide ~130 miles if it had a starting altitude of 45,000'. That's better than I expected.

According to this:

https://en.wikipedia.org/wiki/Gliding_flight#Aircraft_.28.22...

The 747-200 also has a glide ratio of 15:1. I can't tell if that's amazing, good, or average.

A sailplane can have up to 60:1! That's pretty impressive!

According to this: A "clean A320" has 17:1. Neat.

https://aviation.stackexchange.com/questions/14814/could-a-c...

Something I never knew was this:

>As someone said above, you have to remember, pretty well all descents are done with the thrust at idle.

So I imagine the glide ratio is pretty important for all-purposes of flight and not just when engines go out.

Re: Air France A380 over Greenland on Sep 30th: Fan and engine inlet separated

#80

Post by KGIII »

candiodari wrote: post #66
SmellTheGlove wrote: post #30

It's amazing to me that modern aircraft engineering is so good that an engine can lose its fan blade entirely at 35000 feet and the plane can still continue on for 2 hours and safely land. An uncontained failure like this is the worst kind, and I know it could have gone worse, but it didn't and that amazes me. I wonder if the cowling contained the initial disintegration but was removed in the process. I'm not an engi…

The thing about it is, that these sorts of things get designed because of evolution. Some engine fails in some way, and it gets redesigned. Planes fail, ditto. And after >100 years of that, we have pretty safe planes. What most amazes me is that despite the scientific knowledge we "have", we can't design a new engine from first principles directly. We do it through trial and error. Lots of hilarious/horrible error.

It is kind of nest how they have progressed, as well. It is sometimes little things that make a big difference. It iterative process, I suppose.

Rolls Royce prides themselves on hiring interns. The little cone piece in front of the jet engine had issues with icing up. This had plagued jet engines for years.

They tried all sorts of ways to fix it, including complex methods of supplying heat.

One of their interns just happened to hear about this problem and suggested they simply make it out of rubber. Sure enough, it worked and the problem with that pointy bit freezing was solved.

I'm sure it has a formal name and that it is probably not pointy bit or little cone piece. I don't actually know anything about jet engines, I just watched a documentary about Rolls Royce's jet manufacturing.

Anyhow, that wasn't something that could probably have been designed with first principles. Someone, pretty much in passing, pretty much had to have that creative spark at just the right time and with just the right information.

It's things like that story that make me think humans are going to be in the loop for a long time still and that AI taking over the world is still a long ways away.

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