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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

#121

Post by kortex »

KGIII wrote: post #80
candiodari wrote: post #66

Earlier quoted context omitted.

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…

> 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.

I've found that the world continues to turn contingent on tremendous amount of what I call "dark wisdom" - crucial pieces of knowledge not found in any server, spec sheet, or manual. Usually inside the noggin of one or a few people. It just seems like a consequence of maintaining complex systems. In order for AI to fully take over, it would have to control and account for every corner case of every system, from mining the ore, to fabbing chips, to replacing wires chewed by rodents.

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

#122

Post by waqf »

gvb wrote: post #111
rwmj wrote: post #91

Earlier quoted context omitted.

At first I was surprised they didn't use the emergency slides, but I suppose once the aircraft is on the ground and there's no evidence of a fire or similar, it's safe so there's no immediate need to deplane the passengers.

The risk of minor injury (sprains, etc.) is pretty high for slides and there is some risk of serious injury (broken bones and worse). They are used when the alternative risk is death.

It doesn't seem fair to use the rate of injury during an emergency evacuation as a measure of what could be achieved with the same slides under non-emergency conditions.

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

#123

Post by lloeki »

katastic wrote: post #79
KGIII wrote: post #76

Earlier quoted context omitted.

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 r…

Finesse gives you two things:

Quite directly, from ground altitude, a range within which to look for a place to land. As you mentioned the impressive finesse of gliders gives you more room, but gliders won’t generally be flying as high as cruising powered planes.

Combined with speed, a timeframe within which you have to observe, orient, decide and act. Here, both top speed and stall speed give you some hints, and within which there’s a best speed where finesse is optimal. You can imagine how it’s very different between an A320 and a glider, the former for which time runs quickly, you have to decide where to go in as few minutes as possible, the latter for which decision time brought back at a human thinking time scale makes it less stressful but you have to keep cautious of your goal for a longer stretch of time.

Obviously that’s without counting on soaring, which A320s can hardly benefit from (I suppose they can but would largely not move up and certainly not turn since it would would incur too huge drag).

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

#124

Post by FabHK »

hlandau wrote: post #120
dominotw wrote: post #118

Earlier quoted context omitted.

>A transport category aircraft is required to have enough power to continue climbing Can a plane takeoff with just one engine ?

Yes. Twinjet airliners must be able to take off if one engine fails at or after V1.

Which, incidentally, means that twins are quite powerful - a twin has 100% more engines (thus, power available) at takeoff than needed, while a quad has 33% more.

Thus a twin has 50% more power than a similar 4 engine. At least conceptually-ish.

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

#125

Post by FabHK »

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.

> ~130 miles

That's statute miles (or 111 nautical miles or 205 km). It's quite impressive, really.

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

#126

Post by FabHK »

jaclaz wrote: post #102
leoc wrote: post #100

Earlier quoted context omitted.

Obligatory Gimli Glider: https://www.damninteresting.com/the-gimli-glider/ http://www.gimlicommunityweb.com/history/gimli_glider.php .

Also (older accident): https://en.wikipedia.org/wiki/British_Airways_Flight_9 >Ladies and gentlemen, this is your captain speaking. We have a small problem. All four engines have stopped. We are doing our damnedest to get them going again. I trust you are not in too much distress.

That must surely top the list of most awesome pilot announcements (and, simultaneously, best British understatement).

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

#127

Post by FabHK »

kogepathic wrote: post #81
cialowicz wrote: post #65

Earlier quoted context omitted.

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

> The engines are designed so that a detached fan blade stays contained within the cowling. Yes, but uncontained failures can and do happen. Qantas Flight 32 is an example of an uncontained engine failure on an A380, though with a Rolls Royce engine instead of Engine Alliance (GE + P&W). [0] I do think they're very lucky that this uncontained engine failure didn't cause more damage. QF32 was heavily damaged by debris…

I'm fairly sure there are many other things that'll kill me first (hello, lack of exercise), but I do wonder where a detached turbine blade might cut through the fuselage and any passengers contained therein, and thus try to avoid the rows parallel to the engine.

However, I'm wondering - would the blade go straight lateral? Or, relieved from having to pull the whole damn plane forward, would it fly forward and hit the fuselage in front of the engine? Or, slowed down by the air resistance, would it hit the fuselage behind the engine?

Best, I suppose, to sit up front in first class...

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

#128

Post by FabHK »

justinjlynn wrote: post #112
bdamm wrote: post #87

Earlier quoted context omitted.

Very remarkable indeed, considering the damage to the landing gear, flaps, fuel tanks, and engine controls. The airplane at the time it landed was way out into the experimental flying zone. When people talk of pilot-less airliners I have to think of incidents like this. Pilots do make mistakes and people die as a result, but when equipment fails and nobody dies because a pilot does what is needed to land safely despi…

> Sometimes people on board don't even know. That's the ideal general case. You really don't want hundreds of panicked people trapped in a broken tin can thousands of feet above ground while you're trying to handle the situation.

At least you (as a pilot) are behind a solid locked door in that scenario.

However, that brings up another question I've been wondering about: Could the pax/cabin crew of an airplane collaborate in bringing a jet down, by e.g. all together going to the very front of the plane (near the cockpit door), moving the trim up, then all running to the very end of the plane, bringing it into an uncontrollable stall?

I haven't really seen a satisfactory answer to that question. See Quora and Stackexchange (where I attempted an answer):

https://www.quora.com/Would-a-passenger-jet-stall-if-all-the...

https://aviation.stackexchange.com/questions/2507/can-passen...

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

#130

Post by FabHK »

timb07 wrote: post #55
CydeWeys wrote: post #51

Earlier quoted context omitted.

The A380 has four engines in total, and can easily tolerate the loss of just one in normal flight. Adding more engines has been a basic way to increase reliability since the beginning of the field; it's not just modern aircraft engineering. There's no other part of the airplane behind the engines either, so nothing to be hit by debris. What amazes me more is that the newest twinjets are now considered reliable enough…

Actually, adding engines increases resilience, or the ability to tolerate failure. The extra complexity of extra engines actually reduces reliability, since there are more components that can fail.

As the saying goes: If you have an engine failure in a twin, the remaining engine has enough power to take you to the scene of the accident.
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