Qantas A380 uncontained #2 engine failure
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Just for anyone who isn't a German-speaker, you might want to know that when Gretchenfrage writes "eventually" he actually means "possibly". It's what's known in the language trade as a 'false friend'.
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The probability of being hit by one of the 3 large pieces of this rotor is roughly as follows. Hull penetration angle spread of 15 degrees from center of rotor. Rotor broke into 3 pieces giving a probability of heading in the direction of a person in the hull of 15/360x3= 1 in 8. (perhaps up to 18 deg giving 1 in 6.7)
Wing penetration angle spread of 40 degrees from center of rotor giving a probability of heading in the direction of the wing of 40/360x3= 1 in 3.
So with this type of failure from an inboard engine, a wing penetration is twice the chance of a person being hit. Not a lot different from the probability of Russian Roulette. However the wing also provides some shielding effect to the hull.
FF
Wing penetration angle spread of 40 degrees from center of rotor giving a probability of heading in the direction of the wing of 40/360x3= 1 in 3.
So with this type of failure from an inboard engine, a wing penetration is twice the chance of a person being hit. Not a lot different from the probability of Russian Roulette. However the wing also provides some shielding effect to the hull.
FF
Last edited by FluidFlow; 17th Nov 2010 at 21:49. Reason: Better sketches obtained to determine angles
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The crew handled the situation like the professionals they are
This may not be one of those cases. I'll concede that. But I keep an open mind until all the facts are in from publicly verified sources.
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Mountain Bear
In the vast majority of cases this is the truth, however like the Cactus in the Hudson, this one has already shown to be quite the opposite of the norm.
I would be surprised to be eating my hat in 12 months time
In the vast majority of cases this is the truth, however like the Cactus in the Hudson, this one has already shown to be quite the opposite of the norm.
I would be surprised to be eating my hat in 12 months time
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Top-Lame
It usually is the 10 cent seal or the 20 cent washer...the lowest common denominator that evades the sharpest of minds
For my money...give me a Kiwi or someone who has dirty fingernails to actually fix the problem. Tragedy is all these people are out fixing lawnmowers because the people that fly the desks put no value on good old fashioned experience and common sense.
FWIW
It usually is the 10 cent seal or the 20 cent washer...the lowest common denominator that evades the sharpest of minds
For my money...give me a Kiwi or someone who has dirty fingernails to actually fix the problem. Tragedy is all these people are out fixing lawnmowers because the people that fly the desks put no value on good old fashioned experience and common sense.
FWIW
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http://www.bangkokpost.com/business/...-a380-incident
We're all doomed or is there some truth in this?
We're all doomed or is there some truth in this?
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"We're all doomed or is there some truth in this?" Truth in what? Its a cobbled together report from stuff that's appeared on the Net over the last week. Just another bandwagon-jumping sensasionalist bit of journalism...
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Ignoring the tech stuff for a moment, I see the press are getting a bit impatient with RR. This one in particular is rather nasty
Rolls-Royce’s Public Relations Model: Joseph Stalin: Clive Alive on Truth.Travel from Conde Nast Traveler
Is the critisism fair? I'm surprised how quickly RR said they knew what the problem component(s) is(are). Considering its only 2 weeks since the incident the identification of the problem area was amazingly quick.
Unfortunately RR then failed to go the extra step and name the specific component(s) and explain a couple of things like :-
a. exactly how this differed from the T1000 test bed incident
b. when the redesign decision was made (and why) such that current production line T900s don't have the problem
c. why replacing old for new rather than fix old is the best way to fix the problem
As for the press I think they should hold fire until the ATSB preliminary factual report that is released around 3 December 2010.
PS. There's an ATSB update out today.
News:
Rolls-Royce’s Public Relations Model: Joseph Stalin: Clive Alive on Truth.Travel from Conde Nast Traveler
Is the critisism fair? I'm surprised how quickly RR said they knew what the problem component(s) is(are). Considering its only 2 weeks since the incident the identification of the problem area was amazingly quick.
Unfortunately RR then failed to go the extra step and name the specific component(s) and explain a couple of things like :-
a. exactly how this differed from the T1000 test bed incident
b. when the redesign decision was made (and why) such that current production line T900s don't have the problem
c. why replacing old for new rather than fix old is the best way to fix the problem
As for the press I think they should hold fire until the ATSB preliminary factual report that is released around 3 December 2010.
PS. There's an ATSB update out today.
News:
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Originally Posted by top-lame
Does anyone know what the "Internal Engine Component" is to FIX the Trent 900 problem?
http://www.nytimes.com/2010/11/16/bu.../16qantas.html. You won't be able to access the article unless you are registered on the NYT site.
Originally Posted by NYT article
... according to one person who had been briefed on the matter, investigators isolated a problem in an air-transfer tube in the cavity between the engine’s high- and intermediate-pressure turbines. Rolls-Royce is preparing a replacement program for the component, known as Module 51, said the person, who requested anonymity because he was not authorized to speak on the subject.
Last edited by PBL; 17th Nov 2010 at 09:32. Reason: Misunderstood FluidFlow's question/assertion
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Just design it to break into the right number of bits!
Fluid Flow
"probability of heading in the direction of the wing of 165/360x3= 1 in 0.7 or 1.4:1 "
I think if you get a probability > 1 then you should start to worry about the calculation a little. Assuming your 165/360 is fair then you need to be looking at:
1 - (195/360)^^3 = 0.84 as the probability of hitting the wing. (Think of the opposite of all three missing)
Your other figure is hardly affected.
Of course, I assume the number of bits is also a variable here, interesting and nice to see that if it breaks into enough bits the formula for the chance of a hit becomes a certainty but there again the "bit" in question would have little mass. If someone lets us know at what mass these bits are nolonger a danger to the wing then "all" you have to do is design in a weakness for controlled (but more frequent) failure and you have "Containment". Unfortunately there are also an infinite number of these things so at the end of the day it probably just comes back to an energy calculation unless you can get it to fall apart slowly, spreading the energy release.
Apologies in advance - not an engineer.
"probability of heading in the direction of the wing of 165/360x3= 1 in 0.7 or 1.4:1 "
I think if you get a probability > 1 then you should start to worry about the calculation a little. Assuming your 165/360 is fair then you need to be looking at:
1 - (195/360)^^3 = 0.84 as the probability of hitting the wing. (Think of the opposite of all three missing)
Your other figure is hardly affected.
Of course, I assume the number of bits is also a variable here, interesting and nice to see that if it breaks into enough bits the formula for the chance of a hit becomes a certainty but there again the "bit" in question would have little mass. If someone lets us know at what mass these bits are nolonger a danger to the wing then "all" you have to do is design in a weakness for controlled (but more frequent) failure and you have "Containment". Unfortunately there are also an infinite number of these things so at the end of the day it probably just comes back to an energy calculation unless you can get it to fall apart slowly, spreading the energy release.
Apologies in advance - not an engineer.
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They were bloody lucky
There is no doubt the Flight Crew of QF32 wasted a lot of time phaffing about with electronic warnings/checklists. You only have to look at the Swiss Air MD-11 off Newfoundland for proof positive of what can go wrong with major a/c issues.
QF32 was lucky - very bloody lucky. Who knows what could have gone wrong with all that shrapnel having hit the a/c. To waste 2 hrs mucking about with the unknown is bordering on the criminal. Im sure the crew were professional and followed all the published procedures but what a risk to the passengers.
There could have easily been a fire in the wing or a/c body, loss of critical hydraulic pressure, damage to wing spar which could have led to structural failure or a host of other nasties. Apparently the pax could see the skin peeling of the wing ala Aloha Flt 243. Things don't get better when that type of damage has occurrred - they only get worse ove time.
Aloha Airlines Flight 243 - Aircraft Accident - Maui Hawaii
While the crew were happily paging through the error messages the a/c could easily have disintegrated.
Big risk to take in my opinion - given they were only 6 minutes from SIN.
Very bloody lucky.
QF32 was lucky - very bloody lucky. Who knows what could have gone wrong with all that shrapnel having hit the a/c. To waste 2 hrs mucking about with the unknown is bordering on the criminal. Im sure the crew were professional and followed all the published procedures but what a risk to the passengers.
There could have easily been a fire in the wing or a/c body, loss of critical hydraulic pressure, damage to wing spar which could have led to structural failure or a host of other nasties. Apparently the pax could see the skin peeling of the wing ala Aloha Flt 243. Things don't get better when that type of damage has occurrred - they only get worse ove time.
Aloha Airlines Flight 243 - Aircraft Accident - Maui Hawaii
While the crew were happily paging through the error messages the a/c could easily have disintegrated.
Big risk to take in my opinion - given they were only 6 minutes from SIN.
Very bloody lucky.
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The more I read about the recognition that an uncontained engine failure including a disc breaking up (ie not just shedding blades) is a recognised possibility, the more surprised I am that every engine does not have failsafe 100% automatic 100% mechanical mechanisms to prevent an overspeed. Surely it is possible to insert a brake which is triggered automatically as soon as a turbine starts to overspeed, and to also include a fuel cut-off, and possibly movable guide vanes to neutralise torque generated by the hot gas.
Here's a link to an Australian Journo who seems to know what he is talking about:
The Anatomy of the Airbus A380 QF32 near disaster – Plane Talking
Scary stuff
The Anatomy of the Airbus A380 QF32 near disaster – Plane Talking
Scary stuff
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"Rolls-Royce ... knew about the faults that the current airworthiness directive concerning these engines says are likely to have caused an intense oil fire in a structural cavity in the intermediate pressure turbine area of the engine."
"Rolls-Royce had designed and was introducing a fix for the oil leak issues for this into the engines at its own speed. "
"And the questions concerning the timeliness of the Rolls-Royce responses to a known problem, and its capacity and willingness to share them with the airlines concerned will not go away. "
So, bottom line. I'll ask if nobody else will. Is he saying that the engine blowup was due to a problem that Rolls-Royce knew about and failed to remedy in the in-service T900s?
"Rolls-Royce had designed and was introducing a fix for the oil leak issues for this into the engines at its own speed. "
"And the questions concerning the timeliness of the Rolls-Royce responses to a known problem, and its capacity and willingness to share them with the airlines concerned will not go away. "
So, bottom line. I'll ask if nobody else will. Is he saying that the engine blowup was due to a problem that Rolls-Royce knew about and failed to remedy in the in-service T900s?
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"Rolls-Royce ... knew about the faults that the current airworthiness directive concerning these engines says are likely to have caused an intense oil fire in a structural cavity in the intermediate pressure turbine area of the engine."
"Rolls-Royce had designed and was introducing a fix for the oil leak issues for this into the engines at its own speed. "
"And the questions concerning the timeliness of the Rolls-Royce responses to a known problem, and its capacity and willingness to share them with the airlines concerned will not go away. "
So, bottom line. I'll ask if nobody else will. Is he saying that the engine blowup was due to a problem that Rolls-Royce knew about and failed to remedy in the in-service T900s?
"Rolls-Royce had designed and was introducing a fix for the oil leak issues for this into the engines at its own speed. "
"And the questions concerning the timeliness of the Rolls-Royce responses to a known problem, and its capacity and willingness to share them with the airlines concerned will not go away. "
So, bottom line. I'll ask if nobody else will. Is he saying that the engine blowup was due to a problem that Rolls-Royce knew about and failed to remedy in the in-service T900s?
Bigger question is, is he right ? Might be, but there are several other possibilities, and the published information is not enough to determine which is right.
An AD was already issued for increased inspection to cover a problem which looks very similar (but may not actually be the same issue). So RR had notified a problem and put in place mitigating inspections, presumably whilst working on a permanent fix. Possibly the inspections were insufficient.
Possibly this is a different problem, but the same permanent fix - in other words a problem was identified, notified, mitigated in service and fixed in production, but this event is a result of previously unknown consequences of the original design.
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Flying debris questions.
I'd interpret the coarse probability that something hits the wing being greater than one, as simply meaning that there's a decent chance that two things hit the wing.
It would give a strong hint that with a completely let-go #2 engine, which could be seen clearly from the forward lower deck by lack of a rear fairing, there is likely to be damage to the wing, even if you can't see errors, a fuel plume coming out behind, or holes punched in the top of the wing.
If you wanted to assess the risk of such an occurrence, you'd need (at least) to simulate the outcomes, and their likely consequences, perhaps using a large Monte-Carlo suite of probabilistic models of what happens when various bits of various sizes hit various things in various directions. [Very difficult, because of ricochets, the generation of secondary fragments, shock waves in fuel, `who knows what will come out of the engine'...]
It would give a strong hint that with a completely let-go #2 engine, which could be seen clearly from the forward lower deck by lack of a rear fairing, there is likely to be damage to the wing, even if you can't see errors, a fuel plume coming out behind, or holes punched in the top of the wing.
If you wanted to assess the risk of such an occurrence, you'd need (at least) to simulate the outcomes, and their likely consequences, perhaps using a large Monte-Carlo suite of probabilistic models of what happens when various bits of various sizes hit various things in various directions. [Very difficult, because of ricochets, the generation of secondary fragments, shock waves in fuel, `who knows what will come out of the engine'...]
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for SandyW,
In my experience of modern engines they do have overspeed protection devices, both mechanical and electronic but I doubt if even then they can be 100% effective so there's still the chance of failure.
VnV
In my experience of modern engines they do have overspeed protection devices, both mechanical and electronic but I doubt if even then they can be 100% effective so there's still the chance of failure.
VnV