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Qantas A380 uncontained #2 engine failure

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Qantas A380 uncontained #2 engine failure

Old 6th Nov 2010, 16:07
  #521 (permalink)  
 
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multiplied by 10 to the power of n, where n tends towards infinity.

Bits of #2 emerged uninvited through the top of the wing, punching through hydraulics, cabling and fuel as they sailed by.

#1 handled things just like many a good pilot would - steadily and by the book until safely stationary, followed by the urgent need for a stiff drink.
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Old 6th Nov 2010, 16:16
  #522 (permalink)  
 
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@ Kwateow

Does anyone know whether the systems connected to the fire handle are those apparently damaged in this A380?

I've not seen it stated whether the crew pulled the #1 fire handle in an attempt to shut it down.

It may well have worked but on the other hand it's overkill for an engine that's not on fire and can be shut down with a fire hose.
In what way would pulling the fire handle be overkill? What do you think the fire handle actually does?
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Old 6th Nov 2010, 16:18
  #523 (permalink)  
 
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"the probability of the disc being released, is (from memory) and causing a fatal accident, in the order of 10 to the power of -6."

10^(-6) . One in (only) a million. That seems very high. Is that per engine-life (bad enough) or per engine flight hour (really terrible) ?

Last edited by Gegenbeispiel; 6th Nov 2010 at 17:03.
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Old 6th Nov 2010, 16:24
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I guess the fire handle should turn off the engine in any aircraft unless you have an engine separation (auto turn off ).
I am not an airbus dirver, but an engine #2 problem has nothing to do with an enigne #1 shut down
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Old 6th Nov 2010, 16:34
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I wonder????

Brill Forum. Not a pilot, engineer or crew member. Just an interested person/passenger.

Am I right in thinking that engine technical info/status is constantly transmitted via satelite downlinks to RR?

JJ
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Old 6th Nov 2010, 16:52
  #526 (permalink)  
 
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md-100: the supposition is that secodary debris (cowling bits?) damaged the data bus feeding the #1 engine EEC. #1 reportedly responded to control inputs in air, so the problem may have been to do with its EEC's confusion as to whether it was on the ground or not. Or the data bus may have been frayed in the incident and the impact of landing finally separated it. We'll see.

VFD: 513: Good explanation. I'm not sure whether it would apply to Airbuses.

jeflew: BA [used to] routinely download engine and other flight data to their maintenance centre, from whence it might have been forwarded to RR. Don't know whether QF does that.

Last edited by Gegenbeispiel; 6th Nov 2010 at 17:43.
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Old 6th Nov 2010, 16:56
  #527 (permalink)  
 
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Ex RR Mech Eng here (a long timer ago). My gut says (with no real facts yet) this is most likely a disk (or maybe compressor blade) metallurgical problem that was missed in ultrasound/x-ray testing during manufacture. Since these critical parts are tracked from the beginning of the manufacturing process it should be possible to trace it back almost to the plant that made the original ingot. Hope this is the case for the guys in Derby since this would be better than a design defect (which would surprise me).
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Old 6th Nov 2010, 16:58
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Going by the images of this incident, the debris has in all probability damaged the electric cables running along the front spar. Some of these wires would have powered the Electric fire shut-off valve of the Eng#1 and the EEC, hence the loss of control over the Eng#1.

I haven't read all the postings on this topic. The images beg the question how close was this incident to the paris disaster involving AF concord i.e. Debris penetrating the fuel tank resulting in uncontained fire and crash. Subsequent investigations led to the withdrawl of the concord due to design issues.
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Old 6th Nov 2010, 17:03
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Gegenbeispiel,
I second your question... the 1 in a million sounds odd.
Total annual fatal accident rate in commercial aviation, all causes combined, is already well below 1 in a million flights (departures).
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Old 6th Nov 2010, 17:12
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iamhives: according to a press item (Flight) a QF manager called Epstein is saying all of the IP turbine rotor - disc and blades - is missing. Can't see how a separated COMPRESSOR blade could have caused this without wiping out the HP turbine and most of the combustion stuff.

Did you mean turbine blade ?

Last edited by Gegenbeispiel; 6th Nov 2010 at 17:25.
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Old 6th Nov 2010, 18:02
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There was a documentary about RR jet engines this summer, clip here

BBC - BBC Two Programmes - How to Build..., A Jumbo Jet Engine, How to Build... - A Jumbo Jet Engine

suspect the full programme in usual places.

If you spin anything fast enough it will break apart, damage/imperfections just make it happen slower, see a Mythbusters episode on disintegrating CDs
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Old 6th Nov 2010, 18:06
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Once we were on the ground we had an engine running they could not stop and fuel leaking onto the runway. At that point it's really the fire crews have a far better visual on what they have to deal with. At all times we were ready to evacuate, but bear in mind with an engine running it would have been out of one side of the aircraft. Better to keep us seated, let the situation be dealt with, always ready to evacuate if needed.

Sounds like there was a breach in the fuel tank and one of the pictures seem to indicate fuel coming from the aft hole in the wing top.
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Old 6th Nov 2010, 18:11
  #533 (permalink)  
 
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the current probability considered for this type of failure event is 10e-7. The event in itself does not constitute a catastrophic event - the certification requirements require the manufacturer to demonstrate a 1 in 20 case. All in all it has to be shown that an event like this ending in a catastrophe is less than 10e-9.
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Old 6th Nov 2010, 18:19
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All in all it has to be shown that an event like this ending in a catastrophe is less than 10e-9.
Per aircraft per year? Per passenger mile? Per passenger hour?
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Old 6th Nov 2010, 18:21
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Hydroman400,
We're back to the same question... the "probability" is meaningless unless you state whether it's per hour, per flight, per cycle, or whatever.

CJ

PS I've done those sums many many times, but for avionics, not for engines.
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Old 6th Nov 2010, 18:33
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I agree with iamhives #526 message.

This image has to be confirmed, but it seems to me that a large quarter of the broken disc picture is available here.
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Old 6th Nov 2010, 18:38
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I think it used to be "per sob". Soul on board. Each butt in the chair, each time, each belt fasten. I've thought this a long time, but I formed this knowledge years ago, and have faith in it only because no one has corrected me yet, Please do. It inspires faith in me when I fly, so be gentle in one's "disabuse".

The chance winning our lottery is 10(-14) so -9 sounds real safe.

bear, who remembers probabilities are for the living, they are meaningless to those whose misadventure makes them the unlucky few.

iamhives- I think I don't think it was defect. If spline failure at the disc/shaft, the disc migrates aftward, starts to "wobble" (What is the "Bell Center" doing there?). At top speed under Climb stresses (to include AoA issues; inlet air and consequent asymmetrical pressures on the disc face,) simple imbalance can fail a compromised bearing face, imo. The orbit becomes more and more elliptical, stressful, and the failure zone starts at the hub/seam/bearing. Once the splines go smooth, the disc "freespools", increasing greatly in RPM. imo. To be more specific, I think the first fracture was a 90 degree split, radiating outward, until it met with radial and longitudinal imbalances that must have made the disc at least fleetingly want to go in every direction, in chaotic fashion, but prevented from doing so by the asymmetry of the stresses (and leading fractures) themselves.

Last edited by bearfoil; 6th Nov 2010 at 19:03.
 
Old 6th Nov 2010, 19:11
  #538 (permalink)  
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Simply a thought, but the size of these latest Turbofans may want a new manufacturing process, a way of preventing unpredictable (chaotic) failure. It would be wicked expensive, and the risk/benefit may not pencil out, but:

A peened pattern on the surface, concentric circles etched in the disc (both sides) intersecting "spokes" proud of the surface, such that each intersection of relief, proud, defines a failure ring and segment. It would weaken the structure (requiring extra weight to solve this) , but would theoretically provide a predictable and sequentially more robust failure zone, until the hub and inner portion are protected from further fracture/loss. It would command a completely new test profile, a "blade, partial, complete sequence".

Mr. Pratt? Mr.Whitney? How is the lawsuit coming against further import of the RRTrent1000? The 787 suffers as we speak, PW are claiming patent infringement. Or is it a red Herring? Has Boeing actually solved the ripples?

bear
 
Old 6th Nov 2010, 19:18
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QUOTE:
''I'd been under the impression that engine designs early in their lifecycle tended to have these kinds of problems, as even the best testing will never fully replicate real-life conditions.''

The uncontained release of a turbine disc during development testing is an extremely rare occurrence for R-R (Derby) in my experience. Only three instances in 31 years if my memory serves me correctly and one of those wasn't even a civil engine.

R-R, and all other aircraft engine manufacturers go to great lengths to accurately replicate everyday operational conditions during their development testing and go much further than service conditions by running with simultaneous low oil pressure/ high oil temperature, increased cabin bleed off-take (where applicable), increased vibration, increased TGT and speeds, increased wheel case loadings etc. etc. This rigorous testing schedule is required by the authorities well before any new engine type enters service so as to eliminate the sort of incident QANTAS have just experienced. Also, engine manufacturers are required to provide high cyclic data ahead of service hours/cycles to hopefully highlight any possible future mechanical issues that may arise.
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Old 6th Nov 2010, 19:23
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Wouldn't be surprised if there is a sacrificial Trent in the test cell purring away, to provide high cycle/high stress conditions as we "speak". Howdy, DevX

bear
 

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