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Qantas A380 uncontained #2 engine failure

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Qantas A380 uncontained #2 engine failure

Old 5th Dec 2010, 00:42
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Despite being the second line pilot checked out on the aircraft, the captain is relatively junior in rank. With all the training/delayed deliveries going on, it means not a lot of flying.
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Old 5th Dec 2010, 04:24
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Has anyone sought Dustin Hofmann's spin on this incident ?
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Old 5th Dec 2010, 04:36
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If worst came to worst and the aircraft had crashed before returning to Changi, how hard would it have been to actually determine the cause of the engine failure ?
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Old 5th Dec 2010, 07:39
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If the aircraft hadn't made it back to changi they would still have had black box data and also the cockpit voice would cover the actual incident, enough information to establish cause. But the incident could have followed so many possible histories so it's pointless to speculate on 'what ifs' that didn't happen.
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Old 5th Dec 2010, 07:45
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They would have had the Engine and the pieces that landed on Batam. The Batam pieces would have told them the cause on their own.

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Old 5th Dec 2010, 10:54
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212man:

The engine did not 'explode.'

The below is written in American English.

A significant portion of the engine cowling did explode.

This explosion was caused by some event or events in the engine.

Using the below definition of 'explode', from a reputable American dictionary, one might say that a least of portion one of the A380's engine did indeed explode [refer to below definition for explode intransitive verb 1b]

From Merriam-Webster's 11th Collegiate Dictionary:

Main Entry:ex.plode
Function:verb
Inflected Form:ex.plod.ed ; ex.plod.ing
Etymology:Latin explodere to drive off the stage by clapping, from ex- + plaudere to clap
Date:1605
transitive verb
1 archaic : to drive from the stage by noisy disapproval
2 : to bring into disrepute or discredit *explode a theory*
3 : to cause to explode or burst noisily *explode a bomb*

intransitive verb
1 : to burst forth with sudden violence or noise from internal energy: as a : to undergo a rapid chemical or nuclear reaction with the production of noise, heat, and violent expansion of gases *dynamite explodes* b : to burst violently as a result of pressure from within
2 a : to give forth a sudden strong and noisy outburst of emotion *exploded in anger* b : to move with sudden speed and force *exploded from the starting gate*
3 : to increase rapidly *the population of the city exploded*
4 : to suggest an explosion (as in appearance or effect) *shrubs exploded with blossoms*
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Old 5th Dec 2010, 11:36
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thanks kwateow and Zimmerfly for answering my post, and from the preliminary report we know that, with all the failures and the 50 tons overweight, the crew computed there would only be 100 meters left from the 4000 meters runway...
so it was worth burning some fuel after the failure and its consequences appeared however it must have been quite stressful to say, ok the aircraft is controllable, let's hope it stays the same...in the mean time let's deal with all the failures
I guess that in those kind of scenarios you want to figure out what would be the "less worse" situation
I would like to know however how bad was the wing inner structure (regarding spars and ribs) affected and could have it been critical if e.g. the crew computed a landing distance that required to stay even longer airborne in order to burn more fuel to reduce the landing weight ?
A specialized engineer intervention would be appreciated
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Old 5th Dec 2010, 14:17
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If worst came to worst and the aircraft had crashed before returning to Changi, how hard would it have been to actually determine the cause of the engine failure ?
Simple, would take about a half hour to confirm that it failed and how, now the underlying reasons would take just a long as it is taking now.
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Old 5th Dec 2010, 16:55
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JFZ90

Re: Thrust. I take note of number 62 in the cutaway drawing of the TRENT (mm43's welcome contribution!! on page 73). This I take to be helical Splines that terminate into a "Ring Boss" in a groove centered in the Inner race of Bearing Number Two. This would be the take up of any discrepant axial force, forward or back, of the IP Shaft (Compressors and Turbine). It is this specific area I take to be the focus of the AD, since any unusual wear here, would allow slop independent of this Ring Boss.

How in the World RR assembles this complicated machine is well beyond my mechanical ken. Kudos to RR mechanics!!

bear
 
Old 5th Dec 2010, 22:56
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I would like to know however how bad was the wing inner structure (regarding spars and ribs) affected and could have it been critical if e.g. the crew computed a landing distance that required to stay even longer airborne in order to burn more fuel to reduce the landing weight ?
Length of time airborne would not affect failure unless wing burning, once damage established...

In fact perhaps more fuel burnt would though, increase chance of a gust load exceeding compromised structural strength. Landing -ve loads of course another matter
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Old 6th Dec 2010, 04:04
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Length of time airborne would not affect failure unless wing burning, once damage established...
A witness onboard reported fire in the holes in the wing for several minutes. Does the A380 have a fuel inerting system? If so, it may well have saved the day.
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Old 6th Dec 2010, 04:32
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Just a Bit more - -

<http://www.theaustralian.com.au/business/aviation/earlier-problem-for-qantas-a380-engine/story-e6frg95x-1225966048440>

News as of today , 06/12/10 Australian Newspaper.

With the problems this engine has seen in Its relatively short life there must be more Borescope Images than needed to provide answers .

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Old 6th Dec 2010, 05:07
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727 spirit wrote at 5th Dec 2010 06:54:

I would like to know however how bad was the wing inner structure (regarding spars and ribs) affected and could have it been critical if e.g. the crew computed a landing distance that required to stay even longer airborne in order to burn more fuel to reduce the landing weight ?
A specialized engineer intervention would be appreciated
What we have to realize is that the common wisdom here, that the upper flange of the spar was not damaged, is not the entire story. True, it carries the compression stress of the bending in the wing. The problem is that the web (now damaged) braces the upper flange against buckling in compression. The web itself will have tension on one diagonal, but compression on the other; the web stiffeners (both longintudinal and vertical) resist the buckling of the web, but both of these are damaged as well.

Being closer to the buckling load is not something that the pilot can easily feel, as the wing stiffness is not greatly changed. Instead, buckling is a transition from being stable and carrying the load, to being unstable and not carrying the load. The problem is that this will always happen very fast, if it happens.

I had a longer draft, to include an explanation of the mathematical limitations of analysis for a large structural grid (the inside of the wing, plus its cover). But in any case, there is no way to phone in or send telemetery and get back an analysis in real-time. My conclusion was it had to be analysed beforehand. Then:

The flight manual would need a section for suspected uncontained failure of the IPT. Depending on the location of holes seen in the top surface of the wing (could locate wing area holed on a keyed diagram), probable damage would be given. Then measures to cope with the particular damage would also be given (special instructions). In this case:

...Grid Ab: Forward spar damage (Note 1); fuel tank holed (Note 2).
...Note 1: Discount forward spar strength, reguiring limit g to 1.25 (say).
...Note 2: Assume tank will empty; recompute range and time aloft."
...Note 3: IAW note 2, divert to nearest adequate runway.

Note that this assumes the wing will continue to fly even if the forward spar looses all strength to resist bending near its attachment to the fuselage. This may or may not be true. If true, the wing structure survived by design; if not true, then by good luck.

If the plane can fly on two spars with a manageable g load, then you're somewhat home free, as the "what if" analysis is considerably less complex. Of course, the wing framing forms a torque-box, whose strength is directly proportional to the cross-sectional area of the wing enclosed by whatever portion of that framing remains intact. So you'd need more special instructions to limit motions that would overstress the wings in torsion.

In the longer draft, I tried to explain why partial damage is so much harder to evaluate. Perhaps I'll get to that if I can improve it. But basicly the answer to your question "how bad was [the wing]" is: That that is a very hard question to answer. We may be told after months. Or not told.

We might instead be told that the wing is flyable (within reduced limits) even with the forward spar bending strength totally reduced to zero at this point of damage, if that is true. The basic problem with getting an answer to partial damage effect is that you are either adequately braced against buckling (just touching adequate is the usual practice), or you are not, in regard to the critical top flange of the spar.

Buckling is a difficult concept to explain-- we prevent it by dimensional rules, such as the ratio of length to the radius of gyration of the cross-section, depending on the elasticity of the material, for long columns. We brace long columns to make them shorter columns. It is a concept we owe to the mathematician Euler, and have not been able to improve on. We don't use applied loads to calculate a "buckling stress".

OE
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Old 6th Dec 2010, 05:19
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Stub oil pipe

Hi guys,

think I found a picture of where the stub pipe is, it takes the lube oil the last bit from the inner casing to the bearing box (arrow):

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Old 6th Dec 2010, 09:43
  #1655 (permalink)  
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Originally Posted by Old Engineer
If the plane can fly on two spars with a manageable g load, then you're somewhat home free, as the "what if" analysis is considerably less complex.
The front spar carries about 5% of the wing loading, I understand, so it shouldn't be an issue.

The suggestion that the Manual should contain procedures about operating with a substantially damaged wing seems to me a bit odd. Certification requires assessment of the possible damage which can occur through shedding a turbine disc, and that the wing is structurally able to withstand substantial loads, including gust loads, after such damage. I understand it is assumed that fragments will be shed within 5 of the plane of the disc (which is where the upper-skin panel penetrations in the widely-distributed photographs lie), so it may be that this incident induces the regulators to revisit the certification requirements, since some wing damage occurred outside this region, to the rear. I wouldn't think anyone is contemplating additions to the flight manual on flying with substantially-compromised structure, though. As far as I can judge from afar, the structure behaved more or less as designed. Or does someone here have info to the contrary?

Originally Posted by Passagiata
Australia's public broadcaster ABC Radio National has just broadcast a measured one-hour analysis piece, Background Briefing. Will be available for download and a transcript will be on the site in a few days
Thanks for the link. Stan interviewed me for this program and it will be good to hear the result. For those who don't realise how hard journalists work, here is an indication. Stan first interviewed me about 15 years ago for a piece on computerised cockpits; I had to visit a nearby radio station with whom ABC had a connection. Now, it can be done over normal telephone lines. After exchanging e-mails, I talked to Stan informally for about an hour in mid-November, and then for a further hour for the take a week later. I imagine something less than a minute's worth of intro + take made it into the final cut. So that is going to be 3+ hours of his time, at least, for a minute or less of a one-hour show. Consider that work-to-reault ratio spread over all possible interview candidates, plus the ones he interviewed and didn't use (maybe me?). And the piece has to be composed, which is a non-trivial task. In summary, serious work goes into putting something like this together, and the public, which knows in general very little about any of this before someone such as Stan puts in the couple hundred hours to redact it into suitable form, thereby benefits. Unlike some who contribute here, I consider such journalism to be an enormous benefit to democratic society.

(Having said that, I also acknowledge that there are plenty of irresponsible journalists out there. I was once royally misrepresented eleven years ago by a reporter for a major English newspaper, whose sensational story was taken up by news distributors for Australian, German and Austrian newspapers. In Germany, procedures for correction and retraction are a matter of law; so they published corrections. Not so the English paper. Those who care may read about it here.)

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Old 6th Dec 2010, 11:31
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I understand it is assumed that fragments will be shed within 5 of the plane of the disc (which is where the upper-skin panel penetrations in the widely-distributed photographs lie), so it may be that this incident induces the regulators to revisit the certification requirements
The 5 deg only applies to the largest fragments (1/3). Smaller fragments diverge more.

Still no confirmation of what fragments did what damage, nor the severity of the damage to the structural strength.

The casual reader of these message boards has a tendancy to equate eye-ball economic damage with near catastrophe
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Old 6th Dec 2010, 11:36
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I'd be interested the logistics behind the repairs, has any attempt been started on this yet ? I assume the necessary facilities are available at SIN.
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Old 6th Dec 2010, 12:22
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I understand it is assumed that fragments will be shed within 5 of the plane of the disc
According EASA AMC 20-128A on general acceptable means of compliance for airworthiness of products, parts and appliances, for the 1/3 fragment a spread angle of +/-3 is considered, for an intermediate fragment +/-5 and for smaller fragments +/-15.

The intermediate fragment is assumed to have a mass 1/30th of the combined disc + blades. The smaller fragments are assumed to be no larger than the tip half a blade.

AMC 20 would also be a good place to get an understanding of how an aircraft is expected to fare in case of stray discs. It should perhaps even be required reading before being allowed to commence hand wringing and tales of imminent doom.

Last edited by KBPsen; 6th Dec 2010 at 12:56.
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Old 6th Dec 2010, 13:02
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Originally Posted by lomapaseo
Still no confirmation of what fragments did what damage, nor the severity of the damage to the structural strength.
I imagine that any calculations of reduction in structural strength would involve some fairly sophisticated FE calculation, since that is what is used to calculation the contributions of various structural elements in the first place. I'd be - pleasantly - surprised if that could be performed accurately in so short a time frame, given that this is real damage and not hypothetical.

Originally Posted by KBPsen
for the 1/3 fragment a spread angle of +/-3 is considered, for an intermediate fragment +/-5 and for smaller fragments +/-15.
It seems to me that the flap track damage (not the "major damage" as the manufacturer put it) lies outside of even the 15 region. Since all damage is supposed to be covered by the assumptions, this led to my wondering if the acceptable-means-of-compliance guidance would be revisited.

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Old 6th Dec 2010, 13:07
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Quote by Ferpe: ''Hi guys, think I found a picture of where the stub pipe is, it takes the lube oil the last bit from the inner casing to the bearing box (arrow):''

The schematic shown is not of a Trent 900 and is therefore not representative.
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