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Qantas A380 uncontained #2 engine failure

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Qantas A380 uncontained #2 engine failure

Old 17th Nov 2010, 14:33
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There seems to be a lot of talk about what RR knew and when, regarding possible contributions to the cause of this incident. While I will admit to the natural questions arising external from Rolls, there are very important oversights in place to protect the customers and the public from critical mistakes by an aviation manufacturer.

The product is initally certified as safe by the rigorous standards set by the regulator that all its competitors also have to undergo. Should unsafe conditions develop later in-service or even in an in-house development engine, the manufacturer has to report these to the regulator and at the same time present a corrective action plan to the satisfaction of the regulator which includes notification to all its customers.

In my read of all this Rolls and its regulator did not recognize an unsafe condition that required such actions. All this speculation in papers and web sites is just that.

The seemingly connection to this by citing a design improvement change (updated new engines) simply verifies that RR had to present the reason for this change to its regulator and of course secure its approval. Certainly if either Rolls or it regulator saw that the basis for the change was to correct a safety issue, then the corrective action would also have to have an incorporation plan for the rest of the fleet.

Without our public knowledge of this approval process we are in no position to judge the reasons or missed cues. That is the nature of how things work and the issue today is how we must learn from all this.

Of course hindsight is great but let's make this foresight for the future and fix todays fleet ASAP
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Old 17th Nov 2010, 14:33
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Yes, it is, though I used to make my living flying airplanes. But I don't speculate and opinionate on threads like this if it's out of my area of competence, unlike too many others.
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Old 17th Nov 2010, 14:51
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Dak writes:
Prove it.
Here you go, from the NTSB report:

The HPT stage 1 disk separated from the shaft at the conical section of the shaft and was completely missing from the engine. The recovery of the pieces of the ruptured disk revealed that it had broken into three approximately equal-sized pieces, as well as a fourth triangular-shaped piece and several smaller fragments. One piece of the disk, which initially bounced off of the ground before penetrating the airplane, completely severed the airplane’s left-hand keel beam and partially severed the right-hand keel beam before exiting the airplane and becoming lodged in the No. 2 engine’s exhaust duct.
You may find the pdf file named "A06_60_64.pdf" by Googling the tail number, N330AA.

Or visit www.ntsb.gov/recs/letters/2006/A06_60_64.pdf

Darn that inconvenient proof!

infrequent writes:
It survived - but it was on the ground at the time. In the air ? I wouldn't like to bet on it. Note that bits damaged both the engine and wing on the other side.
I'd say the damage would have been a lot less had it been airborne at the moment.

Cheers!
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Old 17th Nov 2010, 15:06
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Thanks RottenRay, however the "Prove it" quip was not aimed at your post, sorry for the confusion.
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Old 17th Nov 2010, 15:34
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Sandy:

Sorry about the tone.
The suggestion that an automatic overspeed control would be inherently unsafe does not strike me as logical, especially when discussing the inherently unsafe aspect of a sudden disc disintegration.
WHile that isn't what I said, I was addressing the converse - that when you automate something to deal with things going wrong, that automation too can go wrong.
The fact is that whatever overspeed protection does exist in the Trent and similar engines it singularly and spectacularly failed in this instance (assuming as has been suggested the disc broke up because of a sudden and huge spin-up as a result of being de-coupled from its shaft) and could have resulted in the loss of almost 500 lives.
That assumption may or may not be valid, so I don't think your positing the facts of overspeed protection failing stands up. As more info comes forth, it may.
Of course if the disc simply broke up at climb power rpm (as may have been the case) nothing would have contained it, and that would have nothing to do with overspeeding as is being postulated by some on here, which was the only issue I was addressing.
Agreed and thank you. Apologies are in order. I saw something else in your post and got all snarky. Shame on me.
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Old 17th Nov 2010, 15:35
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rottenray,

Are you seriously trying to say that the two incidents are the same.

Of course the AA 767 was going to have a few more issue, it was sat on the ground with concrete underneath it!!!
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Old 17th Nov 2010, 15:48
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Ok, I apologise to rottenray.

Having read the rest of some of this nonsense I see he that he is on my side
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Old 17th Nov 2010, 16:07
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Sandy and Groundgripper,

I think you are both right here, the problem with overspeed is detecting what is going on.
For 'simple' things like shaft break you look at the compressor and turbine speeds and compare them with each other and safety limits. For a disc breaking loose from a shaft you would need to have sensors on all the discs and shafts, a nightmare to make workable. Even if you detect an overspeed the shutdown, as was said, usually by fuel cut-off, has to be done very quickly otherwise all is lost!

If I recall correctly some BR700 series engines have a mechanical overspeed protection device - but I am an EEC person so perhaps some mechanical type may have better information.

But we digress, I am afraid, from this incident.

VnV

VnV
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Old 17th Nov 2010, 17:11
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Ex-Cargo writes:
Ok, I apologise to rottenray.
No sweat - I'm enjoying this discussion a lot, and just trying to keep *facts* involved when and where they exist.


Dak writes:
...however the "Prove it" quip wasn't aimed...
Er, my apologies. It's just that your post was so darn close to the other...


Here's something interesting from flightglobal:

Rolls-Royce and Airbus are reportedly looking into replacing up to 80 of Trent 900 engines following the 4 November uncontained failure aboard a Qantas A380.
(source: Zhuhai10: Airbus holds to China Southern A380 schedule)

Does anyone have a sanity check on this?


Cheers!
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Old 17th Nov 2010, 18:06
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Not sure if this incident has been mentioned at all, but this was another uncontained disintegration which occurred on a CO DC10 departing EWR in April of 2000. Didn't get much press, but the two remaining engines were damaged by the departing debris as were a number of other elements of the aircraft. Flight crew took over 30 minutes to return. Only posting this to show that these events do happen more often than some might think, and crews who follow the proper procedures do get the bird back on the ground.

Rare engine explosion could have been disaster
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Old 17th Nov 2010, 18:07
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An interesting pic of what was the Droop Nose drive motor and drive shaft.



From what I have seen of an Airbus presentation, BOAC's posting of yesterday where he listed the known damage to include puncture of the hull underside, but outside the pressure vessel was absolutely spot on.

mm43
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Old 17th Nov 2010, 18:11
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mm43;

What a mess! Thanks for the photograph.

I wonder, (I may have missed a link here or there in the thread), do we have any images yet of the underside of the left wing in board of #2 showing shrapnel entry points?

Cheers,
PJ
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Old 17th Nov 2010, 18:47
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PJ2;

Something will turn up, but I believe that as they demounted #2, they also began removing skin sections from the wing underside in way of the entry points.

A small piece of shrapnel penetrated the skin aft of the #1 door and inline with the upper deck floor stringer. The following graphic shows more clearly:-



mm43

Last edited by mm43; 19th Nov 2010 at 03:51. Reason: updated image
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Old 17th Nov 2010, 19:16
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Wing Damage

Also check out Ben Sandilands Plane Talking article for more very interesting pictures.
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Old 17th Nov 2010, 19:33
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IP Turbine Disk

What intrigues me is the fact that the IP turbine disk contained no blades at all. Any ideas on how the blades released themselves from the disk? There were no broken roots left - just clean fir tree slots. Any engineers out there got a view?
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Old 17th Nov 2010, 19:43
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The offending engine arrived back at EMA (centre of the universe nowdays) on a IL96 freighter today
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Old 17th Nov 2010, 19:50
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SRMman

Thanks for the Ben Sandilands photos.

It's interesting that he said:

"The wing of the jet shows remarkable structural strength in sustaining damage that might have destroyed the airliners of earlier decades."
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Old 17th Nov 2010, 20:20
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Although it's possible to land most heavy jets at their maximum take off weight on the departure runway, it is presumed that all normal landing systems and devices are operative.
Not so in this case; increments to Vref would have to be considered:
No leading edge devices? 20KN.
Reduced hydraulics? 15KN.
Secondary Brake and Anti-skid system???
It appears that system problems restricted the available fuel dump to reduce landing weight so approach speed might have been around 180+KN
With limited spoilers and reverse available you would be taking a really good look at brake energy limits in this situation, usually not well presented in ops manuals for odd configurations! The extra crew would have come in handy. Appears they made a good decision (guess) the armchair experts decided they had 150m to spare, not a lot on a runway the length of Singapore’s.
It will a interesting to know if the blown tyres on landing were due an anti-skid failure or the tyre blow out plugs from over heated brakes.
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Old 17th Nov 2010, 20:29
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infrequentflyer789

The GE disintegration affected #2 and Starboard wing I believe because it was on the deck. The disc and other parts had rebounded off the concrete to carom into right Engine, pylon, etc. That isn't an excuse, of course, but to assume the second powerplant in a twin would fail in the air, based on the GE 767 experience is not valid, imo. bear

SandyW

Overspeed has not been mentioned as a cause at all as of yet, by those here who post anonymously, and do know the status of the inquiry. imo So far, overheat via fire (only I have suggested friction from compromised bearings, and I am not one who knows much of anything,)

To paint a broader picture of this incident, knowing what is known, I think two things appear in focus. lomapaseo explains it eloquently in his asessment of Regulator/Operator 'mission'. Each is different, and together they comprise a complete picture of aviation. The operator calculates from a position of business, to include safety. The Regulator is charged with protecting the passengers' carriage, virtually all safety. There is always some tug and push, because of their separate missions. Left to wander off in pursuit of only one approach, the process gets more and more absurd (and dangerous, or bankrupt). Everything in Life is an agreement, a contract, a compromise of some description. Qantas appears to be in compliance, and the authority seems to have made reasonable demands. In this case, something happened unexpectedly, and those who don't understand the nature of the 'agreement' may snarl without basis at one or the other. The goal is to analyze, propose, and act prudently. Does any one have a better way to do it?

Lastly, and without sounding too praiseworthy, I have a new and profound respect for the Aircraft (380). I'd compliment the flightcrew, and the cabin crew, but they have done what they are supposed to do, as did the aircraft. (just kidding!)

bear

Last edited by bearfoil; 17th Nov 2010 at 21:09.
 
Old 17th Nov 2010, 20:56
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What intrigues me is the fact that the IP turbine disk contained no blades at all. Any ideas on how the blades released themselves from the disk? There were no broken roots left - just clean fir tree slots.
Classic stretched disk maybe
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