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Author Topic: A-380 emergency landing!  (Read 17069 times)
Koen
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« on: 4 November 2010, 18:34:05 »
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SINGAPORE - A Qantas A380 superjumbo made a dramatic emergency landing in Singapore Thursday after experiencing engine trouble over Indonesia, in the first mid-air emergency involving the giant Airbus plane.

A troubled Qantas Airbus A380 plane is seen after an emergency landing at the Changi International airport in Singapore on November 4, 2010.

The double-decker plane, flight QF32, had taken off from Singapore bound for Sydney carrying 433 passengers. It dumped fuel over Indonesia before returning to the city-state's Changi Airport trailing smoke.

Six fire engines swarmed the A380 on landing, spraying liquid on it, according to an AFP reporter.

Part of one of the engines on the left wing, engine number 2, were  missing, and the area around it was black, the reporter said.

Australia's government said no passengers or crew were injured.

"The flight has landed safely at Changi Airport and there are no passengers or crew injured," a foreign department statement said.

Plane debris including what appeared to be part of the tail of a Qantas jet was found in the Indonesian town of Batam, after a mid-air explosion was heard on the ground.

"I didn't see a plane crash but I heard a loud explosion in the air. There were metal shards coming down from the sky into an industrial area in Batam," witness Noor Kanwa told AFP.

Qantas   later suspended all further A380 superjumbo flights until further notice.

The decision was announced by a spokesman at a televised live press conference in Australia.

The spokesman described it as a "significant engine failure"  and "an uncontained engine failure" .
He said "parts left the engine and fell to the ground".

Passengers reported an explosion and sparks.

The airline's six A380s would be grounded until Qantas was confident it could be operated safely, the spokesman said. The maker of the engines on the damaged plane, Rolls Royce, was cooperating in the investigation, he said.

Passengers would be accommodated in Singapore hotels and replacement flights were being arranged.

The aircraft in the incident, the Spirit of Australia, was the first A380 delivered to Qantas, two years ago.

Qantas, which has never suffered a fatal crash in its 90-year history, earlier rushed to deny reports of a crash.

There had "definitely" not been a crash involving one of its planes over Indonesia, a spokeswoman said.

"We're just waiting on a report," she told AFP. "At this stage there's definitely been no crash."

The A380's very first commercial flight operated by Singapore Airlines was on the same Singapore-Sydney route in October 2007.

Since then, fuel and computer glitches have grounded several A380s and at least one Air France flight was forced to turn around and land in New York after problems with its navigation system in November 2009.



more info: http://www.bbc.co.uk/news/world-asia-pacific-11691197

London To Sydney Airbus A380 in emergency landing as engine explodes 4 nov 2010


as a result Qantas has grounded all it's 380s (6).

Quote
Singapore Airlines said its A380 (11) flights would be delayed pending technical checks


Quote
Engine maker Rolls-Royce said it was in the process of checking the 20 A380 planes currently in service - with Qantas, Singapore and Lufthansa - that use its Trent 900 engines


Quote
The other 17 A380s in service - with Air France and Emirates - use another engine.


« Last Edit: 4 November 2010, 18:41:41 by Koen » Logged
FACman
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« Reply #1 on: 4 November 2010, 19:36:11 »
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This is exactly why I'd rather be lucky than good. 433 lucky passengers. All things being equal, I still feel safer in the air than on the highway. Especially since they are still giving drivers licenses to idiots.
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« Reply #2 on: 4 November 2010, 22:55:39 »
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What you dont see:

This is a major incident (actually in aviator speak qualifies as "accident", almost):

- At first sight it seems to be an "uncontained" engine failure, not a good thing at all as not planned for (there are many rules in place that would all suggest a fan or compressor blade rupture would have to be contained at least in upward and inward direction, invented after the UAL DC10 mishap: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/eab0330a3c7a22eb862569b3005d6ace/$FILE/ac33-5.pdf), if rotating parts of the engine fail and get thrown around in directions other than the exaust something is seriously wrong.

I judge this picture from (allegedly) salvaged debris to suggest this is indeed what happened (but NOTE this is pure speculation, I dont even know if the pic is real):



- RR Trent engines have had said troubles over quite some time, my question would be whether we now see an a) design flaw or b) a maintenance flaw or c) an arbitrary accident that could happen every day. A/c had just passed a C-Check, so this alos might be a factor or exclude b).

- it is also obvious that some parts of either the engine or its cowling have penetrated the wing, leaving a hole right in front of the main spar, damn close to the fuel tanks from my POV. Now, again there are different possible interpretations: "Hey, all went as designed, uncontained engine failure will not let debris penetrate the wing where the fuel is" or "lucky bastards, this might have ended differently had the debris penetrated the wing 50 cm further back". No speculating possible here, the investigation will come up with the relevant answer and we will just have to wait (but explains the grounding of the fleet)



- crew certainly did a great job: AFAIK the incident occured on climb after TO (rather max revs at this stage) and so the weight of the plane had to be reduced by jettisoning fuel, this took allegedly 1.5 hours during which the passengers (seeing the hole in the wing) certainly did not really enjoy their flight. Crew will have been dealing with a lot of red and amber in the cockpit, surely a bit wet hands between them (looking forward to the release of the CVR in a year or so). I have read somewhere that more heavy body captains were on a ferry flight, so they probably helped out with informing crew about the damage and helped access reaction schedules from this angle.

- another indicator of the seriousness of the incident is that the (see pix) LG doors all are open, from my POV this would indicate a major hydraulic problem (as they usually close once LG is deployed), again probably due to the debris probably cutting either buses or hydraulic systems (triple on this a/c as I hear from friends in the know, myself I have no clue in this matter).

- #1 engine was not able to shut down after TD, the equipment had to shut it down "drowning" it with water and foam (and you need lots of that, those engines are prepared to take heavy weather), and it took a considerable time (see pic with the water exiting exhaust of what obviously is an engine at full power, NOTE pax desembarking on the other side over stairs). Probably due to the buses of control severed by the debris penetrating wing (FADEC system), that is the area where they pass (and will have to be reviewed: I think landing with one engine on full throttle - it that was its last status in climb - , one reactor dead, and reduced hydraulics with reference to LG doors and flaps - as described above - surely was not something you train for daily):



In total, great crew and Lady Luck shining on them in a freak situation would be my take.

The plane itself will need a long time to get airborne again, that is for sure.

FWIW, and with all layman´s reservatons,

Rattler
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« Reply #3 on: 7 November 2010, 21:52:43 »
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A few things Rattler.
1. It does look like a compressor disc, it also ruptured in the classic 1/3-2/3 with probably a third small piece broken off.
2. A disc failure is almost never contained certainly the rear discs (larger and more mass)
3. Design flaw? Possible but more likely a fabrication fault.
4. Maintenance fault? Again possible, I would have to see the maintenance records to see if any engine modules were replaced.
5. The FADEC problem on number one will cause a few red faces, both at Airbus and RR. Indeed a FADEC engine will maintain the last selected thrust when there is a total failure of power. That might be a carry-over from a Tornado accident in 1983 where the a/c experienced a total power failure and both engines ran away and failed.
<a href="http://www.mod.uk/NR/rdonlyres/77186A18-0C22-43CA-AA81-4A64C4E600D8/0/maas83_22_tornado_gr1_za586_27sept83.pdf" target="_blank">http://www.mod.uk/NR/rdonlyres/77186A18-0C22-43CA-AA81-4A64C4E600D8/0/maas83_22_tornado_gr1_za586_27sept83.pdf</a>
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Rattler
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« Reply #4 on: 7 November 2010, 22:50:00 »
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A few things Rattler.
1. It does look like a compressor disc, it also ruptured in the classic 1/3-2/3 with probably a third small piece broken off.

2. A disc failure is almost never contained certainly the rear discs (larger and more mass)


Indeed, and if I understand it right from the ppl in the know it is the last compressor disk, nothing to contain if that fails and breaks. My comment about containment specifically referred to (accounted for by constrction as far as weight allows) blade failure. As for compressor disks, they *should* never fail in the first place, and a lot of ingeneering energy goes into trying to assure that.

OTOH I have read somewhere (dont recall where) that they had an overspeed issue on this engine one or a few days earlier (and allegedly went on MEL), should this be true and have repeated this might easily exeed the design parameters of a disc (but again, I am no expert on this, just can quote what I picked up on the wire).

3. Design flaw? Possible but more likely a fabrication fault.


Or, as mentioned above, an overspeed issue where both design or fabrication parameters might have been exeeded.

4. Maintenance fault? Again possible, I would have to see the maintenance records to see if any engine modules were replaced.


Personally, though the a/c recently passed a C-check, would doubt a maintenance failure, but this is a hunch only and pure speculation on a gut feeling. Investigation will surely clear that part up, as all data and the plane and the engine made it to the ground (I dont know about the legal situation with the debris having fallen on a nation out of Australian and ATSB jurisdiction, if at all, the problem for clearing things up might orignate from this fact, though I would doubt Burma (?) would create problems on such a matter).

5. The FADEC problem on number one will cause a few red faces, both at Airbus and RR. Indeed a FADEC engine will maintain the last selected thrust when there is a total failure of power. That might be a carry-over from a Tornado accident in 1983 where the a/c experienced a total power failure and both engines ran away and failed.
http://www.mod.uk/NR/rdonlyres/77186A18-0C22-43CA-AA81-4A64C4E600D8/0/maas83_22_tornado_gr1_za586_27sept83.pdf


Totally agree, I am confident and expecting in this respect we will see a list of Interim Aviation Safety Recommendations issued by the ATSB to the manufacturers way earlier than the preliminary of final report.

Another important part of the incident is the hydraulic problem that I mentioned and that by now has been confirmed (landing with half of the spoilers deployed only - in the press they are insistin on non-deployed "flaps" hdbng - flaps were deployed and the problem was clearly with the spoilers as can be seen by everyone in the attached pax vid). This is serious, as I am sure you will know, because if you add spoiler/flaps and probably breaks and reverser problems to a situation with one engine out and the other uncontrollabe on the same wing (+ overweight) I am quite certain you need a very well qualified crew and good CRM (+ favorable weather and RWY) to bring this bird down safely, worked out as we all know.

Again I believe this will have to be addressed by investigators and manufacturers, as far as I see it (and read the phrasing somewhere else) overall they made it down on "luck and swiss cheese".

Qantas A380 emergency landing Footage (4 November 2010)


In PMs some forum members questioned my claiming the accident a/c to be grounded a long time. The reason is simple: The wing skin of an A 380 is *huge*: 120 feet long, all in *one piece*, 2.5 cm thick at the root and only 5 mm thick at the tip, you cannot simply "weld" or "patch" it: This will require either a completely new skin fix or even a new wing (depending on the internal damage: Spar?), and all manufacturing lines are blocked for years with orders AFAIK. As a consequence the a/c might be a complete write-off in the end.

To give you an idea on how complicated the construction of a wing of the A 380 is (and something like it has never before been endeavoured), check this interesting vid, I am sure many of you will not have even imagined the extent of the technical challenge behind the construction of such a wing:

Airbus A380 - Wing Construction - HD


Rattler
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« Reply #5 on: 8 November 2010, 07:34:21 »
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Yep, the wing fix will be leaving a few engineers scratching their heads for a while. I know that the wing is a one-piece structure but I don't know how it's built. I assume that it's two chemically milled skin sections joined together with internal struts. A very strong wing but incredibly difficult to repair. BDR repairs tended to involve a sheet of mild steel (6mm thick) and Jo-bolts.
I hadn't heard of the engine overspeed, I assume that there is a mechanical governer as well as the FADEC to ensure the engine never exceeds design limits. It would be interesting to see how much it oversped.
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« Reply #6 on: 8 November 2010, 21:24:02 »
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interesting stuff guys  salute

the latest I heared is that the Quantas guys found oil leaks on the RR engines?

http://hercules.rr.com/news/topic/article/rr/9000/25906952/Qantas_CEO_Oil_leaks_in_3_engines_of_its_A380s
http://www.independent.co.uk/news/business/news/a380-oil-leaks-prompt-rollsroyce-shares-slump-2128311.html
Quote
SYDNEY — Tests have uncovered oil leaks in three Rolls-Royce engines on Qantas' grounded Airbus A380s, the airline's CEO said Monday, as engineers tried to identify the cause of an engine failure on one of the carrier's superjumbo jets last week.
Australia's national carrier grounded its six double-decker A380s, the world's newest and largest airliner, after an engine burst minutes into a flight from Singapore to Sydney last week, scattering debris over Indonesia's Batam island. The plane made a safe emergency landing in Singapore.
Engineers conducted eight hours of extensive checks on each engine over the weekend.
On Monday, CEO Alan Joyce said engineers have discovered oil leaks in the turbine area of three engines on three different A380s.
"The oil leaks were beyond normal tolerances," Joyce told reporters. "So Rolls-Royce and our engineers have looked at what we have gathered as an accepted level and they have passed that threshold."
"All of these engines are new engines on a new aircraft type," he added. "The engines are not performing to the parameters that you would expect with this."
Because of that, he said, all of the airline's A380s will be grounded for at least an additional 72 hours.
"We are not going to take any risks whatsoever," Joyce said. "We want to make sure we have a 100 percent safe operation."
All three affected engines have been removed from the planes for further testing, and will be replaced with spare engines the airline has on hand, Joyce said.
"As a consequence, it's now narrowing our focus on that issue," he said.


Quote
A380 oil leaks prompt Rolls-Royce shares slump
Manufacturing giant Rolls-Royce suffered another shares slump today after the chief executive of Qantas said oil leaks were discovered in three engines on board its superjumbo fleet.
Qantas grounded six giant A380s after an engine burst minutes into a flight from Singapore to Sydney last week, scattering debris over Indonesia's Batam island.
Qantas boss Alan Joyce said engineers found leaks beyond an acceptable level in three engines, built by Rolls-Royce, on separate A380s.

Rolls-Royce, which is working with Qantas on the investigation, has seen its market value fall more than £1.5 billion since the incident. Shares shed 4% or 23p to 567.3p.
Singapore Airlines, which also flies the superjumbo aircraft, said today that its inspections had found no problems with the Rolls-Royce Trent 900 engines.
Qantas and Rolls-Royce engineers carried out eight hours of extensive checks on each engine over the weekend.
Speaking earlier today, Mr Joyce told a press conference: "The oil leaks were beyond normal tolerances. So Rolls-Royce and our engineers have looked at what we have gathered as an accepted level and they have passed that threshold."
He went on: "All of these engines are new engines on a new aircraft type. The engines are not performing to the parameters that you would expect with this."
Mr Joyce said all of the airline's A380s would be grounded for at least an additional 72 hours.
Mr Joyce added: "We are not going to take any risks whatsoever. We want to make sure we have a 100% safe operation."
The Australian Transport Safety Bureau, which is leading an international investigation into the blow-out on the A380, appealed for help from residents of Indonesia's Batam island to find a missing piece of a turbine disc.
Debris was scattered over the island last Thursday when one of the A380's four engines failed minutes into a flight to Sydney, with 466 people on board. The engine was quickly shut down and the plane returned to Singapore and safely made an emergency landing.
Qantas passengers stranded by the grounding of the A380s are expected to be flown to their destinations within 24 hours, Mr Joyce said. The airline is adding flights from London and Los Angeles to help clear the backlog.
Passengers on board the flight described seeing flames pouring from one of the engines as it made its landing. Images taken of the jet after the emergency landing revealed that one of its giant engines had been badly damaged.



Quote
As a consequence the a/c might be a complete write-off in the end.


should I see this, very simply approached, when a car has an accident but with all airbags exploded it has more chances to be a total write-off?
« Last Edit: 8 November 2010, 21:32:59 by Koen » Logged
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« Reply #7 on: 9 November 2010, 07:21:45 »
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Indeed, just like a car, if the cost of repair is higher than a certain percentage of the book value then the insurance company will write it off.
The owner may buy it back if they wish and rebuild it, even if it costs more. They rarely do that obviously.
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« Reply #8 on: 9 November 2010, 07:52:05 »
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It is rumored that the insurance will not pay for the 3 engine ferry flight to France, where the wing would have to bee repaired, for worry of the risk of losing the whole a/c due to the hole in the wing. Of course, it could be partially dismanteled and transported by sea, but this cost, together with the wing replacment/repair will be high.

If it reaches the 350 Million Euros price of a new one I dont know but doubt it, so it still might be feasible to have it repaired but will take a long time.

As far as the RR engine and the oil found, it is now under investigation whether this is a resnance leak caused by the higher power of the Quantas models (compared to Lufthansa, e.g.).

Qantas uses a slightly more powerful model of the engine, they need this to allow for full Take-Off weight for their long haul routes over the Pacific. In this model the electronics allow higher revs for take off (and the engine is certified for this) and it now is supsected that a resonance frequency problem with those revs might be the reason for the oil lines starting to leak oil.

If that should be confirmed, first solution would be to change the chip to normal configuration and until RR fixeds this problem have Quantas go with less passengers (I have read somewhere that it would have to carry 5% less pax for the normal config), something the airline of course not is looking forward to as it might make the a/c lose its rentability.

FWIW,

Rattler
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« Reply #9 on: 9 November 2010, 19:20:41 »
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It is rumored that the insurance will not pay for the 3 engine ferry flight to France, where the wing would have to bee repaired, for worry of the risk of losing the whole a/c due to the hole in the wing. Of course, it could be partially dismanteled and transported by sea, but this cost, together with the wing replacment/repair will be high.

If it reaches the 350 Million Euros price of a new one I dont know but doubt it, so it still might be feasible to have it repaired but will take a long time.

As far as the RR engine and the oil found, it is now under investigation whether this is a resnance leak caused by the higher power of the Quantas models (compared to Lufthansa, e.g.).

Qantas uses a slightly more powerful model of the engine, they need this to allow for full Take-Off weight for their long haul routes over the Pacific. In this model the electronics allow higher revs for take off (and the engine is certified for this) and it now is supsected that a resonance frequency problem with those revs might be the reason for the oil lines starting to leak oil.

If that should be confirmed, first solution would be to change the chip to normal configuration and until RR fixeds this problem have Quantas go with less passengers (I have read somewhere that it would have to carry 5% less pax for the normal config), something the airline of course not is looking forward to as it might make the a/c lose its rentability.

FWIW,

Rattler


thx for the info, so a chipped version that due to the higher revs causes a certain vibration causing a tube or connection to turn loose and spill oil...
the chipping was done by RR I presume?
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« Reply #10 on: 9 November 2010, 20:08:40 »
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As far as the RR engine and the oil found, it is now under investigation whether this is a resnance leak caused by the higher power of the Quantas models (compared to Lufthansa, e.g.).

Hmm, I find that a little strange. Vibration loosening an oil line. All bolts/nuts/flange nuts are generally locked in some way (self locking nut, spring rings, locking tabs or wire) vertainly in something as important as engine oil. Vibration fretting gaskets? Not something I'd expect. Any cracking of oil lines would give large oi; leaks but could be easily solved by changing the lemgth of the affected lines. Gas turbines are notorious for destructive frequencies. If you have ever looked closely at all the plumbing you will notice that a great number of pipes have extra length and seemimgly unneccessary bends and loops. They are normally there to counter resonance frequencies.
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« Reply #11 on: 9 November 2010, 20:49:21 »
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As far as the RR engine and the oil found, it is now under investigation whether this is a resnance leak caused by the higher power of the Quantas models (compared to Lufthansa, e.g.).


Hmm, I find that a little strange. Vibration loosening an oil line. All bolts/nuts/flange nuts are generally locked in some way (self locking nut, spring rings, locking tabs or wire) vertainly in something as important as engine oil. Vibration fretting gaskets? Not something I'd expect. Any cracking of oil lines would give large oi; leaks but could be easily solved by changing the lemgth of the affected lines. Gas turbines are notorious for destructive frequencies. If you have ever looked closely at all the plumbing you will notice that a great number of pipes have extra length and seemimgly unneccessary bends and loops. They are normally there to counter resonance frequencies.



not an expert at all but when we worked on the engines we indeed wired the bolts
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« Reply #12 on: 9 November 2010, 22:41:26 »
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@ Koen: Yes, chipped by RR, but still below certified thrust parameters for this engine type, so no prob there, had been (theoretically) tested sufficciently during design phase.

As far as the RR engine and the oil found, it is now under investigation whether this is a resonance leak caused by the higher power of the Quantas models (compared to Lufthansa, e.g.).


Hmm, I find that a little strange. Vibration loosening an oil line. All bolts/nuts/flange nuts are generally locked in some way (self locking nut, spring rings, locking tabs or wire) certainly in something as important as engine oil. Vibration fretting gaskets? Not something I'd expect. Any cracking of oil lines would give large oil leaks but could be easily solved by changing the length of the affected lines. Gas turbines are notorious for destructive frequencies. If you have ever looked closely at all the plumbing you will notice that a great number of pipes have extra length and seemimgly unneccessary bends and loops. They are normally there to counter resonance frequencies.


While having looked more than once at turboprops (also by RR, the Tyne Mk22) but never at turbofans and hence would not consider me anything even near to a turbine expert, I only wanted to report that this "seems to be under investigation" as that is what I have gathered from the press and the net.

Might as well turn out it had nothing at all to do with the massive oil leaks into either the combustion chambers or the IP - Intermediate Pressure -  turbine (Trent is three-shaft with an intermediate turbine driving the fan over a reduction gear, and it seems that after all this part went astray and not a compressor disk) Quantas found during 8 hours RR recommended duration tests on their Trent engines.

Still, it remains a significant finding that this leaking only occured on Quantas Trents 972, and not on Singapore or Lufthansa 970 Trents (who underwent the same 8 hour tests on Sunday), the difference between the types being the mentioned thrust increase on the 972s.

If we take the intital finding (oil leak) for granted, then this is the base the investgators are starting from:

Quote
Qantas boss Alan Joyce said engineers found leaks beyond an acceptable level in three engines, built by Rolls-Royce, on separate A380s. "The oil leaks were beyond normal tolerances. So Rolls-Royce and our engineers have looked at what we have gathered as an accepted level and they have passed that threshold."


Quote
Singapore Airlines, which also flies the superjumbo aircraft, said today that its inspections had found no problems with the Rolls-Royce Trent 900 engines.


Quote
Rolls-Royce engineers carried out eight hours of extensive checks on each engine over the weekend.


Here two relevant articles to my claim, one from yesterday, one from today:

Wall Street Journal: A380 take-off may be the problem

and

CNBC: Qantas reviews way it runs A380s in engine probe

A first theory derived from early problems with the Trent 900 series, descibed here, whereby heavy wear on the IP turbine (concentrical) shaft might have allowed the whole Intermediate Turbine section to move backwards and phyical get in contact with statioc turbine parts seems to have been discarded by now.

FWIW,

Rattler
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« Reply #13 on: 10 November 2010, 08:09:12 »
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Good points Rattler.
I'm also familiar with the Tyne.
I was a little unsure as to the id of the disc. It had been named as a comp disc failure by a fair number of people who I thought knew their stuff.
My first thought seeing it was turbine judging by the blade mounting (fir tree) compressors are normally pinned into place. However the disc is a lot thinnier than I would expect, especially in a HP turbine (judging by the size).
Disc failure due to bearing failure? Hmm.
It is certainly a stress induced failure, that much can be seen by the size of the remnant.
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« Reply #14 on: 10 November 2010, 10:28:52 »
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I was a little unsure as to the id of the disc. It had been named as a comp disc failure by a fair number of people who I thought knew their stuff.


N ot surprisingly so: I think the compresor disk failure was the first theory that emerged when "uncontained disc failure" was established as the probable cause directly after the incident. Indeed so far the most uncontained disc failures involved compressor disks.

My first thought seeing it was turbine judging by the blade mounting (fir tree) compressors are normally pinned into place. However the disc is a lot thinnier than I would expect, especially in a HP turbine (judging by the size).

My thoughts also, very thin, but I have looked at some graphic and the IP compressor and 1 stage turbine disc (which - correcting my statement from last post: Fan is actually driven by the 5 stage LP turbine - ) run together on the 2nd shaft and seeem to be significantly thinner than other turbine discs judging from the graphic.

Here the schematic design of the Trent family, nicely separating the different pressure areas:



On the cutaway it can be seen the IP turbine disc indeed is not very thick:



and then on the incident engine you can see this the location of the part that is missing, so probably either HP or IP turbine disc:



Now, if we knew which of the two is geared (as to be judged from the fragment) we could ID which disc that fragment is from exactly.

David Epstein, Qantas general manager, says here of the number two engine: "There doesn't appear to be a disk there at the moment. Virtually that entire area, the intermediate chamber of the engine, has disappeared."

A interesting article at flightblogger (where I also stole the last graphic from) has it as this:

Quote
The intermediate-pressure turbine, which is part of Rolls-Royce three-shaft engine architecture, is unique among the large commercial transport engines. Competitors Pratt & Whitney and General Electric have a two-shaft architecture. The three-shaft architecture allows each part of the engine's core to spin at an optimized speed. The three shafts, which run concentrically, host the low, intermediate and high pressure elements.

The intermediate pressure (IP) compressor and turbine, which are hosted on the same shaft, are allowed to rotate faster than the fan, requiring fewer stages. The result is a shorter and lighter engine.

The Trent 900 architecture features a 116in front fan, which acts as the engine's single-stage low pressure (LP) compressor, followed by an eight-stage IP compressor, six-stage high-pressure (HP) compressor, single annular tiled combustor with 20 fuel injectors, single-state high pressure turbine (drives the HP compressor), single-stage IP turbine (drives the IP compressor) and a five stage LP turbine (drives the front fan).



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« Reply #15 on: 10 November 2010, 22:03:07 »
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By geared disc am I to assume they mean the PTO for the ancilliaries? It would explain the bell forming on the inner edge. That would make it a HP disc and as good is, the first. If so, it could have been far worse.


* Victor XL232 002.jpg (48.58 KB, 480x377 - viewed 521 times.)
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« Reply #16 on: 10 November 2010, 22:20:16 »
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My idea for this expression was that it would drive the gearbox that works all the aux stuff, but I am not firm in tech speak relayed to turbines.

Just ran into an unattributed list of damage done during the incident, looks not only my primary accessment of plenty amber and red in the cockpit was correct, but also looks as if everybody was way luckier than we so far have assumed (of course, only if this list shoould hold true, posted at PPrune Forum):

Quote
* massive fuel leak in the left mid fuel tank (the beast has 11 tanks, including in the horizontal stabiliser on the tail)

* massive fuel leak in the left inner fuel tank

* a hole on the flap canoe/fairing that you could fit your upper body through

* the aft gallery in the fuel system failed, preventing many fuel transfer functions

* fuel jettison had problems due to the previous problem above

* bloody great hole in the upper wing surface

* partial failure of leading edge slats

* partial failure of speed brakes/ground spoilers

* shrapnel damage to the flaps

* TOTAL loss of all hydraulic fluid in the Green System (beast has 2 x 5,000 PSI systems, Green and Yellow)

* manual extension of landing gear

* loss of 1 generator and associated systems

* loss of brake anti-skid system

* unable to shutdown adjacent #1 engine using normal method after landing due to major damage to systems

* unable to shutdown adjacent #1 engine using using the fire switch!!!!!!!!

Therefore, no fire protection was available for that engine after the
explosion in #2

* ECAM warnings about major fuel imbalance because of fuel leaks on left side, that were UNABLE to be fixed with cross-feeding

* fuel trapped in Trim Tank (in the tail). Therefore, possible major CofG out-of-balance condition for landing



Also, Singapore Airline grounded its A380 fleet today after a flight crew refused TO because of leaked oil in one of the engines and changed three engines in the fleet.  Then, it was Lufthansa to announce they changed 3 engines as a "precaution".

If this is connected, might after all be a design problem and not an operator problem..

Questions over questions...

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« Reply #17 on: 10 November 2010, 22:56:25 »
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Indeed many questions.
I have just read that the Trent does drive it's generators off the IP which I find surprising. The normal architecture of multi-spool engine has the HP spool on the outside making it the easiest to fit a PTO for your extra's (fuel pump,oil pump etc). That photo is what happens when a turbine disc enters a fuel tank (two in the case of XL232). There wasn't much left when the flames died down. Fortunately no casualties.
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« Reply #18 on: 11 November 2010, 09:42:32 »
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Yes, as already mentioned, the IP drive all the auxiliary stuff through a reduction gearbox to downspeed the 8300 rpm it revolves at (thats what I had thought was meant when they called this turbine disc "geared", with "gear teeth"?).

Another interesting question would be whether the diagnosed oil leaks and spills have been found always on the inner engies (#2+3) or evenly distributed. As the inner engines have thrust reversers while the outers have not this would open another lane to investigate.

A newly EASA published AD (Airworthiness Directive) shades a better light on what might have happened in detail, relevant excerpts below (highlights by me):

Quote
EASA EMERGENCY AIRWORTHINESS DIRECTIVE
AD No.: 2010-0236-E
Date: 10 November 2010

-snip-

Quote
Reason: An uncontained engine failure has recently occurred on a Rolls-Royce
Trent 900 involving release of high energy debris and leading to damage
to the aeroplane.

Analysis of the preliminary elements from the incident investigation shows
that an oil fire in the HP/IP structure cavity may have caused the failure of
the Intermediate Pressure Turbine (IPT) Disc.


This condition, if not detected, could ultimately result in uncontained
engine failure
potentially leading to damage to the aeroplane and hazards
to persons or property on the ground.

For the reasons described above and pending conclusion of the incident
investigation, this AD requires repetitive inspections of the Low Pressure
Turbine (LPT) stage 1 blades and case drain, HP/IP structure air buffer
cavity and oil service tubes in order to detect any abnormal oil leakage,
and if any discrepancy is found, to prohibit further engine operation.
The requirements of this AD are considered as interim action.


In layman speak this would mean an oil fire in the space between the HP and the IP turbine disc.

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« Reply #19 on: 11 November 2010, 19:24:04 »
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So it could well be oil lines adrift. That is fortunately an easier fix than a turbine disc redesign.
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