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Qantas A380 uncontained #2 engine failure

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Qantas A380 uncontained #2 engine failure

Old 17th Nov 2010, 11:55
  #1081 (permalink)  
 
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Are those folks alive today because they were on an A380?

Maybe this is too early, but when all the facts are known I hope someone will study whether:

1) An A330, with similar engine size and destructive potential, would have survived the wing box hit (thinner spars I presume). And...

2) Same question for a 747-400 or 747-8i, probably built to 1970's certification standards concerning structural damage tolerance.
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Old 17th Nov 2010, 12:12
  #1082 (permalink)  
 
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Turbine overspeed protection

VnV,

I have never come across an engine with the sort of turbine overspeed protection device I mused about. There has been no mention of such in the Trent engine, and I feel sure that if it had had one it would have been mentioned as having failed to do its job! Can you, given your experience, name a few engines that are so protected?
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Old 17th Nov 2010, 12:38
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Overspeed Trent 900

Engine Protection Systems
Introduction
The Protection System is incorporated into the EEC and provides hardware to perform the following functions:
LP & IP Rotor Overspeed protection
LP Turbine Overspeed protection
Thrust Control Malfunction (TCM) protection
LP & IP Rotor Overspeed System
The EEC monitors the LP & IP compressor shaft speeds (N1 & N2). If the measured values are above the defined limits, overspeed of the engine is detected and the engine is automatically shut down.
Turbine Overspeed System (TOS)
The EEC compares the LP compressor speed with the LP Turbine speed. If the speed difference is more than the limit, it is an indication of a shaft breakage and the engine is automatically shutdown.
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Old 17th Nov 2010, 12:41
  #1084 (permalink)  
 
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Sandy:

One of many handy features of having pilots on board aircraft is that when an engine overspeeds, the pilots retard the power levers, or shut down the engine, depending on what mode of overspeed in being experienced. The various flight manuals, systems composition, normal and emergency procedures, and application of checklists are practiced and learned for a very good reason: an engine's clever little electronic and hydroelectronic and mechanical bits may go wrong.

Most aircraft engines have an overspeed governor of some sort, some have more than one. Some are mechanical, some are electronic.

I will suggest to you that allowing the robot (which can go wrong) to kill your engine without your input is a good way to lose an engine right when you can't afford to.

Respectfully, I find your appeal to "perfect automation" an appeal to unsafe flying.

@ no-hoper: thanks for your list. I may have overstated the case, particularly in re Power Turbine overspeed.
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Old 17th Nov 2010, 12:47
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Originally Posted by kwateow
Maybe this is too early, but when all the facts are known I hope someone will study whether:
To be really honest, when this much of an engine lets go survivability is always going to be largely down to luck. You can try and move critical stuff out of the likely firing line, but wiring and plumbing have to run down the fuselage and wing and cross that line at some point. Also difficult to see how you can get the wing, including fuel tanks and leading-edge, out of the likely impact zone, without moving the engines to the tail (where uncontained failure is also known to be fatal...).

1) An A330, with similar engine size and destructive potential, would have survived the wing box hit (thinner spars I presume). And...
Can't do you an A330, but this is the results on a 767:
the HPT stage 1 disk was found in four pieces that were recovered from the left engine's pylon, the belly of the airplane, the right engine's exhaust duct, and from a vacant lot, which was approximately 2,600 feet away from the airplane, on the south side of the airport across runways 7L/25R and 7R/25L. Liberated debris from the left engine resulted in numerous holes in the fuselage as well as the left and right wings that had numerous holes in the fuel tanks from where fuel leaked that fed the fire that burned the left wing and left side of the fuselage aft of the wing.
Pictures: GE investigates cause of American Airlines Boeing 767-200 uncontained CF6-80A engine failure that led to aircraft fire-06/06/2006-Los Angeles-Flight International

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.

2) Same question for a 747-400 or 747-8i, probably built to 1970's certification standards concerning structural damage tolerance.
How about 747-200F, ie. El-Al, Amsterdam. Major engine (mounting) failure took out adjacent engine and hydraulics and damaged wing including slats - that last being fatal.
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Old 17th Nov 2010, 13:09
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To be really honest, when this much of an engine lets go survivability is always going to be largely down to luck.
So true. But engineers did a lot to raise the odds of survival.

How about 747-200F, ie. El-Al, Amsterdam. Major engine (mounting) failure took out adjacent engine and hydraulics and damaged wing including slats - that last being fatal.
According to the accident report, pilots lost control returning to the airport. It might have been survivable otherwise.

In this respect the Qantas crew did a good job in getting a plane in a very bad shape back on the ground safely. Planes in better shape than the A380 have been lost.
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Old 17th Nov 2010, 13:09
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At least it sounds like the latest Airbus factory installed Trent 900s do not have the same problem anymore.

Here is a pic of the QANTAS no. 2 eng:

Qantas A380-Notlandung: Trümmersuche beendet - FLUG REVUE
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Old 17th Nov 2010, 13:10
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Oh dear, oh dear

Controls severed for adjacent engine and it was locked in full climb the entire time, fuel system damaged and they couldn't move fuel to trim, hydraulics out and they had to use emergency brakes, slats jammed and they did a complete assymetric landing. Spar severed and multiple holes in fuel tank with 2 composite ribs collapsed internally, fuel everywhere. Multiple fuselage punctures, none in to the pressure bubble fortunately. Hoizontal stab is distorted because of the overweight landing with the untrimmed fuel. How it didn't catch fire is a miracle.

Airbus are talking about dis-mantling it and bringing it back to Airbus to try to repair it. Totally not Qantas problem. Problem is the composite ribs. They can repair the spar somehow but they can't get to the ribs without dismantling the entire wing.


Uncorrobotated but a reliable source.
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Old 17th Nov 2010, 13:16
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Turbine Overspeed

OK guys. I was actually a jet pilot so am fairly familiar with the usefulness of pilots and that sort of thing and have certainly had to handle some fairly hairy engine incidents myself, so no sarcasm please. In some situations even lightning reactions by a pilot are no safeguard. Furthermore Kegworth was actually precipitated by pilot error! 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. Modern jets have a great deal of reserve power and in the context of multijets it is obviously basic to be ready for a sudden loss of thrust at any stage of flight including TO, which would not normally lead to disaster. 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. 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.
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Old 17th Nov 2010, 13:20
  #1090 (permalink)  
 
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I'm entering this discussion with some trepidation as a retired aero engineer (who many years ago did work at Derby for a few years) but:

Engine Protection Systems
Introduction
The Protection System is incorporated into the EEC and provides hardware to perform the following functions:
LP & IP Rotor Overspeed protection
LP Turbine Overspeed protection
Thrust Control Malfunction (TCM) protection
LP & IP Rotor Overspeed System
The EEC monitors the LP & IP compressor shaft speeds (N1 & N2). If the measured values are above the defined limits, overspeed of the engine is detected and the engine is automatically shut down.
Would this have helped in this case? The IP shaft would have been winding down as the IP turbine end separated, so no overspeed would have been detected.
Turbine Overspeed System (TOS)
The EEC compares the LP compressor speed with the LP Turbine speed. If the speed difference is more than the limit, it is an indication of a shaft breakage and the engine is automatically shutdown.
Again, this wouldn't take into account the overspeed of the IP turbine, would it?
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Old 17th Nov 2010, 13:42
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Quote by Barit1:
But the "common knowledge" is that the T1000 engine that failed on 2 Aug was intended for a deliverable 787 (ship #9?). Why was this engine undergoing a development test, "well in excess of service conditions"? That doesn't seem a defensible practice.''

''Common knowledge''? I don't know where this rumour has come from, but that was a pure development engine and as such would never be put into service. There are only four R-R powered aircraft in the flight development programme.

The first 'customer' engine was only put on test 3 weeks ago.
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Old 17th Nov 2010, 13:45
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and they had to use emergency brakes,


emergency brake? ha!
Uncorrobotated but a reliable source.
RUBBISH!
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Old 17th Nov 2010, 13:51
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Groundgripper,

Thanks for contributing. All the overspeed protection built in to the engine relies on it being controlled or even shut down by managing the fuel flow as far as I know. First thing of course, I don't think we actually know that the IPT did overspeed before breaking up. As you say if the IP disc de-coupled from the shaft no overspeed would be detected, in fact quite the opposite! Overspeed resulting from decoupling would be unstable and as far as I know there are no sensors on the engine which would detect an overspeed of a disc loose on its shaft. Even if there were, what mechanism would there be to stop the disc overspeeding given that there would still be hot gas flow on it (the HP compressor would still be feeding the combustion chamber) and no load from the compressor. The only way to stop the catastrophic overspeed would be a mechanical system to directly brake the disc before it totally disintegrated. Not easy, but given the risks that seem to be present, I think the issue may need to be addressed.
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Old 17th Nov 2010, 13:53
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Originally Posted by infrequentflyer789
Can't do you an A330, but this is the results on a 767
...
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.
To be fair, wasn't that because the ejected parts ricocheted off the ground and back up the other side, rather than going straight through?

TN
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Old 17th Nov 2010, 13:56
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Prove it.
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Old 17th Nov 2010, 13:56
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paull

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.
Yup, you have an understanding of this. The regulation addresses this on the basis that three equal size infinite energy segments are released simultaneously. The regulation also considers lesser size fragments but historically only one of these is expected to have infinite energy.

Unfortunately designing dotted lines on spinning parts to assist them breaking into small bits adversely affects how often they break and go boom in the night.
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Old 17th Nov 2010, 14:01
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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?


HE is saying the RR knew of the problem and were tardy in their response and possibly not entirely upfront about the problem and it's possible consequences

and

he is also saying that QANTAS shouldn't divest itself of its responsibilities in the maintenance of it's aircraft.

They have a duty to understand that RR will act in the interest of RR and not of QF. QF need either much stricter oversight of their relationship with RR or they need to maintain the engines themselves. (choose your poison here)

in any SLA you need to fully understand the systems that the SLA covers and be able to protect the operation so that the provider cannot and doesn't only fulfil the min requirements, esp in something that can damage your brand.

in computing there are many cases of companies/govts etc taking back the operation of their various systems because outsourcing hasn't provided the necessary level of service. I would be less than shocked if the same thing happened in the airline industry.
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Old 17th Nov 2010, 14:08
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"Problem is the composite ribs. They can repair the spar somehow but they can't get to the ribs without dismantling the entire wing.

Uncorrobotated but a reliable source. "

There are composite ribs but they are located more outside.
Ribs 7/10/11 are metallic ones.
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Old 17th Nov 2010, 14:24
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Interesting that since I commented (above) that "the [real] pilots have left the room," there have been 18 posts, not a one by a member of any professional flight crew.

I think I'll go now.
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Old 17th Nov 2010, 14:29
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This is your tag entry. Isn't it?
Occupation:freelance writer
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