Sunday, 21 December 2014
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Airlines forewarned of Rolls-Royce engine issue

Rolls-Royce was warned months ago about the safety of the engine model powering a Qantas aircraft forced to make an emergency landing yesterday.

The airline’s chief executive, Alan Joyce, said this morning that a ‘design issue’ may have caused the engine failure on the Airbus A380 aircraft forced to return to Singapore shortly after take-off.

This followed the emergence of warnings made in August by the European Aviation Safety Agency (EASA) of ‘wear, beyond Engine Manual limits’ and conditions that ‘present a potential unsafe condition to the aeroplane’ in relation to the Trent 900 engine.

In an airworthiness directive, EASA said wear was found on the splines of the intermediate pressure (IP) turbine that required inspection. Rearward movement of the turbine ‘would enable contact with static turbine components and would result in loss of engine performance with potential for in-flight shut down, oil migration and oil fire’, it said.

Joyce said the problem with the Qantas aircraft was an engine issue and not related to the airworthiness of the plane. ‘We believe this is probably most likely a material failure or some sort of design issue,’ he told reporters in Sydney.

Rolls-Royce issued a statement yesterday saying the process of precautionary engine checks was underway. A spokesperson told The Engineer it was important to note that the investigation was still at an early stage.

Eyewitnesses reported seeing one of the plane’s engines explode before the plane carrying 440 passengers and 26 crew returned to Singapore. The aircraft landed safely and, according to Qantas, there were no injuries to any passengers or crew.

Airbus said in a statement that it had asked all A380 operators with Rolls-Royce engines to inspect the planes. Qantas has grounded its fleet of A380s but Singapore Airlines has resumed flights after delays yesterday.

Commentators have suggested multiple explanations for the engine failure, emphasising that a full investigation would be needed for a concrete verdict.

Dr Ranjan Vepa, lecturer in avionics at Queen Mary, University of London, said: ‘The uncontained engine failure could also have been caused by a combination of circumstances that could have triggered a sequence of enabling events leading to the uncontained engine failure almost immediately after take-off.

‘This naturally tends to make one suspect that the engine was probably hit by something that caused the engine inlet to be blocked, which in turn could have triggered a sequence of events leading to the turbine trying to operate faster or even a “fire” within the combustion chamber.’

John Turton of the Institution of Engineering and Technology Aerospace Network, said: ‘From the initial reports it appears that this incident was caused by some kind of uncontained failure in the hot end of the engine.

‘The underside cowling parts that were blown off are around the turbine area and there has been one piece of video looking out from the cabin that shows a radial puncture through the upper surface of the wing, apparently adjacent to the turbine section.

‘This would indicate that there was considerable force involved in ejecting material from the engine in this location.’


Readers' comments (24)

  • "I expect that the potential speed of parts expelled from a jet engine during a catastophic failure would be so considerable that any "armouring" would have to be exceedingly robust and therefore impractically heavy.
    Anyway, as yet the cause is unknown, so I dont see the need for extra engine shields..."

    Please forgive my resorting to Wikipaedia but I'm afaraid I don't have time to find chapter and verse on the internet http://en.wikipedia.org/wiki/Blade_off_testing . Containment issues may be related to the initial failure but stands as a seperate concern, and therefore should be addressed as such.

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  • Jim Le Shed, I take it from you synopsis of events thus far you don't have an aerospace engineering background, or judging by your understanding of failure risk and centrifugal force you have no technical background whatsoever??

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  • I saw a tv-program in discovery from TRENT 900 engine for A380 testing and I believe they said that there is an armour to protect plane agains turbine blades.
    In the program they caused a turbine blade failure and tested the armour I think.

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  • Looks like a serious maintenance issue for Qantas.

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  • This sort of thing is within my area of work. However, having no access to either the engine concerned or any investigation data means that I am only able to offer an "educated speculation" at this point.

    To me, the most significant photos of the incident are those of the internal parts of this engine that fell to earth. These appear to be of a fractured I.P. or H.P. compressor rotor disc and of a section of the compressor stator guide vanes. This indicates a destructive compressor failure, not of the turbines, as other photos show the turbine casing to be intact.

    I'd say it was quite well contained within the nacelle. For such large and heavy objects at high velocity only to tear away the cowling, made of composite material, at the rear of the engine is evidence of this. If not contained they would have punched straight out through the side cowls. The damage that occurred to both the wing and engine cowling also shows that the offending objects were ejected aft, showing containment. This said however, it is impossible to completely contain such destructive damage. But well contained it appears to be, and with a minimum of other damage to the aircraft. I'd say: Well done, Rolls Royce.

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  • This sort of thing is within my area of work. However, having no access to either the engine concerned or any investigation data means that I am only able to offer an "educated speculation" at this point.

    To me, the most significant photos of the incident are those of the internal parts of this engine that fell to earth. These appear to be of a fractured I.P. or H.P. compressor rotor disc and of a section of the compressor stator guide vanes. This indicates a destructive compressor failure, not of the turbines, as other photos show the turbine casing to be intact.

    I'd say it was quite well contained within the nacelle. For such large and heavy objects at high velocity only to tear away the cowling, made of composite material, at the rear of the engine is evidence of this. If not contained they would have punched straight out through the side cowls. The damage that occurred to both the wing and engine cowling also shows that the offending objects were ejected aft, showing containment. This said however, it is impossible to completely contain such destructive damage. But well contained it appears to be, and with a minimum of other damage to the aircraft. I'd say: Well done, Rolls Royce.

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  • Although I was cautious because there may be the possability of allowing defined "safe paths" for part egress from the engine I consider it unlikely - I was just trying to raise the question without seeming to be "Rolls Royce bashing" or "Airbus bashing." As a safety requirement it is far easier to specify that engines must contain failed parts rather than trying to protect all possible impact points for parts coming out the side of the engine. Because of projectiles "spreading out" as they leave an engine it is, I suspect, also a lot lighter and cheaper to impliment as a total solution. There is also the cost and time involved with certifying a single engine design from this point of view rather than seperate airframes. I cannot catagorically say that I am right - I am not involved in aircraft engine design - but as an engineer with experience in aerospace design I shall now put a stake in the ground (although please note that I initially tried to avoid this) and say that I think Rolls Royce seem to have a major problem related to non-containment. The reason I believe this isn't because of the loss of cowlings but rather because the hole in the top of the wing above the engine seems to have been formed by an item leaving vertically at high velocity. I keenly await the results of the investigation by Rolls Royce and hope that I am wrong. In the mean time this may provide further information http://jeremy.zawodny.com/blog/archives/008574.html

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  • Pictures of the engine and plane if provided, can give some clues of failure

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  • A thought for Stephen Mosley to consider. How long is a piece of string? In my 32 years as a mechanical engineer in the aircraft engine industry I have never seen two identical results of engine failure. However, 30 years ago the aircraft would likely have crashed from this.

    We could make wide-sweeping statements about containment, simply because some material from the failed parts went overboard. To prevent this an engine would have to be totally encased in some manner, then being obstructed from its purpose of giving thrust!

    Some of these ejected parts would be 5kg. to 10kg. or even more, not just a few grams. The bypass duct is completely open and un-obstructed. It has to be for obvious functional reasons. Disintegration products go where they will, with no absolutely predictable pattern. Very little other damage occurred to the aircraft, which is evidence of containment. Not complete containment, but containment within limits of reasonable safety and good engine design parameters. Just as you can't say how long the string is, you can't exactly say where the fragments will fly. Contained it was, within these limits. Well Done Rolls Royce!

    At take-off power these machines operate very near to the edge of what is mechanically possible. A failure of this kind will actually help the experts in this area to improve their designs, giving us better engines as a result. Far better to leave it to the experts!

    To see what an un-contained engine failure really does, and what it looks like, please read the material on this site:

    http://www.c141heaven.com/64/pic_64_0614.html

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  • A fair enough point, please note that I have gone to great lengths to explain that I know enough to think it is a serious matter of concern but not enough to state catagorically that it actually is so! My understanding is that the requirement is a straight forward containment one and as such no bits should come out of the engine anywhere except the back. If there is more subtlety to it, then it becomes a question of what actually departed the engine at high speed and whether it shouldn't have .In fact my original post aludes to such a possibility but perhaps I was unwise to let myself be drawn into trying to justify why such concerns shouldn't be just dismissed as groundless or speculation. As I say, I await the report with my fingers crossed for my opinion (and I agree that it is no more than that) being incorrect.

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