Qantas Ground A380

[Sooty655]

Rolls Royce are now saying here that they are making progress in understanding the problem, and that it is specific to the particular type.

Which implies that they have recently had separate and different uncontained failures on two similar engine designs - interesting coincidence.

[Xplumberlives]

Rolls Royce are now saying here that they are making progress in understanding the problem, and that it is specific to the particular type.

Which implies that they have recently had separate and different uncontained failures on two similar engine designs - interesting coincidence.

Could it be SABOTAGE?

[Sooty655]

Found this link on PPRuNe suggesting Qantas high-thrust take-offs may be causing oil line cracks due to resonance.

[Mayfly]

Thanks Sooty - that makes interesting reading.

[Sooty655]

Rolls Royce issued a statement yesterday.

Nothing new, but it is from the horse's mouth.

[RLN]

With Rolls having real time telemetry, they probably knew the engine had let go before the pilot did.

[Sooty655]

With Rolls having real time telemetry, they probably knew the engine had let go before the pilot did.

Yeah, but I reckon the pilot probably noticed before they had time to call him back.

[RLN]

It would be interesting to see the traces and readouts of the engine on previous take - offs compared to other airlines with the same engine, but who don't use as much power on take - off as Quantas.

[Dougs]

the power used on takeoff is even at maximum still well below what the engine should be reliably capable of so it would be unfair to blame Quantas for there enthusiastic takeoff procedures the failure looks to be a known fault in the design in the turbine area dont be surprised to see a recall in a few weeks time to rectify the fault imo. ;-)

[Mayfly]

But isn't it more to do with resonance bands than limits?

Sooty will put me right here and no doubt in engine speak..but I think with the Olympus 201s there is one band pilots try to stay clear of & the 301s 2 bands,

are they not saying that whilst the power used is well with in Limits - it's a band that causes more vibration?

or am I miss understanding - if it doesn't go bang - oh wait it did !!!

[Xplumberlives]

The GOLD Standard!

Women, KNOW YOUR LIMITS!!!!!








Aren't kittens FLUFFY?

[RLN]

But isn't it more to do with resonance bands than limits?

Sooty will put me right here and no doubt in engine speak..but I think with the Olympus 201s there is one band pilots try to stay clear of & the 301s 2 bands,

are they not saying that whilst the power used is well with in Limits - it's a band that causes more vibration?

or am I miss understanding - if it doesn't go bang - oh wait it did !!!

All turbines have "critical speeds" and are known where they are to manufacturers and operators. They are well away from operational speeds so that shouldn't be a problem. You are right though, those defined speed ranges cause much more vibration. Our Steam Turbine has 3 critical speeds and is designed to get through them as quickly as possible - even so, the control room vibrates as it goes through those speeds.

[Nickolas]

But isn't it more to do with resonance bands than limits?

Sooty will put me right here and no doubt in engine speak..but I think with the Olympus 201s there is one band pilots try to stay clear of & the 301s 2 bands,

are they not saying that whilst the power used is well with in Limits - it's a band that causes more vibration?

or am I miss understanding - if it doesn't go bang - oh wait it did !!!

All turbines have "critical speeds" and are known where they are to manufacturers and operators. They are well away from operational speeds so that shouldn't be a problem. You are right though, those defined speed ranges cause much more vibration. Our Steam Turbine has 3 critical speeds and is designed to get through them as quickly as possible - even so, the control room vibrates as it goes through those speeds.

Bet the girlie engineers don't go through the critical bands quite as quick as the guys then.............

[Dougs]

mayfly i am led to believe that the issue is not resonance but a lubrication fault at one of the bearing points on the engine which by some design flaw end up dry with catastrophic results.

[Bovril]

mayfly i am led to believe that the issue is not resonance but a lubrication fault at one of the bearing points on the engine which by some design flaw end up dry with catastrophic results.

but if im reading all the correctly its a lubrication leak caused by being in the resonance bands.. fracturing oil lines etc

[Gully]

Singapore Airlines also changing Trent 900's on their A380's due to oil staining found during engine inspections: http://www.bbc.co.uk/news/world-asia-pacific-11723778

Hard to believe it's a wholly unconnected issue.

Gully

[Sooty655]

The various posts above are in fact refering to somewhat different sorts of vibration problem.

RLN is correct that all rotors have a "critical speed", and that this is by design well outside the normal operating speed range. This is generally more of a problem with the bigger heavier rotors used in industrial gas turbines.

Mayfly is right that the Olympus (and many other jet engines) have resonance bands in which operation is avoided when possible. This is usually because of vibration of individual blades, and may be induced by the rotor frequency, or blade passing frequencies, or a combination of the two.

As currently reported, the Trent 900 problem appears not to be either of these. It seems that the rotor speed at certain take-off conditions matches the natural frequency of some oil pipework which is then failing - my guess would be that the failure mode is fatigue cracking.

I have not seen any report yet suggesting whether the oil leaks lead to oil starvation and subsequent bearing failure, or oil fires and subsequent overheating of the disc, but from the pics of the failed engine parts, overheating seems to me to be the more likely explanation.

[Xplumberlives]

Very Interesting!

[Mayfly]

I see RR have made a trading statement & say £1.5 Billion has been wiped off the companys value

[Xplumberlives]

That will please the Yanks!

[Sooty655]

Rolls Royce are now saying here that the fault is due to a specific engine part (they don't say what), and they are sourcing replacements.

[Xplumberlives]

So I wonder if it is a supplied part and will that explain the lack of containment?

[Sooty655]

Sounds like it is related to the oil system - they refer to it causing oil fires. If the turbine disc is allowed to become overheated, either directly from the fire or from an associated failure in the cooling air system, the loss of containment is virtually guaranteed. The only turbines that can contain a disc failure are the big beasties in RLN's power station (and even then it would probably be marginal).

[Xplumberlives]

Oh I do hope the part in question is from an American supplier!

[Sooty655]

Oh I do hope the part in question is from an American supplier!

If it is, either it was supplied to Rolls Royce spec, or it was inadequately inspected by Rolls Royce, so the options for buck-passing are probably limited.

However, it would indeed be poetic justice.

Rolls Royce have issued a statement today - nothing we didn't already know.