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A380 engine failure - Qantas

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A380 engine failure - Qantas

Old 5th Dec 2010, 15:10
  #101 (permalink)  
 
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DERG:
At TO the 972 would gulp a few gallons per SECOND in the Qantas 388 at full load. Makes ya just slaver your chops don't it!
Incredible. Do the sums for SFC, you'll find your number would make the Trent a very uncompetitive engine.

(Unless, perhaps, you're referring to total fuel flow for four Trents on the ship...)
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Old 5th Dec 2010, 15:23
  #102 (permalink)  
 
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DERG - Thank you for that. But spline wear seems to be a problem on all Trent 900 engines, hence the AD. Are you suggesting that they all suffer from oil leakage into the combustion system, causing the harmonious vibration?
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Old 5th Dec 2010, 15:35
  #103 (permalink)  
bearfoil
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CAAAD

You present as an engineer, not a comedian, and I among others very greatly respect your comments. Rather than waste your time on snark, what do you think of my previous post? I expect to learn from you, if you are serious.

Do you think it possible that what looks like a "Misaligned line bore" could actually be wear instead? I say this because there are no telltales, no "bit marks". Any cutting tool will leave a signature if all the bore is to face is the passage of clean oil, The "Offset" is remarkably smooth, suggestive not of Carbide, but wear instread. Thoughts?

regards,

bear
 
Old 5th Dec 2010, 16:12
  #104 (permalink)  
 
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Bearfoil
I am with you on this. I think that shaft coupling spline wear on engines with such limited hours and cycles is very unusual. Splines are coated with wear resistant coatings to prevent premature wear. Today's modern high-bypass fan engines are designed to stay on wing for many cycles and hours before removal, teardown, inspection and component repair or replacement. Some stay on wing for as long as five years of operation accumulating many cycles quickly (shorter routes). Spline wear is not a problem that you normally think of or worry about. Engines are generally removed because of a deteriorating EGT margin. This is generally due to hot section degradation, particularly the combustor and turbine rotor blade tip seals. Obviously operating conditions and individual operators have a lot to do with on wing engine life.
This spline situation on the 900 is very odd indeed. Just some thoughts.

Turbine D
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Old 5th Dec 2010, 16:27
  #105 (permalink)  
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Turbine D

All things otherwise equal, the common (least obtuse) factor would be oiling. Oil can withstand very high mechanical friction, given tolerances close enough to prevent metal/metal contact. If so, the problem distills to lack of oil, or too large tolerances, or some combination. I think the oil is not at fault, so it is most likely wear, beyond limiting Lubrication values. This is to say, Mechanical forces sufficient to diminish Oil's filmic properties. The TRENT is a proven concept, so what's new? More and More Thrust?

I think not. I believe it may have to do with un-attenuated vibration and/or insufficient oiling. Now the Authority has identified Oiling properties as the root, so what follows on is more than likely mitigable circumstances: eg. Vibration.

The RR Bearing mechanism seems to be proprietary. Will the need to know the results of investigation trump Commercial Protections? I would think so.

"We know the problem, but it's a secret, and we fixed it." .....Won't "Fly" I think.

Edit: What are your thoughts on the "Stub Pipe? I would rule out flubbed manufacturing. First, the "Line Bore" mistake would snap any machining tool I'm familiar with. There is insufficient mass to counterbalance the "eccentric". The ledge on the bore is too smoothe to class as defect in manufacturing, I see it as wear induced. The "defect on the tip" is likewise not due to machining, the metal composition of the pipe would have left resistance marks, "chatter". It is too smoothe, suggesting a polish, and why would anyone polish an incision into the lip if the goal was inspection? The fractures are fresh, they are rough, and unsmoothed. The alignment of the smooth "Off-Bore" defects with the fracture location suggest a common axis of wear, suggesting a rotating mass in the bore (aspirator?), or a coupling that is misaligned. All the defects exhibited in the Photograph happened after the installation of the engine, and the beginning of service, IMO. IMO.

One other thing. If a borescope can be inserted into the Bearing cavity, and there are "Vanes" on the Stub Tip, no wear would be noticed. I think this is why the Authority in the AD required an assessment of "Clogging" at the Vanes?

bear

Last edited by bearfoil; 5th Dec 2010 at 16:40.
 
Old 5th Dec 2010, 16:39
  #106 (permalink)  
 
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Bearfoil
Relative to the stub pipe, I inadvertently forgot to mention the most important question of a component failure analysis. Is the material used the correct material? And if it is, is it within specification compositional limits? To determine this, a sample must be extracted for spectrographic analysis as close to the fracture as possible without destroying the fracture surface itself to eliminate off-composition material as being a factor.

Relative to the off-center counter boring, I am having a hard time envisioning how this could happen at the component manufacturing stage. In simplistic terms, one centers the cylinder in relationship to the cutting tool, lock it down and begin the machining process to the required depth.
so I can't figure out why or how it got to the shape depicted in the photo.

Turbine D
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Old 5th Dec 2010, 16:44
  #107 (permalink)  
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Sampling of course, but at the weak point of the part? With potential for corrupting the failure's site? An artifact that suggests "Machining", rather than Sampling? I take your point of course, but again, I see a concentric with the "defect" (wear?) in the bore!!

For me, I try to imagine what is not present in the evidence that may have played a part in failure, so bear with me. The RR architecture is supposedly proprietary, so at this point, we may not see more.

If there was an "Aspirator" on the tip of the Stub, and it fouled, it would have created extra drag on the oil pump. The "Swirl Marks" on the tip may be an artifact of siezed ball bearings, having contributed heat of failure to the wear's face. If the Oil was under Pressure of delivery, the load would be absorbed by a ball bearing contact. Again, I think the Concentric orientation of the tip defect with the bore "Ledge" is telling.

bear

Last edited by bearfoil; 5th Dec 2010 at 17:25.
 
Old 5th Dec 2010, 19:13
  #108 (permalink)  
 
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bearfoil - I choose my words carefully, and I try not to give offence and avoid sarcasm. Also I try not to be light hearted but it's a bit difficult when faced with some posts.

But to get to your point.

No, I don't think the offset counterbore is wear, the surface is too uniform. It appears to be a false cut during manufacture.

I do not understand the geometry of the component as depicted in the photo, and I have no idea of the mating parts and surrounding scenery. Hence I find myself unable to comment.

Oh, all right, then, the stub pipe could be an integral part of a housing casting, in which case the counterbore could have been done on a boring machine. An accidental offset of the spindle would have done the trick.

I honestly think we need more information such as a detailed GA or the relevant pages of the Overhaul Manual before we can get down to informed speculation.

I do not believe there is any fancy aspirator type device involved. The counterbore looks tailor made for a pair of O rings. I would not expect lubrication to be by means of a mist. Oil jets more likely.

As Iomapaseo often says, we should leave the real professionals, Investigators, RR and so on to get on with the job. I have no doubt that they will do a terrific job.

Trouble is, I find it impossible not to respond to some of the more extreme imaginings found on here.

Oh, and can we be a bit more careful with the vocabulary please, and only use terms that are recognised in the Trade.

Last edited by CAAAD; 5th Dec 2010 at 19:17. Reason: comedian
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Old 5th Dec 2010, 20:06
  #109 (permalink)  
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CAAAD,

Recognize "Terms of the Trade"....hmmmm

I am unaware of restrictions relating to terminology, and I don't recognize you as a Mod. Are you one? I doubt it.

"Must respond to imaginings". Your responses to these seem dismissive, You are not opposed to imagination, are you?

You have couched yourself as a "Professional". May be a Continental thing, but in my experience, Professionals do not belittle others, since that is the surest sign of a non-professional.

The idea here is to "......have a little fun...". I would hope that does not mean "at the expense of others."

"Real Professionals". Here I find your comment woefully off target. How in Heaven's name can an anonymous forum have any deleterious affect on the "Work" of the "true" Professional?

"Leave the Professionals to it". Really? May I suggest that they are doing fine, with or without "Tech Log".

I come here to share, to have fun, and practice my writing. Most of all, I am here to learn. Without Imagination, I dare say, there would not be flight. Isn't flight the reason we are here?

respectfully, bearfoil
 
Old 5th Dec 2010, 21:17
  #110 (permalink)  
 
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bearfoil - I'm sorry if I've caused offence. Just to clear the air a bit

I have never couched myself as a 'professional' anything. And not a Mod.

It is often easier to understand a point of view if it is phrased in conventional terminology.

And I repeated a point often made here , that we will not know the details of the investigation until the findings are made known, so excessive conjecture is not very productive.

But I thought my comments re the stub pipe fracture weren't too bad.
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Old 6th Dec 2010, 07:17
  #111 (permalink)  
 
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Conjecture

Please don't make this more complicated than it is. This failure was common in the early part of the 20th century. This is VERY basic mechanical engineering. A 20 yr old second year Mech Eng student can tackle this easily. RR are not noted for sharing information and that is the ONLY problem that second year Eng student would have.

BEAR your post of 5th Dec 2010 15:41 fits my theory. OK the metallurgy is complex but please remember they are seeking to make this engine's mass as LOW as possible.

Also remember that disc thingy?(senior moment) that exploded out goes round in the opposite direction to the rest of the internals.

CAAD it is fun to theorise and we, well, I anyway, can do this cause 466 lives were not lost. All Trents? No..not all..but this T972 variant in this situation YES. Specific too.

TURBINE D "so I can't figure out why or how it got to the shape depicted in the photo" Are you serious? It was shoddy work.
What else can it be?

I trust the NTSB. I do not trust RR or Airbus in being open about events.

Please remember that product testing involved 466 people and Qantas was somewaht ignorant of the events going on elsewhere regarding this engine. You will note how the Germans have kept silent through all this apart from a very definite eary statement: "We see no reason to stop flying our 380." That was the day after the accident.

And again: this is a VERY basic engineering failure. OK we have a fancy oil bearing and some high end metallurgy and high energy transfers for total mass of engine..but that is all. We have all the tools to find out what happened.

The biggest problem are the PEOPLE involved. The politics. The cost. And the disgrace.
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Old 6th Dec 2010, 15:47
  #112 (permalink)  
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DERG

On page 70 there is a "Slice" through the TRENT and with it a graphic that shows the LP and IP rotating the same direction, it is the HP that contra rotates, as I view it. A bone to pick with an earlier drawing that shows trajectories out the case of The IPT. The trajectories begin above the axis of rotation. If that is accurate one assumes the Projectiles would have exited to port.

Ferpe's schematic might be the TRENT 700. If the oiling is similar on the 9, take note of the "coupling" at one end of the stub pipe shown by arrow. If it is a couple, the end presented as the stub pipe in the "pics" may be the penultimate opening of the delivery tube, this would indeed provide an explanation of what I see as "Wear" rather than manufacturing "Defect".

The TRENT 700 is 2000 pounds lighter than the GE carried on some 777 airframes, it is this lighter weight that was a selling point for Operators of the TRENT on this Boeing. DERG, light weight is quite important in this accident, as it was in BA038.

One of the contributing factors to the Fuel starvation in 038 was vibration on Thrust select on short final. It is "known" by the AAIB to have shaken loose "Migratory Ice", that impacted the FOHE, causing cavitation and spool down.

Here, with QF32, vibration seems to have been a factor; another would be mechanical stresses focused on this "Connection" feed to delivery. The arrowed oil tube is supplying the dual roller bearings at LPT, so it may not be the correct "Stub Pipe", in question.

DevX has responded emphatically re: "Drawing". My request would be of him to supply a picture (of the TRENT 900) isolating the "stub pipe" in question, to determine if indeed the end shown to the public is one half of a "Quick Couple".


Once again, I note tube architecture that suggests other than the delivery end of an oil supply system, and that the damage appears to be Wear, not "Bench Numpty".

Ever ready to occupy the end of the "Limb", I will say the loss of oiling was caused by the severing of the supply line from the delivery line. I have seen fluid couplings fail with that signature under seriously more docile environments than TRENT @ max chat. Standing to be corrected. Anybody?

bear

Last edited by bearfoil; 6th Dec 2010 at 16:39.
 
Old 6th Dec 2010, 18:13
  #113 (permalink)  
 
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Seeking Truth

Bear...there is a guy called Page who I call a true vocational professional engineer....see:

Page

I see RR take total responsibility for these engines and Qantas pay money direct to RR per flight hour. The only thing Qantas engineers will know is how much turbine oil was being used when it returned home. They still don't know how much had to be added at destination ports.

Since 1995 I have watched how the unbiquitous MBA graduates have eaten away at engineering authority. When I was the tender age of 22 I could call a STOP at any stage until an issue was sorted.

My own is son is 22 and at university for his diploma. He was taught on the tools from the age of 15. He already has exercised the "STOP" option on his course much to the surprise of his tutors. Makes me, and I have to say his tutors, very happy!

The telemetry affixed to these machines really is a JOKE. All they are there for is to minimise RR costs. They ARE NOT there for the benefit of Qantas or the general public.

Yes Bear the T972 is much lighter than the GE equivalent and this is the reason Qantas bought it...so they get max revenue especially on the routes from California. They had no reason to doubt that RR knew WTF it was doing.

What i really want to know is WTF was done when this machine was up at the Lufthansa facility in Germany for the "C" check. I also want to know why SQ was changeing T970 engines like dirty underwear.

There is NO WAY that RR will meet Qantas in open litigation because we will see what a tin of worms RR has cultivated. For those of us who care about people more than our bonus this catastrophe has torn away our faith.

For those engineers who read this: if the company you work for is taking chances with anything then WALK AWAY. There are plenty of good companies around the world who DO care. Sell up and emigrate. The best guys I know all know work worldwide. Not always for the big players either.

Unlike avionics the mechanical engineering problems are often easily identified to a skilled engineer. Believe me there will be quite a few guys on the tools that knew this T972 was unhealthy. They had mortgages to pay and their supervisors should be no where near a commercial transport aircraft.

Qantas needs to employ a bunch of top notch mobile engineers to get maintenance in hand, rewrite the leasing contract and restructure the chain of command. The way 466 people were used as Guinea Pigs sickens me to the core.
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Old 6th Dec 2010, 18:15
  #114 (permalink)  
 
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Mr John Page

Dept Eng Uni of N S Wales Australia
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Old 7th Dec 2010, 00:19
  #115 (permalink)  
 
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Failed pipe and oil fire

Regarding the broken pipe, there are some statements in a patent taken in 2003 by RR. See US6516618B1
In the text also an oil-fire resulting from a break in the scavenge pipe is discussed.
There are also two drawings which may hint to where the counter-bore could be.

Regards
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Old 8th Dec 2010, 19:38
  #116 (permalink)  
 
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Another advice

http://www.faa.gov/other_visit/aviat.../SAFO10021.pdf

At this point the RR case has collapsed there are so many flaws in this Trent series it is unbelievable. All comments welcome.
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Old 8th Dec 2010, 19:55
  #117 (permalink)  
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I must respond. This SAFO bulletin referenced an OIL SPEC change, and related to subsequent coking on TRENT 700.

The tube in question was an oil vent tube, a design certified to withstand ignition by backflow into the scavenge system.

TRENT 900 Issues: Poor quality control of critical oil tubes manufacture. The fix is agreed to, no new issues have arisen, and I am ready to board Qantas out of SFO.

Poor Form: A very real lack of information targeted to passengers who actually care about the equipment they travel in.

The Bad joint turns out to be a connection after all, involving missed maintenance as well as quality issues.

A poor ATD (attention to detail) in performing mandated inspections following issuance of AD. "Oil Leak? What Oil Leak?"

Another missed opportunity to Sell Safety to the traveling public, instead of offering puerile excuses and "explanations" from twits who think kerosine is to light the Barbie.

bear happy landings
 
Old 8th Dec 2010, 19:55
  #118 (permalink)  
 
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DERG

If you read the SAFO, you would realise that it is aimed at ALL engine manufacturers and ALL operators. How it adds up to "the RR case has collapsed" isn't clear to me.

Perhaps you would care to give it a bit more thought before you try to explain.
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Old 8th Dec 2010, 22:53
  #119 (permalink)  
 
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Diversification
Interesting post!
Did anyone notice in the drawings that the counter bore is actually displaced relative to the outside diameter of the part? Drawing inaccuracy or intentional? Look at Figure 1 in the patent carefully to see what I mean, at least on this particular design.

Turbine D
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Old 8th Dec 2010, 23:38
  #120 (permalink)  
bearfoil
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Turbine D re:
US PatOff 6516618

In the Patent description there is reference to a single scavenge line, where I believe the 972 has a "Gallery". Language describes an interesting mechanism for "Fail-Safe" re: Fire, since the Oil Pressure increases rapidly when Gas Path contents enter the scavenge line. This increase is referenced as "Constantly Monitored", thus allowing a manual cage of the engine, predating I would say even FADEC? I don't notice the offset in the drawing, is it the image on Page One?

The 972 failed pipe is I think a supply line, and the damage to the "Tip" (Which End?) might be either aspirator (Mister), or "external" coupling? It is not clear from released data, either written or pictorial.

Sorry, almost missed the "point"; if "Offset" I would not rule out a designed for "Eccentric" that augmented aspiration of the lubricating Oil. (Misting).

I still maintain that if a mfg. defect, there is patent "Wear", suggesting ongoing leakage, ("Top your Oil, Captain?") a result of missed or deferred Maintenance.

bearfoil
 

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