DERG
 

Here is the link to the patent. The leaf seal is made by Alstom, Baden CH
Leaf seal, in particular for a gas turbine - Patent 7828297
Very interesting development!!

Patent details here.

United States Patent: 7828297

.... and see this Patent. To Rolls Royce 1980

United States Patent: RE30206

DERG
 

We have been into that FAG brochure before. Must admit that no one untill now has picked the fact that all of the bearings used are non off the shelf. It has to be specials seen the environment they are used.
That makes me remember a very short / brief note in the newspaper here, probably about 2 weeks after the QF 32 desaster. Schaeffler Group - the Holding that FAG belongs to - has released a note to the press that their bearings were NOT the cause of the failure!! and had performed as expected !!
With all the developements in this thread over the past weeks I now believe that this press info might have some kind of importance for the outside evaluation of the causes.

Good Progress
 

Thank you all for the help with this.

Jo
Thats good info. Looks like we have a shaft balance problem so far. But not sure as yet More work to do.

All help much appreciated.:ok:

Eng Note:

SKF has made ALL the bearings so far. They also make the T1000 bearings? So why not the T900?

Engs never leave a trusted supplier. So looks like INA/Schaeffer were willing to take on a new design concept.

Is this it?
http://www.schaeffler.com/remotemedi...e/0001614C.jpg

looks like they also got a contract on the EA/GE engines on the new B787 and on the T1000 too.

Looks like more heat transfer for less mass but we will see.

I call cheap shot. Coastal Command and the Nimrods had been doing practically nothing other than saving people for the last 50 years. Bad form sir.

And engineers will tender for a different supplier if the "usual" one cannot supply the materiel required. It's possible TKG were simply overbooked or did not have the available resources to develop what was being asked.

application of bearings
 

On behalve of our "brother warrior" DERG I am posting here some links he sent meanwhile. I think they are all very useful for fact finding.
Application of bearings - SKF.com / Products / Interactive Engineering Catalogue/Rolling bearings

Furthermore there are these:
This the key video but DOES NOT DISCUSS TORSION OR TWIST ON THE SHAFTS
Also does not discuss CONCENTRICITY of THREE SHAFTS
http://www.eng.ox.ac.uk/thermofluids...pt#452,17,Heat Transfer between Rotor and Seal

Schaeffer ROLLER bearing
http://www.schaeffler.com/remotemedi...e/0001614C.jpg

Schaefer
For 787
FAG bearings selected for Boeing 787 aeroengines

Okay, that´s it for the moment, hope it all works

just one more on bearings
 

Here is another link that contains useful information.
this link is interesting but needs time to read

http://medias.schaeffler.de/medias/en!hp.tg.cat/tg_hr*ST4_1652155275;bONjntrf0IKb

no direct ref to aerospace though

resonance and balance
 

I want to come back to DERG´s last entry before he encountered the "Thunderstorm".
I too believe that since SchaefflerGroup / FAG as the bearing supplier has denied a failure of their bearing(s) as a primary cause, the case is down to the bottom where a closer look should be taken on resonance and to a lesser degree on balance.

Since it was mentioned in this thread repeatedly that vibrations are common in jet engines and balancing is a well controlable issue. Only conclusion left is resonance in parts of the engine ?? probably or more likely the shafts ?

Because the engine still eats its spline connections, the AD is not recalled yet, though softened to the extend that inspections for a new engine come first after 200 cycles and than it continues with 100 cycles. But what kind of ongoing field test is that with an engine supposed to last thousands of cycles ???

Digging Deeper
 

Dozy I beg your pardon. I too am annoyed that they have broken up the Nimrods. I am annoyed too about this T900 failure because the Comet was prone to the same fault as we are focussed on in this thread.

and moving on...

"Solutions for vibration problems involving the excitation of a natural frequency (resonance) are frequently difficult to obtain based solely upon experimental data." Thats what FAG says and moreover:

"Finite Element Analysis (FEA) is a numerical technique that can be used to approximate the structural dynamic characteristics of vibrating mechanical systems, the understanding of which is paramount to any root-cause failure study involving excessive vibrations."

The problem is that FAG have little experience in this field compared to SKF.

This is where METROLOGY began, the original paper from 1955:
http://mdrl.mne.psu.edu/papers/bearinganalyzer.pdf

This is how RR service agents themselves tackle vibration testing in the field, after the engine has left the factory and needs fixing.
http://www.skf.com/files/446130.pdf

And this is a dynamic exploded view of the bearings as they fit into a gas turbine, which is the smoothest running machine known to man: it HAS to be just to stay together.
Engine & gearbox - SKF.com/Industries/Aerospace/Applications

As Annex has told us as reported in his local newspaper:

"since SchaefflerGroup / FAG as the bearing supplier has denied a failure of their bearing(s) as a primary cause"

They did not say this was the first time they had designed and built a series of bearings for an aerospace gas turbine or indeed the entire bearing mounting system from one end of the engine to the other. :ouch:

So how come they got the contract? Well YES how come? :hmm:

Thier design had less mass, the mounts were "vibration reducing" and they saw the big cake of the EA business in N America for the B787. They even set up a manufacturing facility in Canada to serve EA. They want to be up there with the new generation of lean engines.

Not a good start!

All replies most welcome.

Bearings/Splines
 

Gentlemen

I've yet to read the new links...... Will take some time later on. In the Navy, it's called an "Even Strain". Any rotating assembly can lose its stress/containment v/v a vibration. In other words, at particular frequencies, a Shaft can "Float" in its bearings. This is not good at all, for it allows chaotic and random (intermittent) 're-acquisition/loss' of constant bearing loads, and extreme heat and wear. It also beats the Oil out of its proper position at the Shaft/Bearing effacement.

Essentially then (as the result of Float), an independent Shaft (And its coupling) are "free" of containment in highly engineered clearances. Note for example the position of the Spline coupling (IP) short of the Plane of its thrust bearings. This allows out of 'bearing boundary' chatter, this geometry has puzzled before.

Think 'False Bearing', and a situation in which the Engine's shafts beat their mountings to a 'pulp'. Vibrations are thoroughly covered of course, but unusual "Novelties" ?? As in a transient Resonance at certain load, a relaxation of "Even Strain", a certain RPM, and Thrust value.

As to "Aft Migration" of the IP Stub shaft (aft shaft), this happens when Splines are worn beyond a certain value such that continued Resonance rapidly fails the Tooth/Trough pairs. The position of the Splines out of direct and balanced (Planar) position relative to the Bearing #2 can instantly aggravate the rigid couple into a disconnect (wear through) of the coupling.

The likely genesis of the vibration causing the Float would be the Fan.

Static balance of the Fan I'm sure is demanding. The Fan itself has issues (well addressed) in dynamic thrust that can unbalance the equation, and shift exterior and intense loads into the core.

Happy... been a good learning exercise
 

Thats as far as I go with this. I know that RR and Airbus between 'em have taken steps to make the A388 totally safe. Think Lufthansa starts the FRA to LAX service soon and I would be happy to fly with them!

Any free tickets for a flight on any A388 then please send me a personal message :)

Anyone know the answer to this from Flying Lid? As a former resident of Singapore I am just interested.

The first time I flew out of Changi the BA 747 had a contained engine failure on climb out, necessitating a fuel dump and return to Changi, so this all seems rather déjà vu to me. But that was a long time ago.

Bearings

Additionally, knowing that the Ball Bearings act as Thrust bearings and Axial bearings under load, we can describe the "Limit" Sphere as certainly Three Dimensional. The Balls operate in a "Tube", and react against their race depending on loading. If there were only thrust loads to attenuate, the Wear Print would be at the "Forward and Aft" corners of each metal run. A total of four separate areas. If Radial loads present, these four areas would expand, as the force of the Shaft expresses itself in radial directions as well as in axial stress. If these loads are balanced, (reasonably), there could be an expectation of this design working through and beyond its service life.

This is not the case. Mechanical loads vary widely depending on several designed for aspects: Axial shift depending on translation of Thrust, RPM and lubrication, plus vibration, put variable and tested for loads on this bearing.

As above, if the individual balls are demanded to snub stress in three dimensions, the wear print will eventually affect the entire face of the Race. Under constant load in three dimensions, Oil can be wiped, and metal to metal can accelerate wear. The "C" mod AD requires an initial inspection at 200 cycles, then the next at 100 cycles after it. Why?? As installed, the 'new' bearing is at minimal tolerances. With use, the tolerances widen. As before, I describe a logarithmic failure graph with wear. The more it has worn, the faster (rate) it wears. 200 cycles is about a year, 100 about six months.

Inspections are ordered to find wear. That means, wear is expected to be found. Initially, wear is less concerning, but with sloppier tolerances, inspections are demanded more often. Eventually, the bearing will require rebuilding, or replacing with new. How this affects the original Certificate is between RR and the operators and regulators. And the travelling Public.

So the "A" of the abcde failure cascade is Duff bearing. Not support structure, not oil pipe, not EEC, not Oil Fire. Think..... The Oil Fire caused Aft migration of the IP Shaft? No.

Fire is an instant and chaotic failure, but it cannot wear out bearings and Splines in mere seconds. Especially one meter forward.

Bear
 

Yes and thats why the thing runs at 180C. mean and 196C max.

I wanted to send you a PM about this but this software has me marked as naughty poster....it won't let me. Anyway, I think all should know why this engine runs hot.

Anyway changes are a foot and propulsion units are set to change. This T900 will be the final example of this technologyin use now.

This is the future:

* Open Rotor: Last fall, GE announced a joint study with NASA related to an open rotor or unducted fan engine design. In the 1980s, GE successfully ground-tested and flew an open-rotor engine that demonstrated dramatic fuel savings. Since then, GE has advanced its data acquisition systems and computational tools to better understand open-rotor systems. GE also gained extensive experience with composite fan blades in its GE90 engine and GEnx engine"

Regards

DERG

The friction produced in the Ball Bearing structure heats the oil, and higher as the wear continues. Once worn to even small amounts, the cycle begins. The vibration caused by harmonics and the damage itself makes quick work of the "Three Way Bearing??"

Will ever increasing viscosity and "Additives" be required as the Cycles advance?? Perhaps as a final "correction", the requirement of "Hypoid" grease??

One can say that the Ball Bearings do an excellent job of restraining mechanical forces. They are not meant to perform at their high level of design when encountering "Novelty". A record of Oil Temperatures v the log of thrust, time on wing, cycles, etc. Would be instructive, and rather simple to produce.

Bear
 

They have got that data already.

The big main bearings are through flows. The only grease filled bearings are down in the power take off...the gearbox that drives ancillaries. They are cool and away from combustion heat.

In my view they have taken this particular design to the limit. They want to hit all the new targets with the stuff they have now. Thats impossible.

I think there is only one additive that may be able to help the oil people and it is called "graphene". Then again that is carbon and they already have a coking issue so I am guessing.

This is a good site and tells us how propulsion is going in the future. I just hope they choose the right gang of subcontractores when it comes to bearings:)

GE Aviation entering new propulsion era with multiple R&D programs

Regards

Radken
 

I would like to thank all of you who have taken the time to share with the uninitiated so much of your knowledge and experience about things turbine.

While most engineering talk is way over my head, much of my “between the lines” understandings of what you engineers are saying has imparted to me a very real sense that all may not be as well as we thought in the engine design, engineering and testing business. Ahh, but for human foibles the world, though, would not be quite as interesting. It’s quite a shame to actually learn that the reality of “bean counter impingement” has not been somehow (novelly) been formally brought into the calculus of flow modeling and the totality of turbine engineering. LOL

From my A&P point of view (long sentence to follow), if it is true the T972 (1000?) is a tad light, a tad flexy, a tad shaky, or a tad too refined, and therefor, a little “edgy,” and maybe a little under-tested as a novelly “experimental” engine, then RR it seems may have overstepped in the competition to get to the top or stay on the top. In the process they apparently may have taken advantage of “we the public” in a truly callous way.

The general conclusion in this thread, to the effect the uncontained failure just simply should not have happened (for the reasons so far given), seems quite correct to me. And, it begs the question as to the processes and compromises that were forced on the engineers by the “beaners.” Just how the competitors in the ultra high-tech a/c turbine business can enter and reenter time and again the chariot race competition for every engine size and spec demand that comes down the pike, while simultaneously being forced to develop, adopt, and/or almost insanely embrace the cheapest, lightest, engineered to the “max” solutions for everything, is mind blowing. Oh, it’s business as usual! I get that. But It’s the uniqueness of the airborne product that exposes the large “red zone” of error tolerance peculiar to devices which hurtle through the air.

Last year we watched, fascinated, as a lovely cruise to Mexico on a new, high tech $200 m, 150,000 gtw ship (designed to the latest marine standards).... suddenly turned disastrous as a “contained” oil fire, suddenly, “surprisingly” took out all the big Warsala diesels driving the propulsion gens. Oh, fire took out all the back-up gens as well, likely because the control room was involved. Truth be known, it apparently came close to sending 5000 people swimming. But for just a little bit of good fortune they could have easily been a thousand miles from land, lights out, with no steerage, and broaching in 50 foot seas.

However, as we know, it’s still quite another thing to be cruising on a new high-tech $300 m airplane which itself suffers “surprising” propulsion and control problems rooted, truth be known, in engineering compromises..... but, also, by fate smiling favorably upon them, were fortunate for the RTB option they had. Had they been another hour or two gone it’s possible the outcome would have been far different.

Here comes a new point, possibly addressed previously, but I’ve not read such...

it seems to me not much has been made of the fact the 380’s No. 1 could not be shut down OG from the cockpit. I haven’t gleaned from any discussions that the crew thought #1 had been fodded, and I can’t recall if it went into “degraded” mode either after the #2 blowout. I don’t recall reading they attempted to shut it down in flight. In fact, it seems #1 must have been following throttle as commanded. Who’d want to shut down an operating engine unless ???

But from what we learned about their ground problem, we did witness failure of the manual #1 fuel shut-off. The eng ran OG for, what, five hours? The console fuel cut-off instructs the FADEC to s/o both the engine MEC and, simultaneously, the main fuel feed s/o valve in the upper wing/pylon area? Is that correct? If this is the way it is, to me it means they’d rubbed up pretty tight against “lady luck” out there at altitude. They were very, very fortunate that the #1 shut-off process wasn’t called for by reason of fire. On top of this, also, no mechs apparently were OG in Singapore either who were qualified on this new engine, at least to the point of thinking they could open it up the case and shut it down mechanically. I’ve seen it done on a CF6 at the gate with a similar problem, but many knew that engine.

Do any of you know if the T972 FADEC parameters “sense” eng/nacelle/pylon fire indication, and, if warranted, autonomously shut off main fuel at the wing, while also commanding MEC fuel off to the manifolds? Would that be part of the new automated flight deck as part of the “work load reduction” automation push?

bear, Derg:
the grease is not a solution - keep in mind that the bearings need cooling which comes from the flow of cooling medium - in this case oil or oil mist (depending on load/speed). So the best idea to get better cooling is to make sure the bearing will get more oil mist or cooler oil mist. On the other hand there are some Trent9xx engines working relatively long time so there is a lot of examples supporting tha case that thereis a technical possibility to achieve this.

Ball bearings are made to tight tolerances and than are selected to make sure that the balls within one bearing are almost the same dimension to achieve that there is always a lot of balls to carry the axial load (the radial load is always carried by limited number but due to high bearing diameter and elastic deformation of the balls and the raceway it would be always more than one. The manufacturing and selection tolerances are really tight - some measuring equipment mentioned in the docmenets suggested has accuracy of 2nm so i may safely assume that selection may be carried into groups with tolerances in region of 20nm. That is really precise and we may safely assume that the balls are practically equal in size. The other problem are the raceways which can not be selected but have to be preisely machined, than precisely assembled and then they behave the way the mounting itself. And the dimensional changes here are several times bigger than in the bearing itself. No wonder the design here is demanding and critical to bearing longevity.

And the further the splines are from bearing plane the shorter their life span is. Sometimes critically short.

Open Rotor
 

DERG & Bear
Her is a link to a site, "Then and Now:

YouTube - Family tree

Interestingly, the turbine mid-frame (location similar to that of the IP/HP frame in the Trent 900) that had been removed on the CF6-80C2 engine, returned on the GE-36 UDF as it was the main support for the propulsors (fan blades). It was a much different design and it was an extremely complex structure, never fully refined before the project ended. IMO, there were some vibration problems that existed that needed to be eliminated.

Ge 36 Udf
 

In those mentioned years of the early 1980´s I was a representative of our Federal Adminstration of Air Navigation Services and a detached member of not less than 11 Noise Abatement Commissions. As I remember the UDF engines caused a real uprise by evironmentalists because of the level of noise they produced.
A more technical item I remember were unwanted resonances / vibrations of the aircraft structure. I thought they were caused by the shockwaves of the counter rotating fans. I do not remember any report about engine inherent vibrations, but assume they were existent because of the so much different and radical desighn.

Ref. the ongoing oil and bearing discussion. Is there somewhere a list of oils that show the maximum permissable oiltemperature for Jetengine oils ?? Is it correct to say that the Trent 900 runs at borderline oil temperatures ??
I know there was the one or the other hint in that long lasting thread, but want to ask to shortcut.

limping bird
 

Would also like to join fchan`s question about the damaged airplane sitting at Singapore. With all the ongoing engine chats we have lost abit the trck of that part of the story.
So, what´s the status and plans for this aircraft ??
Since she held together on the accident day it seems likely that only some well thought enforcements / emergency repairs will make a flight to Toulouse no big challenge. Probably in some shorter hopps to stay at lowest possible weight.

Radken
The FADEC provides protections against the following engine malfunctions:
N1, N2 over speed, and EGT over limit
LP shaft rupture
Fan instability
Engine flameout in adverse weather conditions
Overthrust
Engine stall

(source A380 FCOM)

Is she still in Singapore?
 

Flying Lid, fchan, Annex14

See this thread...
http://www.pprune.org/dg-p-reporting...write-off.html

Radken

"your knowledge and experience about things turbine." I am a civil engineer and that is a good thing, I learned about turbines as a result of this accident. I guess the only witness acceptable to a lawyer here would be TURBINE D.

Some will say ahem..WTF does he know..Haha.. Well I can tell you that the wing structure of the A388 is really kinda strong. The miracle was that the fluids did not burn when the wing was damaged. God was certainly with that flight until the engine was shut down some hours later.
That is not say that the Qantas crew was in anyway lacking, quite the opposite.

As for the fact that it could not be shut down I know that airbus has made some soft wear changes to the control system as Trent 972 has told us. It must be remembered that this aircraft design had a priority of less mass. As an example all of the wiring looms are made from aluminum wire instead of copper.

Wojtek

Are you seeking to teach us about bearings? A grease packed bearing is cooled by energy transfer to mass. An "nm" is a nanometer, and WOW that is tight. Wojtek I are you sure they can get the metal down to that level of accuracy? I honestly cannot see any technology known so far that can do that is steel...but maybe these balls are made from ceramics. Ceramic bearings are the latest trend.

I see what you mean about "overhung" forces yes. Where the bearing is the pivot and load point for a long shaft between several bearings. Well YES...that essentially is the turbine design.

Annex

"Ref. the ongoing oil and bearing discussion. Is there somewhere a list of oils that show the maximum permissable oiltemperature for Jetengine oils ?? Is it correct to say that the Trent 900 runs at borderline oil temperatures ??"

Most of the specs are set by the the U.S. Department of Defence. MIL specs. I believe it is true to say that no other aerospace gas turbine in CIVIL avaition runs at a mean temperature of 180C. Of course as Barit has told us it depends where you measure the temperature and some have suggested that the T900 measures this at the hottest place.

196C maximum is hot. The hotter the oil the more of it escapes into a gasseous state which leads to "coking" but everytime the engineers have checked the T900 no coking has been found.

In my book the high temperature tells a tale of high energy transfers. Certainly if I was the engineer responsible for a T900 I would be taking oil samples everytime the the thing came home, no matter what time of day.

Of course this is another issue: The MBA crowd would say "excuse me!" That is a RR job, or they would say: "Hey, that will take time and cost money...no..that is a RR job...and they have that responsibility". It all depends on your company culture.

The MBAs want the planes in the air making revenue. They really do not see "the big picture". Quite often they need firm advice.

Command Environment
 

This will interest a lot of readers.:ok:
Love the way the customer plays with the electric seat position!

This is the way the machine is controlled from the flight deck:
YouTube - Airbus 380 Flight Deck ( Dubai Airshow )

Notice:
The airport ground maps that are stored on line on the FMS.
The reason why the reverse thrust is only on the inboard engines.

The additional computer that slides out with the display on the side.
The fact that the controls follow a similar pattern to existing Airbus products.

Derg

bearings: i am learning from this thread rather than trying to teach anyone ;) even if having some experience from high precision machine tools spindles which needed the speeds and accuracies of similar range. Only the forces were somewhat different :)

Accuracies: when reading the documents suggested by earlier posters (especially http://http://mdrl.mne.psu.edu/papers/bearinganalyzer.pdf ) i have learned how much the bearing testing and machining has advanced - look at data presented there ;).

WojtekSz
 

:ok:

Yes we are all learning ALL of us are. Including RR and Airbus.
We ALL learned from this accident!

Your English is excellent! Please repost that link: the link will not connect for me! Thank you.

thanks ;) this one should do better :
http://mdrl.mne.psu.edu/papers/bearinganalyzer.pdf

Yup see the issue
 

yeah, i know there is some difference between micro and nano - i was boring holes to micrometer tolerances ;)
still we are discussing the accuracy of balls and the track: overall bearing characteristic may be 100nm which is still only 0,1um but selecting the roller balls can be easily done to better tolerances.

to picture what is 1 nm = the increase of the OD of the 10mm steel ball heated by 1C ! :}

Yup
 

Maybe the balls are ceramic. :suspect:

Derg
i believe the problem is actually not the bearings but the structure supporting the bearings - forces, temperatures and vibrations do significantly impair bearings geometry and hence the behaviour. The conditions are far from ideal. Rough environment calls for tougher solutions with wider spec tolerances so bigger ball diameters. I am sure RR must know it from their experience!
The splines are eaten neither by temperature nor nominal forces - must be significant uncontained forces from vibrations induced by parasitic resonance. Check the engine vibrations signature depicted in Fig 1of your link http://www.robots.ox.ac.uk/~davidc/pubs/ieeeaerospace.pdf - this does look like asking for bad resonance to happen.
But overall - watch the name: David Cliffton. Yes, he works on 'novelty detection' but to my feeling he will get it right. Both links from your post #328 are worth really careful reading. Thanks for research and posting them :D

Probabilities
 

OK Woj I checked out this guy....

"His related research has resulted in patented early-warning systems for the jet engines of the Eurofighter, Airbus A380, and Boeing 787 Dreamliner, and for manufacturing processes that build such engines. He provides consultancy in machine learning to Rolls-Royce PLC and Oxford BioSignals Ltd., a university spin-out company."

He is employed as a full time "line" lecturer and teaches under grad basic math and post grad Bayesian math. I see he also has a strong interest in the medical field so I would guess this failure annoyed him from a moral viewpoint. A vocational person, for sure.

He also works as a consultant to RR.

In his paper
"Bayesian Extreme Value Statistics for Novelty Detection" in your link you posted the clue to this failure is very clear:

"An engine-specific approach to novelty detection has been
shown to be possible, in which the characteristics of data
from individual engines is learned – this often provides
better performance than generic “fleet-wide” models of
normality [21,22], in correctly identifying behaviour that is
abnormal for that engine, while minimising the number of
false-positive alarms generated."

In other words engines inherently are DIFFERENT. They are unique and they are seeking the normative values. Unfortunately there are not a lot of T900s around. T972s even less. They did not have enough DATA SETS. Clue number 1.

Now it is easy to quote sections of a paper to make a biased claim and I urge all readers to read the whole paper to make their judgement of just WTF is going on here, excuse me.[/LEFT]
"Future research will include the application of the technique
to vibration phase, and to non-vibration data sets, such as
“performance parameters” (engine temperatures, pressures,
etc.), which have previously been used with off-line density estimation
approaches [23]".

Well that about wraps it up. RR were running with this without the full data. The "novelty" threshold was set too high to minimise false alarms.
Basically they were taking a big risk.

I make it clear that the responsibility DOES NOT not rest with Mr. David A Clifton.

We will just see how long this post remains on this site. Some of us want the full picture.

Derg:

look also at the second article mentioned: http://www.eng.ox.ac.uk/samp/pubs/clifton_transfer.pdf and check fig 2.2 referring to trent 900 engine with data "...constructed from 200 hours of flight data recorded over a period of one month."
So the data is there BUT look at the width of the red band in the middle or rev range and at the high end. Over there there is practically no chance to detect anything viable!

i would suggest that all of us interested in turbine engines monitoring read carefully both of these articles - luckily to all of us you have been able to dug out and publish links to such extremely valuable reading. It looks like a good peek under the hood of RR maintenance program ;)

thank you!
 

Woj

Yes I missed that..thank you for taking me back to that link.
There is specific data in this link about the T900 testing programme.

At last we are getting close to some answers..thank you!

Yes Yes..

this document!

http://www.eng.ox.ac.uk/samp/pubs/clifton_transfer.pdf

:ok:

Test Data T900
 

Yes Woj I see exactly. That's one HELL of a wobble!

If readers would open the above link and go to page 14.

The graph of amplitude on the LP shaft.
(inches per second amplitude vs shaft speed %)

Redlines are upper and lower recorded movement in inches per sec.

Blue line is the mean...the average.

Context: THIS IS DATA FROM THE T900

This is IN FLIGHT data from 200 hours of testing.

Think we can assume this would be a T970, maybe, but we don't know the airframe it was fixed on.

The graph tells us that when the throttle is set to 61% we have:

A wobble of between 0,42 inches and 1.20 inches per second WOW!

It has been pointed out that is OK. I hope TURBINE D can help us out here.

To many of you the consequences of this will be self evident.

Most of the data in this document uses the T500 as the source. But there are several references to the T900 and T1000 in the document which is worth reading very carefully.

Then we have the additional uncertainty of data for the T972 as used in the Qantas.

Hiya
 

Thanks. In a word NO. :O This stuff takes some ploughing through.

So you say that the "amplitude" is accn? So that should be seconds (-2)?

If so the graph is not labelled properly. That axis is velocty...s to (-1)

So you say the actual distance covered in the wobble is the reciprocal?

Regards

P.S. This is just one of the THREE transmission shafts in this T900 turbine. I can see why SKF wanted no part of this.

You know what....The MBA courses love statistics...easy way to try and justify BS. No joke. Really ANNOYS me!

I just wish this guy and his supervisor would STAY in the medical field.

WojtekSz

The Supporting Structure of the Bearings and its shortcomings are well known, they are addressed by RR themselves, I believe. The IPT Case containing the IPT Disc and the LP/NGVs with Platform are supported by a center bore that is itself part of the Casing. These are ten Radial and hollow struts that are fastened to the Case with special fasteners (bolts). The AD does address the chronic loosening of these bolts, and requires their re-torquing at specific intervals. "Re-Torquing", "Borescoping", "Oil Inspections"; these are known "Palliatives". Palliative in the sense of treatment, not cure. The underlying consideration for the life of this powerplant is the rehabilitation back to profiles certified in its original certificate.

The squishy part is determining, and by whom, what constitutes Safety in pursuance of keeping this engine on wing. I can simply repeat that the cause of the chronic wear and shortened life of this machine is and was known. It is Vibration, and resonance; a "novelty" dependent on whom one asks. The core bores, bearings, and webs are subject to not additional stress, but normal stress that was unaddressed. It may be pedantic, but I think it is accurate. It is not a mystery, it never was. The engine landed on wing early, with insufficient test and a lurking problem that cannot be controlled given present design, not insofar as adherence to the certificate is involved. Decisions made about the future of the TRENT are forthcoming. Replacing moving mass every three hundred cycles may treat the disease, but it won't cure it.

Bear - TURBINE D
 

I believe RR estimated that the T972 in use with Qantas had a life of 70 cycles only. Yes only 70 cycles Good move on the Qantas management to take the "power by the hour" deal.

Does anyone have a link to the data plots from this accident engine please...I have lost the link. They were available but cannot find them.

TURBINE D can you help us out with this wobble stuff. Thanks.:confused:

Data Plots
 

Here is the link to the #2 engine data plots, they are at the very end of the report.

http://www.atsb.gov.au/media/2888854...ort.pdf#page=0