QANTAS A380 Uncontained failure.

[bearfoil]

barit1 DERG

The Centrifugal Breather is located in the external gearbox. It is on the rear face of the gearbox between the oil pump and the Fuel Pump (HP). Aerated Oil, returning from the bearing boxes via the vent pipes and scavenge system, enters the oil tank, where it de-aerates (partially). The oil is sent then to the Centrifugal Breather where it attempts to pass through the rotating retimet, but is centrifuged out, to return to the Oil Tank. The air is dumped overboard. The Oil returns through the Oil Scavenge Pump Elements.

[Ferpe]

There is one piece of evidence to what is the root cause of the oil pipe cracking which has not been debated here. In the court filing that Qantas filed there is the following statement (from flightglobal http://www.flightglobal.com/blogs/wings-down-under/2010/12/fixing-rolls-royces-disposable-a380-engines.html) (http://www.flightglobal.com/blogs/wings-down-under/2010/12/fixing-rolls-royces-disposable-a380-engines.html)

However, the extra thrust exposes the engine (http://www.flightglobal.com/articles/2010/12/14/350901/high-thrust-trent-900s-limited-to-75-flight-cycles.html) to 540 psi at P30, which causes the engine to experience "high severity", the affidavit says. Rolls-Royce's interim suggestion (http://www.flightglobal.com/articles/2010/12/14/350901/high-thrust-trent-900s-limited-to-75-flight-cycles.html) to Qantas has to been to derate the engines in order to "reduce the engine pressure ratio in the 'P30' area of the engine and therefore increase the life of the oil transfer tubes within the HP/IP support structure", the affidavit says.

This seems to indicate that the pressure causes movement of the structure where the stub oil pressure pipe enters into the bearing box. My conclusion is that on the A and B engines the support structure between HPT and IPT is simply not strong enough to stop the bearing box from moving at max thrust to such a level that it affects the pipes fatigue life. The solution is a strenghtend support structure. It is a big operation and explains why in the A version the problem was dectected but to late to fix it for production of the engine, the B mod is a reinforcement of the original structure and the C mod is a redesigned support structure that fixes the problem (but had to be extensively tested before applying it). The flight blogger concludes that the oil pipe needed strengthening, this is an easy fix and should not have required 3 different versions of the engine therefore I don't think this is the fix in the C mod. Further the crack is where the stub oil pipe meets the bearing box, if the box is moving a stronger pipe is not the fix, you need a more flexible and durable pipe but primarly a box that is not moving.

So what is the communities thought about this piece of evidence;)?

[Annex14]

Well, I am glad to see that after that excursion into oil related items we have come back to technical questions. Oil supply, that is my strongest believe, has never been a problem in this engine failure. The monitoring readings published by ATSB clearly show that there was sufficient / normal oil pressure on the feeds untill the very last seconds of the usable life of that engine.
So now the question should concentrate on what has, respectively what will RR change to make these Trents as healthy as planned ?? A lot of approaches to the problems identified in this thread are thinkable, to start from cheap to expensive:
usage of sturdier oil feed tubes? re-desighn of bearingchamber and use of stronger bearings ? re-desighn of supporting structures ? re-desighn of shafts ? or the finite decision, a re- desighn of the entire core engine ?
Would be interesting to read if anywhere a leak has opened in that wall of silence RR is hiding behind ?
I think the basics of that engine are delicate and the craftsmenship with which the modules are assembled and put together are out of doubts. So what is left ?? A real engineering fault ? Or just a too early stop in development and testing, ordered by the beanscounters ?? Anyway, as it looks something very substantial must have slipped through the controlling systems! Probably just an internal communications break / interruption ?? Probably a set of wrong priorities ?? Looking foreward to more and substantial information!!
Jo

[radken]

This is off the main line direction in this thread as to the whys and wherefores this engine seems to be suffering from some "built-in" shortcoming(s), but I was wondering if one of you could address a few questions as to the failure mode of the LPT disk itself. As a non-engineer, I've been musing about the "normal" operating speed of these turbines vis-a-vis the rotational speed necessary for self-destruction. (I'm retired... and I can afford to play golf and muse)

My questions start with a very basic one, which is, in the quest for efficiency and low mass, are these units designed to spin in a near supersonic regime, or do they experience tip velocity excursions approaching SS, say at the highest power settings, like N1 does?

Its moot to the cause of this engines demise, but, regardless of whether the LPT may or may not ever operate near the "shock" regime, at some point after the output shaft separation, and prior to disk impingement with the stators, could the free wheeling disk (blades) have been almost instantly accelerated past Mach 1 prior to the disk burst point? If so, could the blades have failed first from "swallowed shock," their sequential departure thus initiating intolerable out of balance, and, therefor, premature disk rupture?

If management of near supersonic blade tip velocity is, in fact, a parameter in this engines software, its actions in this regime and any harmonic issues impinging on the bearing box would have been completely addressed... No surprises there, right?

My, oh, My! You all have an extremely interesting discussion on-going here.

[Turbine D]

Ferpe

Good post!:ok:

You may possibly hit the "Mods" (nail) on the head.

[TZ350]

Hopefully some of you gentlemen can advise me, re, on page 3 of the PDF file

http://workspace.imperial.ac.uk/medynamics/public/JDing_Trb2008.pdf

the illustration shows an " External spline run-out " on the external component. Is this the " 2.65 mm spline crown " dimension as mentioned in the original AWD, re the spline wear problem and is this a result of uncontrolled/unexpected wear of the thrust washers from vibration/harmonics ? Is the disintegrated turbine disc the equivalent of the " Internal component " ? I appreciate that this drawing is not type specific, but I have been confused as to what the 2.65 mm referred and there were no mentions of which axial faces were wearing.

Also, is the helix on the splines designed to continually apply the thrust loading towards the thrust washers ? Thank you..

[bearfoil]

The "Tube" is not the problem :ugh:. It is the result. No matter the cause of the damage to the "Stub". Misbore or Vibration, Box movement (!), etc. The Support Structure is insufficient. In other words, the Core has mass issues, as DERG points out (as have I).

The Splines too, are not the problem. They are also a result.Oil problem? Certainly, but again, not the cause.

If the Splines were the only issue, There would be no AD, there would have been a revocation of the certificate. "Inspections only" certify that both Rolls and EASA were cognizant of the procuring cause. Again, Simply Certifying the "C" Mod as curative means that the source of the problem was KNOWN, and from the beginning. We do not know if the "C" is the complete answer, simply because QANTAS is not flying it, nor have the EASA certified the Engine as yet, UNDER THE ORIGINAL CERTIFICATE. Inspections are still required.

Think about that. This Engine has had two rebuilds since approval, and still the Engine is not released for its predicted service life. The Engine is still in TEST, can one see it any other way?? Either the engine itself with the C is complete, and needs no re-cert, or it is not, and its reliability is subject to doubt.

10 hours over water. That's the "good news". The bad? Ditch, Crash, loss of life.

Vibration, Resonance, lack of sufficient mass, destructive rapid wear. This engine had an oil fire on the stand, Remember? What happens when the Stub (IP) shaft is severed next time? At some point, the word Burst will have to be retired. It is insufficient to describe what may as yet prove out.

[lomapaseo]

radken

This is off the main line direction in this thread as to the whys and wherefores this engine seems to be suffering from some "built-in" shortcoming(s), but I was wondering if one of you could address a few questions as to the failure mode of the LPT disk itself. As a non-engineer, I've been musing about the "normal" operating speed of these turbines vis-a-vis the rotational speed necessary for self-destruction. (I'm retired... and I can afford to play golf and muse)

My questions start with a very basic one, which is, in the quest for efficiency and low mass, are these units designed to spin in a near supersonic regime, or do they experience tip velocity excursions approaching SS, say at the highest power settings, like N1 does?

Its moot to the cause of this engines demise, but, regardless of whether the LPT may or may not ever operate near the "shock" regime, at some point after the output shaft separation, and prior to disk impingement with the stators, could the free wheeling disk (blades) have been almost instantly accelerated past Mach 1 prior to the disk burst point? If so, could the blades have failed first from "swallowed shock," their sequential departure thus initiating intolerable out of balance, and, therefor, premature disk rupture?

If management of near supersonic blade tip velocity is, in fact, a parameter in this engines software, its actions in this regime and any harmonic issues impinging on the bearing box would have been completely addressed... No surprises there, right?

\

Happy to see that you are at least prone to asking questions before forming ill advised opinions:ok:

You questions about speed have two parts imbedded in them. One part has to do with aerodynamics which of course has something to do with shock waves. The secoind part is a structural question which has a great deal to do with stress and strain.

Talking about speed of sound at the largest diameter (of a rotor) in the fan is easier to comprehend since it operates at a more familiar ambient temperature and pressure. On the other hand deep inside the engine the pressures and temperatures are quite extreme so the speed of sound would be far different. Simplistically the engine revolves around a defined cycle and as such the designer goes for the most effeciency per pound of thrust per pound of fuel. Thus one designs the compressor to operate at the highest pressure that can be obtained without tip stall or any other perturbation you might want to call it, including shock waves etc. The turbine driving the compressor had about the same tip diameter so its surface speed at its tips are about the same.

The bottom line after this is to ensure that centrifugal stresses are kept within an acceptable envelop with substantial margins against combinations of overspeeds and vibratory modes that might combine and produce rapid fatigue cracking. This is basic regulatory stuff and codified in the design regulations.

The problem comes in when the operation of the engine is outside of the certifcated conditions. Either from mis-operation of the engine (including maintainence) or mis-manufacturerd parts.

Vibratory modes are predictable and calibrated via experience including the hundreds of hours in development testing before the engine is certified. So obviously no mis-designed or undertested severe failure conditions are expected in service before any recommended maintainence cycles. assuming of course no mis-operation or mis-manufacturerd parts.

I've tried to keep this brief and cover some nuggets of your questions.

Just one editorial comment; don't confuse low mass with low cost or low safety margins. Margins of safety are regulated and it's stiffness and dampening that make it possible to design for light weight and still meet safety margins, else all the plumbing visible around the outside of engines wouldn't be called tubing but would be made out of thick steel pipe

[bearfoil]

lomapaseo

"Vibratory modes are predictable and calibrated via experience including the hundreds of hours in development testing before the engine is certified. So obviously no mis-designed or undertested severe failure conditions are expected in service before any recommended maintainence cycles. assuming of course no mis-operation or mis-manufacturerd parts."

Problem. That is not ill-informed, but it is wrong. It is the casual expectation of results that gets engineers into trouble. Most vibratory modes are known, especially when building a "replica" of a known model (TRENT). The 900 is quite different from the others, in RPM, discrepant RPM, and bearings. I predict it is exactly what you casually discard that is the problem, just as you have predicted that all vibratory modes are predictable.

[HazelNuts39]

The 900 is quite different from the others, in RPM, discrepant RPM, and bearings.
MAX PERMISSIBLE ENGINE ROTOR SPEEDS
(Based on the limits stated in FAA TCDS for RB211 TRENT 500-series and 900-series, % converted to RPM)

.........Trent 500 ... Trent 900
HP ...... 12954 ....... 11932
IP ......... 9045 ......... 8117
LP ........ 3608 ......... 2787

Are these the differences you are referring to?

[bearfoil]

Yes, just those. Keep in mind, the QF32 #2 IPT failed at a Thrust value of 72,000 POT. This power is commanded by the added Data Entry Plug, (DEP). The Max RPMS are limits that pertain to the base engine; by claim, the 900 can produce 80,000 POT. Where is the extra Power derived? The failure of the EEC to control the first bump of Added Thrust either in not sampling the "Oil Fire's" production of wavering power, high temps and Oil Pressure anomalies, or over "limit" RPM shows us that the engine is not dependable at this very first Power increase (72). This engine is a different "TRENT". The discrepant RPM limits are evidence of this.

[Turbine D]

lomapaeso

To add to your explanation to radken: Assuming the disc began to stretch, because of overspeed and presence of higher than designed for temperatures in the bore area, the turbine blades could have started to unlatch at the tip shrouds. Since the tip shrouds provide blade dampening, it would have been the beginning of the end for the turbine blades very quickly, even without any contact with other adjacent components. The extreme unbalance created would be catastrophic to the disc already operating beyond its design capability.

[bearfoil]

Turbine D

It is an assumption that there was Stretch due excess Heat. Would not the Disc fail instantly even at in limit RPM once the Drive Arm fractured? Also, Contact of any description IPT/NGV Platform would be exactly simultaneous with aft movement of Shaft??

Given the AD's, and their warning of Metal/Metal with aftward drift, isn't the better assumption that the Disc Fractured after contact with Stationery Parts, melted, Disintegrated, and caused burst?? I see no need to entertain Fire, or Blade shear to explain this Engine Explosion. The simpler explanation is generally assumed to be the more likely cause, No?

Applying Occam, then, we can simplify the assumed failure to include no fire, no overspeed (save after fracture), and no need to index the Failure with cockpit data (displayed), at least insofar as it is not immediate in nature, and relies on the EEC, which failed to control the engine in the first place? This demands on actual events in the IPT locale, and taken in sum, they argue against a failure due to Fire.

In this way: Any fire would need time to act on the IPT bore. The more logical assumption is that the bearings (balls) wore beyond their ability to prevent axial (aft) movement, and the Drive Arm was pushed into the Stator Ring. The ten Radial Struts here, were under suspicion via AD targeting their Bolts on the case. They were to be inspected during Strip or borescope. The Splines, oddly enough, at this point, though worn, may not have actually caused the failure. The Splines were subject to inspection, but were just canaries in the mine; What caused the Spline wear also caused the Bearing wear, also caused the Oil Problem, etc.

So we take serious note of the AD's in the Burst, or we rely on The Manufacturer's claim that the Burst was caused by Oil Fire. It is more or less that simple, IMO.

[bearfoil]

Good grief

Thanks DERG. It looks like a good read. I notice the paper releases the TRENT for Flight. Let us hope they mean TEST Flight. When modelling, it is precisely the novelty that Cannot be seen. Modelling relies on abstract Thought, it does not think, nor does it conclude. IMO. It is generally the "novelty" that kills when it strikes, having no follow on Fail safer. again, IMO.

[barit1]

bearfoil:When modelling, it is precisely the novelty that Cannot be seen. Modelling relies on abstract Thought, it does not think, nor does it conclude.

How true.

There's a T-shirt somewhere that says " G*d laughs at numbers ". Not only in turbomachinery, but in AGW.

[Turbine D]

DERG

A good find and good read !

Here is something that the FADEC/ECU didn't do on QF32's Trent 900 engine #2 six years after this study:

A three-speed model of normality was able to identify as novel an event which gave rise to diverging speeds prior to automatic shutdown of the engine on the test bed.

Humm, what happened?

[Turbine D]

Bearfoil
My Quote:
Assuming the disc began to stretch, because of overspeed and presence of higher than designed for temperatures in the bore area, the turbine blades could have started to unlatch at the tip shrouds.

In this post I was responding to another quote on how the IPT blades could have failed without physical contact with other neighboring components. It was not an attempt to explain the total failure, where it started and how it progressed.

But, in that you brought up the subject of the disc:
isn't the better assumption that the Disc Fractured after contact with Stationery Parts, melted, Disintegrated, and caused burst?? I see no need to entertain Fire, or Blade shear to explain this Engine Explosion.

Take a look at the photos of the recovered section of the IPT disc in the ASTB report. In the fracture surface photo, note the structure close to the bore on the forward side and the shape of the bore surface forward to aft.. In the photo of the rear face of the disc, note how one turbine blade root seems firmly in place, but another has a significant gap present in the corresponding disc slot and there is no indication of metal to metal contact at the disc rim or blade slot area. Also note the ductile bend of the power arm drive where it is present.

Now think about something, what are the two elements required to permanently form or deform metal where the normal material ductility is less than 10%?

[Flapping_Madly]

Just tried to look at the photo in the ATSB report in this topic when it was in Rumours and News.
Couldn't.

Only 2 pages available in R & N .

Am I missing something?:confused:

[Turbine D]

Flapping Madly

Try this link, then click on the link to download the full report.

Investigation: AO-2010-089 - Inflight engine failure - Qantas, Airbus A380, VH-OQA, overhead Batam Island, Indonesia, 4 November 2010 (http://www.atsb.gov.au/publications/investigation_reports/2010/aair/ao-2010-089.aspx)

[bearfoil]

flapping madly

I'll send along a pdf in a moment.

Turbine D

I doubt there was fusing of the Metallic bits at the Rim (IPT). First, the speed at which they travel, and the relatively low mass they contain (relative to the Drive Arm) don't allow for time on station to effect a puddle. The Stator Vanes Platform describes a cylinder (barrel) with only its rim effacing the IPT Rim/Blades' roots. The Rim(s) are closer to one another than the Drive Arm/Stator Ring. Thus the Blades would leave, concurrently with the disintegration of the Platform (and its aft fixed Vanes), prior to DA melt. I feature the Drive Arm slipping aftward until the IP Rim contacts the NGV Platform. This conflict shatters the platform as the Blades unroot. The Drive Arm continues aft into the Stator Ring, where melting and Fracture occur simultaneously. Once fractured, the Wheel itself splits in threes, and blows out the case. Loss of Blades cause Stall (HPT)(Bang 1), and the blow out of the case causes the second "bang".

The metal deposition at the flaring Bore, comes from the melted remnants of the Drive Arm Join with the bearing sleeve. The "Foldback" ( of portions of the edges of the Drive Arm) have to do with your poser re: insufficiently ductile metal permanently deformed??

I'd have to say two elements needed would be "Heat, and Hammer".

We need to remember that the supports that mount the Stator Ring to the Case were a constant problem, vis a vis the fastening bolts. The bolts were chronically coming loose..A guess at their looseness would be dramatic vibration in this area.

[DERG]

Yup..the thing tore itself apart. Maybe the fire lasted a second or a few, the dark stains on the wing structure could be oil mist or carbon soot from a fire. Unless we could get in there and smell it we don't know. But the tear on the drive arm looks like a plain tear. Amazing the thing did not continue to burn, against the odds I would guess.

[Turbine D]

What I wanted you to look at in the photo, Figure 15, Page 21, was the fracture surface near the forward face of the disc (golden color) very close to the bore. enlarge it. Look at the stepped lines that have been created in that area and the directional orientation. It could be these lines represent plastic deformation (slips). You answered the question correctly, Heat and stress (rpm's) combined. It is the only way the drive arm could bend that much without snapping. Also, there is no sign of rubbing on the IPT disc rim, meaning this portion of the disk, at least did not contact the stator ID band behind it. My thought is the disk tore out of its fastening mechanism, at the 580 power drive arm bolt holes because of plastic deformation (stretching). Also, it seems there were 4 fractured pieces of the disc. The three that were not found went out over or under the fuselage to the right according to the exit trajectory sketch in the report. The found disc piece came out of the engine to the left based on where it was found according to the labeled map.

[bearfoil]

Turbine D

Hi. From the larger (135 degree) piece of Turbine Wheel recovered, I note the lack of flange, (bolt area). Instead, there is what EASA called a circumferential Fracture in Edelweiss, Miami. So I conclude the Drive Arm remained intact forward of the Wheel bore where it fastens to the L shaped Bearing sleeve. The Shaft flange makes up the aft portion of the bolted together assembly. It resembles a sandwich, in section.

We have made note of the molten metal "plated" to the flaring portion of the Wheel bore, so melted metal is known, and the folded over remnant of bore indicates your sub-ductile peening of this area. Also, there is Metal "Spatter" mentioned in the ATSB report, located on the aft face of the Turbine wheel. Your note of the lack of heat rub at the rim demonstrates the lack of effacement with the Stator Platform, as the Platform effaces the Blade roots, not the rim of the IPT. Here we are again at "Push and Shove" of the IPT Blades out in the forward direction from their fir tree roots, as the Wheel slips backwards into the Plane of the Stator Platform. If we find a Blade from the IP Wheel, I think the effacement Blade to Platform will show, and may even show molten metal.

I've yet to look at the Steps in the Wheel. Am I looking for "Spiral" or "Radial" stepping?? While we are at it, please look at #16. The segment of NGV Platform facing the aft Rim of IPT shows clearly the tracks of circumferential contact at the effacement IPT Wheel Rim/NGV Platform. It has characteristics of patent wear, not critical failure. The outer surface of the NGV Platform and the edge of the Platform itself show where chaotic contact Blade/Platform may have separated all the Blades. Note the missing metal where the Blade roots contacted the Platform??

This may sound farfetched, but so is IPT Burst. In looking at the fracture face of the recovered wheel piece, I note a layered area sub surface, with the surface seemingly uniform above it. This obviously degraded area looks like patent damage to me. To You??

The trajectory of the found piece was obviously eastward. I have a problem with the "drawing" of the location of the missing pieces in the core, then out the case and "up". The origin of the pieces are shown above or below the longitudinal axis of the engine. If the piece, for instance, shown above the L/A was a part of the Wheel, it would not have exited to starboard. At this point in the core, its rotation is clockwise, and therefore it would have exited to port. Now this may be picky, but it is misleading. Also, no one knows for how long the pieces remained inside their circular prison, (case). They could have rolled around its perimeter and exited anywhere.

[bearfoil]

Hazelnuts39

Sorry for taking so long. By "baseline" I mean common rated thrust, in this instance Maximum Continuous Thrust for the 900. Upgrades are for thrust that is available short term? So here, at burst, the 972 was not performing any different than a 900 would be. Maximum continuous thrust in the climb, or some lesser value?? What is different? The DEP makes available for short periods augmented thrust from the same core. The restriction on this excess thrust is the crux of the discussion, imo. Either it is a proven design, or it is not, and if not, it has no place bolted to a wing, only to a stand. So my question is as before? Where does this rather substantial thrust come from? The same Core? At the same RPMs?? This implies a merely "derated" 900, and an "augmented" 972?? There is to me a discrepancy.

[DERG]

The engine is certified right up to 84 so the 72 version should have been "a walk in the park" The thrust comes from the fuel and that depends on the central processor.

"Either it is a proven design, or it is not, and if not, it has no place bolted to a wing, only to a stand."

This 900 engine was designed to be experimental in service: whole raft of documentation tells us just that. Of course it had no place on a civil aircraft. No probs in military applics: see here

http://www.robots.ox.ac.uk/~davidc/pubs/ieeeaerospace.pdf

Hell of a lot of work to do by RR and Airbus. Flight Aware has not published any flight times on the QFA12 service, probably cause they are only using minimum throttle and carry less payload. Not all the flights are A388s either, my guess is they send the B74s when they need to carry a real load. No wonder the Qantas B74s are munching engines, the are working hard!

From post#317:

"The focus of ACARE was to set a strategic research agenda aimed at meeting the environmental challenges set out in the European Aeronautics Vision for 2020. As a result, Rolls Royce (RR) and other companies in the aeronautical industry were faced with challenges including reducing fuel consumption and CO2 emissions by 50%, reducing external noise by 50%, reducing NOX emissions by 80% and reducing the environmental impact of manufacture, maintenance and disposal of aircraft-related products. At the forefront of responding to ACAREs pan-European research challenge is the ability of companies such as RR to investigate, through high-performance computing (HPC)-based simulations, innovative methods of design and operability of aircraft products."

A roundup flyer sheet:

Systems Analysis, Modelling and Prediction Group (http://www.eng.ox.ac.uk/samp/ac_cond.html)

Thats the design goal. Therein lies the clue to the T900 and its woes.

TURBINE D Yes I see the part. That looks like it was in a plastic state when it parted. Yes a fire.

When I was trawling through the internet I came across a very few references fom the USA to "modelling", I mean design modelling as applied to aerosapce engine.

The few that I did find were mainly published by NASA.
They were VERY conservative and made it clear that "a model" was just that "a model".

Would I be correct in thinking that the USA prefers the known to the unkown when it comes to aerospace turbofans?

[HazelNuts39]

I would think that the 'baseline' is the variant with the highest thrust rating, i.e. the RB211-Trent 980-84, sealevel static TO thrust rating 84,098 lbs, flat-rated to ISA+15C. The thrust levels of that rating must be achieved without exceeding operating limits of RPM and TGT. The manufacturer selects rating(s) so that they they have some margin relative to the operating limits. The lesser ratings are 'derates' and have greater margins than the highest rating. In TO ratings Trent 900 (https://docs.google.com/leaf?id=0B0CqniOzW0rjZDcyZTM1YTUtODY2Ny00MjJiLTlkNDQtZTdiOWQ xN2Q2OWUx&hl=en_GB&authkey=CMG60NoC) the various ratings are shown at the flat-rated temperature. The dashed line shows schematically the thrust corresponding to the operating limits, whichever is most limiting. The line is drawn arbitrarily, because the documents don't tell us where it lies. It's actual location will be different from engine to engine, and the margin will reduce as the engine deteriorates during its service life.

Prior to certification, proof of integrity of the engine operating at the declared operating limits must be provided by analysis, component testing and, finally, by a 150 hr endurance test which represents an accelerated life cycle of the engine. 'Modelling' is a design tool, not proof of compliance with airworthiness standards.

[DERG]

The engine with a 70 cycle lifespan. Bettya that was not in the sales presentation to Quantas! Thats the life RR gives the 972 in Qantas operations.

Some of you may think that a bird strike is a "novelty event"..

Well this author does too...been waiting for this! :rolleyes:

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

Sleep Well!:ok:

[bearfoil]

HazelNuts39

Nomenclature. It is important I understand your description. A "Baseline" machine to me is its original "Design". One seldom starts with the nephew and progresses toward the Grand Uncle. So it seems to me counterintuitive in the least.

I note your numbers and explanations, and I believe your representation of the 900 family. So I would ask, if the most powerful powerplant has the same construction, core, wheels and limits (Temperature and RPM), as the least powerful, then this appears rather strange. Airbus "found" 6k lbs. of extra weight on the whale, necessitating more thrust available at Take-off at MGW. The result was the 972, I believe, a hurried iteration with a new Data Entry Plug. Why on Earth develop an engine with X Thrust, then derate (make unavailable) its Power??

Can you help me out with a more basic explanation, then?

thanks

bear

[DERG]

Howdy!:cool:

Airbus found 6 metric tonnes of over design mass on the airframe which is closer to 13 000lbs

Greets!

Hey take a look at this about half way through you can play with the cross section of the shafts...amazing torsion these are under...amzn.

http://www.eng.ox.ac.uk/thermofluids/people/david-gillespie/b1-mechanical-engineering-project/B1%20Project%20Kick%20Off.ppt#453,18,Heating from Seals

[HazelNuts39]

Why on Earth develop an engine with X Thrust, then derate (make unavailable) its Power??Perhaps you should ask RR plc. I suspect it's just marketing strategy. The market is willing to pay a certain price per pound of thrust, so the lower rated versions probably have a lower price tag, as well as lower maintenance costs. The higher rated versions provide 'growth potential'.

EDIT:: a hurried iteration with a new Data Entry Plug. Any proof of that? It is not the first engine that RR has developed, nor the first application in a new airframe. Ever heard of a completely new airplane that didn't turn out heavier than planned?

regards,
HN39

[bearfoil]

Marketing v Safety then? Thanks for your rapid response.

bear

[bearfoil]

RR makes noise of its constant monitoring program. It is impressive on screen (video) but is essentially a real time ACARS, (shout out to AF447). With a minimum one minute lapse in sampling, it is about as helpful. Perhaps the profit is here, in the NEW, HIGH TECH! Power by hour format. Some of what was traditionally treated with serious professional scepticism has become marketing Fluff prior to proof.

bear

[DERG]

Why not put two T1000s inboard and two T800s outboard?

[bearfoil]

Ya know, that is not a bad idea. Wait, let's Roid 2, and 3, and eliminate 1, and 4, and .........wait, that's the 787.

[Shell Management]

Marketing v Safety then?

No - derating increases engine life and higher power testing irons out problems earlier. :ok:

One hates it when hyperactive amateurs suffering from confirmation bias jump to conclusions beyond their competence or knowledge.:=

[DERG]

Hey we are trying to help RR out here...:)

[bearfoil]

Derate is identical to over-built. Shell makes excellent polymer, and adhesives, and used to do decent research in Emeryville. (:=)

(it was NOT easy synchronizing those fingers)

Derating also can be political; as such, it allows for "squishy" parameters, and "Test on Wing".

"Open 'er UP" can describe Throttle, and engine Case also.

bear

[DERG]

:ugh:Gas costs $11 per US gall here in the UK.:ugh:

[Shell Management]

Yes DERG and Bearfoil, and those contributions are to this thread irrelavent like most of your posts.

'Trying to help Rolls Royce' - how arrogant is it possible to be?

[bearfoil]

I think ad hominem is not helpful, let's desist. Yes?

[HazelNuts39]

bearfoil;

RE "Test on Wing": You mean the thousands of hours and flight cycles accumulated in the AB flight test programme prior to entry into commercial service?

[Turbine D]

DERG & Bearfoil
Design, Testing & Certification Requirements To Gain Engine Type Certification
I thought it might be interesting for you to see and browse the various requirements set forth by the US FAA to gain type certification for a turbine engine. Many of the questions being posed in recent posts are covered somewhere in this document. I would assume the European requirements are the same.

Electronic Code of Federal Regulations: (http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=ad5bceee8d809b880e9651d8ef9e2635&rgn=div5&view=text&node=14:1.0.1.3.16&idno=14)

Also, there are Advisory Circulars that give guidance to specific topics. These are not mandatory as there may be other ways to demonstrate compliance to the specific topic. Examples are:

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2033-3/$FILE/AC33-3.pdf

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2033.14-1/$FILE/ac33.14-1.pdf

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2033.63-1/$FILE/AC33.63_1.pdf

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2033.27-1/$FILE/AC33-27-1.pdf

You will need to copy and paste the advisories into your browser to view them.

In another post I will talk more about modeling, analysis and monitoring.

[DERG]

I see the shell person has gone offline, you know we had a good run on here before that kind of intimidation. They actually have a USA 0800 nuber for bullies on line, but this web site is in the UK I think.

Maybe he knows the guy from QuinitiQ the " lube scientist" the former mine detection robotics salesmen.? Steve Lee he is called. Who knows?

Now too look at these new USA links. When I was searching Turbine it was notable that USA concerns readily accepted "modelling" as tool and not the exalted technique it appears to be overhere.

[DERG]

The accident T972 did not comply with this for starters
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2033.63-1/$FILE/AC33.63_1.pdf

[Turbine D]

DERG

Yes, I noted the same thing (Shell Person). It's too bad some people play the "phantom" critic role and contribute nothing to the technical discussions of the day. :ugh:

[bearfoil]

HazelNuts39

"test on Wing". I think my comment was a bit flippant, I did not mean there was an actual recognized and formal test. I meant to characterise what some may see as a "De Facto" situation. A regime of rigid inspections enforced in an attempt to "monitor" known and potentially disastrous "unknown" conditions. The potential for disaster is patent in EASA's description of the "conditions". Down to a ten cycle inspection, known and very troubling wear could result in "Loss of the Aircraft".

I remain troubled by what I see as distraction; an attempt to sever the "Oil Pipe" fiasco from the AD, a "May have resulted in..." going unaddressed (at least here), and data and comment by the manufacturer at fault taken at face value.

Perhaps I am completely off base. There may be too much discussion? I am simply mystified at some of what I am reading, and by the apparent lack of concern. This flight came within a speck of going down, and for reasons that were addressed by AD's in an ongoing and co-operative manner for an entire year.

[barit1]

Shell Management:

No - derating increases engine life and higher power testing irons out problems earlier.

Spot on, SM. Almost every OEM has done it, or has wished they had.


One hates it when hyperactive amateurs suffering from confirmation bias jump to conclusions beyond their competence or knowledge.

NO! I don't see any of that on this thread, do you? :rolleyes:

[mike-wsm]

On another thread there is mention of adding Shell Person to ones 'ignore list'. I just did that. Oh, and I added one other also. :O

[Turbine D]

DERG & Bearfoil

Modeling & Analysis

Today, every unique component in a new aircraft engine is designed using a 3D modeling program. There are no longer masses of 2D blueprints produced (except for special requests). 3D programs such as Unigraphics or Catia are widely used in the aircraft business. Upon completion of the component being designed on the computer, the electronic files are saved and passed on for various purposes to various entities:
1. In-house analysis groups that determine the designed component's suitability in meeting the various parameters basic to the design, e.g. fatigue life, vibratory stress limits, temperature parameters, weight limitations, etc.
2. Suppliers that will produce the basic component, casting, forging, inspection gauging, etc., who in turn will forward the electronic data to their suppliers that build the tooling that will produce the component.
3. Manufacturing Centers that will machine the components where the electronic data is programmed into the units that will be used to machine, produce and inspect the final product.
So modeling is today's way of life and it has reduced the number of mistakes that were common in the past. It is not to say there are not pit-falls, there can be as Airbus found out on the A-380 program. In their case, although one common program (Catia) was used to design the electrical wirings system for different sections of the fuselage, two different version were used and when it came time to put the sections together, the electrical wiring didn't go together causing a ~2 year delay.
So if you model every component in a turbine engine, is it possible to assemble all the components together on the computer to see what the engine looks like in total? Why yes it is and it has been done. Then, is it possible to look at the engine on the computer and run it and perform dynamic analysis of vibrations, pressures, temperatures, transient conditions, clearance controls, SFC, etc? Well, yes but, some things have to be done first. Since many of the analysis programs were developed at different times, the codes used do not mesh together at all. So if the individual codes were to be redeveloped using a common code an actual engine can be put through its paces on the computer while checking key metrics and engine behavior characteristics. Mind you, this can be all accomplished without buying or producing any physical parts. This is the direction engine design and manufacturing is headed, if not already there at this moment.

Monitoring

Aircraft engine producers have known for sometime that the money (profit) is not in the sales of the original engine (often they are sold at cost or below cost early in the program), but in the subsequent sales of spare parts or replacement parts. Today it takes an investment of $2B to develop and certify a new large turbofan engine and it takes a long runway program to break even. In the meantime, airlines worldwide struggle to make money with the ups and downs of fuel costs and revenue passengers in ever changing economic times. To cut costs, many have disbanded their engine overhaul shops and therein lies a new business for the OEM's, provide this service. To do it right, real time engine monitoring is a necessity to set realistic fees to provide this service (Power by The Hour, Total Care, whatever). And so you will see increasing levels of realtime downloading of engine operating parameters (as many as a hundred or more parameters) to both the airline and OEM's appraised of operating conditions while working together to keeps the engines performing and in the air, out of the overhaul shops as much as possible, a win-win situation for everyone.

This is how I see the engine business going forward in today's computer driven world.

[DERG]

Yes I see clearly that will be the reality.

In my book this failure was something out of 100 year old accident report, something you would dig up in a mouldy old "Mechanical Eng Failures of 1911"

Whatever was the cause there was a HELL of a breakdown in communications and respect between the different parts of RR. and Airbus. They spent 15 months flight testing alone.

The fact that we have only TWO main supliiers viz GE and RR does not, in my view, help the civil aerospace industry. The fact that we have TWO sets of environmental protection targets to meet does not help.

The EADS set up in my view has many other cultural/language problems to over come as you highlighted with the simple connector variance.

Unlike MIT which is very much an egalitarian our top academic facilities are distant from reality, insular and less approachable. Our military facilities in Europe have been decimated and in that process we lost many skills that so could easily prevent this accident.

I'm tired. If the shell person comes back tell him I use pure virgin olive oil in summer and mix it with a little kerosine in winter. That usually is enough to move 'em on.:E

[Annex14]

Was a bit on "idle" for a while. Now I have a problem to cope with all the scientific and engineering entries. But what now I have clearly in mind is, all that is necessary to make a new engine running as planned and predicted and sold to a customer is at place, ready to be adopted and used. Or not ??
Like to quote DERG first.
quote:
Whatever was the cause there was a HELL of a breakdown in communications and respect between the different parts of RR. and Airbus. They spent 15 months flight testing alone.

Very correct !! But what makes you believe they also tested engine vibration in flight ??? What would you say if that wasn´t done probably since the very early RB 211´s or the Trent 500´s ?? What if there already some results came to be known and set aside because they didn´t "fit" the economical targets ? Probably also the pride of some desighners or engineers ??

I know, these are very hypothetical remarks and questions. But imagine if my blind shots turn out to be point hits !!
If that would be true, no silly oil stubb problem or bearing chamber vent or support structure enforcement would help. It ends in something that we might see in about 15 - 18 month, if everyone works as expected.

[KBPsen]

Perhaps if the hyperbole, conjecture, accusations and outright drama could be toned down or even dispensed with, this might become an interesting thread. As it is there's a whiff of Jerry Springer about it.

That certain participants set out from a conclusion rather than attempting to arrive at one, doesn't do much for quality either.

[mike-wsm]

There is always the possibility of modelling a complete engine, but in my experience in another field total modelling is not always helpful and indeed can be misleading. I found computer models to be very helpful when applied in smaller ways that permitted understanding of the results, in the same way that simple maths provides a better understanding than a complete math model. The models are always to some extent idealised and I doubt whether vibrations could be effectively modelled because there are so many random elements to include. And random is difficult for computers because they suppose that random is actually random whereas in reality it is not, a Monte Carlo type programme is drastically over-pessimistic when compared with other engineering techniques such as rss, which allows for the statistical improbability of everything being on the very worst limit in any one product.

With apologies for uk english spelling.

[Old Engineer]

DERG wrote under the header First Failure as follows, today at 12:38:


The accident T972 did not comply with this for starters
http://rgl.faa.gov/Regulatory_and_Gu.../AC33.63_1.pdf (http://rgl.faa.gov/Regulatory_and_Gu.../AC33.63_1.pdf)


This is a 15-page document. Four pages in at paragraph 2.3.c there seems to me to be a failure to comply, in the matter of the spline damages. The AD's concerning this problem seem to identify it as having the potential to cause uncontained failure of major components of the turbine engine. The AD's further prescribe a program of extensive and frequent inspections, which at one time were down to every second cycle. What is the margin of safety in an every second cycle inspection program? Or for that matter, in an every 20-cycle inspection program-- is this the current revised inspection frequency possible under that program? (I'm having a little trouble keeping up, the changes come so fast.)

In any case, this handling of this spline problem appears to be either an "Engine design or operating restriction(s) that allow(s) and manage(s) accumulation of high-cycle fatigue damage for [a] component, [which is] not acceptable if the failure of that component would cause a hazardous engine effect. ..."

This would appear to preclude the operation of the Quantas 380's as now configured into LAX. I note that Qantas' appears to have no intent of doing so.

Have I missed something?

OE

[mmciau]

OE,

As I understand it, Qantas cannot fully utilise the A380 out of LAX as it did before the failure. RR is only allowing a derated engine at the present.

Mike

[DERG]

"Very correct !! But what makes you believe they also tested engine vibration in flight ??? What would you say if that wasn´t done probably since the very early RB 211´s or the Trent 500´s ?? What if there already some results came to be known and set aside because they didn´t "fit" the economical targets ? Probably also the pride of some desighners or engineers ??"

Oh I think they tested vibration OK during the 15 months. But I bet the test engines were EAs or 970s not 972s. Humanity is far from perfect I agree.

"This would appear to preclude the operation of the Quantas 380's as now configured into LAX. I note that Qantas' appears to have no intent of doing so."

Qantas depended on getting an A388 that was fit for the purpose. They have to operate the A388. The B74 fleet is being over worked as it is trying to fill the gap. Qantas is not the culprit.

"Perhaps if the hyperbole, conjecture, accusations and outright drama could be toned down or even dispensed with, this might become an interesting thread. As it is there's a whiff of Jerry Springer about it."

You hit the nail on the head. Confrontation with the truth and dealing with issue. Nothing more dramatic than a plane with 469 people on it circling around while the pilots try and work out why the engine exploded.

This thread seems interesting enough for the many visitors who come here. Rolls Royce were incompetent in so many ways way above the level of Jerry Springer, a documentary media program more akin to the Discovey Channel would be appropriate.

Ther is always Al Jahzeera, they did a good job digging out the B737 build fiasco.

[Turbine D]

Old Engineer

Good to have you back! It has been awhile since your last post, must be the winter weather...

I thought it would be interesting to post the certification requirements as presented in the US FAA regulations. You have noted a particular item that stands out and DERG did the same. I am sure there are more that seem applicable. As I see it, the OEM (original engine manufacturer) meets with the government regulator and submits a process for certifying a subject engine. During that meeting or subsequent meetings, it is decided exactly what the requirements will be for certification. Is it a totally new engine? If so, it requires all of the steps outlined for approval. Is it a derivative engine or growth engine from an existing family? Well, maybe this will be required but this will be waived based on history. And then the certification process begins and proceeds to engine type certification. Keep in mind that even if you go through a flight demonstration program on a different aircraft and a 150 hour endurance demonstration in a test cell, not all the potential problems may have surfaced or have been wrung out. So then, the engine receives its type certification, deemed to be flight worthy, and is ready for the real application, lets say on the A-380 aircraft.

The aircraft certification program is focused on the aircraft, although the same regulatory agency is in charge, just a different set of people and expertise are highly involved. So then, if during this aircraft certification program there are engine abnormalities along the way, how are they handled? What if there are, during the course of flight testing (1-2 yrs.), an abnormal number of engines removed off wing for various unnamed problems, beyond planned engine removals? Assume a significant number. Where do responsibilities rest, with the OEM, with Airbus, with the governmental regulatory agency? How was it handled? In my mind, this is where the breakdown occurred on the 900 and A-380. It wasn't during the original engine certification process, except for possible should have done but didn't possibilities. There was a lot of pressure by the producers to deliver the goods to the customers as the program was significantly behind schedule, viability of businesses rode on a favorable outcome of the flight test and aircraft certification program, so how were technical problems with the engines handled by the regulatory agency during the aircraft certification phase? I will let this up to the individual's imagination, I have mine.

Turbine D

[DERG]

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2033.63-1/$FILE/AC33.63_1.pdf

OLD ENGINEER
Much appreciate your help here. The link you posted up in #357 did not connect so I reposted it.

The clue to the failure of the T1000 test on Aug 4 2010 is in this document.

U.S. Department of Transportion FAA ADVISORY CIRCULAR of July 25 2007 initiated by ANE-10. Adivisory Circular # 33.63-1

[Trent 972]

DERG, If you wish to selectively quote from
The Key Document Faa A.c. 33.63-1, then perhaps you should also give consideration to paragraph 2b. on the first page. ie.

2. Who does this AC apply to?
.....
b. This material is neither mandatory nor regulatory in nature and does not constitute a regulation. It describes acceptable means, but not the only means, for demonstrating compliance with the applicable regulations. We, the Federal Aviation Administration (FAA), will consider other methods of demonstrating compliance that an applicant may elect to present.

I should think that TCDS NUMBER E00075EN (http://rgl.faa.gov/Regulatory_and_Guidance_library/rgMakeModel.nsf/0/09b47c27a9cfb982862573080054f9ea/$FILE/E00075EN.pdf) is the FAA's position on the Trent 970/972 engine.

However , if it happens that you are on the FAA board, then please accept my apologies.

[Trent 972]

mmciau,30 Jan 2011.
As I understand it, Qantas cannot fully utilise the A380 out of LAX as it did before the failure. RR is only allowing a derated engine at the present.
Mike

Wrong. The majority of QFA 380's are cleared for Full Power Take-offs out of KLAX or anywhere. This I know, from 1st hand experience.

[bearfoil]

TRENT972

Keep reading your referenced selection. 2b is a rough reiteration of the Authority the FAA exerts on compliance issues. It is essentially a "Heads Up" to the applicant.

It is a statement for clarification, and as such leaves purposeful and narrow openings for latitude in following the process. If you know dogs: Not a "Collar", per se, but a "choke chain".

Advisory? Absolutely. Also a SUPERVISORY. The FAA hasn't the equipment or the talent the manufacturer does, so the FAA allows the Company to do all the research and development. Also, of course, the manufacturing of components.

If you know flying: "Pull Up, Terrain".

TRENT Cleared by whom?

[DERG]

Thanks for that. I am not on the FAA board. I think the engineering is relatively simple when you compare it to the social structures that gate keep the blaming and shaming.

Why are some flights on QFA12 done with B74s?

[Trent 972]

Bearfoil, you will note that the TCDS NUMBER E00075EN (http://rgl.faa.gov/Regulatory_and_Guidance_library/rgMakeModel.nsf/0/09b47c27a9cfb982862573080054f9ea/$FILE/E00075EN.pdf) predates Faa A.c. 33.63-1
It is essentially a "Heads Up" to the applicant. What applicant? Certification was already accepted. That horse had already bolted.
To argue that the development of the engine could comply with an advisory standard (that may have already been completed to an acceptable alternative) after FAA acceptance of the Trent certification, is an unworthy argument.


TRENT Cleared by whom?
1.Rolls Royce
2. QANTAS
3. The Aircraft Flight Manual
4. Airbus FCOM
5. Me, as I pushed the Thrust Levers to TOGA on take-off out of LA, recently.

If you know flying "Pull your head in" - but I doubt you will.

[SKS777FLYER]

Bearfoil: "Open 'er UP" can describe Throttle, and engine Case also.

OMG ! Now, THAT is funny! :}

[DERG]

Why are some flights on QFA12 done with B74s?

[Trent 972]

DERG, I'm not a scheduler, so I can't answer that question. My best guess is that it takes about 40 hours for a 380 to do a SYD or MEL - LAX return flight and we don't have enough 380's to operate 2 daily by 7 days a week, services to LAX, as yet. (and keep them on the SIN/LHR flights as well)

[bearfoil]

Trent972

Much Respect, Captain, F/O. I have to assume then that all the Authorities are satisfied. I don't see any listed as to compliance with The Certificate as regards unlimited operation. AD? Certainly you missed the most important ones, the FAA 337 or waiver? Share with us the Mechanicals?? Loads?? Calcs?? Limits??

Head withdrawn into Carapace.

bear

[Trent 972]

Bear, The ol' FAA 337 - wherein one must
Complete the form as instructed in this AC, excluding item 3, and ensure that items 6 and 7 have been properly executed. Give a copy of the form to the aircraft owner/operator and send a duplicate copy to the FAA Aircraft Registration Branch within 48 hours after the airframe, aircraft engine, propeller, or appliance is installed on an aircraft and approved for return to service.
Now which A380 sports an American N registration? Bueller, Bueller ....Anyone?
The answer to your last question is commonly known as MOD C (all 4 engines)- no restrictions to use of.

[Shell Management]

Trent 972 At least some of us understand what you are saying. Thanks!:ok:

Of course some others contributors are overspeeding, beyond their fatigue life...:uhoh:

[DERG]

Bear...going back to your theory of group think. It seems the FAA and the EASA rubber stamp each others work. The FAA relies on the data produced by RR because it has been approved by the EASA.

As TURBINE D asks
"Where do responsibilities rest, with the OEM, with Airbus, with the governmental regulatory agency? How was it handled? In my mind, this is where the breakdown occurred on the 900 and A-380".
and

"viability of businesses rode on a favorable outcome of the flight test and aircraft certification program"

No business had more to loose than Qantas. The SIA CEO has made noises last week wanting an answer from RR, he is a very patient man in my opinion.

I don't think the ATSB has the resources to nail down if this was a design fault in the T900 series itself but I do expect the ATSB to report, without any regard to the happy relationship the FAA has with EASA or RR or anybody else.

It could well be that RR cannot balance this T900 and the misbored pipe did it us a big favour.

As TURBINE D states:

"so how were technical problems with the engines handled by the regulatory agency during the aircraft certification phase? I will let this up to the individual's imagination, I have mine."

If the failure was due to a faulty oil pipe..then fine.

Shell Management
What oil do you recommend for the 180C mean temps in this T972?
Maybe you have an additive?

[DERG]

If the engine had expolded over Manhattan I bet the FAA would be a little more vigorous in giving out the all OK tickets. CNN would have made a few noises.

[Turbine D]

Trent 972
The Key Document Faa A.c. 33.63-1, then perhaps you should also give consideration to paragraph 2b. on the first page. ie.

If you refer to the master certification document:
PART 33—AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES
You will note under "vibration", it basically states (my wording, not verbatim) that adequate testing must be done to demonstrate vibration is not a problem. So then, the circular about this subject is issued to "guide" the requester through the process of testing for vibration during the certification process as there may have been many questions in past and present regarding what is acceptable to the FAA. The circular implies "Here is a way to accomplish vibration testing that is acceptable to us, but there are other way that may be acceptable as well." It is a unhappy day to have spent $1M or $2M on an engine test to only learn it didn't meet the certification criteria in the FAA's eyes.

Turbine D

[Trent 972]

Thankyou Turbine D.
Please provide the documents to prove that
....that adequate testing must be done to demonstrate vibration is not a problem.
Was NOT done.

I would also like to see the document from the FAA that informs
...it didn't meet the certification criteria in the FAA's eyes.
After I've had a chance to read them, I'll be more than happy to discuss the ramifications.

[Shell Management]

Trent 972 - there isn't. Overactive imaginations are running free.

Why all this discussion on FAA on a European designed engine fitted to an Australian aircraft anyway?

DERG

Refer to the Operating Instructions for information on approved oil specifications for the Trent 900 old chap.

[DERG]

"Why all this discussion on FAA on a European designed engine fitted to an Australian aircraft anyway?"

This might be a dog eat dog industry Shell but when it comes to life and limb we are united.

[Turbine D]

Trent 972

Please provide the documents to prove that
Quote:
....that adequate testing must be done to demonstrate vibration is not a problem.

Electronic Code of Federal Regulations: (http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=ad5bceee8d809b880e9651d8ef9e2635&rgn=div5&view=text&node=14:1.0.1.3.16&idno=14)

From this document:
Subpart E—Design and Construction; Turbine Aircraft Engines
§ 33.63 Vibration.
Each engine must be designed and constructed to function throughout its declared flight envelope and operating range of rotational speeds and power/thrust, without inducing excessive stress in any engine part because of vibration and without imparting excessive vibration forces to the aircraft structure.

Subpart F—Block Tests; Turbine Aircraft Engines

§ 33.83 Vibration test.
(a) Each engine must undergo vibration surveys to establish that the vibration characteristics of those components that may be subject to mechanically or aerodynamically induced vibratory excitations are acceptable throughout the declared flight envelope. The engine surveys shall be based upon an appropriate combination of experience, analysis, and component test and shall address, as a minimum, blades, vanes, rotor discs, spacers, and rotor shafts.

(b) The surveys shall cover the ranges of power or thrust, and both the physical and corrected rotational speeds for each rotor system, corresponding to operations throughout the range of ambient conditions in the declared flight envelope, from the minimum rotational speed up to 103 percent of the maximum physical and corrected rotational speed permitted for rating periods of two minutes or longer, and up to 100 percent of all other permitted physical and corrected rotational speeds, including those that are overspeeds. If there is any indication of a stress peak arising at the highest of those required physical or corrected rotational speeds, the surveys shall be extended sufficiently to reveal the maximum stress values present, except that the extension need not cover more than a further 2 percentage points increase beyond those speeds.

(c) Evaluations shall be made of the following:

(1) The effects on vibration characteristics of operating with scheduled changes (including tolerances) to variable vane angles, compressor bleeds, accessory loading, the most adverse inlet air flow distortion pattern declared by the manufacturer, and the most adverse conditions in the exhaust duct(s); and

(2) The aerodynamic and aeromechanical factors which might induce or influence flutter in those systems susceptible to that form of vibration.

(d) Except as provided by paragraph (e) of this section, the vibration stresses associated with the vibration characteristics determined under this section, when combined with the appropriate steady stresses, must be less than the endurance limits of the materials concerned, after making due allowances for operating conditions for the permitted variations in properties of the materials. The suitability of these stress margins must be justified for each part evaluated. If it is determined that certain operating conditions, or ranges, need to be limited, operating and installation limitations shall be established.

(e) The effects on vibration characteristics of excitation forces caused by fault conditions (such as, but not limited to, out-of balance, local blockage or enlargement of stator vane passages, fuel nozzle blockage, incorrectly schedule compressor variables, etc.) shall be evaluated by test or analysis, or by reference to previous experience and shall be shown not to create a hazardous condition.

(f) Compliance with this section shall be substantiated for each specific installation configuration that can affect the vibration characteristics of the engine. If these vibration effects cannot be fully investigated during engine certification, the methods by which they can be evaluated and methods by which compliance can be shown shall be substantiated and defined in the installation instructions required by §33.5.

[Doc. No. 28107, 61 FR 28433, June 4, 1996]

Hope this helps...

Turbine D

[Turbine D]

Shell Management

Why all this discussion on FAA on a European designed engine fitted to an Australian aircraft anyway?

1. It is believed that the FAA & EASA have similar requirements on aircraft and aircraft engine certifications. Both agencies talk to one another and accept back and forth certifications depending on where the aircraft/engine is being designed and built. In the case of the A-380/Trent 900 series, the ball is in EASA's court. In the case of the A-380/GP7200, EASA certified the aircraft, FAA certified the engine as it was developed by GE/PWA in the US.

2. The aircraft is not "Australian", it is of European origin, an Australian airline bought the package (A-380/Trent 900 series) as did other airlines.

3. The FAA accepted the certification packages, but probably depending totally on the EASA's certifications without much ado. No US airlines have purchased A-380/Trent 900 series aircraft. However, for flights into and out of US airports, a comparable FAA certification must exist or there wouldn't be Sydney to LAX flights.

4. Living in the US, it is easy to obtain FAA certification requirements as presented in previous posts. EASA certification requirements are not so easy per-se, perhaps you might contribute similar EASA documents for comparison.

5. The Trent 972 failure on the Qantas A-380 was not a ho-hum event. Anytime a disc bursts out of the engine, it is life threatening. And so, how did this happen? Was it preventable? Were problems identified, leading to this catastrophic event, not fully addressed? Why is there disassociation between what happened on Qantas verses seemingly prior related problems which were either partially addressed or not addressed at all at the time? What were the roles and responsibilities of the various players involved? How have they met their responsibilities?

6. Isn't this what the Tech Log is all about, exploring the possibilities?

Refer to the Operating Instructions for information on approved oil specifications for the Trent 900 old chap.

So what oils are approved for the Trent 900 series engines? It isn't clear in the Type Certification Document.

Turbine D

[HazelNuts39]

And so, how did this happen? Was it preventable? Were problems identified, leading to this catastrophic event, not fully addressed? Why is there disassociation between what happened on Qantas verses seemingly prior related problems which were either partially addressed or not addressed at all at the time? What were the roles and responsibilities of the various players involved? How have they met their responsibilities? To ask these questions is one thing. To answer them without the benefit of knowledge is another.

[Annex14]

I wouldn´t be too sure that within the "Brotherhood of PPRuners" there are not some members that have the right answers at hand.
But to use and rephrase your words:
To ask this questions is one thing. To answer them in public might be of such an extend to the players involved, that it is wiser to handle the case with care and caution.
As I understand the ongoing discussion. Primary goal is safety. As an - important - side effect, we all want to hear from the "officials" what the root cause of that QF 32 desaster was. Well, we can wait.

[HazelNuts39]

it is easy to obtain FAA certification requirements as presented in previous posts. EASA certification requirements are not so easy per-se For starters:
EASA Home Page (http://www.easa.europa.eu/home.php)

CS-E (http://www.easa.europa.eu/agency-measures/docs/agency-decisions/2010/2010-015-R/CS-E_Amendment%203.pdf)

Trent TCDS E.012 (http://www.easa.europa.eu/certification/type-certificates/docs/engines/EASA-TCDS-E.012_Rolls--Royce_plc._RB211_Trent_900_Series_engines-04-24052007.pdf)

[bearfoil]

The Certificate is based on Data. Ignored or unaware, the applicant needs to supply this data. It is forthcoming. The bottom line is Spline Wear. The engine had an oil fire in test. The engine exhibited some anomalous vibration and resonant transients that beat it to a pulp over shorter than allowable (and Certificated) time.

These are the issues, and the rest is corn soup. Who expects a problem of this magnitude to casually enter the Public Domain?? Nice discussion, though.

[Turbine D]

Thanks for posting the EASA sites!

[Old Engineer]

Turbine D has drawn a little heat for asking some questions, in the last few posts above. But nonetheless one of Turbine D's questions was of considerable interest to me, that regarding the specifications of the [QF32] engine oil. And Turbine D asked that question directly to Shell Management, whom I think we are entitled to assume has the background to answer it more fully than he did. The exchange:

Question:

So what oils are approved for the Trent 900 series engines? It isn't clear in the Type Certification Document.



Answer, by Shell Mgmt, addressed to DERG:

DERG
Refer to the Operating Instructions for information on approved oil specifications for the Trent 900 old chap.

Well, I see now the question was DERG's, restated by Turbine D. I find the answer to be a bit circular, at least to me in my ignorance. The AC Captain who posted in the original oil thread here that he'd been down the AC oil road once before and never wanted to go down it again has my full sympathy. I too have been down the oil road with the oil manufacturers. But here goes, yet again and ever hopeful:

1. The type certification document says that the oil shall be as specified by the manufacturer. [I omit mention of the reams I read as to which manufacturer [AC or engine], and as to whom holds the certificate, and whom incorporates it by reference; not to mention where the oil may be obtained.]

2. The AC manufacturer now says that MJO II or MJO 294 may be used; the AC QF32 was shipped with MJO II installed; the failed engine appears to have been using MJO 294 [I may have to correct the "memory item" 294 on edit]. When the changeover occurred may have been at the 3-year repair point, but I did not see this published anywhere. Some or all of the other engines on QF32 continued with the originally installed type of oil.

3. Now comes the problem. Perhaps the Operating Instructions contain the actual specs of the oil, which is only identified by name in the public documents. [My deduction at the moment is that the A380 Operating Instructions either are distributed need-to-know basis only, or do not yet exist.]

4. Of course, the Mobil (or ExxonMobil, which may or may not be the same thing) website for oil contains the specifications for the oil in question. The problem is, these voluminous specifications are next to useless in the jet engine context. I give one example at #5 and 6 ff:

5. Viscosity of the hot oil: 5 centistokes at 100-degrees Centigrade. Well, I don't think the viscosity at 100-C has been of any interest since pressure radiator caps were added to water-cooled automobile engines sometime in the 1930s.

6. What are we given instead: MJO-xxx (whatever) is provided with extended range viscosity stabilizers. Give me a break. What is the viscosity of these two oils at 180-C and 196-C?

7. On to another question. What is the base stock of these two oil types? Well, for MJO II it is fairly clearly identified as a highly refined mineral oil base. Okay, I'll accept that as an answer. But for MJO-294, the situation become murky indeed. It was identified on a document posted here [at least of quasi-official standing, I will look it up] as being an HPC oil. However, I located a MIL spec discussion in which MJO-294 [number from memory, will edit] is identified as an SPC oil, which whatever it is, is not an HPC oil.

8. I think the MJO-294 must be also a highly refined mineral oil base, but with the addition of PG additives, but what do I know? ExxonMobil describes it as an "advanced oil", IIRC.

9. The question of whether both these oils have a mineral oil base bears on two questions. One is the question of lubricity, at which the mineral oils excel. The other is the viscosity buildup that occurs to such oils when the evaporation rate removes the lighter fractions preferentially, and "topping up" is frequent. It will be frequent if the operation is at the specification operating limit temperature for evaporation-- a 12-hour flight to LAX would consume half the contents of the engine oil reservoir.

10. ExxonMobil have an HPC oil under development. It is unobtainable in the US as of December, if it is available anywhere.

11. I get the feeling there is a desire to have the oil last between major off-wing inspections/overhauls. Perhaps this is because MJO-294 (again, number subject to edit) is a potent orthophosphate insecticide. For crying out loud, even the US tv police sitcom "Castle" took notice of this within the last month. Where do these people find these things out, let alone accurately? [That's not a question that needs an answer.]

Shell Management, I assume you must know the answers to the questions and uncertainties I discussed above: Meaningful viscosity data, base oil and expected T-972 oil temps enroute LAX as it affects viscosity buildup due evaporation on the long-term hand, and viscosity loss at high temp in new oil on the short-term hand-- these are the uncertainties which I think need to be known. It would be helpful to know your views on oil change intervals. Your views on whether Engine #2 might have been operating with an oil likely to have insufficient lubricity would also be helpful.

Hopefully you will not be constrained in your position at Shell from discussing Exxon products. Or you might prefer to make a discussion from the standpoint of Castrol products, which perhaps are more likely to have been used by RR in the development of the engine. Thanks.

[DERG]

Thanks for that R and R outage away from the tough stuff. I have to say that my question to Shell would have been in the circumstances where I had him physically up agin a wall.

The oil sellers annoy me. I have done a fair bit of tribology and the best lubricant on the planet is nature's olive oil.

You can "crack" imineral oil all you want..comes nowhere near the mighty olive. I am so glad I am nowhere near Shell, I am very short tempered.

[Turbine D]

Old Engineer

In this presentation, there is a table listing the approved oils meeting SAE 5780 specification requirements, BP, Shell & Exxon/Mobil.

http://isoclean.net/uploads/GE_turbine_oil_specification_pres_STLE.pdf

By the way, are roller bearings more sensitive to oil viscosity changes at higher temperatures than ball bearings?

[Shell Management]

Oh dear. Some people are jumping to very big conclusions and suffering from homo-erotic based fantasies too.

BTW the Operating Instructions are for the Trent not the A380.

[Turbine D]

Shell Management

the Operating Instructions are for the Trent not the A380.

Thanks for this information, we knew this.

[Shell Management]

TurbineD

When you say:

Shell Management

Quote:
the Operating Instructions are for the Trent not the A380.
Thanks for this information, we knew this.


Are you using the 'royal we'?

If you R_E_A_D the thread tou will notice Old Engineer wrote:

3. Now comes the problem. Perhaps the Operating Instructions contain the actual specs of the oil, which is only identified by name in the public documents. [My deduction at the moment is that the A380 Operating Instructions either are distributed need-to-know basis only, or do not yet exist.]

[Turbine D]

Shell Management

Are you using the 'royal we'?

If you R_E_A_D the thread tou will notice Old Engineer wrote:

If you go to the Spotters Forum and look at the first thread, it contains this:
Spotters it has to be said are not always welcome in the professional forums, and for good reason, because some of them make a nuisance of themselves and upset the pros and natives.

Need more be said?

[Turbine D]

I have a question on the TCDS:

http://www.easa.europa.eu/certification/type-certificates/docs/engines/EASA-TCDS-E.012_Rolls--Royce_plc._RB211_Trent_900_Series_engines-04-24052007.pdf

On Page 4, Item 4 - Equivalent Safety Findings:

JAR-E740 150 Hour Endurance Test


What exactly does this mean? Did the engine not pass this test? Was a subsequent test performed and it passed? Was the test waived?

What is the opinion of this particular item?

[lomapaseo]

I wouldn´t be too sure that within the "Brotherhood of PPRuners" there are not some members that have the right answers at hand.


Amen to that, but with all the posturing by folks with ready made answers and blame at hand who obviously don't have a clue, there is little sense in adding to the wasted bandwidth of this thread.


As I understand the ongoing discussion. Primary goal is safety. As an - important - side effect, we all want to hear from the "officials" what the root cause of that QF 32 desaster was. Well, we can wait.
Jo


There is that "we" again. What some of us want who fly on this machine, is that enough is known to fix the problem so that it is unlikely to repeat itself. The details of design and certification are in the province of engineers who are tasked with the everyday job involving same. Asking Joe on the street corner to comprehend the design and/or certification and to add his two cents is a waste of time.

Thats' why we have a "Continued Airworthiness" process and the ability for the public to submit meaningful comments to this level of regulation.

So far from what I've read on this board none of the comments submitted so far would overturn this regulatory action.

What design changes RR or its regulators chose to make furthur down the road are theirs to make without public comment.

[Trent 972]

Turbine D
Link below to video. The answer to the 150 hour test can be found at the 3.41 mark. Took me 8 seconds on google to find it. (Perhaps it was all done in a sound stage and it's just another conspiracy). I'm still waiting for you to prove that the FAA wasn't happy with the Trent certification as you claimed yesterday. Posting decades old certification requirements
(PART 33—AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES)
doesn't meet the standard of proof to support your claim made in the prior post.It is a unhappy day to have spent $1M or $2M on an engine test to only learn it didn't meet the certification criteria in the FAA's eyes

YouTube - Rolls Royce Trent Certification (http://www.youtube.com/watch?v=oq7YAVg9K74)

[DERG]

There has been little band width wasted in this thread so far. I am sure the website proprietor is very happy with the numbers of visits this thread has attracted. There are a few of us who have persistently sought answers in this thread with reference to known information. If the Qantas accident had resulted in fatalities I would not be posting here.

Readers will notice this particular group does not discuss airframe and control problems that the Qantas accident involved. The goal here is to educated ourselves. Knowledge is power, as they say.

The A380 and the T900 series engines are very much in the public domain and as the MBAs would say "we are all stakeholders in this enterprise". Some of us in the EUR paid taxes that set up the EADS company. Those like me, in the UK, pay taxes that are redistributed to RR for research and development.

There could well be members of this forum who have personal pecuniary interests in RR....a pension from them or shares in the company. Others might be motivated by pride and are in denial about what happened in this case.

[DERG]

Yes that video is informative. The Trent is a series of different engines and this example shown here is not the T900 series.

The argument some of us have is that the Trent 900, in the process of certification, used existing data from the test bed from previous Trent series engines.

As the FAA advisory states: if existing data exists then use it. The problem is that the DATA for the T900 is UNIQUE.

We want ALL the data from the T900 series made public so it can be be examined by the engineering community. WE, the concerned members of the public, want the data from that T972 which exploded.

I have no doubt at all that Rolls Royce has taken steps to make the engines in service safe. In so far as risk to the public is concerned, I believe that it has been minimised as far as possible.

Rolls Royce have a duty of care to the public and I believe they have acted since this accident.

Now as far the suggestion that has been made that RR and the regulating bodies can do as they please, that their business is private, strikes me as somewhat disturbing.

[Annex14]

Well Sir, good job !! Excellent bashing!! But, excuse me, what is the difference of such an entry compared to the cited opinion of "Joe at the street corner" ??
And if you have a problem with my use of the word we in my post, I agree we wipe it and replace that word with an I.

Yes, I take advantage of the "blessings of an outside observer" but yet I am as concerned about safety and the sequence of actions - or non actions - after this frightening engine failure as you seem to be.

It´s the doubts I have in that by you cited "Continued Airworthiness" process and the speed and vigour of necessary corrections to that engine.

Yes, Qantas is flying the A 380 again across the Pacific and - as was stated - using full power. But as far as I am informed that "disgusting" AD about the spline wear is still in force. That must be considered as a hint to the fact that the root cause of the engine problems isn´t resolved.

I agree in what DERG wrote, RR for sure has taken measures to make those operations allowed under the valid AD´s as safe as possible. But future will show wether or not that is enough. I have my doubts.

[DERG]

Jo

You have to realise that lomapaseo has a completely different philosophy than the general public. I can see English is not your first language. This poster is no fool as we can see in his post #306. So what motivates this poster to make a statement like:

"So far from what I've read on this board none of the comments submitted so far would overturn this regulatory action." ?

Well I would suggest that this poster is absolutely confident that the FAA and EASA has no power whatsoever in protecting the public from danger.
That the existing cosy relationship between manufacturer and regulator will NOT and MUST NOT be challenged.

Now this very much reminds me of a command economy and if anything has scared me even more than the "novel event" when the T972 exploded.
You will know these attribute well from the pre 1989 days in Europe. Now some might say that is an extreme anology, but others will recognise the political implications, where the State can no longer protect is people from the few.

The few being those "inside" the club. Those outside the "club" are often described by insiders as "self loading freight". Now sooner or later the SLFs get wise to those who have a genuine interest in serving the public and those who are there to abuse the trust given to them by the politicians.

Not unlike the Roman Empire.

[Trent 972]

WE, the concerned members of the public, want the data from that T972 which exploded.

Rolls-Royce PLC
PO Box 2000
Derby.
Phone - 01332 661461
Fax - 01332 661630

[Annex14]

Derg
Thanks for clarifying. You guessed correct, there is a "mother tongue barrier" and even all these years in ATC haven´t overcome some shortcomings.
As far as my answer to lomapaseo is concerned I feel that "one gets what he gives" and I can stand that for my part of the story.

Trent 972

With greatest respect to your experts opinion, your confidence is impressive. May I cite old Mr. Lenin that once stated : Confidence is fine but Control is better!
Not that I want to question your inside view of events, but I am sure you are aware that the "spline eating cause" in those engines you use still needs to be removed. Or is there silently, without information of the public, a "D mod" engine in use ??
Please, don´t feel offended, no hard feelings!! I keep my fingers crossed for you and all of those relying on that technology.

[Turbine D]

Trent 972

I'm still waiting for you to prove that the FAA wasn't happy with the Trent certification as you claimed yesterday.

The circular implies "Here is a way to accomplish vibration testing that is acceptable to us, but there are other way that may be acceptable as well." It is a unhappy day to have spent $1M or $2M on an engine test to only learn it didn't meet the certification criteria in the FAA's eyes.

I think you misunderstood what this comment meant, it wasn't a claim the FAA was unhappy. It was a statement in general to explain why the FAA guidance circulars exist in addition to the certification requirements. It is to prevent misunderstanding or misinterpretation of the certification process for certain elements of testing. Should this happen, a significant amount of money could be wasted because of a required "do over". These regulations not only apply to RR, P&WA and GE, who are very familiar with certification requirements, but other engine producers that may not be so familiar. The comment was not directed at the Trent 900 certification as you suggested.

Sorry if I confused you...

[DERG]

I tell you what Turbine D..if that engine had spewed out over NYC the FBI and NSA would have had that data within 12 hours of the event. I am damn sure the FAA is very happy the Qantas A388 enters and exits over the Pacific Ocean. When it comes to NSA stuff it doesn't matter what admin is in 1600 Penn..they all tow the line.:cool:

[DERG]

Media contacts - Rolls-Royce (http://www.rolls-royce.com/press/contacts/index.jsp)

[HazelNuts39]

...if that engine had spewed out over NYC ... then the NTSB and FAA would have been involved in the same capacity as the authorities of Indonesia are in the QF32 occurrence.

[bearfoil]

I think, imho, that posting, reposting, and arguing about RR communications people and the relative political aspects of NTSB/ATSB isn't particularly helpful. All of the Public Agencies are political by nature, they rely on the experts for Data and compliance. The PR at RR have a disincentive to divulge proprietary Data to anyone, and if they aren't even aware of this sensitive data, what is the point?

I think the essence of this discussion has to do with Thechnical considerations. To that extent, I relish the give and take here, friend or "foe"; it is a novel and elegant way to gain knowledge without the burden of Semester Tuitions.

[DERG]

I was going to have a head long fling into the people behind this accident. Who does what in the company etc. If the major directors who perhaps had other interests that might conflict with the interests of RR and the EASA. The politics of international aerospace business. Aims and Objectives..that kind of stuff.

I am particularly interested in the decommissioning of the UK Ministry of Defence and how the people who worked there will take to the new job of saving people rather than killing them. That sort of stuff.:\

[Annex14]

Ref. your question in post 388 about rollerbearings and sensivity to oilviscosity probably the added link may be of help ?? Not sure, but looked around and found this.

Speeds and vibration - SKF.com / Products / Interactive Engineering Catalogue/Rolling bearings (http://www.skf.com/portal/skf/home/products?lang=en&maincatalogue=1&newlink=1_0_46a)

[bearfoil]

Hi. I think OE has said that rollers have more loaded area than an equivalent Ball bearing. Deep groove may be different? Is there "flattening" of the ball, to give a more "lens shaped" loaded surface??

[DERG]

If you look up "RB211-H63"
Does the clue to the T900 series troubles stem from this hybrid?

[DERG]

Please open up this

http://www.eng.ox.ac.uk/thermofluids/people/david-gillespie/b1-mechanical-engineering-project/B1%20Project%20Kick%20Off.ppt#388,11,Existing Seals – current solutions

Now this will take a little time and unless you are a really dedicated:8 which I have to say I am, then skip the hard bits! The colours and design of this presentation is WONDERFUL so take the time. I must thank David Gillespie and Budimir Rosic from Oxford Uni Dept of Eng Sc.

It starts where is says THE BIG PICTURE

Go to THE SEALING CHALLENGE part

See the three cross sections of the shaft...with you mouse click on them...you see how the shape changes..that is why we have the spline wear and are losing the oil.

OK So how to fix!

See EXISTING SEALS

Now see THE NEXT GENERATION OF SEALS

EUREKA! That is the fix RR has done to the T900s..latest seal design.

WHOOPEEE!:)

All we have to do now is solve the excessive spline wear!:ok:

This is the patent detail of this seal:
Leaf seal, in particular for a gas turbine (http://www.freepatentsonline.com/7828297.pdf)

[DERG]

From this we know that SKF, wunnerful bearings by the way, do NOT make the baearings for the 900.

SKF to supply main bearings for the new Trent 1000 engine from Rolls-Royce - SKF.com/Welcome to the news & events portal/News archive (http://www.skf.com/skf/news/html/popup.jsp?contentId=191144&language=en&lang=en)

this is unusual. It means the bearings are specials. The hunt goes on.:cool:

[DERG]

FAG supplies all engine bearing supports and numerous components for the Rolls Royce “Trent 900” engines for the world’s largest passenger aircraft."

http://www.schaeffler.com/content.schaeffler.de/en_2/_global/download/pdf/pressrelease_3343488.pdf

"It is testament to FAG’s expertise and
experience within the aerospace industry
that we were chosen over other
manufacturers to supply all of the main
shaft bearings and components for this
prestigious aircraft’s engine."

In this document there is also a VERY interesting report on fake bearings. We all need to read this.

http://www.schaeffler.com/remotemedien/media/_shared_media/library/schaeffler_2/magazine/downloads_12/inmotion_2005_03_gb_gb.pdf

[Annex14]

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 (http://www.freepatentsonline.com/7828297.html)
Very interesting development!!

[forget]

Patent details here.

United States Patent: 7828297 (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=7828297.PN.&OS=PN/7828297&RS=PN/7828297)

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

United States Patent: RE30206 (http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2FRE30206)

[Annex14]

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.

[DERG]

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/remotemedien/media/_shared_media/company/communication/press/press_release/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.

[DozyWannabe]

I am particularly interested in the decommissioning of the UK Ministry of Defence and how the people who worked there will take to the new job of saving people rather than killing them.

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.

[Annex14]

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 (http://www.skf.com/portal/skf/home/products?lang=en&maincatalogue=1&newlink=1_0_76)

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/people/david-gillespie/b1-mechanical-engineering-project/B1%20Project%20Kick%20Off.ppt#452,17,Heat Transfer between Rotor and Seal

Schaeffer ROLLER bearing
http://www.schaeffler.com/remotemedien/media/_shared_media/company/communication/press/press_release/0001614C.jpg

Schaefer
For 787
FAG bearings selected for Boeing 787 aeroengines (http://www.machinebuilding.net/n/n0583.htm)

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

[Annex14]

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 (http://medias.schaeffler.de/medias/en%21hp.tg.cat/tg_hr*ST4_1652155275;bONjntrf0IKb)

no direct ref to aerospace though

[Annex14]

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 ???

[DERG]

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 (http://www.skf.com/portal/skf/home/industries?lang=en&contentId=599475&offerId=0.000336.341341.599460.599475.599466)

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.

[bearfoil]

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.

[DERG]

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 :)

[fchan]

Is she still in Singapore? Will she be fully repaired there, or patched up & flown to France for full repairs ? Or is she unrepairable given the substantial wing damage and machined tapered thickness slab construction of the wing skin?


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.

[bearfoil]

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.

[DERG]

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

[bearfoil]

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.

[DERG]

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 (http://www.airframer.com/news_story.html?release=4106)

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?

[WojtekSz]

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.

[Turbine D]

DERG & Bear
* 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"

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

YouTube - Family tree (http://www.youtube.com/watch?v=4lip8lPWFLo&feature=player_embedded)

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.

[Annex14]

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.

[Annex14]

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.

[Trent 972]

Radken
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?

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)

[LandIT]

Flying Lid, fchan, Annex14

See this thread...
http://www.pprune.org/dg-p-reporting-points/435797-a380-vh-oqa-write-off.html

[DERG]

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.

[DERG]

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 ) (http://www.youtube.com/watch?v=0QqByJvuBzk&feature=related)

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.

[WojtekSz]

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 (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 ;).

[DERG]

: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.

[WojtekSz]

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

[DERG]

"The results are repeatable to the 100 nm level
and may be used to identify bearing characteristics"

Thats 10 to power negative 7 (metres). That's achievable!
10 to power negative 9 is developing in "nano engineering"
As yet not in public domain.

Look up "micro" and "nano".

[WojtekSz]

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 ! :}

[DERG]

Maybe the balls are ceramic. :suspect:

[WojtekSz]

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 (http://www.robots.ox.ac.uk/%7Edavidc/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

[DERG]

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.

[WojtekSz]

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 ;)

[DERG]

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:

[DERG]

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.

[DERG]

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.

[bearfoil]

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.

[DERG]

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:

[Turbine D]

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/ao-2010-089%20preliminary%20report.pdf#page=0

[Turbine D]

I've looked at the recent posts and informative sites regarding vibrations and what can result. I think Bear gives some good information regarding support structures and what may be going on in these newer engines.

First, if you think about the fan and all related rotating airfoils attached to one end of a cylinder, and the LPT rotor attached to the other end, 7 feet away, you have a dumb bell in a static sense. If you pick up the dumb bell at one point near the center, both ends will sag downward, the LPT end more so as it will generally be heavier. So then, to prevent this from happening in reality, a series of static structures are designed and placed to provide the backbone of the engine. These structures must maintain alignment between rotors and stators and their design is dictated by the need for stiffness, more so than strength. The major sources of load for an engine translates into forces on the structures such as maneuver loads (turning), CAT (clear air turbulence), acceleration/deceleration, gyroscopic forces, moments through the bearings into the frame hubs that support the bearings, unbalance in the rotors, internal variable pressures in the engine flowpath and lastly, thermal differences induced by the airfoils compressing the air and then the hot gasses flowing from the combustor through the turbine components. There is also the dynamic behavior of the engine and interactions with the airframe to which it is affixed. All of these features must be combined with design features and analysis to enable the static structure components to handle different types of loads.

For the designer, there are all kinds of analysis programs to assist in determining the adequacy of the structure design, redundant structural model, finite analysis model and a complete engine structural model and a first engine bending model. In addition,designs are verified by static load testing that can include built-in defects to test design robustness. Extreme engine testing can test for structural capability under extreme vibration. Low cycle and high cycle fatigue capabilities must be examined. Based on all of this, limit conditions can be determined and set so that a well designed structure will not show any sign of deformation or contribute to a loss of performance even if the limit is exceeded in a one time event. So as you can see, the engine structures are key to having successful engine capable of meeting the mission advertised to the customers.

Good structures must be capable of absorbing vibrations and not amplifying them and there are many techniques that can be incorporated to accomplish this. I used the word "robust". Care must be taken to not reduce weight of structures that could compromise long term structural integrity although this is often looked at during weight reduction/saving campaigns to improve performance.

Vibrations and rotor unbalances are always present in an engine and they change as the total engine cycles grow over time. So the engine backbone must be capable of handling all of these variables as they occur.

[WojtekSz]

Turbine D:
thanks - it is a pure pleasure to read such posts :)

Good structures must be capable of absorbing vibrations and not amplifying them and there are many techniques that can be incorporated to accomplish this. I used the word "robust". Care must be taken to not reduce weight of structures that could compromise long term structural integrity although this is often looked at during weight reduction/saving campaigns to improve performance.could you pls tell a little more on techniques to absorb vibrations? The lower the weight and stiffer the shape the higher is the supporting structure natural frequency but doest is solve the vibration problem?
Looks like multiplatform optimization (technical characteristics vs unit costs vs weight vs project time etc) :)

[bearfoil]

Turbine D

On the money. A good argument that the 900 is not in the same family as the prior iterations of TRENT would be that the destructive issue at the heart of the dilemma does not affect the others. In using this, RR suggests that the 900 is in fact substantially different from the others.

The problem is distilled as usual into likely courses of action. The question is this..... Will for once the authorities demand a revocation, or will they succumb to pressure to keep the troubled engine in service, although it has obvious service life issues? These issues cause an accelerated loss of dependability, such that mere inspections beg the question!!

Have you searched for the specs on the "C" Modification? Given the reported limits on service, the obvious conclusion is that this powerplant is a "work in Progress". Odd that no one will address the issue, but merely defend the indefensible. I only have the "B1" manual, so my limits are strict. I do know from sources that virtually no oil issues were found in the eighteen months prior to the Burst. I also know from sources what the precise issue is. If so, the fix has some pretty lofty obstacles to a simple cure.

DERG

The seventy cycle limit was required by EASA, not "reported" by RR. No doubt there was a consult, there always is. The consult in August produced the relaxed (lax) inspection cycle amendment in September to allow Spline Wear per se to be "averaged" or normed, using each pair as a contributor instead of the "worst worn" disqualification. It was this very relaxation that allowed the Burst to happen, clearly the wear had proceeded such that certain "pairs" were not even functioning.

[Turbine D]

could you pls tell a little more on techniques to absorb vibrations?
It is not an easy question to answer as each engine is different and solutions are different. Some examples might be the type and design of seals used in the bearing box area (seals can be good dampeners), perhaps the number of struts used or even their orientation relative to engine centerline could be another solution. But the finite element analysis program gives good indications as to which technique or techniques might be most advantageous to use if a problem is apparent. One other thing, you can raise the vibrational frequency of a frame without reducing weight by use of a stiffener ring on the OD of the frame so the frame is not resonant with most vibrational modes in the operating range of the engine. A separate item that affects vibrations is the distance separating the engine mounts that attach to the pylon. The further they are apart, the vibrations become larger should an unbalance condition exist in the rotor system of the engine. All these things must be considered in the frame structure design and analysis.

[barit1]

One technique I have seen is to de-tune the bearing mounting by a combination of viscous damping with spring centering. The viscous part can be accomplished by a squeeze-film clearance between the outer race and static frame hub, pressurized by the oil supply.

Similar in principle to the suspension in your automobile or aircraft, but tuned to a much higher frequency.

[DERG]

On page 16 of http://www.eng.ox.ac.uk/samp/pubs/clifton_transfer.pdf

A subjective judgement is made by the author: this takes a little while to sink in...please persist

"Applications in which a false negative classification carries a higher cost than a false positive classification" ( THEY MEAN CANCER CELLS IN PEOPLE. This means the medical doctors will persue you in court if the get it wrong)

"Conversely, applications in which a false positive classification carries a higher cost than a false negative" (THEY MEAN AIRCRAFT ENGINES..this means that unless the relatives of 469 people bring a class action in court, life and limb is worth less than an engine repair...OR...the insurance will cover it.)

Here it is in their words:

"Systems for the identification of abnormal operating conditions in gas-turbine engines are of this type: the cost associated with a false positive
classication is high, often involving significant examination of equipment and maintenance processes."

The only way anyone sane would consider this is with the knowledge that the A388 had FOUR engines that would not fail all at once: and uncontained engines failures are rare statistically

Now I just wonder if, after realising the Qantas A388 had 469 lives at risk, they suddenly realised that the costs would be higher than they imagined.
Then again it did have FOUR engines.

No.. this is unacceptable. They set out a scheme that had a priority of financial risk reduction without realising they had 469 lives at risk as opposed to the ONE life they have in assessment of cancer patients.

This would be a very good "moral" assignment for our pals in management.
A good one for the lawyers too. The only way this will be solved will be in court.

This academic team should stay with medical statistics. They themselves are a risk to society if they use their "academic clout" to provide a lever for ill advised and naiive commercial managers.

[WojtekSz]

Turbine D, Barit1
thanks for good examples - it really is a case by case operation then ;) like fine tunung relative natural frequencies so they would not happen together. Does this tuning also include the frequencies induces but burning chambers? These seem to be a source of (possibly the most) significant energy vibrations within the engine case.

Derg, Bearfoil
to me the way chosen by EASA is to FORCE the RR to act faster, even if by now they have realized that the class action would cost them a fortune and lost contracts, is asking for painfully frequent maintenance. This way RR has a chance to improve the solution (especially that the exact reason is known) while still statistically safe and without loosing the face.
After all changes to internal engine structures are difficult to prepare, make and implement fleet wide. New seals would not be able to absorb the energy emitted during TO/GA

The solution - advice to public to stop flying A380 with RR engines for a while - the question is how public can be sure the replacements program have been completed?

Excellent case of raison d'etat...

[DERG]

The only hope we have is the ATSB. They are the only ones that do not have a political or economic interest to consider. I guess the only thing they could do is bannish the engine altogther from use on Australian registered aircraft. I dare say off the record a few would agree with that.

There is no question that this mistake has cost RR a lot of money. They will be very carefully attending to these T900s. If another one goes bang they basically have lost all reputation. I would ride on the A388 with the RR Trent because I know that it is safe....well the probabilities are that it is safe..cannot see another novel event happening.

There is a saying about accidents, very much used on this thread; "when all the holes in the cheese line up" Yeah....we had a new engine design using an inexperienced supplier (FAG) and a duff bunch of academics advising the usual bag of dull crayons in management.

It really has been the way NOT to do things. RR made every mistake in the book. As always the general public will be mostly unaware of the background hustle. The deals will be made out of court and business will go on as usual. As Bear says:

"Will for once the authorities demand a revocation, or will they succumb to pressure to keep the troubled engine in service?"

GE will be watching all this in total disbelief. Of course the Schaeffer/FAG bearing manufacturer has opened a plant in Canada specifically to supply GE with bearings for their aerospace gas turbines. I don't think the USA or Canada will be as trusting as RR was.

The unbelievable part to me in ALL this is how RR were led to believe that the telemetry would give them " one and a half hour warning" of a serious engine problem. Just how a bunch of spophistic academics can lead a company like RR to the depths of total incompetence is truly amazing.

[forget]

DERG I am a civil engineer ...... I learned about turbines as a result of this accident. (In 12 weeks!)

DERG It really has been the way NOT to do things. RR made every mistake in the book.

Am I the only one who finds these claims a little incompatible. :confused:

[DERG]

That's why they hire us to head up projects, we take no prisoners. We can add up too. :E

[descol]

It has probably been mentioned somwhre - ... can anyone let know which of the A380 carriers are using RR and which are GE ?
Thanks

[DERG]

RR trents used by Lufthansa, Singapore, Qantas.
Rest are Engine Alliance (GE)

[bearfoil]

Those on the ground who have not sold off the Titanium are using hundreds of TRENT bits as paperweights.

[DERG]

Turbine D has been a hell of a help on here. Generally the "nay sayers" and "meddlers" have stayed well clear. We did a GOOD JOB on unravelling this mess..:ok:

[Turbine D]

WojtekSz

Does this tuning also include the frequencies induces but burning chambers? These seem to be a source of (possibly the most) significant energy vibrations within the engine case.

I think you will be surprised to learn that this is not a major concern in the combustor, and that is not to say vibrations are not created by the mixing and burning of the fuel. Vibration responses are looked at during the design phase using a sophisticated analysis program but, the major concern is that of LCF (eventual crack initiation) due to the thermal gradients throughout the engine cycle, i.e., cold to hot to cold. The reason vibration is not such a problem is the unique way it is handled. The "flame" is contained inside the combustor liner. The liner is "free floating" inside the combustor pressure vessel meaning it is not firmly attached to the pressure vessel in any way. The liner itself is cantilevered by bolting it to the stage 1 HPT nozzle ring. At the turbine nozzle attachment point, a 360° leaf seal is used to prevent hot gas leakage, but it also provides dampening. The actual liner is constructed from several individual pieces. The dome (front end where the fuel nozzles inject fuel) is one piece. It is bolted to the inner and outer liner walls with a series of self locking bolts. The bolts serve as dampers and prevent vibration from transferring to the fuel nozzles that are attached to the main fuel supply tube ring. So there is vibration but it is dealt with by unique design mechanisms to prevent it from being a problem.

[WojtekSz]

Turbine D:
thanks - your clear explanation + some web search produced much better understanding that the combustor tech can be very simple (available to enthusiasts) or complicated (professional big power aeroturbines). But the vibrations may be contained and to certain extent controlled.
http://www.users.zetnet.co.uk/gas/cutway2.jpg

Is LCF based on using cooling airflow, protective coutings, disposabe elements to prevent temp buildup or polishing and rounding the edges to prevent cracks? Most probalbe a mix of the above but are there any other interesting techniques?

[Turbine D]

WojtekSz

In answer to your combustor question concerning LCF, just about everything you mentioned is done to improve combustor life. Primarily, I am more familiar with combustors that are not lined, meaning nothing is disposable, but other combustor designs use tiles that can be replaced. The liner walls are cooled with air through a series of small holes to provide a film of cooled air. The flame side of the liners are thermal barrier coated to reduce the magnitude of thermal gradient, e.g. cold - hot - cold. Attention is paid to rounding all edges to minimize potential crack initiation sites. Regardless of the extremes this component sees, they last a long time. Life is very good on engines that fly long distance routes, 10-14 hours in the air, fewer cycles and long hours. There are set periods of time/cycles where boroscope inspection of the combustor is done on wing. If an engine comes off wing regardless of cause, the combustor is inspected. At a specific set time, the combustor is removed and weld repaired as necessary and reassembled with time starting as if it were new. This can typically be done 4 times before it is scrapped.

I should add, the newer combustors utilize twin swirlers that perform better to mix the air with the fuel creating a leaner burn, lower temperatures, improved fuel burn and longer combustor life.

[DERG]

TURBINE D

"I should add, the newer combustors utilize twin swirlers that perform better to mix the air with the fuel creating a leaner burn, lower temperatures, improved fuel burn and longer combustor life."

So we have a cool end where the big intake fan is, and a hot end where the exhaust gas is released. We have your analogy of the central shaft running from fornt to back...about 7 feet..in the case of the T900 upon which all of the various twirlers and compressors are affixed. Then we have the ancillaries the power take off shaft down to the gearbox and another shaft to start the engine. Much appreciate your input..thank you!

OPEN FORUM

Deduction 1.

Looking at the latest GE design we see that the big intake fan is made from carbon fibre. GE also use a fibre case to house the engine. So I think I am correct is assuming the GE products are using carbon fibre technology where as RR are using advanced metallurgy for the blades and old technology for the case.

Deduction 2.
Because the intake fan is lighter in the GE engine it is easier to balance and has inherently less kinetic energy to be lost in vibration. So the big mass at the front end is now "tamed".

Deduction 3.
Running temps. The 180C and 196C max temp of the T972 that failed is higher than other civil aviation engines to date. We have read the data in the Oxford University document and it is noted that 10% or more of RR engines fail the final passing out test due to imbalance. And a higher rejection rate is detected when the engines are overhauled at the RR appointed agents. The high running temps are cause by vibration inherent to this design.

Deduction 4.
Manufacturing tolerances. The RR design is difficult to manufacture beacuse of the nature of the concentricity of the drive shafts and the fact that is has three distinct compression stages. GE, I believe, use two stages.

Deduction 5
Given that the RR product is inherently difficult to balance it is clear that the existing in service methods of detecting an inbalance are inadequate.
On one drawing I see only one vibe detector noted but this was a schematic and there may be more than one.

Deduction 6
RR agents themselves cannot detect vibration or allow engines that are outside the norms back into service.

Deduction 7
RR are aware that the 3 spool design has inherent flaws but are unwilling to adopt a new design because the costs would be to high.

Deduction 8
As we see the fractured oil feed pipe as published in the ATSB report we must assume that the quality checks on parts from outside suppliers is poor.

Deduction 9
Communication failure. As the fractured oil pipe is clearly of poor manufacture we must deduce that the department which does the invigilation does not realise the importance of that part. In other words they have no concept about the vibrations inherent within the machine.

Deduction 10
Management Character. The commercial managers were easily persuaded that the monitoring system using the probablility model was robust. Because the work was done by assumed experts they did not apply rigour in seeking confirmed evidence. As far as we know they did not hire MIT for instance.

We know that a company called Schaeffer with the brand names FAG and INA were given the contract to build the entire bearing set and support structure. This was the first time this company had built this..the entire assemble with supports... a complex and critical part for a civil avaition aerospace gas turbine.

Deduction 11
The failure to be able to shut down the #1 engine on the stricken Qantas A388 was unforseen.

All repiles most welcome.

[lynn789]

its been suggested that previous RR design errors have been caused by the RR legend of mechanical perfection influencing RR engineers

[DERG]

Yeah I can believe that.

[WojtekSz]

Derg:
have you invented a new Deduction Generator ;) ?
Looks like too much of a guesswork at play, why don't we stick to facts pls
Fan - carbon fibre is lighter but more expensive. Companies do gamble with new technologies sometimes.
Balance - lighter does not easier to balance - depends on quality of machining, and the rotational speed also and this is low speed ...
Oil Temp: are you sure we can use the data from such article to make such bold statement about 10% engines not passing final tests? Any wise manager would make a fortune by properly implementing 6sigma methodology there to squeeze it down to 1% in 24 months. High oil temp may be caused by vibration but these are caused by 3 shaft design principle. It is a strategic gamble by RR to pursue this road.
Manufacturing tolerances: OK, see point 3.
Vibration detection: usually small vibrations are more dificult to detect ;)
Vibration allowance: as far as i understand, one cannot use the maintenance stand to measure vibrations during engine operation
3 spool design: it has own advantages thou, simply something was not ready in Trent 900 version when started selling it
Oil feed pipe: ever heard scape pipe? (sometimes referred to as scapegoat)
Communication failure: another reason why kaizen principles should be implemented in RR.
Management Character: You have assumed sth based on an univ paper so why shouldn't they? Roller bearings and managers must have tough b..s. Univ papers are seldom treated as robust. At least here... And MIT is from USA, right? For scientists there are two models: coach them or buy them - if you want to get govt support better coach them... Recently Barcelona home grown team plays much better team than Real Galacticostly stars (search for Spanish soccer results) :) Selecting new suppliers in tough times is usually caused by search for economic solutions. Takes time to gain experience.
The failure to be able to shut down the #1 engine on the stricken Qantas A388 was unforseen: a big lesson that i am sure has been properly thought over.I do not know the results but from the discassion over here it is not a simple problem.:}:}:}

[DERG]

My Facts are as good as YOUR Facts..:cool:

[WojtekSz]

yeah, you're right but would you build anything valuable (say: a 0,1M$ house or a 10M$ bridge or a 10M$ turbine engine) based on such facts as we have here ;)
I would say these are good for discussion or creating opinions but too weak for making real decisions.

[Turbine D]

WojtekSz

I couldn't let this pass without some comments:

1. The composite material may be more expensive, but the end product isn't. You have to look at the bigger picture. Here is a site that gives you a picture of the machining that is required (none). Also, think about what is all required to produce a hollow titanium fan blade and inspect it for all the things that could present a problem.

GE to Auction GE90 Fan Blade at Oshkosh (http://www.aviationweek.com/aw/blogs/business_aviation/index.jsp?plckController=Blog&plckBlogPage=BlogViewPost&newspaperUserId=2f16318d-d960-4e49-bc9f-86f1805f2c7f&plckPostId=Blog%3A2f16318d-d960-4e49-bc9f-86f1805f2c7fPost%3Ab2dfcdcd-559b-45c5-823e-b6e083af67dd&plckScript=blogScript&plckElementId=blogDest)

The GE90 composite fan blade was not a gamble, the technology was there to do it and it was done.

2. Balancing of the GE90 fan is easier, remember, no machining of the fan blade, only the simple disc and attachment slots.

3. Read the Oxford/Rolls Royce study again. From 4/9/02 - 9/30/03, 11 Trent 500 production engines failed pass-off testing for abnormal vibrations. These are known in the business as "hanger queens". In 17 months, you can barely afford to have one hanger queen, let alone 11. This is indicative of systemic problem that requires lots of attention.

4. The best phrase here is an acronym: K.I.S.S. It means "keep it simple, stupid".

5. Small vibrations are not as hard to detect as unknown vibrations.

6. Vibrations can be measured on an instrumented engine in a test cell. The problem is they may not be the same vibrations encountered in flight on the wing of the aircraft, but, it is a good start.

7. The advantage of a three spool engine is shorter length. Therefore a shorter nacelle can be used that normally produces less drag and better aerodynamic performance for most aircraft. However, the disadvantage is the SFC of a three spool engine is generally less than a longer two spool engine and it could turn out to be a wash. It has been reported the GP7200 engine has better SFC than the Trent 900 in the same nacelle, not a surprise.

8. Only the weak link in the chain.

9. Continuous improvement is important in any business and every organization making up the business including top management. This starts at the very top, water always flows down the staircase and rarely up.

10. Maybe going back to the Trent 500 days, there was some handwriting on the wall there, that was missed as the technology envelope was pushed.

11. A lesson learned on the A-340 that hit the wall on the ground in which they couldn't shut off the engine for 5 hours was thought to be a not repeatable incident.:ooh:

[WojtekSz]

Turbine D, Derg:
hey, you are both right !- there are basic problems somewhere within RR design and business but being an European i am a little biased towards trying to understand RR problems while not being British i do also understand that US has made flying a huge business not without merit. Certain competition is always good for us customers - for me it is good that Boeing has Airbus and GE+PW has RR to watch at. Problem starts when established leader looses the edge over its followers or the followers take shortcuts to try to overcome the leader.
But actually the biggest threat comes from what has been defined as 'innovate downwards' movement that has been started long time ago by certain Sam Walton and transferred into aviation by SouthWest Airlines later. So instead of 'citus-altus-fortus' we have 'everyday low prices'. And people got used to this: all of us! And this attitude has deep consequences - american car producers are just recovering, nike is not making any shoes in US, a new stealth plane was recently presented in China ;)
Cheaper is fine as long as customers allow for lower quality because without profits there is no development and no quality. Just look how many more customers want to fly A380!
Unfortunately times of Apollo and Concorde are gone...

[DERG]

"would you build anything valuable (say: a 0,1M$ house or a 10M$ bridge or a 10M$ turbine engine) based on such facts as we have here http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/wink2.gif
I would say these are good for discussion or creating opinions but too weak for making real decisions."

Civil Engineers are involved in many projects which are multi disciplinary and the most recent failure was the BP, Trans Ocean and Halliburton accident in the Gulf of Mexico. I was not involved.

Unlike building an engine to a set pattern each job is different so we are familiar in using first principal methods to achieve the result. And all the time we have the finished project in view while building. Safety is paramount.

The value of the project in terms of money is important to the accounts but our job is to build the structure "on schedule, on quality, and on budget". This is often impossible.:suspect:

I have to say that building a gas turbine is relatively less stressful because you have total control of the variables. In that sense mechanical engineering is easier because you know the materials, the environment and loads and temperatures it will have to endure.

The designers, the architects, are often ambitious in what they want to build. "Walt Disney" concepts in perfect world where the sun always shines and the ground never moves.

The facts we have here are abstract ideas based on what we have seen and read. Would I build on them? Or maybe you should ask would I invest in the product or the company using facts we have uncovered. No, I would not.

[Turbine D]

Although being a little off subject, in the USA, Southwest Airlines is a real good thing, not a innovate downward business at all. They developed a business model long ago that has withstood the pressures of the aviation business in both good times and bad. They adhere to the K.I.S.S. philosophy, point to point flying, no expensive hubs, one airplane model (Boeing 737's) and reservations only through their site. You can fly anywhere in their system for $120 one way and at times, $59. There are no extra fees, add ons, no charges for checked luggage. While the US majors were all filing for bankruptcy, Southwest was making a good profit. Why? Because they had money to hedge fuel and recognized the need to do so when others didn't or couldn't. I can fly to Florida for $198 on Southwest verses $425 on Delta, roundtrip. The seats are the same or better, the airplanes may be better, 737 verses a regional jet on Delta, and the service is great. It's not the same as Walmart.

[avgenie]

I just came off reading a book "How Boeing Defied the Airbus Challenge" written by a retired Boeing executive Mohan R. Pandey and my head is full of ETOPS. The book implies that the additional ETOPS rigor in design/testing enhances the overall safety. Does anyone know or have the expertize to say if RR would have probably found the problems if the engines were required to undergo the additional rigor required for ETOPS certification?

[DERG]

Yeah...excellent question! :ouch:

[radken]

DERG

As to no. 11 in your list - the “unforeseen”, I know this 380 thread is primarily concerned with the engine event itself, rather than the effects of its shrapnel on other systems/structures. However, it does seem that in PPRune it’s the only thread to use right now to point up and discuss the matter that it is Airbus itself, and not RR, which has also let down the flying public v/v the No. 1 fuel cut-off issue. But they’re not alone.

It’s quite discomforting and significant to know, without any doubt whatsoever, that the QF32 crew would have had absolutely no control (except fire bottles- if they would have worked) over a fuel fed engine/pylon fire at #1 at any point after the #2 burst. What a way to discover a long existent “unforeseen” engineering oversight, to be forced into the full realization that lack of well designed redundancy in this critical system truly endangered everyone on board. The truth is, though (I believe), no cmcl jets have redundancy in this area.

So, we get to learn from QF32... and we get to learn it without loss of life. How wonderful and fortunate is this unusual opportunity for EADS/Airbus to sit back, take a deep breath, clear the mind, and begin thinking about obligations to others besides their “bean counters.”

Trent 972 pointed out that the A380 FCOM shows “fire” is not one of the sensed FADEC parameters. That makes total sense. I’m sure it’s this way for a very good reason. An engine shut-down decision based on supposed fire is much more in the purview of the skipper than it should ever be as the purview of some remote device, which itself may have been instructed erroneously by any number of other devices, themselves of dubious reliability.... such as fire detect loops. But when called for it'd better work!

I can only add that the re-exposure of a previously demonstrated (Turbine D - A340 versus the wall) weak link in what should be an “infallible” engine/pylon fuel cut-off system should be addressed by Airbus (Boeing, etc.) ASAP. Redundancy in hydraulics, electrics, tank plumbing? Why not in fuel shut-off, too? It apparently could be real handy at times. It may not be “Rocket Science,” but it sure sounds like good “Jet Science.”

[DERG]

"Trent 972 pointed out that the A380 FCOM shows “fire” is not one of the sensed FADEC parameters. That makes total sense. I’m sure it’s this way for a very good reason. An engine shut-down decision based on supposed fire is much more in the purview of the skipper than it should ever be as the purview of some remote device, which itself may have been instructed erroneously by any number of other devices, themselves of dubious reliability.... such as fire detect loops. But when called for it'd better work!"

I know Airbus made a statement that they had made changes to the software so this issue was addressed. Just how or what they did they did I don't know. I agree entirely about automation and I have argued a for big red "master off" button elsewhere on this site. I know Airbus have issued statements to encourage a return "to basic flying skills", to always keep up the skill, because I think they too are scared at how much crews rely on the machine.

I don't view Airbus as a culprit in this event. Structurally the wing structure took the missiles very well and there was clearly enough redundancy in the design. The Qantas crew was very confident that the aircraft was doing OK-ish until they could not shut down #1. To me this was the most dangerous part of the event until the passengers were off.

As to the loss of the controls by the missiles: the electrical loom did not cause a fire and there was a circuit some where that could energise the motors that drive the hydraulics. There were five qualified people on the flight deck to work out what the machine was telling them and they were able to sift the chaf from the wheat. They all had previous Airbus experience so knew the basic systems well.

If the escaping fluids had caught fire it would have been a total loss and I would be nowhere near this thread passing opinions. I am not sure it was good fortune though. There is a concept called "the unforseen point load" which will be familiar to civil engineers. Basically this means that at any point on the structure it is subject to improbable events or abuse. I am sure that Airbus had considered and addressed this possibility.

The fact that sparks from the broken wheels did not ignite the fuel was again luck perhaps..but maybe they had chosen a certain alloy for the wheel construction that did not spark so easily. The brakes must have been red hot too.

Looking back, the first thing that came to mind was the way the emergency fire crews dealt with the still running engine, fuel on the floor, hot brakes and rims and 469 souls still on board. It was then that I saw a need for an external stop control. An emergency panel that rescuers could access to shut down the fuel flow.

I agree with the pylon failure yes. That should be easy enough to do. This A380 was designed as a load carrier and as such made some compromises.

[Turbine D]

avgenie

I am not sure. If the 900's were on a two engine aircraft, they probably would not have ETOPS approval beyond the lowest level at this point in time. But, they would still be flying.

ETOPS certification involves assessment of aircraft and engine reliability and enhanced training requirements of the aircraft operator's flight crews, mantenence personnel for both aircraft and engines and even the personnel that do the route planning.

The current approval standard for 180-minute ETOPS is 0.02 shutdowns per 1,000 hours of engine operation. That’s amounts to an in-flight shutdown rate of one every 50,000 hours. Many of the world’s 92 ETOPS operators are achieving 0.01 shutdowns per 1,000 hours or, for twinjets on eight-hour ETOPS flights (accumulating 16 hours of total engine time per flight), an average IFSD of one every 6,200 flights. This level of demonstrated safety has prompted many operators and authorites to opt for longer planned diversion times, from 240 minutes to virtually "unrestricted" ETOPS. Statistically, twin engine planes have a lower likelyhood of a diversion compared to 3 or four engine planes.

ETOPS REGULATORY REQUIREMENTS

a. All two-engine airplanes and three- and four-engine passenger-carrying airplanes operated under part 121 are required to comply with 14 CFR 121.161. This regulation imposes special requirements for ETOPS for these airplanes. These operations are defined as:

(1) Two-Engine Airplanes. These are flights whose planned routing contains a point farther than 60 minutes flying time from an adequate airport at an approved one-engine inoperative cruise speed under standard conditions in still air.

(2) Passenger-Carrying Airplanes with More Than Two Engines. These are flights whose planned routing contains a point farther than 180 minutes flying time from an adequate airport at an approved one-engine inoperative cruise speed under standard conditions in still air.

If you would like detailed information to the requirements and how they must be satisfied, copy and paste the address into your browser for the the FAA site below:

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/2e0f31985abd83ef8625746b0057fd06/$FILE/AC%20120-42B.pdf

[bearfoil]

Turbine D

The TRENT 700 has two documented cases of dual engine failure in ETOPS service.

[forget]

The TRENT 700 has two documented cases of dual engine failure in ETOPS service.

Extended-range Twin-engine Operational Performance Standards.

Wouldn't that cause a problem?

[bearfoil]

It did. One Hull Loss and one anxious relight.

[forget]

What sort of engine failure allows a successful re-light?

[bearfoil]

Poor choice of words, forget. The engines kept running, but at idle thrust. The Flight had to descend to 13k AGL before regaining climb thrust. Over the Rockies.

OPS: Oscillating Pucker Syndrome.

[forget]

Poor choice of words! I'll say. You claimed two Trent airborne failures which weren't failures at all. What about the other claim?

[bearfoil]

fuel starvation requiring an emergency (ENGINE) AD qualifies as a failure to me. One a/c was lost due lack of thrust, another came within 13k feet of impacting remote Mountains. Our give and take could get arcane and adversarial; I'll stipulate that we have an impasse.

With this caveat. The FOHE in these incidents/accidents is also under suspicion in the QF32 Burst, along with the EEC's inability to shut down the QF32's #1 and #2. The FOHE is the only oil cooler on board both iterations of these variants. The OIL in 972 is a known issue, as to temps, and service life at poured specs.

The fact that some believe the 972 has no FADEC fire point is not relevant, the panel showed FIRE (via EEC) on the ECAM, interposed between two alerts for "OVERHEAT", yet the Engine (S) both were allowed to run on. And ON. The Architecture in TRENT installs is borderline AD worthy at any given moment. Emirates over the wall Hull Loss, BA038's Crash, and QF32's Serious Incident.


edit. To others. Isn't it a matter of concern that the loss of #2 and the runon of #1 are indicative of a common fault?? To me it is obvious; am I alone in noting the original lack of shut down of #2 and the run on of #1 ?? The EEC technically caused the Burst AND the Loss of #1 via mud ingestion?? The High Oil Temp may not have been the result of Bearing overheat, but the lack of Cooling at the FOHE, which then allowed the bearings to O/H, and Fail?? There is a great deal more to this than meets the eye. EG "OIL Aeration, Misting, OverTemping," etc.

[Turbine D]

Forget

Bearfoil didn't mention this one.

DCA04IA002 (http://www.ntsb.gov/ntsb/brief.asp?ev_id=20040528X00693&key=1)

It was eerily similar in results to the Qantas QF32 except for the fact the IPT disc didn't burst because it moved back into the stator behind it with the rotor blades contacting the nozzle vanes slowing the disc rotational speed below the burst point. The problem on this engine was coking that clogged the oil venting system and with surrounding heat, caught on fire. The aircraft was on an ETOPS route after departing Miami, Florida.

What sort of engine failure allows a successful re-light?

Fuel starvation, if the cause of starvation can be corrected; Compressor stall, if there is enough time and altitude to preform an air start. Just two examples, there are probably more.
Here is an example of a successful fuel starvation re-light, Boeing 767 with GE-CF6-80 engines:

On June 30, 1987, shortly after a Delta 767 took off from Los Angeles with 205 passengers on board, Capt. John Gilfoil mistakenly moved the fuel-control knobs to the "cut off" position while intending to move other switches on a nearby engine-control panel.

With both engines shut down, the 767 dropped from 2,000 feet to 500 feet above the Pacific Ocean, before Gilfoil restarted the engines and flew on to Cincinnati.:ok:

[forget]

DERG. The FORGET poster has follwed me around last day or two and the intent is malicious.

Followed you around? Strange, other threads show the reverse. You flatter yourself, I wouldn't waste any malice on you. What I have done, when you've posted your silly opinions on subjects of which you know SFA, is to respond. You can be an amusement at times, but mostly just a bloody annoyance. Try http://www.pprune.org/tech-log/442103-crazy-radio-issue-help-needed.html Full deck comes (very much!) to mind ....

I'll leave you lot to re-define engine failure. DREG, a word of advice - leave any response until it's worn off.

[barit1]

DERG:


The FORGET poster has follwed me around last day or two and the intent is malicious.

Recall when you perceived my committing (nearly) the same offense? I'd like to know what you eat for breakfast that affects you so.

All the same, best to check six... :ooh:

[bearfoil]

forget has been on site for 12 years, and has thousands of posts. I have seen some incisive and thoughtful work of his, anyone can be brash, or impatient.

Fear the laid back pilot, eh?

[DERG]

:suspect:Pax Romanis..yes Bear, thank you, AGREED:cool:
Barit1 I thought me and you were reconciled?

So are RR aerospace turbines generally sub standard compared to GE/EA et al.?

This evidence from elsewhere on this site:

"RB211-535 19,000 hours average time to first shop visit, The RB211-535E4 achieved the world record for on-wing life without removal for over 40,000 hours over nine years in operation for a 757."

RR has such a tip top reputation here in the UK in keeping with the above statement.

And generally:

"Most engine removals are for deteriorated thrust rating or EGT margin. Modern engines are getting towards 30,000 hours on wing and if I remember corectly the old Concorde Olympus were more like 300!"

Then from Turbine D we have this: Edelweiss incident

"DCA04IA002 (http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20040528X00693&ntsbno=DCA04IA002&akey=1)"

"Both engines were Rolls-Royce Trent 772-60/16 turbofan engines and were installed on the airplane when it was delivered new from Airbus on November 21, 2000; neither engine had been removed or overhauled since they were installed. Both engines had accumulated 15,169 hours time since new (TSN) and 2,348 cycles since new (CSN)."

Note: RR have limited the T972 to 70 cycles total life

and here from the guys in the shops

http://www.pprune.org/engineers-technicians/441924-gas-turbine-engine-mtbf.html

Moreover these airliners are not dropping out of the skies, I see them often on the 6 500 mile hike from central Europe to the W Coast of N America spinning their silken contrails as they battle the western winds. This has been going on for 45 years or more beginning with the B707, never a deviation from the steady progress across the sky

Despite the fact that GE appears to have the advantage of newer technology and access to better academics, RR are not done yet.

[Turbine D]

DERG

Don't get too hung up over hours representing engine life. The best measure of aircraft engine life performance is cycles, that is, how many cycles are accumulated on wing before the engine requires removal and overhaul. It would be expected that engines on an extended range aircraft flying 10-14 hours routes would accumulate hours rapidly but cycles less so and would stay on wing longer compared to an aircraft that does short flights of 2 hours or less, but with 6-8 multiple flights per day.

Hours are easily understandable by the average person and quite a few advertisements cite long hours accumulated (bragging rights) before engines come off wing.

Even TBO (time between overhaul) cycles vary between operators using exactly the same aircraft and engines. It depends on general operating conditions, high altitude airports, or hot, dry, dusty conditions (desert airports), exposure to sea salts (corrosion), e.g., airports near the sea.

The exception to this would be gas turbines used in electrical power generation or natural gas pumping. There, hours, really defined as years, are the important factor. There are no cycles to speak of. Turn it on, take it up to operating speed and expect it to run 20 years with little attention if the designs are good.

[bearfoil]

Indeed. had a chance to work at a power station here in Cali. JT8Ds. Fire and forget. Simple designs, robust build, and constant monitoring. The secret was to scrub intake air to nil fod. The cleaners were changed often, and the fuel was inspected daily. In its niche, the Turbine is a brilliant workhorse.

Service Life in this incident is pretty much a red herring, imo.

Safety is the salient issue, not economy. The first picture of the 972 off wing showed the absence of the EEC. Anybody know where that little beauty ended up?? For it is here that the failure is found. Any engine will blow up when run under heavy load with compromised condition. The Kill Switch killed the kit.

[DERG]

There are 28 companies who make industrial turbines. I think it is interesting to see how RR sits in this application.

In terms of mechanical drive generators only one company makes a model that produces more power than RR. That of course is GE.

"The Kill Switch killed the kit" Yeah...

Perhaps we are at some cathartric point in the course of technology. At RR we have a bunch of people who cling on to the 1950s because they just can't find the right road to take. They do their best to make it happen and suddenly events take them right back to the days of the Comet.

The young engineers are used to making the virtual world real. Then suddenly the ghost of the past wakes up and says "We tried that in 1949"
The Hughes corporation comes to mind.

Anyways time for some entertainment....to date THE BEST proven load carrier on the planet...
YouTube - The Steve Miller Band - Jet Airliner Boeing 747 Take offs (Watch in HD) (http://www.youtube.com/watch?v=VqozIpPPct8)

[radken]

I rediscovered the link below which was contained in the previous thread from the PPrune rumor mill before the topic was moved to the Tech area. There are likely many now participating in this present thread who haven’t read this very interesting and revealing interview of a senior ck pilot who was onboard QF32. It’s not often “we the public” get to read or hear in such candid fashion the particulars of such a momentous event - litigiousness being what it is at least in the US.

For instance, I had forgotten (see previous post) there is an engine fuel shut-off feature associated with the cockpit “fire” buttons.... I don't know if that also includes the pylon valve but would presume so. The pilots were surprised to discover, however, that #1 was literally OOC. In line mx., when these systems are “tested” in hanger or on the gate there are no engines running, so who’d know if a particular s/o redundancy would actually be functioning or not? Bottles would be disconnected and what could ECAM tell you that you could believe? There was such severe damage out there in that wing that possibly no amount of redundancy engineering would have saved the day anyway.

The whole thing will probably be made into a movie soon.

http://www.aerosocietychannel.com/aerospace-insight/2010/12/exclusive-qantas-qf32-flight-from-the-cockpit/[/URL]

If the link doesn't work you can find it archived (I believe) at aero's site...

[DERG]

This failure is something I am hoping the ATSB will address. If the safety authorities are to be respected they need to enforce something as basic as this.

[NigelOnDraft]

Deduction 11
The failure to be able to shut down the #1 engine on the stricken Qantas A388 was unforseen.
..a big lesson that i am sure has been properly thought over.I do not know the results but from the discassion over here it is not a simple problem.

11. A lesson learned on the A-340 that hit the wall on the ground in which they couldn't shut off the engine for 5 hours was thought to be a not repeatable incident.
It’s quite discomforting and significant to know, without any doubt whatsoever, that the QF32 crew would have had absolutely no control (except fire bottles- if they would have worked) over a fuel fed engine/pylon fire at #1 at any point after the #2 burst....The truth is, though (I believe), no cmcl jets have redundancy in this area.
..in what should be an “infallible” engine/pylon fuel cut-off system should be addressed by Airbus (Boeing, etc.) ASAP. Redundancy in hydraulics, electrics, tank plumbing? Why not in fuel shut-off, too?
I think some are getting too hung up on this. There is "redundancy" in the engine shut off, AFIAK there are 2 physically separated electrical circuits to do this, and in this event, both got cut.

To create "a tragedy", seems therefore to require 4 very unlikely specific events:
A failure that is uncontained (as here, unusual and has to be addressed)
>1 fragment that causes damage elsewhere (I saw somewhere design assumes 1 fragment)
These 2 (or more) fragments fortuitously cutting the separate redundant paths of an important system
That system's failure then leading to a signifcantly increased safety problem.
If you over-concentrate on "shutting" an engine down, you end up with engines shutting themselves down of no accord - a far greater, IMHO, safety issue :sad:
We had 3 of 4 "unlikely" events, P of the 4th is small?

Or look at it another way, if you over-emphasise the need to shut engines down, then maybe Airbus could have designed the shut off curcuits to "self monitor", and if both circuits were cut, to shut down the engine. Sound a good design? Maybe, but in this case it would have given them a double engine failure :{

A manual shut off valve? (in the pylon?) - OK, maybe a good idea, but really enhancing flight safety? In both the quoted cases, once an engineer is in place to operate it, everybody was, or could be off, and well clear anyway.

I suspect the ATSB will look at it, but I disagree they will place strong recommendations on addressing it. As an airline pilot, I am wary of too many "safety systems" being too cleaver - they usually cause more problems than they solve. I am "nervous" of the software in the Trent that can "shut the engine down" without warning / pilot control.

[bearfoil]

QF32 had a major problem with its monitoring and fuel control vv shutdown in the first place. Problem solved (?) with new software. #2 should have shutdown well before Burst. That was danger enough to have brought down this flight. Two cold engines on one side is not a good thing. I am with you, losing #1 due auto shutdown would have been not good. The Burst caused the very real worry of loss of this flight. So to answer the Burst with more "Automatic Shutdown" seems contra sensible. The EEC and monitoring programs were at fault. Looked at from a failure trail pov, the Burst was secondary to cocked up controls at the outset, No?? There is a fair amount of attention being paid the Data Entry Plug and its interface with the two channels of the EEC I'd wager.

[DERG]

"I suspect the ATSB will look at it, but I disagree they will place strong recommendations on addressing it. As an airline pilot, I am wary of too many "safety systems" being too cleaver - they usually cause more problems than they solve. I am "nervous" of the software in the Trent that can "shut the engine down" without warning / pilot control."

If the ATSB cannot mandate this VITAL shutdown device
they are superflous to the industry..

All it needs is an external valve that rescuers can access.*

*NOTE: Colleagues on this thead have correctly pointed out this would be impossible due to the danger of access a running jet engine.. OK lets call it a MASTER OFF switch. It is ridiculous that telemetry can "read" these engines 12k miles away yet we cannot turn 'em off.

[bearfoil]

A valve that a groundperson could reach would be (have to be?) positioned within reach on the engine or pylon. By the time QF32 was on the ground, danger of in flight fire was by definition not possible. The fuel leak was at the forward spar near the Fuselage, and interior the wing. At best, #1 could be stopped with such a provision, but we know through unfortunate circumstance (TooLoose) that run on is relatively safe. Fuel fire was avoided by QF32 by mere chance, mid air, one of many fortunate blessings. One could even argue that because #1 ran on, fuel was removed from the penetration area of the wing, perhaps forestalling a mid air fire. IMO.

[barit1]

If you think QF32 #1 engine continued running is a problem, consider this:

Fighter aircraft with inlets behind the cockpit, belly landing, disabled pilot unable to "pull the plug" on operating engine. How do you safely rescue the pilot? :ooh:

[NigelOnDraft]

QF32 had a major problem with its monitoring and fuel control vv shutdown in the first place. Problem solved (?) with new software. #2 should have shutdown well before Burst. That was danger enough to have brought down this flight.I am with you, losing #1 due auto shutdown would have been not goodI have not followed this thread to the detail of you / some others.

However, what you/others seem to be saying here/previously is that there is software in the Trent that can shut the engine down automatically. Such software failed in this case to act, and was rapidly modified post event. That such software exists was "news" to me, and I would be nervous unless it was 100% bullet proof. It should not be there to "protect" the engine, but solely to prevent "in extremis" failures that will result in serious uncontainned failures. Else there is a risk it mirrors:losing #1 due auto shutdown would have been not good - the day we get engines auto-shutting down unnecessarily is a bad day... automation gone too far.

All it needs is an external valve that rescuers can access.Complete and utter waste of time, safety-wise. If the recuers can reach the engine, they will have got the pax out first. Little safety benefit, might save a bit of fuel / noise and get aircraft moved earlier, maybe save an airframe. But not people.

If the ATSB cannot mandate this VITAL shutdown device they are superflous to the industry...Disagree 100%, suspect we'll leave it at that ;)

[Turbine D]

In general, I agree with you, auto shutdown of an engine by a computer is not a good thing.

Focusing only on the #2 engine (the one that failed), it was operating in auto-thrust mode. The EEC apparently detected a un-commanded reduction in N2% and immediately called for increased fuel flow thereby increasing the N3% eventually to 98% before reducing fuel flow. By then, it was too late to prevent the eventual disintegration of the IPT disc due to overspeed.

IMO, I suspect the EEC was reprogrammed to view reduced N2% and the start of increased N3% as a problem and the need to reduce fuel flow, not increase it. This may have saved the day, possibly. However, reducing fuel flow is not an auto shutdown, the decision to shutdown the engine is and should be the flight crew's decision.

[lomapaseo]

If the ATSB cannot mandate this VITAL shutdown device
they are superflous to the industry

The ATSB job is to investigate set forth the causal factors and make recommendations.

They are not regulators nor should they mandate changes that may be impractical.

Once the full report is released I'm sure that knowledgeable safety experts will support practical changes.

This thread is suitable for discussion of facts and points of interest.

Is there anything newly released out there:?

[Annex14]

Reading myself after several days of absence through the meanwhile placed 75 posts, I got a bit the feeling of a rollercoaster. There are - as usual one is tempted to say - many well founded posts with useful information. But there were - once again - amusing attempts of a peeing competition recognizable, who and where and on which side of the pond the best engines are made. Finally I reconned also some useless baloneys. Thought we are a rather professional circle.

That all reminded me to Murphys law, not the short version but the one Robert Murphy, Ed´s son has passed on:

"If there's more than one way to do a job, and one of those ways will result in disaster, then somebody will do it that way."

I believe excactly that killed engine #2 on QF 32.

I also think that it is the centre point the discussion in this thread has disclosed. I believe that those possible root causes or contributing causes identified can be listed this way.
- vibration of unexpected strength and probably unknown origin
- problems with the oil system
- probably problems with the bearings
- known and probably also in this model existing problems with oil vent tubes
- unexpected problems with stiffness or strength of the support structure of
bearing chambers

One word to the idea of an external switch somewhere close to the engine or pylon. I would like to meet that hero that is willing to get so close to a running engine of that size to activate that switch.
Another word: I emphatically agree in the reluctancy of NoD to rely on a "fully automated robot". In my opinion any computer or automatic device can be only as good as the brain that has desighned it (s.a. Murphys Law).
Therefore any artificial intelligence needs a human brain controlling it.

[Suzeman]

Just been advised that A380 VH-OQD on QF32 LHR - SIN has diverted into DXB. Not the same a/c as that involved at SIN, but obviously some problem that made the crew decide on this precautionary diversion.

[Annex14]

Well, you call it unsubstantiated rubbish, many of the participants in this thread - as the top line says - call it Rumors !!
Could be that all these many entries - the collection of thread 1 and thread 2 approaches about 2500 !! - are apain in RR´s neck. As usual they would have preferred to run this in the "noble" and silent way they usually handle these cases. Okay with me and many others, but to think independant fortunately has not yet become forbidden in this free world.
So as you seem to have a deeper insider knowledge to the case, feel free to "teach" those "unknowing".
And by the way, a bit more personal information than just "Seattle" would be of great help to balance the base of knowledge.

[Turbine D]

I suspect that if your location (Seattle) is accurate, you may very well be an RR employee, on assignment at Boeing, probably in support of the Trent 1000 on the Boeing 787. A clue is your use of the word "rubbish". In the States, we seldom use this word, but the word "refuge" or more commonly, "garbage".

With over 2500 posts, this thread is in reaction to a very, very near tragedy on the Qantas Airbus A-380 given the catastrophic failure of the Trent 972 engine. It is also a reaction to Rolls Royce's response to this event. The silence from Rolls Royce has been deafening.

Some of us have been in this aviation business for all our working careers in one role or another and because of the deafening silence from Rolls Royce, we speculate as to the cause/causes of this Trent 972 failure, whether or not there were specific indications that such a failure would eventually transpire, and whether or not corrective actions have actually taken place that don't require repeated inspections at short intervals among other things.

So, this thread is what it is, like it or not from your perspective. You can contribute but perhaps that may not be in your best interest, so the "silence is deafening" route may be your best alternative.

[Turbine D]

Yes I am in Seattle, no I have nothing to do with RR or the 787.

Glad we got this one point cleared up! :ok:

Now for the rest? :confused:

[lomapaseo]

Oh and whilst at it read the economist article and see what they feel about RR silence. I'm not convinced that I agree that RR should have been as silent as they have been but the aerospace industry appears satisfied.



RR need only satisfy their current customers, regulators, potential customers and the investors.

The investors need only seek out technical based opinions beyond this from independent experts.

Since such experts are not in evidence in this thread (name, title, bio) then the technical design-redesign opinions expressed here are only to impress the browsing reader.

[BigG22]

'Having spent sometime reading this thread for the first time I am very disappointed by the amount of unsubstantiated rubbish that is spouted. RR have played this close to their chest publicly, but do any of you know what they have been doing with the airframers/airliners and authorities. Thought not.

Bearfoil, DERG, annex14 etc. some of the junk you are spouting as fact is unbelievably wrong. Anyone that believes your rants should think again.

Bearfoil where do you get your facts from, do you know anything about engines/EEC's, DEP's you posts are some of the worst I think I have ever read.'

I am saddened to read your post.

Perhaps if you followed this thread from the start you may have realised that there have been many genuinely knowledgeable and respected contributors who share a genuine concern for safety, and seek to identify the physics of the QF32 failure in order that 468 pax and flight crew might never be similarly endangered.

This forum is very unique in that it brings together those who fly the planes, and those who contribute to their construction and who advance the technology. This can only be good and potentially of enormous value, because no matter what our age - we can never cease to learn.

Of course in a public forum, there is bound to be a certain amount of 'noise'. But i think the pilots and engineers here are well able to filter that out? And in any event is there something bad about throwing thoughts around? I think it's called 'brainstorming'?

I think that perhaps I speak for all to say that you are welcome here if you believe you can contribute to the discussion and to an improved understanding in a positive way.

Personally, may I thank those who sit up front, and those who are engineers in whatever capacity on the ground for their constructive and well considered thoughts shared here.

[Turbine D]

Thank you for your very thoughtful post. Indeed, there are some of us that are trying to understand what caused the engine failure on the Qantas Airbus A-380 in the interest of passenger safety. Unlike some of the posters that imply that only the stockholders, investors, regulators and potential customers be satisfied, I believe the users, the paying passengers besides the flight crews also need to be completely assured of the safety after a near catastrophic event, such as this one, that occurred. It has nothing to do with how far we may be removed from current technology as some have suggested but the honesty in dealing with what has taken place and assurances that it is not going to happen again. The problem is not with the aircraft, in fact, it saved the day. The problem is with the lack of assurance from the engine manufacturer that the problem has really been completely solved going forward. As I see it, I have yet to see any believable assurances, especially with remarks such as this from the very top of the organization:

Sir John Rose spoke publicly for the first time about the problems with its Trent 900 engine used on the Airbus A380, parts of which exploded last November on a Qantas flight from Singapore to Sydney.

The company said that such “uncontained” engine failures occur roughly once a year in the global civil aviation sector. Rolls-Royce last suffered such an engine fault in 1994.

Now we know this not true, there have been at least two, one occurring on August 30, 2010, out of San Francisco, a Trent 700 engine, also on a Qantas aircraft.

Re-arranging the deck chairs on the fore-deck, while the band plays on in the main lounge to comfort the stockholders, is not what this is about.

There is enough credible information on both sides of the pond to suggest that this event was not only predictable to occur at some time, but also preventable. It is with this in mind that we explore what happened and attempt to assemble some thoughts, ideas and our experiences as to the sequence of events leading to the failure and postulating what may need to be done to keep a replay from occurring.

It is nice that some of us are willing to share in this forum, while others, perhaps with even more knowledge, are willing to play the "I know more than you do, but I am not saying" role.

Thanks again,:ok:

[barit1]

... there have been at least two, one occurring on August 30, 2010, out of San Francisco, a Trent 700 engine, also on a Qantas aircraft.

Not quite. It was QF74, a 747/RB211 (http://www.aviationkb.com/Uwe/Forum.aspx/au-aviation/9296/ATSB-news-release-QF-74); IPT detached from the shaft, but shed its blades (ripping case open) before reaching burst speed.

The other related case was a T1000 on test bench, early Aug. 2010 IIRC.

[rottenray]

u416967 writes:
It is obvious that a lot of the newer "technologies" are little understood, particularly with regards oil temperature, oil systems and controls.:rolleyes::rolleyes:
Yes, well, that's what has been under discussion here. The subtle undertone of this thread deals with how not fully understanding these "newer technologies" and how they actually work in the real world can affect commercial air trans as we know it.

Let me qualify myself. I don't work in the aviation industry, I'm not a pilot.

Now, to take you to task for some of your earlier and rasher statements regarding the quality of this thread and those who drive it.

This thread has been both fascinating and an education for me as I have followed the discussion; the many contributory posters (bear, turbine, loma, et al) have brought forth valid information as well as insight.

Frankly, to walk into this discussion and call most of it rubbish or garbage does not add anything to its value, and if that is the best contribution you can make, I would suggest that you hold it for a cocktail lounge somewhere and argue over designer cocktails with those who haven't put a lot of effort into trying to discern exactly what caused an engine, one of the most-touted engines, of a 5-star engine builder to self-destruct on the wing of a Qantas flagship aircraft.

Before you decide to reply with some snarky comment to this post, I suggest you re-read this thread and all the links found herein. You might at that point decide that you were in fact completely wrong in classing most of this discussion as refuse.

Cheers!

[rottenray]

writes:
Rottenray, you have just stated that you have learnt most of what you know from this thread.Now, where, exactly, did I write that?

(for those who wish to fact-check, and for u415967 to review, this is the post... (http://www.pprune.org/tech-log/437978-qantas-a380-uncontained-failure-14.html#post6244342))

all that counts are the authorities and they will have all of the information around themYes, you're quite right. The authorities are the ones designing engines, airframes, and infrastructure. And building all of it.

And the authorities never, ever have to enlist the help of outside talent - like engineers, experienced line mechanics, et cetera.

I will refrain from entering into any more discussions on this subject.There is a God!


Carry on, guys - and thanks for the discussion so far!

[DERG]

"Bearfoil, DERG, annex14 etc. some of the junk you are spouting as fact is unbelievably wrong. Anyone that believes your rants should think again."

The most unbelievable fact is how the RR management took the junk as presented by Oxford University and used it in a way that resulted in endangering the public. When the public buys a ticket to ride on these aircraft they do not believe they are entering a lottery.

The BBC interviewed an aerospace analyst last week who stated that "RR know they have a problem". Then we have the article in the THE ECONOMIST, a weekly once noted for its objectivity, that reads more like some thing from THE INVESTORS CHRONICLE.

Now as far as the claim that some of us are partisan, we are biased toward GE or RR..well I for one have learned enough on this thread to make an educated guess just which engine I would trust my life with. Those of you who cannot make a judgement yet should reread this whole thread.

RR are taking a hell of gamble with people who place their trust in the T900s with their lives, not money as in the stock market, with life and limb. You think this is hyperbole...?

[Trent 972]

Suzeman- Just been advised that A380 VH-OQD on QF32 LHR - SIN has diverted into DXB. Not the same a/c as that involved at SIN, but obviously some problem that made the crew decide on this precautionary diversion.



A Qantas plane flying from London to Singapore was diverted out of Iraqi airspace on Monday, the Australian flag carrier said, after officials on the ground refused to recognise a pre-approved flight plan.
QF 32 had to divert to Dubai to refuel as a result, a Qantas spokesmodel told AFP, describing it as an "unusual" incident.
"The flight path was interrupted by Iraq Air Services who would not allow the aircraft into Iraq airspace due to them not recognising the authority (to enter) and the pre-approved flight path request," the spokesmodel said.
Qantas was now liaising with Iraqi authorities to determine why the plane had been denied entry

All 4 Trent 972's working perfectly. :ok:

[DERG]

Very good news Trent!

Barit

The stuff that the military do and the stuff the civil avaition does are connected intrinsically but are incomparable in terms of day to day routines. Is that not obvious Barit?

The problem arises when the UK Ministry of Defence people find themselves at the whim of Adam Smith. They suddenly realise that they have a bunch very greedy people to please, many with the morals of a rattle snake.

Indeed the public they once "served" are now seen as pawns in a game.
Of course Airbus, RR and almost all the big aircraft manufacturers have some income from military projects. These people are given only parts of the picture for reasons of security.

What they do not realise is that civil aviation has no "state secrets". In this sense firms like QuintiQ are immature and still unconnected with civil responsibility. viz. LITIGATION

Moreover we have evidence that the academics they employ readily provide them with ammunition to make probalistic projections about mechanical devices they really know SFA about.

Not military hardware, a civil airliner with over 450 people on board flying over populated communities.

OPEN TO FORUM

Some of you maybe asking IF the manufacturers know everything about the aircraft they sell.

This link is interesting:
AvioConsult - Aircraft Expert and Consultant - Home Page (http://www.avioconsult.com/index.html)

This will take a couple of hours to fully digest but is well worth reading.

[Turbine D]

Good information on other uncontained failures. They can occur more frequently on engines that are nearly 40 years old and for one reason or another, are not well maintained. Now, I don't want you to think that I am making this up or a "sciolist" as you like to put it. So here are the facts, read on:

AD Aimed At Delinquent CF6 Operators | AVIATION WEEK (http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=mro&id=news/avd/2011/02/07/08.xml&headline=AD%20Aimed%20At%20Delinquent%20CF6%20Operators)

By the way, the CF6-45 engine was designed for the Boeing 747-100SR (short range), especially for ANA and their short routes inside Japan. Just thought you would like to know.

[Suzeman]

Thanks for the information Trent 972

Presumeably it had to divert back and then round over Saudi.

Glad it was a paperwork issue and nothing technical :ok:

[Turbine D]

I wasn't counting the Trent 1000. The second one I was referring to was this one: http://www.ntsb.gov/ntsb/GenPDF.asp?id=DCA04IA002&rpt=fa
FAA Airworthiness Directive
During 2004, an incident was reported involving uncontained multiple intermediate-pressure (IP) turbine blade release on a Trent 700 engine. The blade release was the result of an overspeed of the IP turbine rotor that was initiated by an internal fire in the high-pressure/intermediate-pressure (HP/IP) bearing chamber. Post-incident analysis and investigation has established that blockage of the HP/IP turbine bearing oil vent tube due to carbon deposits was a significant factor in the failure sequence. The Trent 800 has a similar type design standard to that of the Trent 700 and has also been found in service to be susceptible to carbon deposits in the oil vent tube.

[DERG]

Readers will note that THE ECONOMIST ran a very subjective and somewhat biased story about the future of RR.

Rolls-Royce: Per ardua | The Economist (http://www.economist.com/node/18073351)

It is no suprise to learn that a non executive CHAIRMAN of RR is: SIR SIMON ROBINSON

"Appointed to the Board in 2004 and appointed Non-executive Chairman in January 2005. He is the founder member of Simon Robertson Associates LLP and a non-executive director of HSBC Holdings plc, Berry Bros & Rudd Ltd, and The Economist Newspaper Limited.

He is a director of The Royal Opera House Covent Garden Limited and a Trustee of The Eden Project and the Royal Opera House Endowment Fund. He is the former President of Goldman Sachs Europe Limited, a former non-executive director of the London Stock Exchange, Invensys plc (formerly BTR plc), Inchcape and a former chairman of Dresdner Kleinwort Benson."

HSBC is one of two clearing banks for RR.

Futhermore HELEN ALEXANDER a non excutive director of RR also has connections with THE ECONOMIST:

"Appointed to the Board in September 2007. Helen Alexander was Chief Executive of The Economist Group from 1997 until July 2008, having joined the company in 1984. She has an MBA from INSEAD. She was Managing Director of The Economist Intelligence Unit from 1993 until the end of 1996"

Source:
Rolls-Royce Group plc
65 Buckingham Gate, London SW1E 6AT. Company number 4706930,
UK VAT number GB 345 8860 22.

[WojtekSz]

U415967:
looks like you may have not spent too much time reading all this forum before starting to write ;)
I am not here to cause arguments or to give you my opinion on the matter, as it doesn't count, all that counts are the authorities and they will have all of the information around them. The fact that the A380 with Trent 900 engines are flying shows that all of the authorities are happy with the explanation given for the unfortunate accident that occurred on the QANTAS A380. And possibly that is why RR is currently at 3rd iteration (C) of the solution for fixing the T9 - right? So who was accepting the previous iterations? RR by itself or the authorities? I understand thay you are aware that the authorities would not exist if not the big companies who do operate on this market. Just read what Derg has posted a moment ago about 'unbiased' opinion by the economist..

I know that you are all intelligent people, so I suggest that you start to believe what is in the ATSB reports and any other accident report there is, as usually they aren't incorrect.in your reading you must have somehow omitted some of the French reports where raison d'etat was definitely more important than other facts ;) - see Habsheim and recent Concorde crash...


I am sorry if people don't value my opinion, however I know for a fact that most of the speculation on here is incorrect in some way. I will not be giving more details but suffice to say, I do know what I am talking about on this and am close to it unlike most other posts on here, especially those by the vociferous few.If you really know more than prove it or quit writing unsubstantiated opinions.
I am sorry but we are trying to stick to discussing the problems with Trent 900 and not healing some sore personal egos ;)
History has proven that those who really know either keep doing or keep quiet
Welome to PPRuNe :)

[WojtekSz]

Derg:
exposing such information to public poses a threat to national security :ugh:
Now you can understand why some countries do close internet access at all - remember what some BIG money makers say - big money like it quiet.
:}:}:}


thanks for this info :ok:

[Annex14]

Nice background information, one could have expected such a vitae.
However, allow me to remember you to the saying that "caution is the safer part of bravery".Or with other words, I fear that you are opening another "broadside".
So better lets exchange these kind of info in pm´s or mails ??
And as barit1 has stated in another context - always check your six;)

[DERG]

Thanks for your concerns. I was born on the west side of the iron curtain and I uphold the values of freedom. The day we become scared is the day we have lost that freedom. 165 million people died in war last century and another 469 people almost died as a consequence of this nonsense with the RR engine. Nah...these folks do not scare me.

[bearfoil]

Sorry for the delay, here is a summary of EEC controls re: shutdown in flight. (T9).

The engine protection system is incorporated into the EEC. Its hardware performs the following functions:

LP and IP Rotor Overspeed protection.

LP Turbine Overspeed protection.

Thrust control malfunction protection.

EEC monitors LP and IP compressor shaft speeds (N1, N2). this is done via a Phonic wheel on the shaft of each, forward of the Ball bearings. If speeds of these shafts are above an indexed value, the engine is shutdown. The LP Compressor shaft is also compared constantly with LP Turbine module, and if discrepant, the engine is assumed to have had a shaft loss, and the powerplant is shutdown.

Thrust Control Malfunction (TCM)

EEC monitors engine thrust, both Turbofan Power ratio, (TPR), and N1 Speed. If either exceeds commanded values by an indexed limit, TCM prot operates by reducing Power, or it will shut the engine down, depending on Airspeed and altitude. Flight Controls Primary Computer (Prim), provides a discrete signal hardwired to the EEC active channel, which then allows engine shutdown.

Each channel of the EEC has a hardware protection which is separate from all other EEC functions. Comparators determine if an overspeed or TCM have passed threshold; if a fuel cutoff or reduction is set, Programmable Array Logic (PAL) functions alert the opposite channel, and if both channels agree, a signal is sent to the protection motor in the HydroMechanical Unit (HMU).

If in degraded operation, (power supply or processor failure), shutdown can be commanded by one PAL.

One other thing. The LP and IP shaft speed is sensed by Phonic wheels, the HP shaft speed is derived from the actual RPM sensed at the Alternator, off the Gearbox drive. The EEC settles on Fuel flow by sensing the RPM of the N3 ONLY. This seems counterintuitive, but may circuitously explain why the engine, at the threshold of Burst, was given additional Fuel.

Seems relatively Human exclusive to me.

[barit1]

The engine protection system is incorporated into the EEC. Its hardware performs the following functions:

LP and IP Rotor Overspeed protection...

Remember - In the case of IP rotor, apparently protection is provided only for an intact rotor (my emphasis). If the IPT becomes detached, then the EEC has no clue what the IPT is doing, since the phonic wheel is on the IPC shaft.

But as we have previously discussed, a rapid N2 unspooling without like N3 change is indicative of mechanical failure (e.g. IPT detaching), and there seems to be the potential to "catch" this in the software before destructive overspeed occurs. In QF32's case, there is an apparent six-second window.

[Turbine D]

Bear, thanks for the explanation of the EEC logic for a three spool engine.

The EEC settles on Fuel flow by sensing the RPM of the N3 ONLY. This seems counterintuitive, but may circuitously explain why the engine, at the threshold of Burst, was given additional Fuel.

Is this common on all three spool engines or unique to the Trent 900? It seems rather odd to me but I don't profess to understand the EEC logic on a 3 spool design.

[bearfoil]

N3 Speed is furnished by the dedicated Alternator, which is powered through the gearbox by the HP Rotor. Two separate single Phase N3 windings supply N3 speed to each of the two channels in EEC. EEC utilizes this data to monitor speed, control the engine, and sense N3 Overspeed.

If there is a total loss of Shaft speed signals, EEC generates a "synthesized pair of shaft speed signals" (N1 and N2) for the cockpit, and uses N3 actual to "maintain transient Control." Turbine D, this is book on the TRENT 900, the others, I do not know.

[DERG]

Here we go...you will like this...

Captain Fantastic (http://sixtyminutes.ninemsn.com.au/article.aspx?id=8209663)

Hell of a mess that engine made.
Holes all over the place.
Shame the Bayesian sophists were not on the 'plane.

This is as far as I go with this unless we get yet more WET replies.
This is where I and the BABUSHKA drive shafts of RR say a final goodbye.:suspect:

[infrequentflyer789]

Unlike some of the posters that imply that only the stockholders, investors, regulators and potential customers be satisfied, I believe the users, the paying passengers besides the flight crews also need to be completely assured of the safety after a near catastrophic event, such as this one, that occurred.


I can assure you that stockholders have no extra information for their satisfaction that hasn't already been posted here. Big investors - maybe, but I suspect not, they are interested in finance not engineering anyway.

As to assurances, as pax, yes they would be nice, but I'd rather they didn't bother assuring me that the issue was fixed if, in fact, it isn't. From what's been discussed on this often fascinating thread, I'm not sure it is fixed, yet.

With an investor hat on, I think my biggest concern would be that even if the current AD regime has plugged the safety gap, how are RR making a profit on PBH contract on an engine that only does 70 cycles on the wing ? If the engine is safe but it and its contracts become a financial millstone round RR's neck, then it's no better for the company.

[bearfoil]

I see your vintage here on PPRuNe is about the same as mine. Funny, what drew me in was another TRENT goof. I still don't see any satisfaction re: the "Mystery Fuel" on BA038.

It is par for the course that given enough time, and sufficient urgency to travel, SLF pick up their carry-on, there teeny bottles, and launch. It truly is a safe way to mobilize, and it is also par for accident/incident threads to start loud, and end with a whimper.

Such is life in the big world of air travel. It isn't as safe as it could be, but it is very very safe, for all that. The sand in the knickers is it could be better. It is shy of the mark for defensible reasons, but I have never thought money should be in there, anywhere. Not even if facing Banko, as RR may well be. They have chosen the standard path, the way of least complaint, the way of wink and a nod with people who should be a bit more stern with the Corpos.

Nothing will ever diminish the level of sheer disaster QF32 faced that day in November. Nor will anything bring back the folks aboard AF447. We are entertaining mechanical doo doo, but Pilot Error is in there as well. Used to be, a Captain could tell Juan Trippe to pound sand, and date his wife on top of it. There was a goofy obeisance to, you know, authority.

Now, accountants dress in Pound Notes, or Franklins, and call themselves boss.

What utter bull****.

[Turbine D]

infrequentflyer789

With an investor hat on, I think my biggest concern would be that even if the current AD regime has plugged the safety gap, how are RR making a profit on PBH contract on an engine that only does 70 cycles on the wing ? If the engine is safe but it and its contracts become a financial millstone round RR's neck, then it's no better for the company.

Yes, as an investor, there is a big concern. First, to develop a new engine, certify it, and then put it on the wing of a new aircraft being certified usually involves an investment of $2B US. And then, the first engines are usually sold at a loss as you are not far enough down the learning curve to produce a profit. Then there is the matter of how big the program will be (there is competition), e.g., a large number of engines over a long period of time. And finally there is the matter of the "Total Care" program.

The engine service program (Total Care) is really (should be) the big money maker but it is based on an actuary type system, the expected performance of the engine in the field over a time period before significant servicing, repair or replacement parts are required. These contracts typically are 10 years or more and the amount charged per engine to the airlines doesn't go up much over time to cover the cost of a bad start.

So with the problems at the moment, there is a significant setback of the new engine sales break-even point and the service end of the business is getting hit with costs that were not expected. Both are negatives on the bottom line.

There is always the possibility that when all costs are added up and the program doesn't produce enough profitable sales in the long run, the money lost will never be recovered.

[avgenie]

Hi Turbine D
Appears you are one of the resident experts on engines. I understand the FAA's 2007's new ETOPS regulations require ETOPS certification even for four-engine airplanes if they will operate on ETOPS routes. I understand Boeing will be the first manufacturer to certify a four-engine airplane to ETOPS standards when it certifies the 747-8. I also learned from a book I recently read that Australia will require a similar certification for all airplanes including the 747, A380s in a few years. If so, reading your following comment:

So with the problems at the moment, there is a significant setback of the new engine sales break-even point and the service end of the business is getting hit with costs that were not expected. Both are negatives on the bottom line.

There is always the possibility that when all costs are added up and the program doesn't produce enough profitable sales in the long run, the money lost will never be recovered. Will this looming ETOPS certification further worsen the cost situation? Thanks for your expertise

[radken]

My old uncle was an elec engineer for WSTNGHSE/GE (dynamo’s/cmcl power) back in the 40’s - 70’s and, my-o-my, the stories, some hilarious, he used to tell about the “bean counters” v/v best engineering. Now, this latest discussion takes me back to his old words as well as reminiscences of my own revolving around an old axiom I sometimes used to hear in mx about aircraft returning to revenue just out of D Check.

Strange how they’d often suffer one or a half-dozen (sometimes big) grounding squawks right out of the box on their first revenue flight. They’d sometimes wind up at some God forsaken downline station where you’d have to send a half dozen guys, fix it or not, or get a waiver and crew together to ferry the thing to a place where it can be repaired.

The moral was something like, “There’s never enough time or money to put it back together and test it right the first time, but, OH, YEAH, there was always plenty of both later on!” Seems this sarcastic rule might be equally at home today within the hallowed halls of RR (or GE/Pratt/Snecma, etc) as well? I like to think not, at least not of the major safety compromising type... but then I think of my old uncle angrily grousing about “beaner” rule in the land of dynamo's.

Why I think maybe even Boeing corporate might be just a little upset with their own beaners now that we’ve witnessed all the "save a buck" international fiascos that have gone on in development and construction of that neat new airplane of theirs. So glad I’m retired! LOL

[DERG]

No sooner done with one unbalanced engine we move on to the next..
Recommendations without a MANDATE DIRECTIVE and of serious concern..in other words they can do as they please!

HEADS UP!

CF6-45/50

Note: This will test just how robust this site is to pressure from commercial interests at the expense of OUR Safety

"The first recommendation asks that the FAA require operators of aircraft equipped with a particular model engine to immediately perform blade borescope inspections (BSI) of the high pressure turbine rotor at specific intervals until the current turbine disk can be redesigned and replaced with one that can withstand the unbalance vibration forces from the high pressure rotor. The second recommendation asks the FAA to require the engine manufacturer to immediately redesign the disk. The NTSB issued an additional recommendation for a requirement that operators perform a second type of inspection and another recommendation related to the engine manufacturer regarding the installation of the replacement disk."

Document SB-10-20 May 27 2010. NTSB URGENT

More reading here:
Four Recent Uncontained Engine Failure Events Prompt NTSB to Issue Urgent Safety Recommendations to FAA @ AMTOnline.com Top News (http://www.amtonline.com/article/article.jsp?siteSection=1&id=11011)

and officail document here
http://www.ntsb.gov/recs/letters/2010/A-10-098-101.pdf

[forget]

DERG. Only last week you said -

Now as far as the claim that some of us are partisan, we are biased toward GE or RR..well I for one have learned enough on this thread to make an educated guess just which engine I would trust my life with.

And now?

[DERG]

Forget

Profound question yes. I think the better question would be which airplane would I be happy to see my loved ones board. Or indeed any form of transport where I personally have no control over the machinery.

If that journey had to made I would chose which operator, which airline I would trust. There are very few operators which I would avoid. Now you will be asking why the f:mad: does he just not answer the question!

Would I trust the RR T900 as it stands as of now in use with the operators who use it. Yes I would. Would I trust the CF6-45/50 with the operators who use it as of today. No I would not.

As for the T972 in use with Qantas, given the fact that it is replaced..we hope..every 70 cycles and the fact that there are four units on each A388. Yes I would.

What aircraft would I use if I had a free choice for the places my family is most likely to visit? That would be the BAe 146.

[Bolty McBolt]

As for the T972 in use with Qantas, given the fact that it is replaced..we hope..every 70 cycles and the fact that there are four units on each A388. Yes I would.

What aircraft would I use if I had a free choice for the places my family is most likely to visit? That would be the BAe 146.

70 Cycles between changes and OH ?
I am not sure what documentation you are reading BUT whom is changing engines every 70 cycles.

To mention a BAE146 in regard to reliabilty and safety.
( Bring Another Engine ) 146. :ugh:

[DERG]

Thanks for returning to thread Bolty.

So they are not changing the T972s evey 70 cycles. Right.

Maybe they have changed the "chip" to back to the T970 specs?

As far as the 146 goes, as long as you choose your seat well, I believe it will get you there.

Has the 146 had an uncontained engine failure?

[Bolty McBolt]

Maybe they have changed the "chip" to back to the T970 specs

No. Don't think so. The 972 thrust is required for the LAX T/O and as you see the 380 has returned to daily LAX sched.

As far as the 146 goes, as long as you choose your seat well, I believe it will get you there.

Can't recall an uncontained failure except for its operational service in OZ. If the engines weren't poisoning the pax with oil fumes they were failing at a rate that paid for engineers homes in the overtime they generated.
If I were to choose my seat well for a "fruit bat" (Oz name for a 146) flight it would be in the terminal waiting for another type aircraft. ( I am probably being overly harsh) :)
Amongst us engineering types the BAE 146 is the only aircraft you have to check the front and back for bird strikes if reported. Boeing 744 is my pick,

Back to Trent failures.
I have a recollection of Cathy grounding its fleet of RR powered A330s.
Something about an angle gearbox failing structurally due to out-sourcing poor quality control in machining.
The CEO of Cathy grounded all its A330s where ever they were in the world as it was unable to predict a life span of the engines as some engines failed at 3000 hours and some close to 50.
This is a vague memory from the 90s but it would appear this type of trouble has struck before.

[DERG]

Very much appreciate your view Bolty. Thanks for rejoining the thread.

Note: A new thread has been started in the Tech Log about the CF6-45/50 URGENT subject.

The relation to the T972 failure is: HARMONIC EXCITATION LEADING TO UNCONTAINED ENGINE FAILURE.

This is the math used
http://www.aerostudents.com/files/vibrations/harmonicExcitation.pdf

My guess is that RR and Schaeffer were not communicating effectively while these numbers were entered into the design specs.

There was one or many breaks in communication within or without RR during the design process. This would suggest that the design itself is inherently flawed OR that the manufacturing process cannot be configured to reproduce the design specifications.

Only one way this can happen: non communication or incompetent management.

[Annex14]

I believe DERG has quoted press releases that Qantas made earlier this year in connection with an affidavit at a court against RR. Reason beside many other items was the RR - information/recommendation/ mandation what so ever one may call it - that using the T972´s with 540 psi at p30 - as I understand the max. perm. TOP - would make it necessary to change engines - even "mod C " after 75 such cycles.
This information was posted in this thread before and untill now it has not come to public that this restriction was lifted.

So if you write that QF flies daily A 380 service to LAX that either implicates that these flight are narrowly controlled and after 75 cycles the mentioned engine change silently takes place, or there is another modification made on that engine - probably called "mod D" - that has eliminated the concerns that led RR to issue such a severe restriction.

Never the less in my opinion you`re sounding very confident - overconfident may be ?? - having in mind the fact that the spline AD is still valid and even the newest engines must be inspected after 200 cycles and follow on at 100 cycles. (s.a. EASA AD-No: 2010-0242 R1)

Could it be that the members of this net simply have missed an important change in regulatory paperwork for the daily usage of the RR T972 ??

[Turbine D]

Hi avgenie,

Having read through the new ETOPs plan for 3 or 4 engine aircraft, it seems to me that most of the responsibilities will be on the operators (airlines) that fly these long over water routes. Route planning and diversion planning becomes a more demanding issue than what it has been. I don't see it as a big cost item for an engine manufacturer unless there are unforseen problems that develop in revenue service.

For new aircraft/engine combinations, ETOPs is generally applied for and demonstrated during the certification phase. Since most airlines establish contracts for the aircraft and engines separately, I would bet there will be penalty clauses established should either fall short and the contracted ETOPs rating is not achieved or becomes reduced because of problems. This is where the bottom-line of either manufacturer could be impacted depending who has the problem and how long it takes to resolve it.

There is another large customer today, leasing companies. They buy airplanes and engines and lease them to various airline. Since these deals are very complex and vary considerably it is hard to tell how this change will affect them.

[Flapping_Madly]

Forgive me for repeating this post I made in the other thread on 3 December.

Believe me my question is NOT intended in any way to provoke any sort of argument because I am totally ill equipped to have an argument with anyone . But I do wonder sometimes if Rolls Royce make aero engines these days or just assemble them --they seem to buy in bits from all over the world. Does this strain quality control?
When I was a kid the impression was that they made everything -even all nuts and bolts--from alloys they made themselves in their own foundries. They had, it seemed, total control.

Who made the apparently crude oil pipe for them?

As I read the unfolding story on this thread this question of mine nags at me more and more. Is there inherent danger in buying in parts from all over the world instead of making them yourself?

And please can I ask another question?

Why do RR need so many different engines? It seems like every new plane has to have its own engine type. Someone on this or the other thread has already asked why RR do not replace the 900 on the A380 with two pairs of different proven reliable engines to give the same thrust.
Same as before I am not trying to stir anything at all. I am just SLF whose father worked at RR for 40 years in Experimental Dept at Sinfin.

[Turbine D]

Flapping_madly

You ask good questions, no apologies required.

But I do wonder sometimes if Rolls Royce make aero engines these days or just assemble them --they seem to buy in bits from all over the world. Does this strain quality control?
When I was a kid the impression was that they made everything -even all nuts and bolts--from alloys they made themselves in their own foundries. They had, it seemed, total control.

I think the total vertical integration business model dates back to the start of mass production automobile manufacturing. In the US, Henry Ford had and made everything required to produce a car or truck in his own factory.

The same was true during the war years, both in the US and in the UK n the manufacture of aircraft engines. However, with the advent of the jet engine and the globalization or reach of businesses, the vertical model began to fall away. One reason might be specialization where smaller external companies invested both in technology and manufacturing capability to produce certain items of good quality and lower costs than what could be manufactured in-house. Larger companies were tempted to go outside for items as it saved financial resources that would be required to update equipment and manufacturing processes to remain cost competitive. In the end, only the most highly technical items and processes remain in-house. The less technical items can be purchased outside satisfactorily with good quality oversight and planning. Today, this has spread globally as business deals are made to sell product while some of the product content is made in the buyer's country. It does require a good quality organization worldwide and sometimes, on site daily depending on the product being produced. It is also important to have a good technical capability plan and assessment team in place to assure capability before orders are placed. So, yes, Rolls Royce, GE, Pratt & Whitney and others have become more focused on design and assembly of engines and less involved in actual parts manufacturing. The key to success is not skimping on quality oversight no matter where parts are produced.

I will answer the engine question in another post.

I don't know the answer to who produced the stub pipe, but I understand the latest engine revision doesn't have the stub pipe component at all.