QANTAS A380 Uncontained failure.
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DERG
Here is the link to the patent. The leaf seal is made by Alstom, Baden CH
Leaf seal, in particular for a gas turbine - Patent 7828297
Very interesting development!!
Leaf seal, in particular for a gas turbine - Patent 7828297
Very interesting development!!
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Patent details here.
United States Patent: 7828297
.... and see this Patent. To Rolls Royce 1980
United States Patent: RE30206
United States Patent: 7828297
.... and see this Patent. To Rolls Royce 1980
United States Patent: RE30206
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DERG
We have been into that FAG brochure before. Must admit that no one untill now has picked the fact that all of the bearings used are non off the shelf. It has to be specials seen the environment they are used.
That makes me remember a very short / brief note in the newspaper here, probably about 2 weeks after the QF 32 desaster. Schaeffler Group - the Holding that FAG belongs to - has released a note to the press that their bearings were NOT the cause of the failure!! and had performed as expected !!
With all the developements in this thread over the past weeks I now believe that this press info might have some kind of importance for the outside evaluation of the causes.
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.
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Good Progress
Thank you all for the help with this.
Jo
Thats good info. Looks like we have a shaft balance problem so far. But not sure as yet More work to do.
All help much appreciated.
Eng Note:
SKF has made ALL the bearings so far. They also make the T1000 bearings? So why not the T900?
Engs never leave a trusted supplier. So looks like INA/Schaeffer were willing to take on a new design concept.
Is this it?
http://www.schaeffler.com/remotemedi...e/0001614C.jpg
looks like they also got a contract on the EA/GE engines on the new B787 and on the T1000 too.
Looks like more heat transfer for less mass but we will see.
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.
Eng Note:
SKF has made ALL the bearings so far. They also make the T1000 bearings? So why not the T900?
Engs never leave a trusted supplier. So looks like INA/Schaeffer were willing to take on a new design concept.
Is this it?
http://www.schaeffler.com/remotemedi...e/0001614C.jpg
looks like they also got a contract on the EA/GE engines on the new B787 and on the T1000 too.
Looks like more heat transfer for less mass but we will see.
Last edited by DERG; 1st Feb 2011 at 12:07. Reason: extra link
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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.
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application of bearings
On behalve of our "brother warrior" DERG I am posting here some links he sent meanwhile. I think they are all very useful for fact finding.
Application of bearings - SKF.com / Products / Interactive Engineering Catalogue/Rolling bearings
Furthermore there are these:
This the key video but DOES NOT DISCUSS TORSION OR TWIST ON THE SHAFTS
Also does not discuss CONCENTRICITY of THREE SHAFTS
http://www.eng.ox.ac.uk/thermofluids...pt#452,17,Heat Transfer between Rotor and Seal
Schaeffer ROLLER bearing
http://www.schaeffler.com/remotemedi...e/0001614C.jpg
Schaefer
For 787
FAG bearings selected for Boeing 787 aeroengines
Okay, that´s it for the moment, hope it all works
Application of bearings - SKF.com / Products / Interactive Engineering Catalogue/Rolling bearings
Furthermore there are these:
This the key video but DOES NOT DISCUSS TORSION OR TWIST ON THE SHAFTS
Also does not discuss CONCENTRICITY of THREE SHAFTS
http://www.eng.ox.ac.uk/thermofluids...pt#452,17,Heat Transfer between Rotor and Seal
Schaeffer ROLLER bearing
http://www.schaeffler.com/remotemedi...e/0001614C.jpg
Schaefer
For 787
FAG bearings selected for Boeing 787 aeroengines
Okay, that´s it for the moment, hope it all works
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just one more on bearings
Here is another link that contains useful information.
this link is interesting but needs time to read
http://medias.schaeffler.de/medias/en!hp.tg.cat/tg_hr*ST4_1652155275;bONjntrf0IKb
no direct ref to aerospace though
this link is interesting but needs time to read
http://medias.schaeffler.de/medias/en!hp.tg.cat/tg_hr*ST4_1652155275;bONjntrf0IKb
no direct ref to aerospace though
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resonance and balance
I want to come back to DERG´s last entry before he encountered the "Thunderstorm".
I too believe that since SchaefflerGroup / FAG as the bearing supplier has denied a failure of their bearing(s) as a primary cause, the case is down to the bottom where a closer look should be taken on resonance and to a lesser degree on balance.
Since it was mentioned in this thread repeatedly that vibrations are common in jet engines and balancing is a well controlable issue. Only conclusion left is resonance in parts of the engine ?? probably or more likely the shafts ?
Because the engine still eats its spline connections, the AD is not recalled yet, though softened to the extend that inspections for a new engine come first after 200 cycles and than it continues with 100 cycles. But what kind of ongoing field test is that with an engine supposed to last thousands of cycles ???
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 ???
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Digging Deeper
Dozy I beg your pardon. I too am annoyed that they have broken up the Nimrods. I am annoyed too about this T900 failure because the Comet was prone to the same fault as we are focussed on in this thread.
and moving on...
"Solutions for vibration problems involving the excitation of a natural frequency (resonance) are frequently difficult to obtain based solely upon experimental data." Thats what FAG says and moreover:
"Finite Element Analysis (FEA) is a numerical technique that can be used to approximate the structural dynamic characteristics of vibrating mechanical systems, the understanding of which is paramount to any root-cause failure study involving excessive vibrations."
The problem is that FAG have little experience in this field compared to SKF.
This is where METROLOGY began, the original paper from 1955:
http://mdrl.mne.psu.edu/papers/bearinganalyzer.pdf
This is how RR service agents themselves tackle vibration testing in the field, after the engine has left the factory and needs fixing.
http://www.skf.com/files/446130.pdf
And this is a dynamic exploded view of the bearings as they fit into a gas turbine, which is the smoothest running machine known to man: it HAS to be just to stay together.
Engine & gearbox - SKF.com/Industries/Aerospace/Applications
As Annex has told us as reported in his local newspaper:
"since SchaefflerGroup / FAG as the bearing supplier has denied a failure of their bearing(s) as a primary cause"
They did not say this was the first time they had designed and built a series of bearings for an aerospace gas turbine or indeed the entire bearing mounting system from one end of the engine to the other.
So how come they got the contract? Well YES how come?
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.
and moving on...
"Solutions for vibration problems involving the excitation of a natural frequency (resonance) are frequently difficult to obtain based solely upon experimental data." Thats what FAG says and moreover:
"Finite Element Analysis (FEA) is a numerical technique that can be used to approximate the structural dynamic characteristics of vibrating mechanical systems, the understanding of which is paramount to any root-cause failure study involving excessive vibrations."
The problem is that FAG have little experience in this field compared to SKF.
This is where METROLOGY began, the original paper from 1955:
http://mdrl.mne.psu.edu/papers/bearinganalyzer.pdf
This is how RR service agents themselves tackle vibration testing in the field, after the engine has left the factory and needs fixing.
http://www.skf.com/files/446130.pdf
And this is a dynamic exploded view of the bearings as they fit into a gas turbine, which is the smoothest running machine known to man: it HAS to be just to stay together.
Engine & gearbox - SKF.com/Industries/Aerospace/Applications
As Annex has told us as reported in his local newspaper:
"since SchaefflerGroup / FAG as the bearing supplier has denied a failure of their bearing(s) as a primary cause"
They did not say this was the first time they had designed and built a series of bearings for an aerospace gas turbine or indeed the entire bearing mounting system from one end of the engine to the other.
So how come they got the contract? Well YES how come?
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.
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Bearings/Splines
Gentlemen
I've yet to read the new links...... Will take some time later on. In the Navy, it's called an "Even Strain". Any rotating assembly can lose its stress/containment v/v a vibration. In other words, at particular frequencies, a Shaft can "Float" in its bearings. This is not good at all, for it allows chaotic and random (intermittent) 're-acquisition/loss' of constant bearing loads, and extreme heat and wear. It also beats the Oil out of its proper position at the Shaft/Bearing effacement.
Essentially then (as the result of Float), an independent Shaft (And its coupling) are "free" of containment in highly engineered clearances. Note for example the position of the Spline coupling (IP) short of the Plane of its thrust bearings. This allows out of 'bearing boundary' chatter, this geometry has puzzled before.
Think 'False Bearing', and a situation in which the Engine's shafts beat their mountings to a 'pulp'. Vibrations are thoroughly covered of course, but unusual "Novelties" ?? As in a transient Resonance at certain load, a relaxation of "Even Strain", a certain RPM, and Thrust value.
As to "Aft Migration" of the IP Stub shaft (aft shaft), this happens when Splines are worn beyond a certain value such that continued Resonance rapidly fails the Tooth/Trough pairs. The position of the Splines out of direct and balanced (Planar) position relative to the Bearing #2 can instantly aggravate the rigid couple into a disconnect (wear through) of the coupling.
The likely genesis of the vibration causing the Float would be the Fan.
Static balance of the Fan I'm sure is demanding. The Fan itself has issues (well addressed) in dynamic thrust that can unbalance the equation, and shift exterior and intense loads into the core.
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.
Last edited by bearfoil; 2nd Feb 2011 at 16:18.
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Happy... been a good learning exercise
Thats as far as I go with this. I know that RR and Airbus between 'em have taken steps to make the A388 totally safe. Think Lufthansa starts the FRA to LAX service soon and I would be happy to fly with them!
Any free tickets for a flight on any A388 then please send me a personal message
Any free tickets for a flight on any A388 then please send me a personal message
Last edited by DERG; 3rd Feb 2011 at 07:20. Reason: spellings
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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?
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 déjŕ vu to me. But that was a long time ago.
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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.
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.
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Bear
Yes and thats why the thing runs at 180C. mean and 196C max.
I wanted to send you a PM about this but this software has me marked as naughty poster....it won't let me. Anyway, I think all should know why this engine runs hot.
Anyway changes are a foot and propulsion units are set to change. This T900 will be the final example of this technologyin use now.
This is the future:
* Open Rotor: Last fall, GE announced a joint study with NASA related to an open rotor or unducted fan engine design. In the 1980s, GE successfully ground-tested and flew an open-rotor engine that demonstrated dramatic fuel savings. Since then, GE has advanced its data acquisition systems and computational tools to better understand open-rotor systems. GE also gained extensive experience with composite fan blades in its GE90 engine and GEnx engine"
Regards
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
Last edited by DERG; 4th Feb 2011 at 15:15. Reason: additional
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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.
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.
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Bear
They have got that data already.
The big main bearings are through flows. The only grease filled bearings are down in the power take off...the gearbox that drives ancillaries. They are cool and away from combustion heat.
In my view they have taken this particular design to the limit. They want to hit all the new targets with the stuff they have now. Thats impossible.
I think there is only one additive that may be able to help the oil people and it is called "graphene". Then again that is carbon and they already have a coking issue so I am guessing.
This is a good site and tells us how propulsion is going in the future. I just hope they choose the right gang of subcontractores when it comes to bearings
GE Aviation entering new propulsion era with multiple R&D programs
Regards
The big main bearings are through flows. The only grease filled bearings are down in the power take off...the gearbox that drives ancillaries. They are cool and away from combustion heat.
In my view they have taken this particular design to the limit. They want to hit all the new targets with the stuff they have now. Thats impossible.
I think there is only one additive that may be able to help the oil people and it is called "graphene". Then again that is carbon and they already have a coking issue so I am guessing.
This is a good site and tells us how propulsion is going in the future. I just hope they choose the right gang of subcontractores when it comes to bearings
GE Aviation entering new propulsion era with multiple R&D programs
Regards
Last edited by DERG; 4th Feb 2011 at 15:42.
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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?
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?
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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.
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.
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Open Rotor
DERG & Bear
Her is a link to a site, "Then and Now:
YouTube - Family tree
Interestingly, the turbine mid-frame (location similar to that of the IP/HP frame in the Trent 900) that had been removed on the CF6-80C2 engine, returned on the GE-36 UDF as it was the main support for the propulsors (fan blades). It was a much different design and it was an extremely complex structure, never fully refined before the project ended. IMO, there were some vibration problems that existed that needed to be eliminated.
* 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"
YouTube - Family tree
Interestingly, the turbine mid-frame (location similar to that of the IP/HP frame in the Trent 900) that had been removed on the CF6-80C2 engine, returned on the GE-36 UDF as it was the main support for the propulsors (fan blades). It was a much different design and it was an extremely complex structure, never fully refined before the project ended. IMO, there were some vibration problems that existed that needed to be eliminated.
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Ge 36 Udf
In those mentioned years of the early 1980´s I was a representative of our Federal Adminstration of Air Navigation Services and a detached member of not less than 11 Noise Abatement Commissions. As I remember the UDF engines caused a real uprise by evironmentalists because of the level of noise they produced.
A more technical item I remember were unwanted resonances / vibrations of the aircraft structure. I thought they were caused by the shockwaves of the counter rotating fans. I do not remember any report about engine inherent vibrations, but assume they were existent because of the so much different and radical desighn.
Ref. the ongoing oil and bearing discussion. Is there somewhere a list of oils that show the maximum permissable oiltemperature for Jetengine oils ?? Is it correct to say that the Trent 900 runs at borderline oil temperatures ??
I know there was the one or the other hint in that long lasting thread, but want to ask to shortcut.
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.