QANTAS A380 Uncontained failure.
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bearfoil
The problem I see with this is that it would completely wipe out the bearing structure below it and because the IP shaft is so close the the LP shaft, we would see rubbing or damage to the LP shaft. Based on the photos of the pulled LPT module (ASTB Report) there isn't any damage to the LPT shaft.
The recovered portion of the IPT disc (Figure 14 ASTB Report) does not show any damage to the disc posts between the dovetail slots and two of the turbine blade dovetails ("roots") that stayed in the slots look remarkably in good shape. That is why I think the contact point was just above the blade platform (airfoil) or maybe at the blade platform. If it was more toward engine centerline, we would see rubbing of the disc posts.
The way I see it, we are talking about what happened in between 2-3 seconds of time. P30 collapse = compressor stall + bang. This occurred ~3 seconds or less before disc rupture. Now I also think that the IPT disc rupture and the casing ruptures (both IPT and LPT Stage 1 Nozzle + the nozzles) releasing gas pressure would be one bang, all happening within milliseconds of one another.
For some reason, I think the fuel wasn't completely cutoff, but reduced, perhaps because the ECC was programed to recognize a P30 drop (compressor stall) and to provide for rapid recovery (air relight) or the need to restart the engine completely (air restart), but I don't know this for sure. But I think the ECC didn't recognize what else may have happened. This fuel flow could have added to a fire that was subsequently put out by engine shutdown and by the release of the fire extinguishing bottles.
Just some thoughts...
The seperation, Disc from Arm, would not be in any way orderly, and an imbalance (a certainty) would impart an elliptical and irregular orbit to the Wheel.
My drawings show the IPT Blades (Roots) as below ('within the perimeter') of the Stator Vane "Platform". "Cookie Cutter"** shear off of the Roots would force the Blades through and out the front of the fir tree dovetails. Given the "Shake" of the disc (wobble) in its new orbit, the roots would endure a constant force forward, while being mercilessly vibrated, a suitable explanation for their loss from the Wheel??
Now as to Boom, a Compressor Stall is possible, but so is explosive loss of LPT Drum (Gas) contents. A loss of this highly energetic gas forward and through the lost dynamic seal of the IPT would explain also the rupture of the case, pehaps in concert with exit of high energy debris.
For some reason, I think the fuel wasn't completely cutoff, but reduced, perhaps because the ECC was programed to recognize a P30 drop (compressor stall) and to provide for rapid recovery (air relight) or the need to restart the engine completely (air restart), but I don't know this for sure. But I think the ECC didn't recognize what else may have happened. This fuel flow could have added to a fire that was subsequently put out by engine shutdown and by the release of the fire extinguishing bottles.
Just some thoughts...
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To clarify, I describe the roots and root walls as inside (radially) the Vanes Platform, to provide the same as you state, a fairly undamaged Root system.
This is a new architecture in the 900. The Nozzle Guide Vanes on the TRENT 700 (Edelweiss) are placed directly opposite their IPT Blade counterparts. With a fully fractured Drive Arm (Circumferential), the 700's Blades immediately effaced (rubbed) the Vanes, and slowed the IPT. This is regarded as the event that prevented an otherwise catastrophic burst. It is also thought that not only did the Blade/Vane effacement slow the wheel, it stabilized it, preventing further aft travel and chaotic loss.
In your opinion, what are the design/operational advantages of the "New" architecture in the 900??
To clarify, I describe the roots and root walls as inside (radially) the Vanes Platform, to provide the same as you state, a fairly undamaged Root system.
This is a new architecture in the 900. The Nozzle Guide Vanes on the TRENT 700 (Edelweiss) are placed directly opposite their IPT Blade counterparts. With a fully fractured Drive Arm (Circumferential), the 700's Blades immediately effaced (rubbed) the Vanes, and slowed the IPT. This is regarded as the event that prevented an otherwise catastrophic burst. It is also thought that not only did the Blade/Vane effacement slow the wheel, it stabilized it, preventing further aft travel and chaotic loss.
In your opinion, what are the design/operational advantages of the "New" architecture in the 900??
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Turbine D - The FAA, being sensible people, would not have repeated all of the work done by EASA in certificating the Trent. Similarly they will not be very much involved in routine continued airworthiness or lifing or approval of oils for foreign engines of reputable provenance.
As to the oil, I do not believe the GE presentation you identified precludes the need to identify oils approved for individual engines by brand name. I believe it actually describes an approval process.
Changing the subject a little, I thought that turbine blade root cross sectional areas were sized so as to fail in tension in the event of an overspeed. Thus hopefully limiting the extent of overspeed.
As to the oil, I do not believe the GE presentation you identified precludes the need to identify oils approved for individual engines by brand name. I believe it actually describes an approval process.
Changing the subject a little, I thought that turbine blade root cross sectional areas were sized so as to fail in tension in the event of an overspeed. Thus hopefully limiting the extent of overspeed.
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wobble at separation
TurbineD, bearfoil
there is no damage at the end bearings (roller) but the damage may be seen closer to front bearings, where the IP shaft splines are located
what bothers me is the way the drive arm of the IP turbine disk if bent (fig 15 from preliminary report) - outward as if the disk was forced first into the axis of rotation and only afterwards has flown away - but would it has enough place to move like this?
How about such alternative explanation:
separation of the IP disc from the shaft has happened longitudinally when the IP shaft has moved rearwards significantly enough to break out the mentioned drive arm with its 580 bolts instantly. Still this would require the IP disk to stay fixed longitudinally to enable the forced break-out. Roller bearing do enable such shaft movement easily as long as the traveled distance stays within the width of the raceway (here the raceways could be estimated at around 1 inch). To press out (break out) the IPT from the shaft it would need to move backwards by less than 15mm resulting from 2mm gap between the IPT and following vanes fixture plane and some distance to impose enough force to break the disk (for a rigid structure like IPT i guess it could be 5..10mm). This could happen only if the IP midshaft (splines) connection would got loose or separated. Suddenly free front end of the rear shaft, not supported by the roller bearings anymore, would wobble and move rearvards driven by the IPT. But than what would break the disk from the shaft? Two possibilities: (1) high energy from the rotating disk (2) significant longitudinal force coming from the screw used to keep splined shafts together. If the splines get loose, two parts of the IP shaft start rotating against each other, front part stays fixed by the roller bearing but the the rear part of IP shaft presses the IP turbine against anything available to slow it a little just enough to get shafts unscrew from one another (4..5 full rotations would be enough) to press-break-out the IP turbine disk drive arm from the IP shaft. Disc goes free to speed up and fly away. No roller bearing get damaged except the bearing supporting the IP shaft which has to support wobbling shaft .
how the splines could have separated - easily if splines are worn out on outside diameter - fire in the bearing box would suddenly heat up the external surface of the shaft which would thermally increase diameter enough to splines get free - no need for Oldham razor here
does it make sense?
Quote:
The seperation, Disc from Arm, would not be in any way orderly, and an imbalance (a certainty) would impart an elliptical and irregular orbit to the Wheel.
The problem I see with this is that it would completely wipe out the bearing structure below it and because the IP shaft is so close the the LP shaft, we would see rubbing or damage to the LP shaft. Based on the photos of the pulled LPT module (ASTB Report) there isn't any damage to the LPT shaft.
The seperation, Disc from Arm, would not be in any way orderly, and an imbalance (a certainty) would impart an elliptical and irregular orbit to the Wheel.
The problem I see with this is that it would completely wipe out the bearing structure below it and because the IP shaft is so close the the LP shaft, we would see rubbing or damage to the LP shaft. Based on the photos of the pulled LPT module (ASTB Report) there isn't any damage to the LPT shaft.
what bothers me is the way the drive arm of the IP turbine disk if bent (fig 15 from preliminary report) - outward as if the disk was forced first into the axis of rotation and only afterwards has flown away - but would it has enough place to move like this?
How about such alternative explanation:
separation of the IP disc from the shaft has happened longitudinally when the IP shaft has moved rearwards significantly enough to break out the mentioned drive arm with its 580 bolts instantly. Still this would require the IP disk to stay fixed longitudinally to enable the forced break-out. Roller bearing do enable such shaft movement easily as long as the traveled distance stays within the width of the raceway (here the raceways could be estimated at around 1 inch). To press out (break out) the IPT from the shaft it would need to move backwards by less than 15mm resulting from 2mm gap between the IPT and following vanes fixture plane and some distance to impose enough force to break the disk (for a rigid structure like IPT i guess it could be 5..10mm). This could happen only if the IP midshaft (splines) connection would got loose or separated. Suddenly free front end of the rear shaft, not supported by the roller bearings anymore, would wobble and move rearvards driven by the IPT. But than what would break the disk from the shaft? Two possibilities: (1) high energy from the rotating disk (2) significant longitudinal force coming from the screw used to keep splined shafts together. If the splines get loose, two parts of the IP shaft start rotating against each other, front part stays fixed by the roller bearing but the the rear part of IP shaft presses the IP turbine against anything available to slow it a little just enough to get shafts unscrew from one another (4..5 full rotations would be enough) to press-break-out the IP turbine disk drive arm from the IP shaft. Disc goes free to speed up and fly away. No roller bearing get damaged except the bearing supporting the IP shaft which has to support wobbling shaft .
how the splines could have separated - easily if splines are worn out on outside diameter - fire in the bearing box would suddenly heat up the external surface of the shaft which would thermally increase diameter enough to splines get free - no need for Oldham razor here
does it make sense?
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WojtekSz
Of course sensible. This is the very mechanism by which EASA and FAA (by reference) alerted the operators would (could likely) cause catastrophe. The Splines serve at an intermediate joint. By definition this joint has clearances, else it would not allow rotation. Excessive wear of the Splines, detailed minutely by the regulator (via Rolls), allow distress at the coupling. The loss of radial commitment due scrubbed splines is the mechanism of failure. But the wear is caused by something. No sane team would field a system of extreme importance that had disqualifying levels of failure at an interval of 400 cycles since new. Yet this is exactly what was encountered by dozens of supplied powerplants to Airbus.
The IP aft shaft and fore shaft create a perfect environment for damage through vibration of their Splines. Any vibration here, at the Thrust Bearings, in close proximity to the HP shaft and LP shaft is amplified by the joint itself, with elements of whip, and bind. If this is the case, wear would be rapid, and progressively worse through the passage of time. The more the wear, the faster it wears. At the end of the sequence, the Splines are 'immune' from a 400 cycle inspection. It would seem to be more prudent to lessen the interval for borescope as the engine's life exceeds its first inspection limit at shop visit. Perhaps it was not a misprint that the "C" Mod was to have its first borescope at 200 cycles, then only 100 after that. So, 300 cycles and then what?? The "D" ?? It cannot happen that way, it is an admission that this engine is being designed on the "fly", with passengers aboard.
The Roller bearings at the end of the IP shaft end up being the area of least expression of wear, their purpose is radial resistance to stress. It is in this dimension that the failure mode at the Drive Arm presents, hence less likelihood for failure here. The Roller bearings run in a smoothe channel, their axial movement appears to be snubbed by their cage. It isn't farfetched to think that since the Axial drift is snubbed at the Ball bearings, no provision to stop the rollers from drifting was supplied. If the vibration at the LP and IP Shaft area is the problem, the Ball Bearings need to resist not only thrust, but radial and also divergent (chaotic) stress. This is obviously of concern. Instead of a conforming stress to the bearings as designed, each ball is subjected to changing stressors, independently of the others. Wear becomes random and irregular, hastening by a great deal the failure of the bearing itself.
Of course sensible. This is the very mechanism by which EASA and FAA (by reference) alerted the operators would (could likely) cause catastrophe. The Splines serve at an intermediate joint. By definition this joint has clearances, else it would not allow rotation. Excessive wear of the Splines, detailed minutely by the regulator (via Rolls), allow distress at the coupling. The loss of radial commitment due scrubbed splines is the mechanism of failure. But the wear is caused by something. No sane team would field a system of extreme importance that had disqualifying levels of failure at an interval of 400 cycles since new. Yet this is exactly what was encountered by dozens of supplied powerplants to Airbus.
The IP aft shaft and fore shaft create a perfect environment for damage through vibration of their Splines. Any vibration here, at the Thrust Bearings, in close proximity to the HP shaft and LP shaft is amplified by the joint itself, with elements of whip, and bind. If this is the case, wear would be rapid, and progressively worse through the passage of time. The more the wear, the faster it wears. At the end of the sequence, the Splines are 'immune' from a 400 cycle inspection. It would seem to be more prudent to lessen the interval for borescope as the engine's life exceeds its first inspection limit at shop visit. Perhaps it was not a misprint that the "C" Mod was to have its first borescope at 200 cycles, then only 100 after that. So, 300 cycles and then what?? The "D" ?? It cannot happen that way, it is an admission that this engine is being designed on the "fly", with passengers aboard.
The Roller bearings at the end of the IP shaft end up being the area of least expression of wear, their purpose is radial resistance to stress. It is in this dimension that the failure mode at the Drive Arm presents, hence less likelihood for failure here. The Roller bearings run in a smoothe channel, their axial movement appears to be snubbed by their cage. It isn't farfetched to think that since the Axial drift is snubbed at the Ball bearings, no provision to stop the rollers from drifting was supplied. If the vibration at the LP and IP Shaft area is the problem, the Ball Bearings need to resist not only thrust, but radial and also divergent (chaotic) stress. This is obviously of concern. Instead of a conforming stress to the bearings as designed, each ball is subjected to changing stressors, independently of the others. Wear becomes random and irregular, hastening by a great deal the failure of the bearing itself.
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Trent 800 >> Trent 900
The ongoing discussion about rules and regulations applied or questioned by the one or the other member of this circle are, what I would like to call an additional battlefield to take care off. I admit that my imagination stretches far enough to understand the expressed uncomfortable feelings about institutions, operating like state administrations, but responsible for so sensitive items like certification of aircraft engines. However, to be honest, one must concede that no one within these official bodies is intentionally wrong doing. Thought that needed to be said ones at a time.
Since Bolty McBolt brought up the comparison of Trent 800 and Trent 900 engines, this has drawn my special interest. I looked for a way to compare the engines as far as possible visually. That worked by using those RR issued brochures of the Trent 800 and 900 engines cutaways.
Provided RR has not set up these two pictures at different scales and keeping in mind the relative non precise method of measuring parts on a 26 " screen I found these differences between the two engines.
All length measurements show greater values at the T 800 for IPC, HPC, combustion chamber, etc. than on the T 900. The more it surprises me that the distance between the ball bearing Nr. 1 and Nr. 3 and especially Nr. 2 and Nr. 3 are shorter than those found in the T 900.
In connection with these findings a question to the engineers:
Is the tendency to flutter of a longer rotating cylindrical body - HPC-module - compared to a shorter, more compact desighn to be expected on a lower level ? With other words, could one expect to have a longer cylindrical body accelerated to comparable rotating speeds to run smoother and with lesser vibrations ??
What influence- if at all - does that greater distance between bearing Nr.2 and Nr. 3 have on the stiffness of the supporting structure between these two important bearings ??
What also is very obvious in that comparison of engines is the fact that the construction of the diaphragm / plenum chamber in front of the IPT disk is completely different, as is the desighn of the bearing chamber. Also there is no sealing diaphragm between the rear of the IPT disk and the plenum inside the LPT.
So, as Bolty McBolt has mentioned, why in gods name was that T 900 developed and used on the A 380, having a well desighned, functioning, more powerful and line proven engine in the inventory ??
Since Bolty McBolt brought up the comparison of Trent 800 and Trent 900 engines, this has drawn my special interest. I looked for a way to compare the engines as far as possible visually. That worked by using those RR issued brochures of the Trent 800 and 900 engines cutaways.
Provided RR has not set up these two pictures at different scales and keeping in mind the relative non precise method of measuring parts on a 26 " screen I found these differences between the two engines.
All length measurements show greater values at the T 800 for IPC, HPC, combustion chamber, etc. than on the T 900. The more it surprises me that the distance between the ball bearing Nr. 1 and Nr. 3 and especially Nr. 2 and Nr. 3 are shorter than those found in the T 900.
In connection with these findings a question to the engineers:
Is the tendency to flutter of a longer rotating cylindrical body - HPC-module - compared to a shorter, more compact desighn to be expected on a lower level ? With other words, could one expect to have a longer cylindrical body accelerated to comparable rotating speeds to run smoother and with lesser vibrations ??
What influence- if at all - does that greater distance between bearing Nr.2 and Nr. 3 have on the stiffness of the supporting structure between these two important bearings ??
What also is very obvious in that comparison of engines is the fact that the construction of the diaphragm / plenum chamber in front of the IPT disk is completely different, as is the desighn of the bearing chamber. Also there is no sealing diaphragm between the rear of the IPT disk and the plenum inside the LPT.
So, as Bolty McBolt has mentioned, why in gods name was that T 900 developed and used on the A 380, having a well desighned, functioning, more powerful and line proven engine in the inventory ??
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Handbook of case histories in failure analysis
Handbook of case histories in ... - Google Ksi??ki @ transportation components pp.17
provides and intersting example of excessive spline wear in Mirage III flown by RAAF - due to fretting wear. Very instructive pictures. Most probable cause: incorrect machining error
does it look familiar to incorrect machining of the stub pipe?
source and more info at : Fretting Wear in Lubricated Systems - most important points:
Handbook of case histories in ... - Google Ksi??ki @ transportation components pp.17
provides and intersting example of excessive spline wear in Mirage III flown by RAAF - due to fretting wear. Very instructive pictures. Most probable cause: incorrect machining error
does it look familiar to incorrect machining of the stub pipe?
Fretting wear is surface damage that occurs between two contacting surfaces experiencing cyclic motion (oscillatory tangential displacement) of small amplitude. At the contact areas, lubricant is squeezed out, resulting in metal-to-metal contact. Because the low amplitude motion does not permit the contact area to be relubricated, serious localized wear can occur. This type of wear further promotes two-body abrasion, adhesion and/or fretting fatigue (a form of surface fatigue) wear.
- increasing load or unit pressures tend to generate higher wear rates
- Fretting seems to progress more rapidly in friction couples that have smooth surface finishes and close fits.
Changing the subject a little, I thought that turbine blade root cross sectional areas were sized so as to fail in tension in the event of an overspeed. Thus hopefully limiting the extent of overspeed
A common blade attachment max stress level at 100% operating RPM in tension gives a 50% margin in overspeed. Tensile margins are nice when one considers their interaction with vibratory stress levels in a spinning machine (Goodman Diagram) but if you were to design every disk with something greater than the blade margin you would have an extremely heavy engine.
Then one has to consider the mass of the blade being released in a fused overspeed, and whether its practical to design containment for that event. In the end many things are considered together in protecting against overspeeds with the majority of the consideration being placed on limiting the speed the machine can get without being uncontained.
By-the-way, it's more likely that the stretch in the disk will open up the fir tree and release the whole blade before the attachment would fail (common in a disk over heat event)
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Annex14
Can you give me the http: for the Trent 800 RR brochure? I would like to see it.
Thanks,
Turbine D
That worked by using those RR issued brochures of the Trent 800 and 900 engines cutaways.
Thanks,
Turbine D
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lomapaeso
Thanks for your insight here. In fact, you can see this opening up in the ASTB Figure 14 of the recovered disc section where the couple of blade dovetails remained in place for whatever reason.
By-the-way, it's more likely that the stretch in the disk will open up the fir tree and release the whole blade before the attachment would fail (common in a disk over heat event)
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Derg:
thanks
i have posted the link to both books to propose an explanation on how the shaft's splines have gone away as this is the problem RR has to solve. And this may in fact also include some clever redesign work to reduce vibrations, possibly even using some ingenious damping techniques or just making the splines much more durable if reducing vibrations prove to be difficult.
The scavenge oil tube to me is a clear example of extremely poor machining and louse quality control - completely out of the way it is presented in the BBC program on building RR's engines YouTube - Rolls-Royce, How To Build A Jumbo Jet Engine -HQ- (Part 1/4)
it is a MUST see it to learn how much science+effort goes into the engine. Some really interesting things are shown there - i would have written 'suggested reading' but it seems more like 'suggested watching' ?
thanks
i have posted the link to both books to propose an explanation on how the shaft's splines have gone away as this is the problem RR has to solve. And this may in fact also include some clever redesign work to reduce vibrations, possibly even using some ingenious damping techniques or just making the splines much more durable if reducing vibrations prove to be difficult.
The scavenge oil tube to me is a clear example of extremely poor machining and louse quality control - completely out of the way it is presented in the BBC program on building RR's engines YouTube - Rolls-Royce, How To Build A Jumbo Jet Engine -HQ- (Part 1/4)
it is a MUST see it to learn how much science+effort goes into the engine. Some really interesting things are shown there - i would have written 'suggested reading' but it seems more like 'suggested watching' ?
Last edited by WojtekSz; 9th Jan 2011 at 14:57. Reason: spelling + explanation why one should take time to watch the program
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I think the scavenge tube is fed by a tray, or gallery, responsible for collecting hot Oil at the 'bottom' of the bearing case. I think also the challenge for Rolls is to detune the Thrust case from the LP shaft, keeping in mind that Thrust is borne in other areas besides the Ball Bearings. There are struts in the IP case that connect further forward, assuming a great deal of forward push from the engine.
De-Tuning I think will prove insufficient to correct the problem in the 900. To isolate massive vibratory impetus would more than likely involve strengthening the Shafts by adding metal. Inside Diameter? Outside? Both? This motor is already at maximum relative to clearances, weight, and power. If all it meant was adding weight, easy peasy. There are dimensions that actively resist any solution by addition. These dimensions likewise prevent subtracting structure without losing Thrust. Losing Thrust at 72klbs prevents puffing out the rest of the 80k that was sold, and paid for.
Least possible of all is to change the architecture. The architecture was modified already, and away from a proven model. Go Back?? As Woj points out: Back there lies the 800.
De-Tuning I think will prove insufficient to correct the problem in the 900. To isolate massive vibratory impetus would more than likely involve strengthening the Shafts by adding metal. Inside Diameter? Outside? Both? This motor is already at maximum relative to clearances, weight, and power. If all it meant was adding weight, easy peasy. There are dimensions that actively resist any solution by addition. These dimensions likewise prevent subtracting structure without losing Thrust. Losing Thrust at 72klbs prevents puffing out the rest of the 80k that was sold, and paid for.
Least possible of all is to change the architecture. The architecture was modified already, and away from a proven model. Go Back?? As Woj points out: Back there lies the 800.
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bearfoil
the strange thing with vibrations is that sometimes you can get better results by getting the item actually lighter (remember the famous story of Mr Citroen?). The trick is to get away from certain frequency and you can move up or down in frequency by getting the part stiffer or more flexible, lighter or heavier, or both 
900 has different proportions to 800 so the internal structure frequencies has changed and solutions from 800 might not fit the new engine. A new equilibrium has to be searched for.
To isolate massive vibratory impetus would more than likely involve strengthening the Shafts by adding metal. Inside Diameter? Outside? Both?
900 has different proportions to 800 so the internal structure frequencies has changed and solutions from 800 might not fit the new engine. A new equilibrium has to be searched for.
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WojtekSz
Thanks for your YouTube post, it was enlightening. I would encourage everyone to look at the Part 2 of this series:
YouTube - How to Build A Jumbo Jet Engine - 2/4 (Full Version)
About half way through, the process used to make the turbine blades is shown in good detail. Both the HPT & IPT blades are made this way (single crystal) with the IPT blade being solid, non-air-cooled. Also, note the machining section. After I looked at this:
35Year Pilot
I take back the idea the blades were pushed out of the dovetail slots. lomapaseo is correct, the disc stretched, releasing most of the blade dovetails from the corresponding disc slots. Also, the blades are shrouded at the tip and are interlocked by means of the z-form shrouds. This means that all the blades probably fractured near the platform upon contact with the LPT nozzle inner band ring. The machining tolerances of the dovetail forms are so tight, they couldn't be pushed out of the disc slots, unless the IPT rotor blades all came out uniformly in mass because of the shroud interlocks, an unlikely scenario.
DERG
I am not a RR guy so the Trent is a slightly different animal from what I am use to seeing as far as the details go. But, basic design principles apply regardless of manufacturer, RR, P&W, GE or EA.
bearfoil & WojtekSz
I am going to give you my thoughts on the Trent 800 vs Trent 900 and IMO, what I might think of the Trent 900 design in a new post.
Thanks for your YouTube post, it was enlightening. I would encourage everyone to look at the Part 2 of this series:
YouTube - How to Build A Jumbo Jet Engine - 2/4 (Full Version)
About half way through, the process used to make the turbine blades is shown in good detail. Both the HPT & IPT blades are made this way (single crystal) with the IPT blade being solid, non-air-cooled. Also, note the machining section. After I looked at this:
35Year Pilot
I take back the idea the blades were pushed out of the dovetail slots. lomapaseo is correct, the disc stretched, releasing most of the blade dovetails from the corresponding disc slots. Also, the blades are shrouded at the tip and are interlocked by means of the z-form shrouds. This means that all the blades probably fractured near the platform upon contact with the LPT nozzle inner band ring. The machining tolerances of the dovetail forms are so tight, they couldn't be pushed out of the disc slots, unless the IPT rotor blades all came out uniformly in mass because of the shroud interlocks, an unlikely scenario.
DERG
I am not a RR guy so the Trent is a slightly different animal from what I am use to seeing as far as the details go. But, basic design principles apply regardless of manufacturer, RR, P&W, GE or EA.
bearfoil & WojtekSz
I am going to give you my thoughts on the Trent 800 vs Trent 900 and IMO, what I might think of the Trent 900 design in a new post.
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mike-wsm Turbine D
mike-wsm Thanks for posting the link. I am just back from an event and would have to start the answer to Turbine Dīs request.
Hope it works as it did here.
Hope it works as it did here.
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Turbine D
I have also this
Large aircraft engines - Rolls-Royce
May be interesting since it gives access to all the biggies.
Large aircraft engines - Rolls-Royce
May be interesting since it gives access to all the biggies.
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DERG
I agree with you on the ever increasing oil temperatures. The tent is being moved closer to the edge of the cliff.
As things are moved closer together as is happening in the newer engine, heat dispersion is a problem, especially when a hot engine is shut down and the soak temperature rises higher than the maximum operating temperature of the oil. IMO, coking is still a problem and major concern even with the newer oils.
Oil temperatures of 196C max are not acceptable in my view, but you must remember the Trents have three rotors and therefore more heat to disperse than GE products. Another issue that has been over looked is th the fact that the coking (tar like carbon) deposits are flammable.
As things are moved closer together as is happening in the newer engine, heat dispersion is a problem, especially when a hot engine is shut down and the soak temperature rises higher than the maximum operating temperature of the oil. IMO, coking is still a problem and major concern even with the newer oils.
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Fellows......(Fellettes??)
It's been a real slice. Them videos are telling: "This missing assembly could cost Money, so the situation is critical.." All that marvelous effort by folks who are brilliant, and actually care about their work, who are cut off at the knees by the greed and borderline criminality at the back end.
The machinery is first rate, when given an actual chance by the accountants and marketing. None better. The TRENT has become a fiasco, instead of the Beautiful expression of the Art that it actually is. It gives me goosebumps it is so exquisite.
Underneath the grimy newspaper it is wrapped in by cost cutters, and Marketing knuckleheads, lives a true masterpiece, thought I'd get that straight........
Changing Frequencies now, JB is far more fun, but I'll keep this one in the box.
Don't take no wooden nickels.
It's been a real slice. Them videos are telling: "This missing assembly could cost Money, so the situation is critical.." All that marvelous effort by folks who are brilliant, and actually care about their work, who are cut off at the knees by the greed and borderline criminality at the back end.
The machinery is first rate, when given an actual chance by the accountants and marketing. None better. The TRENT has become a fiasco, instead of the Beautiful expression of the Art that it actually is. It gives me goosebumps it is so exquisite.
Underneath the grimy newspaper it is wrapped in by cost cutters, and Marketing knuckleheads, lives a true masterpiece, thought I'd get that straight........
Changing Frequencies now, JB is far more fun, but I'll keep this one in the box.
Don't take no wooden nickels.