Qantas A380 uncontained #2 engine failure
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Flight Idle
Same. Stay and post as you will, The Balance disc gave me an insight into the LP Fan couple. Those who know, aren't afraid to be courteous.
Copying a Textbook? brilliant.
WAIT !! "..Also Rotor axial thrust tends to be cancelled by the Compressor......"
Eureka! Chapter Five, Page 14 of Ventus' Text, Are we done, here?? Is this our "Tug O' War", Barit??
I know, I know........General Electric.
Same. Stay and post as you will, The Balance disc gave me an insight into the LP Fan couple. Those who know, aren't afraid to be courteous.
Copying a Textbook? brilliant.
WAIT !! "..Also Rotor axial thrust tends to be cancelled by the Compressor......"
Eureka! Chapter Five, Page 14 of Ventus' Text, Are we done, here?? Is this our "Tug O' War", Barit??
I know, I know........General Electric.
Last edited by bearfoil; 1st Dec 2010 at 21:33.
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Flight_Idle - Excellent question. That should have been my starting point.
ventus45 - Thank you for finding this great survey of the thrust balance problem. The process offered is on the money.
I find the sentence
to be the crux of the problem, in that a 1.0 psi change on a large piston area can "make or break" the success of a design. Often you don't have a good answer until you get live test data.
BTW - I too think this whole thrust bearing issue belongs in Tech Log, not R&N. There is an abandoned thread there on this A380/Trent event.
ventus45 - Thank you for finding this great survey of the thrust balance problem. The process offered is on the money.
I find the sentence
The accuracy of predicting these cavity pressures is a critical factor in predicting bearing loads...
BTW - I too think this whole thrust bearing issue belongs in Tech Log, not R&N. There is an abandoned thread there on this A380/Trent event.
ATSB Update
Update 1.00pm - 2 December 2010
Manufacturing problem potential factor in QF32 engine failure
The ATSB has issued a safety recommendation about potential engine problems in some Airbus A380 aircraft.
The safety recommendation identifies a potential manufacturing defect with an oil tube connection to the high-pressure (HP)/intermediate-pressure (IP) bearing structure of the Trent 900 engine installed in some A380 aircraft.
The problem relates to the potential for misaligned oil pipe counter-boring, which could lead to fatigue cracking, oil leakage and potential engine failure from an oil fire within the HP/IP bearing buffer space.
In response to the recommendation Rolls Royce, affected airlines and safety regulators are taking action to ensure the continued safe operation of A380 aircraft. The action involves the close inspection of affected engines and the removal from service of any engine which displays the suspected counter-boring problem.
The ATSB will hold a media briefing tomorrow (Friday 3 December 2010) at 10.30am to accompany the release of its preliminary factual investigation report into the QF32 occurrence. ATSB Chief Commissioner Mr Martin Dolan will present the known facts gathered from the investigation and highlight the key safety issues that have resulted from the investigation to date.
The full safety recommendation is available via the ATSB website at AO-2010-089.
Manufacturing problem potential factor in QF32 engine failure
The ATSB has issued a safety recommendation about potential engine problems in some Airbus A380 aircraft.
The safety recommendation identifies a potential manufacturing defect with an oil tube connection to the high-pressure (HP)/intermediate-pressure (IP) bearing structure of the Trent 900 engine installed in some A380 aircraft.
The problem relates to the potential for misaligned oil pipe counter-boring, which could lead to fatigue cracking, oil leakage and potential engine failure from an oil fire within the HP/IP bearing buffer space.
In response to the recommendation Rolls Royce, affected airlines and safety regulators are taking action to ensure the continued safe operation of A380 aircraft. The action involves the close inspection of affected engines and the removal from service of any engine which displays the suspected counter-boring problem.
The ATSB will hold a media briefing tomorrow (Friday 3 December 2010) at 10.30am to accompany the release of its preliminary factual investigation report into the QF32 occurrence. ATSB Chief Commissioner Mr Martin Dolan will present the known facts gathered from the investigation and highlight the key safety issues that have resulted from the investigation to date.
The full safety recommendation is available via the ATSB website at AO-2010-089.
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The information at "The full safety recommendation is available via the ATSB website at AO-2010-089" makes interesting reading, I anticipate the interim report being issued tomorrow will be equally interesting too.
Recommendation AO-2010-089-SR-012
" Examination of components removed from the failed engine at the Rolls-Royce plc facility in Derby, United Kingdom, have identified the presence of fatigue cracking within a stub pipe that feeds oil into the High Pressure (HP) / Intermediate Pressure (IP) bearing structure. While the analysis of the engine failure is ongoing, it has been identified that the leakage of oil into the HP/IP bearing structure buffer space (and a subsequent oil fire within that area) was central to the engine failure and IP turbine disc liberation event. Further examination of the cracked area has identified the axial misalignment of an area of counter‑boring within the inner diameter of the stub pipe; the misalignment having produced a localised thinning of the pipe wall on one side. The area of fatigue cracking was associated with the area of pipe wall thinning.
Critical Safety Issue
Misaligned stub pipe counter-boring is understood to be related to the manufacturing process. This condition could lead to an elevated risk of fatigue crack initiation and growth, oil leakage and potential catastrophic engine failure from a resulting oil fire.
Recommendation
The Australian Transport Safety Bureau recommends that Rolls-Royce plc address the safety issue and take actions necessary to ensure the safety of flight operations in transport aircraft equipped with Rolls-Royce plc Trent 900 series engines."
" Examination of components removed from the failed engine at the Rolls-Royce plc facility in Derby, United Kingdom, have identified the presence of fatigue cracking within a stub pipe that feeds oil into the High Pressure (HP) / Intermediate Pressure (IP) bearing structure. While the analysis of the engine failure is ongoing, it has been identified that the leakage of oil into the HP/IP bearing structure buffer space (and a subsequent oil fire within that area) was central to the engine failure and IP turbine disc liberation event. Further examination of the cracked area has identified the axial misalignment of an area of counter‑boring within the inner diameter of the stub pipe; the misalignment having produced a localised thinning of the pipe wall on one side. The area of fatigue cracking was associated with the area of pipe wall thinning.
Critical Safety Issue
Misaligned stub pipe counter-boring is understood to be related to the manufacturing process. This condition could lead to an elevated risk of fatigue crack initiation and growth, oil leakage and potential catastrophic engine failure from a resulting oil fire.
Recommendation
The Australian Transport Safety Bureau recommends that Rolls-Royce plc address the safety issue and take actions necessary to ensure the safety of flight operations in transport aircraft equipped with Rolls-Royce plc Trent 900 series engines."
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Now breaking news on BBC - 'Airbus A380 engine has serious manufacturing fault':
BBC News - Airbus A380 engine has serious manufacturing fault
Misaligned component, thinned wall of oil pipe etc.
BBC News - Airbus A380 engine has serious manufacturing fault
Misaligned component, thinned wall of oil pipe etc.
Last edited by SummerLightning; 2nd Dec 2010 at 03:49. Reason: Typo
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Investigation: AO-2010-089 - Inflight engine failure - Qantas, Airbus A380, VH-OQA, overhead Batam Island, Indonesia, 4 November 2010
Recent developments
Recent developments
Recent examination of components removed from the failed engine at the Rolls-Royce plc facility in Derby, United Kingdom, have identified the presence of fatigue cracking within a stub pipe that feeds oil into the High Pressure (HP) / Intermediate Pressure (IP) bearing structure. While the analysis of the engine failure is ongoing, it has been identified that the leakage of oil into the HP/IP bearing structure buffer space (and a subsequent oil fire within that area) was central to the engine failure and IP turbine disc liberation event.
Further examination of the cracked area has identified the axial misalignment of an area of counter‑boring within the inner diameter of the stub pipe; the misalignment having produced a localised thinning of the pipe wall on one side. The area of fatigue cracking was associated with the area of pipe wall thinning (Figure 1).
Further examination of the cracked area has identified the axial misalignment of an area of counter‑boring within the inner diameter of the stub pipe; the misalignment having produced a localised thinning of the pipe wall on one side. The area of fatigue cracking was associated with the area of pipe wall thinning (Figure 1).
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It will be interesting to read the preliminary report due tomorrow and its findings especially those relevant to the "cascade of failures" that occurred after the turbine disk liberation event.
One thing is for sure, the human systems up on the flight deck didn't fail in this emergency and kudos to all concerned in bringing this emergency to a safe and successful conclusion.
Qantas A380 Investigation Goes Beyond Engines | AVIATION WEEK
One thing is for sure, the human systems up on the flight deck didn't fail in this emergency and kudos to all concerned in bringing this emergency to a safe and successful conclusion.
Qantas A380 Investigation Goes Beyond Engines | AVIATION WEEK
As investigators try to establish the sequence of events that led to the Trent’s failure, they are also probing the A380 hydraulic and engine control systems’ apparent vulnerabilities to damage. And Rolls has to address concerns raised by senior industry executives over its safety philosophy, as neither the Trent 900 nor 1000 have automatic or mechanical systems to shut off fuel supply in an oil-fire-related ITP failure.
Under scrutiny is why the engines continued to operate once the failures started, amplifying the destruction. Rolls designed the engine to run down intact after a turbine failure, yet it did not.
From an airframe perspective, the failure of the A380’s standard and emergency engine shutdown systems, as well as the apparent loss of one of the two hydraulic systems, may also force system redesign.
Another aircraft system question stems from the fact the No. 1 engine could not be shut down. The high-pressure fuel shutoff valve, normally controlled by the full authority digital engine control on the ground during engine start, is inhibited when the engine is running above idle or is in flight. “Fuel off” is normally selected to shut down the engine in this condition by activating a master lever to the “OFF” position in the flight deck. An emergency shutdown system, which also appears to have failed, consists of low-pressure fuel shutoff valves commanded by pushing the engine fire switch.
The A380’s control surface actuators are powered by two independent hydraulic systems (Green and Yellow), with most surfaces having backup electrical power from one of two independent systems. Images from the AF32 incident show evidence of certain inoperative control surfaces, pointing to a failure of the Green system. According to industry sources, debris from the uncontained failure punctured at least one fuel tank and may also have caused problems with the fuel system controls, which became partially inoperative and prevented some cross-feed functions.
Under scrutiny is why the engines continued to operate once the failures started, amplifying the destruction. Rolls designed the engine to run down intact after a turbine failure, yet it did not.
From an airframe perspective, the failure of the A380’s standard and emergency engine shutdown systems, as well as the apparent loss of one of the two hydraulic systems, may also force system redesign.
Another aircraft system question stems from the fact the No. 1 engine could not be shut down. The high-pressure fuel shutoff valve, normally controlled by the full authority digital engine control on the ground during engine start, is inhibited when the engine is running above idle or is in flight. “Fuel off” is normally selected to shut down the engine in this condition by activating a master lever to the “OFF” position in the flight deck. An emergency shutdown system, which also appears to have failed, consists of low-pressure fuel shutoff valves commanded by pushing the engine fire switch.
The A380’s control surface actuators are powered by two independent hydraulic systems (Green and Yellow), with most surfaces having backup electrical power from one of two independent systems. Images from the AF32 incident show evidence of certain inoperative control surfaces, pointing to a failure of the Green system. According to industry sources, debris from the uncontained failure punctured at least one fuel tank and may also have caused problems with the fuel system controls, which became partially inoperative and prevented some cross-feed functions.
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robdean
From reading the local press, it sounds like a new problem. See this item.
This announcement is certainly completely consistent with RR saying that a fault had been found with a single component.
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It would depend on the direction of flow of oil just what this part compromised. The AD's mention "blocking vanes", theoretically by coking and Carbon. If (a scavenge) and this tube ate its own bits, a plug with consequent oversupply may have passed the seals. Either way, something has to have happened to the seals at the bearings to have caused ignition, imo. There is more to this than a broken ended tube I think.
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The situation of problems in a newly designed engine essential for an newly introduced airframe has occurred before. We have to go back about 40 years. It is the 747 and its PW engine. The details are in "Wide-Body ... The Triumph of the 747", by Clive Irving, publisher Morrow, 1992. You'd want to look in Ch 17, "The Ink and Iced Water Men." [doubtless a reference to bean counters].
As here, the problem arose during a severe economic downturn. Differently, it occurred on the eve of scheduled delivery of AC to first customer. The new engines were very late, and the idea was to bolt them on, certify, and go.
It happened that in cruise even careful movement of the throttles would cause surging in the turbines. Well, the AC vibrated "as if kicked by a buffalo" [or was it a whole herd of buffalo?] at each surge. The high execs of PW and B met on the FD to experience these reports first-hand. Afterward, they had no doubt this had to be fixed before delivery of the AC.
Well, it was obscure why this was happening. A PW engineer had a thought and mentioned it to an engineer at B. His problem was that PW had no way to prove this was the cause. The next day the B engineer suddenly recalled that B had very substantially greater computing power at hand than PW, and decided to do the analysis. The problem was thought by the PW engineer to lie in an airframe/engine interaction.
The engine of course distorted under the stress of high-angle of attack take-offs in the computer simulation. This stress was induced by the pylon attachments. But what surprised everyone was that these stresses were high enough to distort the case past the yield point of the metal, leaving the distortion permanent [and perhaps increasing with number of high-angle take-offs (my comment)]. This disturbed the intended relationship of rotor and stator blades.
You see the fix of 40 years ago in the drawing posted here of the Trent 800. It is the Y-link, or yoked support (forward shown), used to distribute the pylon loads onto the casing, to a greater degree.
It may be that the cracked oil line in the 900 is the immediate cause this time. But light lines attached to heavy objects that vibrate crack all the time, even when they aren't bored off-center (my comment, from my limited personal experience, as the saying goes).
To my view, the excessive spline wear is a far more significant indication of a possible serious problem, one that may underlie other indications of a problem. Correct me if I am wrong, but did I read an AD on the spline wear that permitted the splines to be continued in service past having fully half their thickness worn away?
Sometimes an inner spline is made undersized, such that failure of parallel shafts to maintain the same exact centerline of rotation can be accommodated--just a ref to machinery in general. In such a case, the spline teeth can be given an involute profile (like a spur gear), because uniform motion is still transmitted at all center distances. Within reason, of course, and we'd be talking about very small offsets. Now just like gears, such involute splines would require lubrication.
If the spline wear reached the point permitted by the AD, there wouldn't be any involute profile left (if used). I think offset shafts (if such were the case) would then vibrate to a certain extent. [There are special couplings of a "geared" nature, which will allow for angular shaft deflection at the same time as offsets--it is a recognized problem; but such a device would hardly fit in the jet engine diagrammed here].
I'm going to stop here. I had read parts of that book but never that chapter. But I was already thinking along the same lines, and knew that any similar event would be late in the development--and opened that book right to it. The only thing that hadn't already occurred to me was that the engine casing might be permanently distorted from the take-off loads.
Think again about Qantas limiting take-off loading to three-quarter power. That cancels the LAX route. There seems to be a fair amount of concern about this problem.
OE
As here, the problem arose during a severe economic downturn. Differently, it occurred on the eve of scheduled delivery of AC to first customer. The new engines were very late, and the idea was to bolt them on, certify, and go.
It happened that in cruise even careful movement of the throttles would cause surging in the turbines. Well, the AC vibrated "as if kicked by a buffalo" [or was it a whole herd of buffalo?] at each surge. The high execs of PW and B met on the FD to experience these reports first-hand. Afterward, they had no doubt this had to be fixed before delivery of the AC.
Well, it was obscure why this was happening. A PW engineer had a thought and mentioned it to an engineer at B. His problem was that PW had no way to prove this was the cause. The next day the B engineer suddenly recalled that B had very substantially greater computing power at hand than PW, and decided to do the analysis. The problem was thought by the PW engineer to lie in an airframe/engine interaction.
The engine of course distorted under the stress of high-angle of attack take-offs in the computer simulation. This stress was induced by the pylon attachments. But what surprised everyone was that these stresses were high enough to distort the case past the yield point of the metal, leaving the distortion permanent [and perhaps increasing with number of high-angle take-offs (my comment)]. This disturbed the intended relationship of rotor and stator blades.
You see the fix of 40 years ago in the drawing posted here of the Trent 800. It is the Y-link, or yoked support (forward shown), used to distribute the pylon loads onto the casing, to a greater degree.
It may be that the cracked oil line in the 900 is the immediate cause this time. But light lines attached to heavy objects that vibrate crack all the time, even when they aren't bored off-center (my comment, from my limited personal experience, as the saying goes).
To my view, the excessive spline wear is a far more significant indication of a possible serious problem, one that may underlie other indications of a problem. Correct me if I am wrong, but did I read an AD on the spline wear that permitted the splines to be continued in service past having fully half their thickness worn away?
Sometimes an inner spline is made undersized, such that failure of parallel shafts to maintain the same exact centerline of rotation can be accommodated--just a ref to machinery in general. In such a case, the spline teeth can be given an involute profile (like a spur gear), because uniform motion is still transmitted at all center distances. Within reason, of course, and we'd be talking about very small offsets. Now just like gears, such involute splines would require lubrication.
If the spline wear reached the point permitted by the AD, there wouldn't be any involute profile left (if used). I think offset shafts (if such were the case) would then vibrate to a certain extent. [There are special couplings of a "geared" nature, which will allow for angular shaft deflection at the same time as offsets--it is a recognized problem; but such a device would hardly fit in the jet engine diagrammed here].
I'm going to stop here. I had read parts of that book but never that chapter. But I was already thinking along the same lines, and knew that any similar event would be late in the development--and opened that book right to it. The only thing that hadn't already occurred to me was that the engine casing might be permanently distorted from the take-off loads.
Think again about Qantas limiting take-off loading to three-quarter power. That cancels the LAX route. There seems to be a fair amount of concern about this problem.
OE
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Just a little change in direction for a question: How, when, where is the aricraft being repaired to the physical damage, as seen done to the wing and other places? Would this mean a wing replacement??? It must make for an interesting repair if not through this continuous decreasing thickness of a surface wing skin. Would the aircraft be ferried back to Toulouse after a certain amount of work is completed to ferry. Will they ferry it with 3 engines anywhere???
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Now that a problem has been discovered, I am sure the manufacturers will fix it and the A380 will go on to fly happily for years!
This type of fodder only serves to keep the press (and us) busy. I am sure we will all look back at this in a few years and wonder what all the furore was about.
This type of fodder only serves to keep the press (and us) busy. I am sure we will all look back at this in a few years and wonder what all the furore was about.
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The defective piece, to my admittedly untrained eye, seems spectacularly out of tolerance. Can any engineers shed any light on this? How could it pass even a cursory visual inspection at the manufacturing stage?
What you can see in the picture is the fractured pipe. The defect may not have been visible to the naked eye, in the component, in its complete state. Nevertheless, I would have thought that some form of NDT or borescope examination would have been used.