Qantas A380 uncontained #2 engine failure
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bearfoil:
Most likely, in the oil return (scavenge) from one of the bearing "boxes". Normally I'd expect this to be from the HPT/IPT bearing area, but maybe not.
The oil temps are sensed where?
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From the Sydney Morning Herald site a short time ago:
A rumour broadcast that the Qantas A380 superjumbo that suffered a mid-air engine explosion last month had now been written-off due to structural damage and would be donated to a Singapore museum was "completely untrue", Qantas spokeswoman Olivia Wirth said yesterday.
"[The] aircraft is still in Singapore and will be repaired by Airbus before returning to the air."
A rumour broadcast that the Qantas A380 superjumbo that suffered a mid-air engine explosion last month had now been written-off due to structural damage and would be donated to a Singapore museum was "completely untrue", Qantas spokeswoman Olivia Wirth said yesterday.
"[The] aircraft is still in Singapore and will be repaired by Airbus before returning to the air."
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Remember - Qantas NEVER writes off aircraft, even if it costs more to repair them than they are worth - don't forget the "zero hull losses" boast!
Last edited by marchino61; 13th Dec 2010 at 07:48. Reason: improved wording
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Rolls Royce to report to Qantas this week: report | News | Business Spectator
RR to report to Qantas re preps for pacific flights re-start.
RR to report to Qantas re preps for pacific flights re-start.
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In my previous post regarding the sequence of events taking place on engine 2, I left out two reported and measured parameters:
1. EGT - EGT was normal, 825 degrees C, until the time of engine 2 thrust drop (0201.05) when it began to rise to nearly 950 degrees C at the time of the disc burst.
2. Vibration - According to the data in the ATSB report, vibrations from normal began to be recorded at ~02000.57, peaking at ~0201.01 and gradually falling off although never reaching normal levels. The problem is that the graph in the report uses very close colored ink (green) depicting N2 Vibs and N3 Vibs, only one spool was vibrating. I could't conclude positively which spool was vibrating.
The true location of the stub pipe which failed and all of the sensor locations remain a mystery to me.
lomapaseo quote:
One should not go too far in positing reasons for the parameter changes unless you undertsand and know the contoling parameters in the FADEC relative to N1, N2, N3, RPM,s Pressure and temperatures.
Friction between parts is insignificant. Blade tip clearances are the most significant and temperatures, pressures follow that more closely.
Seeing as how RR have already offered up a FADEDC logic as another temporary means of defense it seem plausible that they know what and why is going on.
In modern day twin spool high-bypass engines, the thrust of the engine is set by N1, fan speed. In this manner thrust is more accurately controlled because all the air intake is pumped by the fan. The core rotor only handles a portion of the airflow. Basic logic in the FADEC is set around this point of thrust control.
However, an assumption on my part would be that a three spool engine (Trent 900), uses N2 speed to control thrust. Am I correct in my assumption? If so, the FADEC logic would be set around this point of thrust control.
rottenray and barit1 makes good points on rotor speed sensing and electronic logic. For sure the IP rotor speed was declining (something was happening), but again we don't know where this parameter was being measured, compressor or turbine.
One other item that intrigues me has to do with the bearings and lubrication of the same. I don't have much knowledge of this but, in the case of ball bearings (thrust bearing), I am thinking more oil is required because of heat generation/heat extraction verses roller bearings. I am also thinking oil is supplied in a more generous manner rather than misting. But for roller bearings (radial loading only) the heating/cooling factors are present, but the supply of oil (quantity) is more sensitively supplied to prevent things such a skidding, etc. and a misting system might be more appropriate. With this thought in mind the oil delivery system depicted in the RR patent of a previous post looks more of a misting design. Recall the diagram was suggested as depicting a stub pipe. If this were to be true rather than hypothetical on my part, it might suggest better location potential within the engine of the failed stub pipe.
Turbine D
1. EGT - EGT was normal, 825 degrees C, until the time of engine 2 thrust drop (0201.05) when it began to rise to nearly 950 degrees C at the time of the disc burst.
2. Vibration - According to the data in the ATSB report, vibrations from normal began to be recorded at ~02000.57, peaking at ~0201.01 and gradually falling off although never reaching normal levels. The problem is that the graph in the report uses very close colored ink (green) depicting N2 Vibs and N3 Vibs, only one spool was vibrating. I could't conclude positively which spool was vibrating.
The true location of the stub pipe which failed and all of the sensor locations remain a mystery to me.
lomapaseo quote:
One should not go too far in positing reasons for the parameter changes unless you undertsand and know the contoling parameters in the FADEC relative to N1, N2, N3, RPM,s Pressure and temperatures.
Friction between parts is insignificant. Blade tip clearances are the most significant and temperatures, pressures follow that more closely.
Seeing as how RR have already offered up a FADEDC logic as another temporary means of defense it seem plausible that they know what and why is going on.
In modern day twin spool high-bypass engines, the thrust of the engine is set by N1, fan speed. In this manner thrust is more accurately controlled because all the air intake is pumped by the fan. The core rotor only handles a portion of the airflow. Basic logic in the FADEC is set around this point of thrust control.
However, an assumption on my part would be that a three spool engine (Trent 900), uses N2 speed to control thrust. Am I correct in my assumption? If so, the FADEC logic would be set around this point of thrust control.
rottenray and barit1 makes good points on rotor speed sensing and electronic logic. For sure the IP rotor speed was declining (something was happening), but again we don't know where this parameter was being measured, compressor or turbine.
One other item that intrigues me has to do with the bearings and lubrication of the same. I don't have much knowledge of this but, in the case of ball bearings (thrust bearing), I am thinking more oil is required because of heat generation/heat extraction verses roller bearings. I am also thinking oil is supplied in a more generous manner rather than misting. But for roller bearings (radial loading only) the heating/cooling factors are present, but the supply of oil (quantity) is more sensitively supplied to prevent things such a skidding, etc. and a misting system might be more appropriate. With this thought in mind the oil delivery system depicted in the RR patent of a previous post looks more of a misting design. Recall the diagram was suggested as depicting a stub pipe. If this were to be true rather than hypothetical on my part, it might suggest better location potential within the engine of the failed stub pipe.
Turbine D
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Turbine D
Hi. From Ferpe's #1647 diagram, he locates the #6, #7 roller's oil supply pipe, and barit1suggests that Oil Temps are sensed in the Scavenge "Tray" beneath the Stub.
If the sensor is in the scavenge (IPT/HPT) it would make sense as the bearings rotate opposite, and the critical temps may be located here. If it is 6,7 oil feed that failed, the temps would climb due to lack of cooling (Oil), and perhaps friction (contrary to lomapaseo's statement "Friction is unimportant"). Dry bearings here might have been the source of Vibration, if the rollers had started to degrade.
The possibility remains that the IPT may not have oversped, but left the Shaft due to vibration and Heat only. The '03 Turbine failure stopped short of blowing out the casing, but incurred a "Circumferential Fracture" around the Drive arm. An IPT bearing failure would cause Hellish out of balance at the Drive Arm/Shaft join.
hat tip
bear
Hi. From Ferpe's #1647 diagram, he locates the #6, #7 roller's oil supply pipe, and barit1suggests that Oil Temps are sensed in the Scavenge "Tray" beneath the Stub.
If the sensor is in the scavenge (IPT/HPT) it would make sense as the bearings rotate opposite, and the critical temps may be located here. If it is 6,7 oil feed that failed, the temps would climb due to lack of cooling (Oil), and perhaps friction (contrary to lomapaseo's statement "Friction is unimportant"). Dry bearings here might have been the source of Vibration, if the rollers had started to degrade.
The possibility remains that the IPT may not have oversped, but left the Shaft due to vibration and Heat only. The '03 Turbine failure stopped short of blowing out the casing, but incurred a "Circumferential Fracture" around the Drive arm. An IPT bearing failure would cause Hellish out of balance at the Drive Arm/Shaft join.
hat tip
bear
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I'll argue, based on the data record, that N2 is sensed at the front end of the IPC. That's a much less hostile environment for a sensor than is the hot section.
Since we've seen the rotors/bearings layout (probably from a training manual), does anyone have likewise for the lube system?
Since we've seen the rotors/bearings layout (probably from a training manual), does anyone have likewise for the lube system?
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Oil System
The Oil temperature is sensed by 2 sensors in the return line, just before the scavenge filter to the reservoir. (GenFam 6-25) So it appears to be averaging the temp of all the returned oil paths ...
N2 - 3 bearings. (GenFam p3-3)
N2 RPM - One phonic wheels with four speed probes. (GenFam 5-
9) I think the phonic wheel is well forward - so measures IPC, not IPT (for a failed shaft).
This should help the reasoning ....
N2 - 3 bearings. (GenFam p3-3)
N2 RPM - One phonic wheels with four speed probes. (GenFam 5-
9) I think the phonic wheel is well forward - so measures IPC, not IPT (for a failed shaft).
This should help the reasoning ....
Last edited by 35YearPilot; 14th Dec 2010 at 01:59.
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Another piece of the A380 Jigsaw - - - - other leaks ??
Secondary oil leak affecting Rolls-Royce Trent 900 engines
It seems that there are other "Leaks" that the complex Power plant Calculations may need to take account of . - - - ,Mea Maxima Culpa for my previous post and its badly aranged Link - - but I think that this may be relevant .
It seems that there are other "Leaks" that the complex Power plant Calculations may need to take account of . - - - ,Mea Maxima Culpa for my previous post and its badly aranged Link - - but I think that this may be relevant .
Last edited by borescope; 14th Dec 2010 at 02:53. Reason: Innacuracies
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Secondary oil leak affecting Rolls-Royce Trent 900 engines
It seems that there are other "Leaks" that the complex Power plant Calculations may need to take account of
It seems that there are other "Leaks" that the complex Power plant Calculations may need to take account of
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More news on this here.
Bearing compartment module behind secondary Trent 900 oil leak
Not so bad that the aircraft need be grounded though.
Bearing compartment module behind secondary Trent 900 oil leak
Not so bad that the aircraft need be grounded though.
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Trent 900 Turbine Disk Material
Someone asked about this way back.
<quote>
Micrograph no
729
Brief description
Ni-Superalloy, exposed microstructure
Keywords
nickel
Categories
Metal or alloy
System
Ni-X
Composition
Ni, Cr 14.4-15.2, Co 13-18, Mo 3.5-4.5, Al 3.0-3.3, Ti 4.2-4.8, Ta 2.5, Zr 0.05-0.07, C 0.05, B 0.01-0.03 (wt%) (Ni-Superalloy)
Standard codes
Reaction
Processing
Exposed at 800°C for 2 500 hours.
Applications
Discs are used for high pressure and intermediate pressure turbine discs in Trent 800/900 series gas turbine engines.
Sample preparation
Ground to 4000 Grade SiC paper and then polished at 6 mm 3 minutes, 1 mm 5 minutes, Colloidal silica 10 minutes.
Technique
Scanning electron microscopy (SEM) in backscattered electron imaging (BEI) mode
</quote>
<source>
DoITPoMS - Micrograph Library - Full Record
</source>
<quote>
Micrograph no
729
Brief description
Ni-Superalloy, exposed microstructure
Keywords
nickel
Categories
Metal or alloy
System
Ni-X
Composition
Ni, Cr 14.4-15.2, Co 13-18, Mo 3.5-4.5, Al 3.0-3.3, Ti 4.2-4.8, Ta 2.5, Zr 0.05-0.07, C 0.05, B 0.01-0.03 (wt%) (Ni-Superalloy)
Standard codes
Reaction
Processing
Exposed at 800°C for 2 500 hours.
Applications
Discs are used for high pressure and intermediate pressure turbine discs in Trent 800/900 series gas turbine engines.
Sample preparation
Ground to 4000 Grade SiC paper and then polished at 6 mm 3 minutes, 1 mm 5 minutes, Colloidal silica 10 minutes.
Technique
Scanning electron microscopy (SEM) in backscattered electron imaging (BEI) mode
</quote>
<source>
DoITPoMS - Micrograph Library - Full Record
</source>
Last edited by ventus45; 14th Dec 2010 at 10:44.
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The flight-deck interview is fascinating. Found the lack of paper reference interesting, also the fact that the performance tool would not work with the configuration handed to it in the first instance.
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35YearPilot
Thanks for the information on oil temperature and spool speed detection. Note the article below:
High thrust Trent 900s limited to 75 flight cycles: Qantas
P30, I assume, is the HP compressor delivery pressure to the combustor. It is still hard to say with certainty which support structure is questionable. Would it be the one holding the #4 and #5 bearings, both ball bearings (compressor areas), or the one holding the #6 and #7 bearings, both roller bearings (turbine areas)?
Another sensor location: The EGT temperature is sensed by a series of thermocouples in the Stage 1 LPT nozzle ring gas path. This comes from the Engine Type Certification Notice. Readings from these thermocouples went straight down at the disc burst point.
Turbine D
Thanks for the information on oil temperature and spool speed detection. Note the article below:
High thrust Trent 900s limited to 75 flight cycles: Qantas
P30, I assume, is the HP compressor delivery pressure to the combustor. It is still hard to say with certainty which support structure is questionable. Would it be the one holding the #4 and #5 bearings, both ball bearings (compressor areas), or the one holding the #6 and #7 bearings, both roller bearings (turbine areas)?
Another sensor location: The EGT temperature is sensed by a series of thermocouples in the Stage 1 LPT nozzle ring gas path. This comes from the Engine Type Certification Notice. Readings from these thermocouples went straight down at the disc burst point.
Turbine D
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Turbine D
Would the drop in Temp. have to do with High Pressure Energetic Gas evacuating the Casing, replaced with very erratic and perhaps even ambient Air? At some point, the Fire evidence of Brown streaks smearing the Cowling would indicate a flow disruption?? A very great loss of Pressure??
The FG report is frankly not newsworthy, other than recapping general Public Knowledge, IMO. It serves to dramatize the ongoing situation, and does not divulge new stuff??? I have taken note of RR's ongoing problems that frankly "skirt" the issues to hand. The software mod is a palliative. The Oil leaks are not well explained, the Release further continues to make murky the location of the oiling problem.
There are TWO HP/IP locales, and the reluctance of the manufacturer to get specific remains troubling. For those who are aware that there are TWO HP/IP "Support Structures" whose oiling trouble is left to the imagination, it is frustrating.
I think as always, an official "Non Explanation" will end up causing a great deal more harm to the Firm than what will eventually be known. IMO
HP/IP ?? How about a little "T" and "C" ?? Then again, it could be the engine makers way of saying: "Both 'Ends' are Involved"..... That's it , Then? It is foggy logic to assume that one end of the IP Shaft, having failed, does not then also destroy the other end?? IMO Any migration aft of the IP Shaft would destroy the bearing set at the Drive Arm. "Molten Bits" peppering the Disc?? Mass that is relinquished as a source of power generation, must be made up for by enhanced Structure.
Would the drop in Temp. have to do with High Pressure Energetic Gas evacuating the Casing, replaced with very erratic and perhaps even ambient Air? At some point, the Fire evidence of Brown streaks smearing the Cowling would indicate a flow disruption?? A very great loss of Pressure??
The FG report is frankly not newsworthy, other than recapping general Public Knowledge, IMO. It serves to dramatize the ongoing situation, and does not divulge new stuff??? I have taken note of RR's ongoing problems that frankly "skirt" the issues to hand. The software mod is a palliative. The Oil leaks are not well explained, the Release further continues to make murky the location of the oiling problem.
There are TWO HP/IP locales, and the reluctance of the manufacturer to get specific remains troubling. For those who are aware that there are TWO HP/IP "Support Structures" whose oiling trouble is left to the imagination, it is frustrating.
I think as always, an official "Non Explanation" will end up causing a great deal more harm to the Firm than what will eventually be known. IMO
HP/IP ?? How about a little "T" and "C" ?? Then again, it could be the engine makers way of saying: "Both 'Ends' are Involved"..... That's it , Then? It is foggy logic to assume that one end of the IP Shaft, having failed, does not then also destroy the other end?? IMO Any migration aft of the IP Shaft would destroy the bearing set at the Drive Arm. "Molten Bits" peppering the Disc?? Mass that is relinquished as a source of power generation, must be made up for by enhanced Structure.
Last edited by bearfoil; 14th Dec 2010 at 16:00.
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Bearfoil
Temperature drop:
My thought of cause would be the destruction of the the stage 1 LPT nozzle ring and casing resulting in the loss of all sensing data. This corresponds to the time of IPT rotor disc rupture/burst.
Turbine D
Temperature drop:
My thought of cause would be the destruction of the the stage 1 LPT nozzle ring and casing resulting in the loss of all sensing data. This corresponds to the time of IPT rotor disc rupture/burst.
Turbine D
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The nozzle ring is missing, that is a fact. Would Temperature be more representative if sensor location was aft of Stage One Turbine?? My instinct says that if a reading is given, the sensor is not destroyed, and if it is, the reading is of course useless.?? The Stage One Turbine has "segmented" loss of Blades. The Turbine Stage 2 has little evidence of blade loss, suggesting that LPTurbine P was contained, until at least the casing departed, followed by complete loss of LPT 'P' forward, purging debris vice Flow?? Complete loss of N1.