QANTAS A380 Uncontained failure.
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ZimmerFly
Timing is everything when it comes to effective P/R, eh? Not to minimize the gravity of the Qantas T900 situation, but more often than not, the release of good news, a self-fulfillment story is overcome by a negative event before the good news reaches the printing press. Could be the creation of sayings such as "knock on wood", etc. Now, a re-do of the survey may show a much different picture.
But the champagne at Rolls-Royce's Derby headquarters may have to be kept on ice for a while longer. The survey was compiled just before the dramatic failure of one of its Trent 900 engines, which exploded while powering an Airbus A380 on a Qantas plane last November, forcing the jet into an emergency landing in Singapore.
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Another novel event...
Another London bound Qantas A380 engine problem – Plane Talking
"A Qantas Airbus A380-800, registration VH-OQG performing flight QF-31 (scheduled dep Feb 23rd) from Singapore (Singapore) to London Heathrow,EN (UK), was enroute near Ashgabat (Turkmenistan) when the crew observed the engine oil quantity for engine #3 (Trent 972) reduce. The crew reduced the #3 thrust to idle, continued the flight to London crossing Europe at FL360 and landed safely in London about 5 hours later."
Source: Aviation Herald.
"A Qantas Airbus A380-800, registration VH-OQG performing flight QF-31 (scheduled dep Feb 23rd) from Singapore (Singapore) to London Heathrow,EN (UK), was enroute near Ashgabat (Turkmenistan) when the crew observed the engine oil quantity for engine #3 (Trent 972) reduce. The crew reduced the #3 thrust to idle, continued the flight to London crossing Europe at FL360 and landed safely in London about 5 hours later."
Source: Aviation Herald.
Last edited by DERG; 1st Mar 2011 at 03:15. Reason: more detail added
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Qantas flies eight whales, none at this point with less than "C" Mod engines (972)
Of Thirty two total engines on wing, two have experienced this oil feed issue in the last two weeks. Assuming the "Working Loose" problem, what Ben doesn't say is that this most recent incident was also likely losing Oil necessitating the roll back.
Mathematically, there is a .33 chance in one hundred that two engines will behave this way on the same flight. It is actually worse than that, since the problem is identical, and rollback for any reason is less likely than losing two when a demonstrated fault has repeated.
Call it one in one hundred.
Thankfully no less an authority than Rolls Royce itself has stated its engines are perfectly safe.
Whew!! No worries, then!!
Of Thirty two total engines on wing, two have experienced this oil feed issue in the last two weeks. Assuming the "Working Loose" problem, what Ben doesn't say is that this most recent incident was also likely losing Oil necessitating the roll back.
Mathematically, there is a .33 chance in one hundred that two engines will behave this way on the same flight. It is actually worse than that, since the problem is identical, and rollback for any reason is less likely than losing two when a demonstrated fault has repeated.
Call it one in one hundred.
Thankfully no less an authority than Rolls Royce itself has stated its engines are perfectly safe.
Whew!! No worries, then!!
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Probabilities
Yes Bear that is what the Bayesian Staticians and the board of Rolls Royce determined. The machine has four engines and even if one failed the probability of a second failure on the same 'plane would be improbable.
Statistics are a useful tool for so many purposes and are much beloved of the social scientists in academic circles.
I am sure Rolls Royce are waiting until the T972s are out of the news but with 32 units in service it is unlikely that this will happen. The only way they can currently prevent the engines from failing is to replace them before another event happens.
Thay can't because:
1. They just don't have enough spare engines
2. They cannot afford to borescope them after every cycle.
3. They are already committed to contracted work elsewhere.
viz. the A380 production line in Toulouse.
4. They cannot allocate resources to redesign the engine because of
new technology impending viz. the open fan designs
5. To employ radical methods to address #2 above would cause a minor
cash flow crisis. Independent aero engineers are not cheap to hire nor will they sign off anything that is unsound.
So all in all the situation will remain as it is for the forseeable future. If RR decided to follow #5 above they could or will be presented with rejection notices which would ground the aircraft. Moreover the ATSB could ground the Qantas fleet of A388s. An impass situation.
The logical solution is for RR Derby UK to suspend deliveries to the Toulose production line in France, and ask the customer to accept the EA engine instead. I am sure if the 14 members on the board of RR had the pragmatic outlook common within the global engineering industry they would enact this policy.
Statistics are a useful tool for so many purposes and are much beloved of the social scientists in academic circles.
I am sure Rolls Royce are waiting until the T972s are out of the news but with 32 units in service it is unlikely that this will happen. The only way they can currently prevent the engines from failing is to replace them before another event happens.
Thay can't because:
1. They just don't have enough spare engines
2. They cannot afford to borescope them after every cycle.
3. They are already committed to contracted work elsewhere.
viz. the A380 production line in Toulouse.
4. They cannot allocate resources to redesign the engine because of
new technology impending viz. the open fan designs
5. To employ radical methods to address #2 above would cause a minor
cash flow crisis. Independent aero engineers are not cheap to hire nor will they sign off anything that is unsound.
So all in all the situation will remain as it is for the forseeable future. If RR decided to follow #5 above they could or will be presented with rejection notices which would ground the aircraft. Moreover the ATSB could ground the Qantas fleet of A388s. An impass situation.
The logical solution is for RR Derby UK to suspend deliveries to the Toulose production line in France, and ask the customer to accept the EA engine instead. I am sure if the 14 members on the board of RR had the pragmatic outlook common within the global engineering industry they would enact this policy.
Last edited by DERG; 1st Mar 2011 at 08:10.
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TRENT
Which is more likely? A TRENT shakes loose an oil couple, (be certain the P/R release includes "External" oil line), or Fuel Stalls in the FOHE due itinerant resonant frequency??
Or are we again up against the dolt who cannot line up a bias on a drill bore?? Times "X"?
How many duff pipes are aboard, Clive?
Look, a safety rollback of an operating powerplant is not cute. It is especially worrisome when it results from "unknown" (unspoken?) problems in a powerplant that has a long history of problems staying in one piece. The trail of failure leading to the uncontained burst includes the current issue, without exception. An institutional mandate exists to ignore the AD, shuffle "blame" around without cease, and act as if nothing is ongoing.
In an engine without a history of breaking, the oil loss and subsequent shutdown would be remarkable, but in this case, the lack of apparent concern is breathtaking.
Is quiet supposed to be a substitute for competence?? As I recall, "Low Oil" on the ECAM, displays with a sensing by the EEC of four quarts left.
Which is more likely? A TRENT shakes loose an oil couple, (be certain the P/R release includes "External" oil line), or Fuel Stalls in the FOHE due itinerant resonant frequency??
Or are we again up against the dolt who cannot line up a bias on a drill bore?? Times "X"?
How many duff pipes are aboard, Clive?
Look, a safety rollback of an operating powerplant is not cute. It is especially worrisome when it results from "unknown" (unspoken?) problems in a powerplant that has a long history of problems staying in one piece. The trail of failure leading to the uncontained burst includes the current issue, without exception. An institutional mandate exists to ignore the AD, shuffle "blame" around without cease, and act as if nothing is ongoing.
In an engine without a history of breaking, the oil loss and subsequent shutdown would be remarkable, but in this case, the lack of apparent concern is breathtaking.
Is quiet supposed to be a substitute for competence?? As I recall, "Low Oil" on the ECAM, displays with a sensing by the EEC of four quarts left.
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"the lack of apparent concern is breathtaking."
Not when you get inside the mind of the Bayesians and the board members of RR.
Like learning a language once your ear is tuned you can understand. This is a calculated risk, simple as that.
There will be projections of total loss costs already planned.
This is difficult to believe but we, the public, are just players. There are no morals involved here. This situation will not change soon.
Not when you get inside the mind of the Bayesians and the board members of RR.
Like learning a language once your ear is tuned you can understand. This is a calculated risk, simple as that.
There will be projections of total loss costs already planned.
This is difficult to believe but we, the public, are just players. There are no morals involved here. This situation will not change soon.
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bearfoil:
I respect your desire to obtain the full truth to this incident.
However, unless one personally has access to all the key inside personnel and communications at all the firms and agencies involved, making such strong and sweeping determinations from the outside proves nothing.
One could derive the same conclusions from observing the daily arrangement of vehicles at the Derby car park.
An institutional mandate exists to ignore the AD, shuffle "blame" around without cease, and act as if nothing is ongoing.
...the lack of apparent concern is breathtaking.
However, unless one personally has access to all the key inside personnel and communications at all the firms and agencies involved, making such strong and sweeping determinations from the outside proves nothing.
One could derive the same conclusions from observing the daily arrangement of vehicles at the Derby car park.
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"One could derive the same conclusions from observing the daily arrangement of vehicles at the Derby car park."
You mean the race horse meeting called the DERBY? I do not wish to be rude but if you believe that the world will be silent you are seriously mistaken.
Many of us have been seriously disturbed at the incompetence and callous disregard to the safety of the public before and during this saga.
The T972 has a serious problem and is currently in service with the continuing problem. This is not going to be swept under the carpet until the problem has been solved.
The ATSB and Qantas have shown an enormous good faith toward Rolls Royce as has the public.
"However, unless one personally has access to all the key inside personnel and communications at all the firms and agencies involved, making such strong and sweeping determinations from the outside proves nothing."
What you mean to say is that the discussion and conclusions we made here are conjecture. The strong and sweeping statement was made by the T972 engine itself when it exploded.
Maybe if one of your loved ones was sitting next to the wing in that A388 that day you would not be so cavalier. The fact is Mr Machaca that many of us will persist with this discussion until the situation is resolved.
You mean the race horse meeting called the DERBY? I do not wish to be rude but if you believe that the world will be silent you are seriously mistaken.
Many of us have been seriously disturbed at the incompetence and callous disregard to the safety of the public before and during this saga.
The T972 has a serious problem and is currently in service with the continuing problem. This is not going to be swept under the carpet until the problem has been solved.
The ATSB and Qantas have shown an enormous good faith toward Rolls Royce as has the public.
"However, unless one personally has access to all the key inside personnel and communications at all the firms and agencies involved, making such strong and sweeping determinations from the outside proves nothing."
What you mean to say is that the discussion and conclusions we made here are conjecture. The strong and sweeping statement was made by the T972 engine itself when it exploded.
Maybe if one of your loved ones was sitting next to the wing in that A388 that day you would not be so cavalier. The fact is Mr Machaca that many of us will persist with this discussion until the situation is resolved.
Last edited by DERG; 1st Mar 2011 at 18:08.
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Many of us have been seriously disturbed at the incompetence and callous disregard to the safety of the public before and during this saga.
Your other posts today, 38 of them so far if the post counter is correct, tell their own story.
I'm prepared to join the campaign. Anyone else out there want to get this incessant drivel stopped?
One can always use the "ignore" button feature (I haven't yet on this site) and/or respond only to posts which move the subject along in a productive manner.
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Machaca
Most unlike your ordinarily well thought out and data laden postings.
In flight uncontained engine failures this year: 2
Commanded rollbacks due Oil and other issues: four.
Engines off wing to be rebuilt with new shafts, bearings, and collateral structures including EEC re program and DEP refit?? ALL OF THEM. EVERY SINGLE ONE.
Purely precautionary, RIGHT?? NOT.
I base my comments on the evidence in the Public Domain. There is more, but unavailable to the Public.
Have you been reading this thread??
lomapaseo Your level headed and reasonable comments are appreciated, as always.
Most unlike your ordinarily well thought out and data laden postings.
In flight uncontained engine failures this year: 2
Commanded rollbacks due Oil and other issues: four.
Engines off wing to be rebuilt with new shafts, bearings, and collateral structures including EEC re program and DEP refit?? ALL OF THEM. EVERY SINGLE ONE.
Purely precautionary, RIGHT?? NOT.
I base my comments on the evidence in the Public Domain. There is more, but unavailable to the Public.
Have you been reading this thread??
lomapaseo Your level headed and reasonable comments are appreciated, as always.
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...the HP/IP structure inspections are not
considered necessary anymore and AD 2010-0242R1 is cancelled.
EASA Airworthiness Directives Publishing Tool
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Everything about the TRENT's shortcomings suggest a vibration environment that was not designed for. Not particularly alarming. However, there are identifiable structures within the Modules that give evidence of an inability to withstand something that should by all reason be a slam dunk. Early Bearing failure, followed by unusual and surprising wear signatures at the single most important structure in the Powerplant, the Joints of the two articulating Shafts. These Splines are not life limiting, ordinarily, as other patent foibles will cause an offwing strip well ahead of any weakness in the Coupling. Just after the Burst, RR stated the failure was in the Rigid Coupling, and even though additional findings have been introduced since, they have not backtracked. Likewise, cancellation of post burst emergency ADs is to be expected; "better safe than sorry".
What is left is the fourteen month journey of the very problem that by Rolls' statements caused the burst. Oil Fire, Overspeed, Transient Ductility in non ductile material, etc. etc. Hot Oil, Oil Tube fracture, and on, and on.
Rolls have accomplished what needed to be accomplished, and without a Regulatory grounding of the Type. This had the added benefit of keeping the "C" MOD Proprietary, and away from Public scrutiny. The Inspections of the "C" Mod are known, however, and how they relieve the manufacturer of disclosure and a further exercise of responsibility is the key to current philosophy relative to the Fox guarding the Chickens. Thus far, just a few feathers, nary a drop of Chicken Blood.
What is left is the fourteen month journey of the very problem that by Rolls' statements caused the burst. Oil Fire, Overspeed, Transient Ductility in non ductile material, etc. etc. Hot Oil, Oil Tube fracture, and on, and on.
Rolls have accomplished what needed to be accomplished, and without a Regulatory grounding of the Type. This had the added benefit of keeping the "C" MOD Proprietary, and away from Public scrutiny. The Inspections of the "C" Mod are known, however, and how they relieve the manufacturer of disclosure and a further exercise of responsibility is the key to current philosophy relative to the Fox guarding the Chickens. Thus far, just a few feathers, nary a drop of Chicken Blood.
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Oil Leaks & Vibration
Anonybocks
My guess would be that the external oil leaks being experienced by Singapore are probably due to vibrations where the tube fastening nuts are vibrating loose. Rolls Royce, in proceeding through the various Mod revisions probably made changes to the frame that support the HP/IP rear bearings to both strengthen and stiffen it and to also eliminate the infamous stub pipe that broke on the Qantas A-380. In doing so, these changes were made "on the fly," so to speak. However, all the piping on the outside of the engine can react differently when changes are made to the engine structure. Not only that, this maze of tubing is the most difficult to wring out in terms of vibrations. There are all sorts of "tricks" that can be done to stop tubing from vibrating, but, prediction it is one thing verses in flight experience. It is easily fixed once it is determined which tube (and the location where) is vibrating. I think that is what is happening now. Singapore has more A-380's in the air on any given day, perhaps at times, 2/3 of the entire A-380 fleet. So they are going to be the flight leaders in experiencing this annoying problem.
My guess would be that the external oil leaks being experienced by Singapore are probably due to vibrations where the tube fastening nuts are vibrating loose. Rolls Royce, in proceeding through the various Mod revisions probably made changes to the frame that support the HP/IP rear bearings to both strengthen and stiffen it and to also eliminate the infamous stub pipe that broke on the Qantas A-380. In doing so, these changes were made "on the fly," so to speak. However, all the piping on the outside of the engine can react differently when changes are made to the engine structure. Not only that, this maze of tubing is the most difficult to wring out in terms of vibrations. There are all sorts of "tricks" that can be done to stop tubing from vibrating, but, prediction it is one thing verses in flight experience. It is easily fixed once it is determined which tube (and the location where) is vibrating. I think that is what is happening now. Singapore has more A-380's in the air on any given day, perhaps at times, 2/3 of the entire A-380 fleet. So they are going to be the flight leaders in experiencing this annoying problem.
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In this case My surmise would be to give RR the benefit of the doubt. Let us assume that this powerplant is under rather intense scrutiny v/v inspections, and compliance. Oil Issues are at the forefront, and it would be counterintuitive to simply lay off loose nuts at their door.
The Oil Pump is located on the external and aft area of the external gearbox, next to the filter, a non-bypass type, ~ 125 microns, cleanable three times. The Pump is a vaned type, equipped with a pressure relief valve set to 600 psi. When this PRV pops, Oil is redirected into the inlet, similar to a spill valve on the Fuel side.
There are nine scavenge pumps arrayed on the gearbox, each with provision for a chip detector of the screw in variety. The Oil goes directly to the FOHE or in the case of cold bypass cooling, to the Air cooler (OIL).
Each of these fittings needs to be cycled at least once whilst in the shop or on the ramp during an inspection, along with the external connections into the core. That is a lot of opportunity for missed checks in the boxes. Only five conditions of loss of Oil since Burst? not so very many.
QF32. Note the Oil Quantity during the EEC log at Burst. It drops a quart or two, then regains its level. I think this is not an oil leak, but could be indicative of a flow problem, not a loss of quantity problem. The oil drains from the bearing boxes via gravity into a scavenge rail, or gallery. Vibration has other outcomes when fluid is flowing, other than nut loosening, imho. Foaming, Sloshing, etc.A temporary drop in "quantity" at the Oil Tank does not necessarily signify missing OIL, only perhaps missing temporarily from the ceramic resistance stacks that feed the EEC with quantity reads.
The Oil Pump is located on the external and aft area of the external gearbox, next to the filter, a non-bypass type, ~ 125 microns, cleanable three times. The Pump is a vaned type, equipped with a pressure relief valve set to 600 psi. When this PRV pops, Oil is redirected into the inlet, similar to a spill valve on the Fuel side.
There are nine scavenge pumps arrayed on the gearbox, each with provision for a chip detector of the screw in variety. The Oil goes directly to the FOHE or in the case of cold bypass cooling, to the Air cooler (OIL).
Each of these fittings needs to be cycled at least once whilst in the shop or on the ramp during an inspection, along with the external connections into the core. That is a lot of opportunity for missed checks in the boxes. Only five conditions of loss of Oil since Burst? not so very many.
QF32. Note the Oil Quantity during the EEC log at Burst. It drops a quart or two, then regains its level. I think this is not an oil leak, but could be indicative of a flow problem, not a loss of quantity problem. The oil drains from the bearing boxes via gravity into a scavenge rail, or gallery. Vibration has other outcomes when fluid is flowing, other than nut loosening, imho. Foaming, Sloshing, etc.A temporary drop in "quantity" at the Oil Tank does not necessarily signify missing OIL, only perhaps missing temporarily from the ceramic resistance stacks that feed the EEC with quantity reads.
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Filter mesh?
I would be most curious how the 125 micron non-bypass filtration was chosen. I might have expected a finer mesh.
Not so sure of the wisdom of directing the relief oil right back into a tight loop. On a very cold start, the relief valve might be open for some time and there could be quite a thermal buildup in a very small loop. Why not direct the bypass into the scavenge side, then back to the tank? Warm up the whole system!
When this PRV pops, Oil is redirected into the inlet...
Some addititional info on SIA TRENT 972 oil leaks.
Interesting to note the statement:-
"The issue that caused the leaks was identified and corrected"
Which would appear to rule out vibration, although no further information is given.
Interesting to note the statement:-
"The issue that caused the leaks was identified and corrected"
Which would appear to rule out vibration, although no further information is given.
Not necessarily
First off, I don't see any link with these latest external leaks to the reported factors in the original thread subject. internal oil leak
However vibration is everywheree in the operating environment of a jet engine. Since this is recognized by the designer the response is to stiffen and/or dampen the responding bodies to ensure that no metal to metal rubbing takes place and/or that vibratory nodes do not exceed acceptable stress levels..
For external parts the most susceptible parts are plumbing which necessarily stands off from its mounting points around the engine casing and snakes back and forth under and over other pumbing or wiring harnesses. The initial development testing purposely excites the whole engine carcass and looks for problem areas in this regard and then provides brackets and fixings to address any issues.
What often happens later is that something gets changed like a new pipe design added or even a new accesory is added by the installer thus setting up a new set of end conditions. Of course it has been known that even maintenace actions on an engine have removed and failed to re-install the specified brackets versus the latest Service bulletin change spec.
Lots of engines have gone through this teething problem and the outcome has been mostly minor in nature but a pain to track down and universally fix.
not saying ths was the case here, but let's keep an open mind unless you have the hard facts of cause-effect-corrective action.
