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.

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.

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!! :D

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.

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.

"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.

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.

Not wrong.

"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.

DERG, I'll try once more. Will you please stop this nonsense. You are a retired civil engineer with not the vaguest connection to aviation. You have admitted to having personal 'problems'. You know SFA about aircraft. You know even less about turbine engines. You are not remotely qualified to comment on the abilities of Rolls Royce. So stop.

Your other posts today, 38 of them so far if the post counter is correct, tell their own story.

No way except voluntarily. Thats the nature of a well behaved internet. Just remember it could be far worse if it were on other sites with folks choosing up sides etc.

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.

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.

considered necessary anymore and AD 2010-0242R1 is cancelled.

EASA Airworthiness Directives Publishing Tool

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.

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.

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.

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!

At first blush, I would suggest that smaller than 125 microns would not be metallic particles, reasonably the only material that would be expected in the OIL system other than OIL?

Re: "Tight Loop". Rolls thought it good to go........

"Which would appear to rule out vibration"

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.

14/274 - note for myself

108TD, 381AP

TRENT 700. Discussed at length in the BA038 Thread, the purported "cause" of Fuel "Starvation" in both powerplants, seven seconds apart, was Vibration. Although Boeing, Rolls and others could not demonstrate the actual trail of failure leading to Hull loss, it was reported that vibration played a role in "Dislodging" Line Ice into the FOHE head. At the Tubesheet, this ICE collected and deposited from the tubesheet face backward, until choking the 177 tubes from fuel delivery. The "Solution" (via AD) then, became to 'trim' the tubes back flush to the FOHE diaphragm. Since no ICE was demonstrated in test at Renton, It is completely appropriate to fix blame for this Hull Loss on vibration alone.

The later incident involving the TRENT on NorthwestAL over Montana produced a fix that had little to do with ICE accretion, but mainly directed the Pilot to descend, and Throttle back, at which time the "ICE" will have "melted" (though the ICE had never been replicated in test, right?)

What follows a retardation of cruise Thrust and loss of Altitude is the migration away from Vibration that may have been causing Fuel issues, absent ICE.

To my knowledge, no information exists in the public record that establishes Fuel Line ICE as the cause either of BA038 or Northwest accident/incidents. airfoilmod and one or two others were on about harmonics and resonant issues in that situation as well as here.

An absence of evidence is not always evidence of absence.

The linkage is apparent, in that fluids in the external plumbing were affected at high levels of Thrust, mechanical damage was evident, and "problems" with fluids supply/cycle/consumption continue........

Likewise a drop in RPM "repaired" the 'problem' almost immediately. Faster than ICE can melt? It could be reported that way, to be sure.

Unlike BA038, the testing appears to be conducted in revenue flight.

Bearfoil : "Yes, just those. Keep in mind, the QF32 #2 IPT failed at a Thrust value of 72,000 POT

Wrong: It failed when at a DCL1 power setting of 96.4% of full thrust = 69,400 lb thrust.

The 900 can produce 80,000 POT. Wrong: It is rated at up to 84,000 lb (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/09b47c27a9cfb982862573080054f9ea/$FILE/E00075EN.pdf) and has attained thrust on a test bed of 93,000 lb

360 hits in in two days..not bad...you have a member here called... w w w does some posts over on Mr Hradecky's site.

Got one of mine deleted over there about saftey issues and regulation...makes ya wonder does it not?

erm... 72,000 POT, rated.

Noted. Your point is?? GE made 127,000 POT on stand. Max continuous is in discussion, No?

Lots of rumours flying about re the repair job on the plane. Apparently nothing has happened and the parties are still fighting it out. Allegations Airbus is nervous about twisting of the frame between the wings.

Torsional stiffness
 

Just as background to the information posted by sound asleep, the torsional stiffness of a hollow prism (such as a wing) would depend on the area enclosed by the structural cross-section of object, in addition to the thicknesses of the enclosing cross-section. Here this would normally be the vertical surfaces of the forward and aft main spars, and the horizontal upper and lower surfaces of the wing between these points.

[Note: To some extent the relatively thick vertical webs of the spars cannot be fully utilized in torsion, as the wing surfaces are not comparably thick; additionally, the square corners on this section add to stresses making these regions less efficient. But these complications are basically the same before and after the incident, and so can be ignored in visualizing the basic problem (if not ignored in analyzing it in detail).]

The problem now is that the forward spar is missing in action to some extent. A tear in a surface loaded in torsion (twisting) is a serious problem, as in general the surface must be continuous to satisfy the mathematical condition of enclosing an area. Discounting the damaged forward spar entirely, the area enclosed would be reduced, perhaps to 3/4 or less compared to the undamaged condition.

This would be so even though the forward spar only carried 5% of the load, as was posted sometime back, IIRC-- presumably the reference was to vertical load. And of course openings in shear surfaces can be reinforced, but this is not easy to calculate. And one can say, well, just plug the geometry, as damaged, into the analysis program. This too can be much more easily said than done, as explained following.

That is, every added node is a problem beyond a certain point. It is always necessary that the load matrix operate on the stiffness matrix in such a way the the output matrix of stresses can, first, actually converge to an answer; and, second, that the output stresses are actually correct values. I omit any references to this as I am speaking from the experience of having had to deal with large-matrix structural grid analyses that did not initially converge, even using very sophisticated programs. One's analysis costs can quickly rise if your repetoire of input tweaks fails. (Well, that's how I did it in my day.) OE

Old Engineer

Howdy, you've been missed.

Is it not nearly impossible to test an engineering solution in situ ??

I think the wing is complete toast.The Port wing, that is. It is virtually impossible to warrant a repair as new, since falling short means a failure, and "overbuilding" produces such losses in efficiency and economy due to weight??

This is not a normal challenge, since the Burst damaged an airframe that had every (contractual) expectation of 'limitless' service life. There is no contractual obligation on the part of any of the three players to repair.

Qantas has no interest in flying a "bird in the sling", Airbus would quote astronomical costs for a one-off (and rightly so), and Rolls (although their Pride is not quantifiable), may not want to risk Corporate survival on a crap shoot. The Insuror(s) will always quote the low ball, but they (most likely) wouldn't push too hard for a rebuild, given the others' interests in coming out whole.

Anything further on the 'seventh note' in the seventh chord??

Fit a new (identical to the original, same weight and warranted) wing?

Absolutely. That makes a great solution. Who would quibble? :ok:

At last - the forum is back on topic!

I agree - new wing or a new acft.

Try that with your auto insurrance carrier some day

In the long run the decision does involve considerations of meeting regulatons as well. Simply opting for feel-good decisions on the fly to suit what sounds best to the user may indeed increase the burden of risk on the insurrer. In the long run all operators will have to pony up increased premiums if the insurrer is forced to accept unanticipated repair risks.

The wing is going to be fixed in situ in Singapore,

The pontiffs of this thread may argue the merits of this but this is the reality.
I would suggest the only thrashing out being done is who is paying the bill.

As to much of the theory regarding engine faults and vibration the cause.
I suggest you steer away from conspiracy and think incompetence the cause.
The recent oil leaks are from engines off the shop floor. Nil further leaks found after fleet wide torque check of oil tubes.

Well BoltyMcBolt.Sir, in all the years I've been reading the stuff on the internet I've never seen a post stun so many others into silence so emphatically.

Those last three sentences of yours stunned me --no doubt.:uhoh:

flapping madly

The die is cast. The problem is well framed, in Regulatory action and in events of nature. The bottom line in revenue flight is to make money, and not kill too many people in its pursuit.

If, as Bolty implies, the entire TRENT issue folder is down to gremlins who cannot read a digital torque, then fair enough. Likewise if it is hungover bench monkeys with double vision who "counterbore" evil into the din.

We will see as events move along. Either the TRENT 900 can produce its touted power without shaking itself into bankruptcy, or it will fail. When 200 cycles loom nye, it will out what the Group has concocted so far as safety/profit.

It remains to be seen who values which side of the equation more.

"Safety is no Accident"

bear

Was a torque wrench used during the installation of these hyd lines/B nuts ?
I doubt very much that one was used.

Old Engineer, et al

The surface tear can be analyzed the same as any other opening in a continuous diaphragm..the opening must be able to distribute the forces around the opening.

The affected members at the 'opening', may need reinforcement to distribute, without wholesale replacement.

With the skin or diaphragm, that is a mere function of the fastening in regards to continuous, so perhaps a different fastener schedule about the affected area.

This event was an impact, so as long as there hasnt been deflection (bending) in the members, there can be no justification for replacement of the wing structure.

others comments..no, no, and no, a new wing is NOT required...if above.

You dont replace your arm if you have a cut.

unmanned transport:You may be interested to know that the B-nut fitting vendors acknowledge alternative tightening methods - other than the familiar torque system. I worked on an engine that used a wrench arc method - and it was quite successful, after a bit of training of the knucklebuster crews.

Barit1
 

Before I first became a field engineer - forty years ago - I had to take a mechanical aptitude test and was then interviewed. His first and, as it turned out, only question was; "How much do you tighten a screw (or nut)?"

I thought about this for a moment and then gave the only answer I could think of;

"Enough."

I got the job. :)

Roger.

barit 1, the question remains, was a torque wrench with current calibration used ?

Even more questions, if a torque wrench was not used, was the engineer familiar with the 'wrench arc' method ?
If he/she was familiar with that method, was it used on each B-nut that was disturbed? Was a leak check performed after the nuts were torqued?

Bolty would know...trust me.