A380 engine failure - Qantas [Archive]

Data Guy

5th Nov 2010, 14:04

AD 2010-16-07. RB211-Trent 970-84, 970B-84, 972-84, 972B-84, 977-84, 977B-84, and 980-84 turbofan engines. These engines are installed on, but not limited to, Airbus A380 series airplanes. Wear of shaft rigid coupling on several engines during strip. Earlier history; Refer to MCAI EASA Airworthiness Directive 2010-0008, dated January 15, 2010, for related information.
AD source and Link > Rolls-Royce plc (RR) RB211-Trent 900 Series Turbofan (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/BD36C747996B02D78625777E00523051?OpenDocument&Highlight=rolls-royce%20%20rb211)
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AD 2010-17-13. RB211-Trent 970-84, 970B-84, 972-84, 972B-84, 977-84, 977B-84, and 980-84 turbofan engines. These engines are installed on, but not limited to, Airbus A380 series airplanes.
To detect cracks in the low-pressure turbine (LPT) casings, which could result in the release of uncontained high- energy debris in the event of a stage 1 blade failure.
AD source and Link >
Rolls-Royce plc (RR) RB211-Trent 900 Series Turbofan (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/BD36C747996B02D78625777E00523051?OpenDocument&Highlight=rolls-royce%20%20rb211)
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Two ADs for other models - but with similar causes. Vent tube blockages.

AD 2010-06-14. 700s series has a problem similar to 800s series. (Boeing 777s) Could this same problem extend to 900s series on A-380s ?
The Trent 800 has a similar type design standard to that of the Trent 700 and has also been found in service to be susceptible to carbon deposits in the oil vent tube. We are issuing this AD to prevent internal oil fires due to coking and carbon buildup in the HP/IP turbine bearing oil vent tube that could cause uncontained engine failure and damage to the airplane.
AD source and Link > Rolls-Royce plc RB211-Trent 800 Series Turbofan (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/A60D0D8013EAFC60862576F5005789B7?OpenDocument&Highlight=rolls-royce%20%20rb211)

AD 2010-07-09. RB211-Trent 700 Series. This AD supersedes AD 2007-02-05. These engines are installed on, but not limited to, Airbus A330-243, -341, -342 and -343 series airplanes.
Background; This AD results from further analysis that the cleaning of the vent tubes required by AD 2007-02-05 could lead to loosened carbon fragments, causing a blockage downstream in the vent flow restrictor. We are issuing this AD to prevent internal oil fires due to coking and carbon buildup that could cause uncontained engine failure and damage to the airplane.
AD source and Link >
Rolls-Royce plc RB211-Trent 700 Series Turbofan (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/A3558D1113C1DCFC862576F900552AC4?OpenDocument&Highlight=ad%202010-07-09)
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Another AD for 900s series but no mention of uncontained explosion.

2009-18-13; Title: Rolls-Royce plc. (RR) RB211 Trent 900 Series Turbofan Engines (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebSearchDefault?SearchView&Query=Trent%20970-84&SearchOrder=1&SearchMax=0&SearchWV=TRUE&SearchFuzzy=FALSE&Start=1&Count=100)
We are issuing this AD to prevent the release of a high-pressure (HP) turbine blade, which could result in an engine power loss or in- flight shut down of one or more engines, resulting in an inability to continue safe flight. Evidence from development testing and flight test Trent 900 engines has identified cracking on some HP Turbine Nozzle Guide Vane (NGV) Convex Surfaces.
AD source and Link >
Rolls-Royce plc. (RR) RB211 Trent 900 Series Turbofan (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/D7BC60865A03C3778625762C004C4412?OpenDocument&Highlight=trent%20970-84)
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Other ADs in a related model ( 800s series) with a mention of uncontained explosion.

2001-26-11; Title: Rolls-Royce, plc RB211 Trent 800 Series Turbofan Engines (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/WebSearchDefault?SearchView&Query=Trent%20900%20series&SearchOrder=1&SearchMax=0&SearchWV=TRUE&SearchFuzzy=FALSE&Start=1&Count=100)
LPC fan blade failure due to cracking, which could result in multiple fan blade release, uncontained engine failure, and possible damage to the airplane.
AD source and Link >
Rolls-Royce, plc RB211 Trent 800 Series Turbofan (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/802FCAABD2A10C7E86256B330066D7B2?OpenDocument&Highlight=trent%20900%20series)
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End

bearfoil

5th Nov 2010, 14:40

lomapaseo

Some questions come to mind. If the IP disc self ejects, are we looking at a disc failure as the cause? Or is it more along the lines of the "Rigid Coupling" feature, which I am assuming is the disc's bearing mount on the shaft? Generally, with turbine engines things get heavier and more robust as the Rotating mass approaches its center, the shaft, itself.

since heavier and more massive assemblies cause more damage when they fail, how specifically is this incident impinging on this model's maintenance and service life ?

Also, my intuition is that Intermediate Turbine is the focus of high acceleration and pressure increase of the air mass, could excess bearing wear be caused by engineering insufficient to contain this stress? Also, could you explain the oft misunderstood difference between the Turbojet and the TurboFan?

Thanks, bear

yotty

5th Nov 2010, 19:24

EASA Airworthiness Directives Publishing Tool (http://ad.easa.europa.eu/ad/2010-0008R1) ..... this might be the cause..

lomapaseo

5th Nov 2010, 19:55

Bear

All avenues of investigation against all causes remain open at this time. Since I have'nt even seen what failed or any clear pictures of a closeup of the engine or recovered rotor parts I can't speculate and add any value to the understanding regarding a specfic incident under current investigation (nothing releasable)

I'll probably get back to you later on this when I have the time, to answer generalalities

lynn789

5th Nov 2010, 21:20

one passenger reported a hole thru the winfg with wires and cables flapping around in it
isnt there supposed to be a scrapnel shield to stop stuff being thrown out and hitting the wings?

bearfoil

5th Nov 2010, 22:03

yotty

nice catch. Short of conclusive, but certainly tracking well (it would seem), to the end result. The terminology is not yank so I infer the "Coupling interface" to mean a thrust bearing.

Thrust, received by the face of the Shaft's shoulder, and negative thrust, if the engine is barfing, must be absorbed through a range of values, including vibration and high energy harmonics. The AD is a follow on to an original, perhaps not in time to preclude this event, even though the inspection alone creates problems relative to mitigation, and might be under "Pressure" to be declared "Deferrable".

Any repair would be a replacement of the disc and possibly the shaft. Time consuming, and expensive, to include a/c out of service. Leases don't take vacations.
I have seen a Shaft set of splines rub the disc face smooth, (generally the Shaft metal is treated to be more wear resistant than the disc hub). If a lubrication issue, flow restriction is necessary of the designed kind, but coking and carbon are not in the design consideration.

Is this about what you had in mind?

bear

lomapaseo

5th Nov 2010, 23:34

Bear

As promised:

The mass of the released part is not nearly as important as its velocity and the shrapnel that accompanies it.

The idea was to fail-safe it to the point that it was extremely unlikely to fail.

Lots of considerations like; cyclic life, freedom from harmful vibrations, wear, fire and overspeed

Even then the aircraft is designed to minimize the impact to safe landing should the failure of this part occur. (good job there ):ok:

So what caused its release:confused:

keep track of the photos and press releases for any hints.

Lots is aleady available to the investigators from the recovered parts, although more part searching along the ground may be necessary.

No sense in speculating ahead of some more facts and "what ifs" are just that since the safety aspects are based on minimisation of combinations and not impractical flat out eliminination

BarbiesBoyfriend

6th Nov 2010, 01:23

Perhaps an engineer could state how much energy is contained in a Trent turbine wheel at take off power, and better still offer a comparison to something more easily understood.

I take it that the specific impulse would be measured in some reasonable unit like Newton metres, or foot pounds?

Or maybe, it's more like a KE thing?

Or is it a Joules thing? It's been a while since last I was in Mr Stirlings physics class.

EW73

6th Nov 2010, 01:26

For me as an operator...

these things happen....though not expected this early in their service life.

following the uncontained failure of the #2, with the accompanying debris shower of the area between #1 and #2, evidenced by the damage (internally and externally) shown in the leading edge area,
my concern here is that, had that debris shower damaged #1 in some way, either in a control system or causing an engine fire. My take of the events following the landing with regard to shutting down #1 engine, is that they had, in fact, no way of shutting off the fuel supply to that engine at any time post the #2 engine failure....and for me, that's scary stuff!

the 737NG has alternate paths for fuel shutoff controls to each engine...

EW73

bearfoil

6th Nov 2010, 01:35

BarbiesBoyfriend

"Parsec Tonnes"?

BarbiesBoyfriend

6th Nov 2010, 01:42

Bear
I hesitate to take issue with as great a pprune mind as yours. especially after an evening entertaining fellow pyromaniacs, but srely tonnes are a unit of weight, ie mass times gravity?

lomapaseo

6th Nov 2010, 01:42

I take it that the specific impulse would be measured in some reasonable unit like Newton metres, or foot pounds?

Or maybe, it's more like a KE thing?

Or is it a Joules thing? It's been a while since last I was in Mr Stirlings physics class.

Yes to the above, just pick your favorite measurement sytem.

For the more common expression you might try

KE= 1/2 * Polar moment of inertia * rotational speed squared.

If I told you 1 million or 10 million foot-lbs would it make any difference?

It's sure to go through anything on the airplane that gets in its way

bearfoil

6th Nov 2010, 01:47

Parsec: Distance

Tonne: Weight.......... A play on Foot Pounds, a version you cite!!

BarbiesBoyfriend

6th Nov 2010, 01:58

Ah.......Fun with physics! No problemo.

I know that there is sweet fa that can contain a broken turbine wheel, thus the red line marked adjacent on old 'Century series' US warplanes.

Just wonder how many much wallop is contained within?

Like a car at 70? prolly too little.

Like a train at 70? nope, that would be more.

Like superman, trying to catch a four ton truck, loaded with Kryptonite? maybe....:ooh:

bearfoil

6th Nov 2010, 02:06

The problem with disc failure is that it represents blade failure "b" multiplied by how many blades remain attached at the perimeter of each part(ial) disc that is ejected.

b(n)(N)(Epartial)= take the train!!

bear

BarbiesBoyfriend

6th Nov 2010, 02:13

bear, ok, blades come off.

The disc tends to follow and this is where the real KE is stored and its energy is what I was wondering about.

Hey, it will wait til tomorrow.;)

sb_sfo

6th Nov 2010, 15:06

Since there haven't been any pictures of damage to the lower wing skin, I'm wondering if this wing needs to be partially re-skinned, wouldn't it need to be done in a factory jig, and would Airbus be able to interrupt the production line to do it? And at what cost? What sort of a field repair is necessary to fly it back to Toulouse? Will this aircraft be back in service within a year?

Mr Optimistic

6th Nov 2010, 16:31

or one half times moment of inertia times angular velocity squared

Moment of Inertia, Thin Disc (http://hyperphysics.phy-astr.gsu.edu/hbase/tdisc.html)

grounded27

6th Nov 2010, 16:57

Anyone want to speculate on repair costs?

RR will probably be liable for them plus lost revenue etc. What ever is in the quantas contract with Airbuss/RR or what is litigated after.

Mr Optimistic

6th Nov 2010, 17:01

you have seconds to change quantas to qantas before they turn up..........

bearfoil

6th Nov 2010, 17:02

My thought was the fail probability was more like 10 (-9). Oh well, at some point, it was 1/1.

barbiesboyfriend re: sequence/failure. My feeling is that this was not blade fail. The trail of lunch is more likely to be a start/failed disc, with its segments most likely retaining blades (if but for a millisecond). Then again if the disc migrated aft, the blades could have severed clean to start the cascade: debris/fail/debris/FAIL . Sioux City (UAL) was such a failure. The disc (why do I remember it was N1?) parted at an existing crack, and the conspiracists claimed the crack had been identified at a C check, but determined to be "within limits" (sic).

Since the entire midsection of this large powerplant is reported "missing", the shaft failed completely, and it is a wonder and a testimonial to RR that nothing more than a one hundred million dollar event needs to be expensed.

I don't think billet/forging/annealing or existing metallurgical defect is at play here. It seems more likely at this point, given the AD's that addressed the specific location of most likely failure, that it is a maintenance/inspection issue. The lubrication flow problem and required inspections, mitigations fall into an easy line of thought. Who wants to borescope this monster? Who else wants to STRIP it? It doesn't get any more remote than this junction to expose a potential million dollar repair. 400 cycles? that is a very pressurized demand on maintenance. For a New Engine? The implications are falling into place as we post. No one wants to be the bloke with the stick at the Hornet's nest. Given the AD(s), and I'm no expert, the (possible) dire consequences for the fleet are incalculable imo.

Let's capitalize the "Q" as well, it is a proper noun. :p

bear

lomapaseo

7th Nov 2010, 01:44

My thought was the fail probability was more like 10 (-9). Oh well, at some point, it was 1/1.

You can calculate anything you want against failure probability, years of total jet fleet operations since 1956 to present or just time on the wing for this specific engine.

The design intent was zero and as such the future expectation must be brought back into compliance under Continued Airworthiness regulation.

The so called 10 (-9) numbers only apply to combinations of aircraft systems and specfically exclude any system like engines which have their own standards e.g. Part 33 regs

Old Fella

7th Nov 2010, 02:48

3pointlanding. What is the point of your post regarding China - Memphis v's Beijing - Memphis? Last time I checked Beijing was in China. As for SFC of American engines v's British engines I believe the RR's hold their SFC efficiency longer through the life of the engine.

NSEU

7th Nov 2010, 06:29

the 737NG has alternate paths for fuel shutoff controls to each engine...

Alternate paths for wing wiring harnesses or simply alternate power supplies (in fuselage)?

From what I've heard, a person could squeeze through the hole in the A380 wing, so it's likely that more than a single wiring loom was damaged (most aircraft front spar wiring runs parallel to each other).

rmm

7th Nov 2010, 07:41

The 737 classic runs one harness from the wing root along the front spar to the spar valve. The second harness runs along the rear spar out to the wing tip, through the wing and then back inboard along the forward spar to the spar valve.
The 800 rather than run the harness along the whole rear spar they took a short cut and ran it through the pylon fairing.

Old Ag

7th Nov 2010, 13:23

So back to the topic at hand. It seems the green hydraulic system failed, a logical conclusion given the catastrophic failure of the #2 engine and possible loss of fluid from that location. So, this would seem to indicate severe damage to that system from shrapnal or the complete destruction of one of the two engine driven hydralic pumps on #2. Correct? Also baffling to me is that there seems to be no isolation valves within the hydraulic system (other than the fire valve). Am I correct to assume that any leak in either of the primary systems leads to a loss of the system? Also interesting to me is that the nose gear steering is not triple redundant. If you lose the green system (which appears to be the case here), you only have the electro hydaulics to fall back on. Pardon the sophomoric questions but I find the though that goes into these designs fascinating.

-Old Ag

barit1

7th Nov 2010, 19:01

I don't have specific numbers, but one engineer friend once compared the fragments of a failed turbine disc (of a RB211 or CF6 for example), as having the mass and velocity of a cannon ball. Good Luck in trying to protect the plane from such damage.

And every engine manufacturer has had more than a few such failures over the decades. There are several possible causes, which the metallurgical people are adept at sorting out.

First - most obvious - is overspeed. In that case, the reason for the overspeed must be nailed down, and/or an overlay control system installed to provide redundancy. Think of a helicopter engine encountering a geartrain failure in the helo transmission. Without such loss-of-load protection, the gear failure induces a overspeed in the engine.

Second - overtemperature operation can degrade the material properties to the point that the disc (or shaft) cannot sustain normal operating loads. (This is what happened in the collapse of the WTC towers on 9/11).

Third - a material defect in the disc may not be detected for a few hundred or many thousands of start/stop cycles - until it finally lets go. This is called Low Cycle Fatigue or LCF. A huge amount of quality inspection and process control goes into disc manufacturing, and the state of the art improves year-by-year. Even so, the predicted safe life (in cycles) becomes part of the certification standards; once a highly-stressed prime-reliable part reaches its LCF limit, it must be scrapped and replaced.

Hope this helps.

Bizman

7th Nov 2010, 22:17

Without bashing any airline, can anyone knowledgeable comment on why SQ was at first reluctant to do any checks on their fleet of 11 A380, then at RR's recommendation, inspected the fleet but were flying 12 hours later with a "Fleet checked" impression given.
I understand a full boroscope is about 8 hours to complete.
QF has found a further 2 engines worthy of removal and stripdown.

Does this indicate that SQ/LH believe the 970/972 differences are sufficient to "protect" them, or that SQ in particular (LH's hours are so low at this stage that theirs was probably a fair call) believe it is a QF maintenance issue rather than a design or manufacturing issue?

Anyone care to comment whether the #2/#3 engines showing up as worthy of inspection indicates that reverse thrust may be a factor?

(Not a reporter. Worked 14 years in the industry in Avionics and overhaul)
Cheers

DERG

9th Nov 2010, 07:43

This engine is only used on the Qantas machines. So over the four units an extra 8,000lbs of thrust is available. Reason: 15 hr flight to Melbourne at max weights.

Would suggest a harmonic vibration has stress fractured the oil lines. This takes us back to 1950s failures. Just why this could not be modelled is a mystery.

Bizman

9th Nov 2010, 10:22

Derg:

"This engine is only used on the Qantas machines. So over the four units an extra 8,000lbs of thrust is available. Reason: 15 hr flight to Melbourne at max weights."

I get that, but surely this only applies for takeoff and the 25 minutes or so to climb to initial cruise altitude. Thereafter, won't almost the same thrust be required to maintain same LRC or higher as it would for SQ or LH with the 970 Trent?

Okay, a little higher weight, so a little more thrust required initially to maintain same altitude at same speed, but at cruise altitude, the thrust difference isn't 2,000 lbs per engine, more likely only 200 lbs per engine for the next 14 and half hours.

I understand the opportunity for harmonic vibration, both mechanical and aerodynamic through the engine, at higher thrust ratings, but again, I don't see how SQ could assume all these factors after the initial failure in QF32. Surely, initially, no-one knew why #2 in QF32 let go. So how come SQ was back in the air after 12 reluctant hours of checks, while QF was still grounded?

What is even more disturbing for me, is that SQ had already had one total IFSD of a Trent 900 on their A380 and is believed to have prematurely removed from wing and changed over a dozen engines on their fleet. They must know the engine is far from mature, particularly in the hot section, and there are still design issues in the hot section that are far from reaching the "bucket" level of a mature MTBF. Every new event like QF32's must surely be cause to sit back and ask yourself what is it that we don't know about what we don't know?
:confused:

DERG

9th Nov 2010, 12:19

At the outset i have to say that I have watched Qantas and this 380 saga closely and at times my heart went out to them. Australia has had rotten luck. Of course Qantas is not that big an outfit and ferrying the machines upto Lufthansa cannot be logistically easy for a C check.

"What is even more disturbing for me, is that SQ had already had one total IFSD of a Trent 900 on their A380 and is believed to have prematurely removed from wing and changed over a dozen engines on their fleet."

My God..that tells a tale. News to me. RR has just announced a £750 million deal to supply China with engines and back up. This is 12 noon zulu Tues Nov 9th 2010.

This accident happened on the climb out so that is the first clue. Of course I agree with you and see clearly your reasoning. You know these failures happened regularly back in the 50s and 60s and for the life of me I cannot work this out.

We are a hell of along way past slide rules and log tables in 2010 and this failure ..? Either the volcanic dust has shot blasted some mass away from the internals or RR have completely screwed up some specs on materials. God only knows.

In some way the turbine oil has got loose, union failure, stress fracture to lines? Now as far as the public is concerned SQ and Lufthansa are immaculate and of course Qantas has been kicked in the balls yet again.

If you note the wear on the splines that also suggests some chattering. I just don't know if these engines had telemetry on them as do say JetBlues do in KJFK. Of course the guarantees JetBlue got were phenomenal. They can not loose. Even Bird strikes are covered.

Then you lost an engine in your one of your 74s. You push 'em hard and thats what they were built for but I have to say that the 380 was/is not fit for the purpose. I would seriously consider sending them back to Toulose. Let them tie them down run up to 98% and see what happens load em up to full, move around the freight.

Even the friggen sea seals have radio collars fitted to them with a satellite telemetry link. Annoying.:ugh:

awblain

9th Nov 2010, 13:48

The question was asked what's equivalent to the energy of the blade disk?

Give or take -

Energy ~ 0.5 * number * mass * (radius)**2 * (omega)**2

number - relates moment of inertia to a hoop of same mass - say 0.6
omega = rotational velocity = assumed 600 radians/s ~ 6000 rpm (?)
mass = 50Kg (maybe a bit low?)
radius = 0.5m (?) - maybe OK including the blades.

Energy ~ 1.4 MJ.

At 70 mph (30 m/s) this is the same as the kinetic energy of a 2.6 ton truck.

So, a car at highway speeds is not going to be too far off the mark.

At 300 m/s, the same energy as a 30kg cannonball. At a radius of 0.5m and omega of 600 radians/s, the circumference moves at 300 m/s, so it's also very like three 10Kg cannonballs being fired straight out of the engine.

yotty

10th Nov 2010, 08:40

Just a small comment here... if the shaft connecting the compressor and turbine breaks, the turbine is designed to move forward to self destruct on the NGVs and stators to prevent an uncontained failure ..least ways it's like that on the 895...

barit1

10th Nov 2010, 11:59

That would be hard to do. If you break down all the static and dynamic air forces on a turbine, they sum to a large AFT component. In other words, the shaft is in tension, and if it ever fails, the turbine rotor shifts aft.

In a multistage LPT, it's generally possible to contrive a system in which the rotor and stator airfoils will clash and thus destroy the driving torque; ergo the rotor grinds safely to a stop.

In the case of the HPT, as soon as the shaft separates, there is no torque driving the HPC, so it soon quits supplying air to the cycle, and the HPT coasts down.

The IPT is another animal. If the core HPC/HPT keeps running, why wouldn't the IPT overspeed? I don't think I'd want to be anywhere in the same county! :eek:

robertbartsch

10th Nov 2010, 12:39

I have not read much at all about the airframe design. Are investigators leaning towards a concluson that it is a RR engine only problem?

lomapaseo

10th Nov 2010, 12:42

In the case of the HPT, as soon as the shaft separates, there is no torque driving the HPC, so it soon quits supplying air to the cycle, and the HPT coasts down.

Of course the timing of the HPC quitting is quite critical, but methinks that the low enertia of the High turbine will be long gone out the side of the engine as it eats the air still left coming out of the combustor

DERG

11th Nov 2010, 13:52

If this fault turns out that it is volcano dust related it is bonanza time :E for technicians, loads of $$! :E

Bizman

12th Nov 2010, 00:06

Extremely unlikely.

If any volcanic dust were present there would glazed pellets in the combustion areas, and pitting of compressor blades. None of this has been reported.

Besides LH has not been near volcanoes of late, yet swapped an engine as result of latest AD

I think RR now has a pretty clear bead on cause & wud be beavering away on a long term rectification

Bolty McBolt

12th Nov 2010, 03:15

awblain Energy of disk ?

I would put the diameter of the HP disc closer 1.1 meter and the weight(mass) around 75 kgs + with blades fitted

The IP disc is larger again but not as thick but I suspect a similar mass.
I remember as an apprentice building up modules that the turbines discs were light enough for 2 people to lift but we didn't as they needed to be put down very gently to protect knife edge seals on the faces

Now the RR G2 N3 spins at approx 12,000 at 100% at climb thrust the N3 would still be above 90%.

Using "awblain" formula above. As "barit" said you don't want to be anywhere near it if either let go. I

Would suggest a harmonic vibration has stress fractured the oil lines. This takes us back to 1950s failures

From what I am hearing its not fractured tubes or oil supply issues. Think along the lines of the hot area bearing fire. RR use labyrinth seals and looks like the high temp air could be getting into the HP/IP Turb bearing compartment cooking the oil causing bearing seize or failure.
This could explain why RR have asked to look at turb blades because if the oil is getting out perhaps the hot air is getting in where it should not.

Just my interpretation of the AD

fruitloop

12th Nov 2010, 04:30

Quote....Just a small comment here... if the shaft connecting the compressor and turbine breaks, the turbine is designed to move forward to self destruct on the NGVs and stators to prevent an uncontained failure ..least ways it's like that on the 895...
WOW never heard of this before !!!

Hobo

12th Nov 2010, 04:46

Sydney Morning Herald 12/11/10 (http://www.smh.com.au/travel/travel-news/qantas-grounding-could-last-for-weeks-20101111-17pg7.html?from=smh_sb)

QANTAS has signalled that its flagship A380 aircraft could be out of service during the lucrative summer holidays, as preliminary investigations pin the blame for the midair emergency last week on an ''oil fire''.

DERG

12th Nov 2010, 17:26

Flash2001

12th Nov 2010, 18:00

Please give all quantities of energy in stone-barleycorns. Velocity and speed should be given in furlongs per fortnight.

The Qantas landing qualifies as excellent!

lomapaseo

12th Nov 2010, 18:17

See if you can dig up something on a Shell turbine oil called ASTO 560.

This oil coked up another RR Trent around 2002.
see:

http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20040528X00693&ntsbno=DCA04IA002& akey=1 (http://www.ntsb.gov/ntsb/brief2.asp?ev_id=20040528X00693&ntsbno=DCA04IA002&akey=1)

It was withdrawn by RR. the oil that is..

I checked and this oil is still widely available, maybe Qantas are still using it. Who knows?

Anyway the bottom line is it was coking the vent tubes from the bearing.

The most significant part of coking in a jet engine is hot air mixing with the oil. Leaking hot air into a bearing compartment through the seals leads to coking in the scavenge system which leads to higher pressure in the bearing compartment which leads to oil blowing out through the bearing compartment seals and possible light off around a spinning disk.

There is also the possibility that seals worn badly enough could leak oil out of the bearing compartment even though no excessive pressure rise within the compartment has been caused by coking in the scavenge lines.

Other possibilities exist so perhaps when the full details of the RR fix become known we can better understand.

rmm

12th Nov 2010, 22:26

Qantas use BP turbo 2197 oil in the 380

DERG

13th Nov 2010, 07:57

Thanks for the repiles

barit1

14th Nov 2010, 01:33

We still have the QF RB211/747 SFO "explosion" and return to SFO (31 Aug), involving the IPT - it shed its blades, and thus the disc did not burst. I've heard claims of "no connection to the Trent events", but no detailed or convincing substantiation of that claim.

Further, it would be pretty hard for QF #2 Trent to encounter volcanic ash when #1, #3 & #4 and the airframe itself show no such distress signature. (I say no distress, because if ash HAD BEEN a factor, R-R would have immediately posited this for whatever commercial value could be gained).

DERG

14th Nov 2010, 08:16

lomapaseo

14th Nov 2010, 12:59

No connection to 74 engines. Qantas push 'em hard because of the route lengths and TO weights. Always were hard on engines.

RR knew of a fault with T970s back in summer 2009. They made a modification to engines on the line at Toulouse. They notifed Euro Cert Authority and they decided to monitor and not to stop operation.

Of the 80 T970 units in service over half already had the newer design. Qantas was left out of the information loop.

The rest is now history.

Quite a concise summary.

My bold above contains an important nugget if true.

To me a "fault" should be identified to a user along with a corrective action program under "continued airworthiness"

OTOH a design improvement to meet a design goal (e.g. time on wing etc.) may simply be an option available to the organization doing the maintenance. One way to tell the difference is to review what was told to the cert authority that approved the change.

barit1

14th Nov 2010, 14:34

If I read this right, QF's 747/RB211 IPT uncontained failure is because "Qantas push 'em hard". Is this an acceptable way of life in the commercial airline industry? If engines are run within certified parameter limits, how many uncontained (read shrapnel) failures should be expected?

In my experience in the industry, the only acceptable number was zero, and a huge effort expended toward this goal. "Pushing them hard" was NO excuse!
:ugh:

bearfoil

14th Nov 2010, 14:42

barit1

If, as suspected, the failure in the 972 is due abuse (pushed 'em hard), a new set of parameters in affixing blame rear their head.

The extra 2k POT have to be certificated, and maintained differently, or at least "via AD". If the extra thrust was adhered to (this is a software limit), no abnormal or premature seal wear can happen, by design, engineering, manufacture, or use.

Identification and disclosure of the problem, with an addressed reg by the authority leaves Qantas off the hook, responsibility wise, but not on the fiscal end, No?

edit: this being tech log, I'll bring up a material issue re: vibration. The bearing oil seals are flexible, and subject to distortion, within limits, to acommodate transient movement of the rim. Given a Climb thrust, at its top, and most heat filled iteration, with attendant relaxation of the seal, its elastic rating becomes critical. With time, does it relax its pressure and resultant "sealing capability?" Oil migration is containment critical?

bear

barit1

14th Nov 2010, 15:14

Inasmuch as the failure occurred during climb, perhaps at MCL thrust, which is no greater than MCT:

Is MCT for the 972 greater than for the 970? If so, I'd expect deterioration to be a bit faster, an economic issue.

But NOT a safety issue.

bearfoil

14th Nov 2010, 17:29

barit1

Precisely that. Compliance = "Safety". It would be encouraging to note somewhere in the Industry that mere COMPLIANCE is a baseline, a minimum, to be enhanced with volitional programs. Who calculates "wiggle room"? "You", "no, You", "no, Him". One can dream.

(Off thread) In racing, one can push too hard a little engine, or get out the checkbook and install a larger one: more power, more fuel, more power in reserve. Of course the rules (In Aviation, Money), control the specifyin'.

bear

DERG

15th Nov 2010, 11:35

Of course it's a safety issue. If an engine is not cooling properly it evaporates the oil, dries up the bearing and bingo the engine explodes.
The temperature rise is not linear. This happens exponentially. If any fault is to be assigned here it is firmly at the door of EASA. They were advised of the problem and elected to monitor rather than halt operations.
Thank God the Qantas crew were tip top and thank God the three missiles exiting the engine did no more damage than occured. BARIT you really do need to read up on basic physics, or alternatively, steer clear of energy based concepts.

barit1

15th Nov 2010, 12:49

Once again:

There are certified, published operational limits. As long as ALL these limits are observed, the engine should run fine at MCT until fuel is exhausted. Is oil temperature not one of these limits?

A bit more background: For almost a decade, I carted a hi-bypass fan around the world, with a portable instrumentation data package, conducting cell correlation tests at airline facilities. The engine had some tired and obsolete hardware, and so was not airworthy; but for comparative performance purposes, it was stable and an ideal transfer standard.

I ran the engine per a test plan THAT IGNORED ALL T/O TIME LIMITS. :ooh:

EGT, speed, oil pressure/temp. etc. limits were observed, but OFTEN I spent 30 minutes or so, continuously above MCT, at various T/O ratings. THERE WAS NEVER A SAFETY ISSUE with this operation schedule. The only failures my team incurred were when some customer-supplied equipment broke.

If a Trent would be at risk in this sort of operation, I have to question the design standards employed.

(Footnote: Oh, yes, one time when "my" engine was being ground-shipped, the lorry driver took a shortcut - and bashed the engine into a rr overpass! :ugh: )

DERG

15th Nov 2010, 15:44

That much is clear: there ARE design issues. I am ALMOST certain that engine performance anomalies were evident before this event occurred. The way this aircraft was punted out from London only to turn back over Poland itself tells a tale.

The way forward is to bring back flight engineers. Now before all of you call me every name under the sun please consider the following... This aircarft had no less than FIVE fully qualified operators on the flight deck when this emergency happened.

Two of the hydraulic systems were disabled, the fuel transfer system was buggered and the machine needed all of the runway to finally stop. I suggest that if only TWO were on the flight deck the outcome may have been very different.

Now tell me if the cost of a flight engineers salary would threaten the commercial success of this aircraft.

lomapaseo

15th Nov 2010, 17:00

Now tell me if the cost of a flight engineers salary would threaten the commercial success of this aircraft.

How on earth did we manage to morph this technical discussion into a flight engineers pay:confused:

kwateow

15th Nov 2010, 19:50

"Two of the hydraulic systems were disabled"

Then why did the spoilers powered by the Yellow hydraulic system deploy?

barit1

15th Nov 2010, 20:58

DON'T argue with him, unless you wish a torrent of invective! :ugh:

DERG

16th Nov 2010, 07:19

Maybe because the little tubes in that system were intact, moreover maybe the little wires to the pumps and valves were not severed by a whacking great 25kg lump that was exploded out of the engine case?

rudderrudderrat

16th Nov 2010, 07:41

Hi Derg,

Two of the hydraulic systems were disabled,

We don't think so because:

"The A380 incorporates two rather than three Eaton Corporation hydraulic systems with an increased hydraulic pressure of 5,000lb/in² instead of a standard 3,000psi."

DERG

16th Nov 2010, 08:48

Thanks for the info.

Not sure if that helps me sleep at night though!

DERG

2nd Dec 2010, 14:59

NTSB advice. see above

Miele Washing Machines need to teach Rolls Roycle how to counter bore fluid lines in nickel steel.

God knows what other parts this particular workshop flung out. Someone needs to send Rolls Royce Quality staff for a mandatory eye test.

What a way to destroy a company reputation. What a waste! Thank God Qantas saved the day.

Now for litigation in court.

barit1

2nd Dec 2010, 18:04

Reminds one, somewhat, of UA232 (http://en.wikipedia.org/wiki/United_Airlines_Flight_232).

Except in that case, UA had a known-high-time piece of hardware, with a known vulnerability, and they placed in back into service with only a cursory inspection.

The present case is a newly-made piece, fresh from the vendor, passed with only cursory inspection.

The open question: How is this event different from QF74 31 Aug, or from the Trent 1000 testbench failure?

Turbine D

2nd Dec 2010, 20:10

Quote: Reminds one, somewhat, of UA232.

The UA 232 fan disk failure occurred with about 5 hrs. of usable life left before mandatory removal and disposal. The disk was ~ 20 years in service. The defect that caused the ultimate failure was detectable but missed during its last UA shop inspection. The defect was present in other fan disks that were sliced from the same billet. Thirty or more years ago there wasn't the sophistication in inspection methods and this was a critical rotating part, highly inspected with the best techniques of the day.

The tube is not really viewed as a critical component and as such doesn't receive as much attention.

The 1000 test stand failure was probably the result of a different cause than the 900 failure, but certainly demonstrated what can happen when oil accumulates in the wrong area of a hot turbine.

barit1

2nd Dec 2010, 21:48

The tube is not really viewed as a critical component and as such doesn't receive as much attention.

This speaks for itself. Oil fires almost always lead to major damage. Who can possibly decide the oil tube isn't critical? :uhoh:

lomapaseo

2nd Dec 2010, 23:48

This speaks for itself. Oil fires almost always lead to major damage. Who can possibly decide the oil tube isn't critical?

The designer, who applies for a design certificate.

If the regulator pops the question the answer is "we got it covered"

I suspect that this is about to change :E

bearfoil

2nd Dec 2010, 23:57

Anticipating Bankruptcy and dissolution, Pan American was soft pedalling maintenance. UAL took possession of some very clapped out airframes. There was a memo after 232 pranged that claimed Pan Am had actually id'ed the fracture, but sent the engine back into service prior to UAL's next check. The memo disappeared.

This is a Rumours site, after all.

Has anybody else wondered why the end of the Stub pipe has such intricate architecture? It resembles the female end of a line coupling. The bell coving at the tip suggests to me a male end misjoined. Is this a Line couple or a suck tube. If the latter, why the ring/land, and shoulder wear, not to mention the coving wear at the entrance to the tube?

From the image it looks one heckuva lot more like in-service wear from incorrect connection, than a degraded inlet aperture of a simple line/scavenge.

bear

ITman

3rd Dec 2010, 04:14

From the ATSB report published today.

"A recent key finding from those examinations was the presence of an area of fatigue cracking within a stub pipe that feeds oil to the HP/IP bearing structure. That cracking was associated with a misaligned region of counter-boring within the stub pipe outlet."

DERG

3rd Dec 2010, 11:16

Good point but I don't agree in this case. In support of your view I would BAN all mobile telephone devices from the assembly areas of aircraft production.

A worrying note was sent out by GE/PandW this last week about oil line integrity in its products. This means that oil lines are being repaired. That means welded. Welding chrome alloy nickel steel formulated to high specs is notably difficult even for those who do it all day and everyday.

In this case the RR oil tube is assymetrical. Weak on one side. Given the vibrations and heat cycles this is subjected too it means that in this case the T972 as used in Qantas 388 it was literally vibrated until it broke.

The oil was probably leaking already due to micro fractures which would have altered the combustion times and set up a further harmonic that wore the spline shaft. Basically the engine was fighting agin itself.

Given all the fancy software design tools the kids use these days it is ironic that we have a failure here that is so familiar and has been with us since 1910.

Ban moble phones in work places a good start. If a company wants to subcontract out work then it should employ a full time qualified engineer on site...even if this is in some far flung part of the planet. This really is a very simple engineering failure.

Rolls Royce will get get stung mightily in litigation over this.

Turbine D

3rd Dec 2010, 13:49

Lomopaseo

I would agree with your assessment. One additional point about these tubes and tube assemblies, chances are they are not produced by the engine manufacturer at all. Given today's world-wide supply chain, these parts are ideal candidates to be manufactured elsewhere, potentially part of offset agreements, e.g., you buy our engines and we will by a certain amount of components from your country.

DERG

3rd Dec 2010, 15:48

The fact is there is only a handful of places where this technology exists.

The one I am familiar with is the reserch dept. run by Dr. Magnus Hasselqvist of the company Siemens in the Swedish town of Finspong.

Of course GE, Siemens and RR are competitors so unless GE and PR will buy the patent and know how from Siemens this will get no where.

You can weld what you want to the alloys Magnus formulates...he is the leader in this field. The formal address is Siemens Industrial Turbomachinery AB in Finspong Sweden and the boss is called Vladimir Navrotsky.

Good outfit.

bearfoil

3rd Dec 2010, 16:10

DERG

I take it you are familiar with the technology surrounding turned tubes, or drilled, as it may.

In the rather sharp pics of the tube's end are two types of odd artifact. The Fractures are straightforward. What puzzles is the brownish off center coving at the lip's edge? It seems to be part of a patent "wear" signature, quite different than the irregular faces of the fractures. It has swirl marks as well. The area at the offset "drill" blunder also seems to have been "worn in" similar to the lip damage. Any thoughts?

I still am not clear on the need for such complex machining if this is but the terminus of a supply line. Everything I see suggests this is one end of a "coupling". If so, the wear evident in the image suggests a poor fit with the mate. Disclaimer: Now that we are all hyperfocused on this oil tube, what of some of the other telltales?

bear

DERG

4th Dec 2010, 06:41

I am familiar with material failures as any trained engineer should be and moreover I am a free agent so I can comment without prejudice to my financial income.

The insitu postion of the pipe stub is unknown to me but there are several prima facie characteristics that should be noted. The ATSB has already noted some facts and should be read carefully.

The ATSB state this is a feed line. In my view it could be the single scavenge line particular to the bearing case on the Trent. We will see in due course. RR has a patent on this design.

The most significant fact, in my view, is the fractured brown discoloured upper edge closest to the camera. This is an old fracture. Just how old I don't know. But certainly old enough to corrode.

Now this means that oil was leaking through this fracture and hot air was getting in. This would have added oil to the combustion process and cause a very slight delay to the energy transfer cycle viz. a vibration...micro second harmonic. This could be the cause of the spline wear.

What I do know for certain is the Rolls Royce are PARANOID about sharing technology. It is no surprise to me that they have been caught out with this. To be fair they try hard to get staff educated but obviously this simple component caught them out. Sad for UK engineering.

bearfoil

4th Dec 2010, 08:37

DERG

It's a bit clearer to me. You state that "Oil was getting in, and hot air." Are you saying this opening is part of a closed system? I repeat my question that the end of this pipe appears to be half of a line coupling, and losing the integrity of the line as the coupling failed may have caused the oil to drown the bearing case? Why is a counter bore necessary at all if this is a terminus to a (unpressurized, and un-checked 'feed')?

bear

DERG

4th Dec 2010, 09:58

Yes, excuse me..got my Toyota Corolla stuck in the snow..four dachshunds..irate wife..and a couple of pet huskies causing distress to all..finally got the thing out and all occupants and home.:ok:

If I am not mistaken the central disc that was exploded out revolves in the opposite direction to the other rotors. I believe this is a feature of RR aerospace turbines if not all in the RB-211 pattern. If someone can confirm this?

So WTF am I taliking about..right? Well we know that this engine is a bypass design and a lot of air does not enter the combustion process. If I am not mistaken I believe this is about 10/15% that gets inducted in the burn section to be mixed with kero.

We know that the oil feeds are subject to hot gas and that the oil should be kept to below 150C. We know that the oil line in question was fractured and I know personally that it was fractured BEFORE this final failure...final failure..shiny crystaline surface on the metal. Old fracture is seen brown oil/corrosion/colour.

Cause of fracture: stress due to harmonic vibration. Only possible cause. Heat cycles added..severe for T-972 'cause of higher energy transfers at max TO weights AND high ambient temps as in S Cal and Australia.

From first principals the engine SUCKS SQUUEEZES BURNS then THRUSTS. The thrust part depends upon the kero/air ratio. The thrust turns the sucker fan at the front. In these new engines all of this is data mapped so the engine KNOWS WTF is going on and adjusts the fuel flow to match.

If you have an oil leak..the turbine oil gets mixed with the kero and changes the burn characteristic..in particular the TIME taken to release X amout of energy. RR are very proud of the fact that their products get more thrust out per total unit mass than the rest. As they boast "High in power, yet low in mass" with " low emissions".

All very well if the kero/air mix is right and the software is not confused. If you have turbine oil mixing with the air then with the kero the whole model is sent to hell. So the thrust turbine thinks it should have X amount of air with a weight of X amount of kero where as the reality is different.
So the different parts of the engine are out of sync.

This sets up a harmonic and the situations gets progressively worse. The vibrations get worse, the temps rise and eventually a part fails due to stress fracture. Of course if the central disc is turning the other way this can make the situation worse.

CAAAD

4th Dec 2010, 11:48

DERG - A very entertaining scenario. But by what means does the fuel find itself with the oil. Is it a Swedish thing? Is Dr Hasselquvist involved?

DERG

4th Dec 2010, 12:00

Caad...amzn how simple the faults turn out to be. Just poor part manuafacture,

Bear
As far as I understand the guy who designed this bearing was sure they could not mess up the manufacture.

It is a continuous flow with pressure differentials in play. The system is vented to the atmosphere but only at a start up. In service the way the oil is contained is very clever using centrigul forces. But it DOES require the oil to say in grade..in that sense the oil has to be ON SPEC. Ie right visco and temp and pressure.

That is why oil oxidation due to volcanic dust is a factor in this design. It is in any turbine but esp in this one with this bearing lube design.

Basically the Trent is like a high strung race horse. Wunnerful when all the variables are on the mark.

DERG

4th Dec 2010, 12:02

Squirts out the fractured oil pipe. Under pressure.

CAAAD

4th Dec 2010, 12:14

Yes, I can visualise the oil squirting out of the pipe fitting, but how does the fuel arrive in the bearing housing?

Ah, Sorry, I think I have misunderstood again. Are you suggesting that the oil mist from the bearing housing finds its way into the combustion chamber and thus upsets the engine control system? To such an extent that rotor integrity is compromised?

No oil fire in bearing housing, then?

barit1

4th Dec 2010, 16:32

DERG - I'm having a hell of a time following post #88.

Firstly - Aircraft engines must burn a variety of fuels. Within the Jet A spec there is a range of specific gravity, a range of Hydrogen content, thus a range of LHV (BTU/lb) that must be accommodated. Add or subtract a bit of turbine oil, and the fuel/oil properties change very little, compared to the variation that already exists in the Jet A spec. In addition, engines are often approved to run on other fuels - Jet B (higher volatility for arctic use), etc.

Now then - at TO the engine is gulping a few dozen gallons of fuel per minute. The total oil tankage is only a few gallons. IF THERE WERE ENOUGH OIL ENTERING THE COMBUSTION CYCLE to make a measurable difference, the engine would start to overboost. Now what will happen?

The governing function of the fuel control or FADEC or EEC will trim back fuel delivery to bring rpm back to target!

So you see my dilemma: First - how will engine oil at a few dozen psi find its way into the main gas path (several hundred psi), and Second, how could this create overspeed?

DERG

5th Dec 2010, 04:54

"Yes, I can visualise the oil squirting out of the pipe fitting, but how does the fuel arrive in the bearing housing?"

Because RR use a patented oil bearing case with only one scavenge line. Lube system works by pump, air pressure differentials and centrifugal forces. Totally different to GE/PE. Very precise and neat design.

DERG

5th Dec 2010, 05:10

Look up "JP8" and you will realise that commercial engines and military engines are two diff animals. If you think the Trent can handle ANY fuel you are mistaken. The way this Trent is designed it gets every last bit of energy from the kerro. Yes I do believe an oil mist would disturb the cycle. We are talking micro/nano seconds.

The days of running jet engines on paraffin are gone with these new units.
They are really efficient.

Remember only about 10/15% of air coming in is used for combustion.

At TO the 972 would gulp a few gallons per SECOND:ok: in the Qantas 388 at full load. Makes ya just slaver your chops don't it!:E

Not sure about overboost cause the software would start to mess with the kero supply. Hence the bad vibes and spline wear. The software will try to correct yes. But all the other parameters don't match the model..hence the stuttering and spline wear.

Did I mention overspeed? I don't think turbine oil was mixing ALL the time but I do think that at the 72K pounds the Qantas A-388 was putting out at TO it was. It would be interesting to know just how much oil had to be added after each flight.

CAAAD

5th Dec 2010, 09:35

DERG - Modern engines are cleared to use a wide variety of fuels and additives. We say 'fuel'. Not sure what kerro is, or paraffin in this context.

But I am very impressed by the power of your imagination in putting together a scenario whereby oil manages to make its way to the combustion chamber and upset the combustion process to such an extent that hazardous vibrations leading to shaft disconnect result.

I'm with Barit on this and consider it a very unlikely explanation.

But do tell us how you think the oil arrives at entry to combustion chamber. I think I may have asked this before but may have overlooked the explanation.

DERG

5th Dec 2010, 12:10

Well I call it kerosine mainly because of the smell...fuel..not definitive enough for me.

The disc thingy :E was exploded out because the oil/air was on fire inside the bearing case.

Now you want to know how the turbine oil got mixed in with the kero...

Well if you look at the photo you will see that the fracture on the part nearest the camera is old. So that pipe has been porous for enough time for the surface to be discoloured.

We know this bearing was in the mid section of the engine. The oil is sent around in pipes which we know are subject to fracture. Air and oil was mixing.

So we have fractured pipes feeding hot oil into the engine domain. The reason why I am convinced this happened is the premature wear on the spline shaft.

Thank you for your comment on my imagination. I can see why the disc exploded out,but I use my imagination to apply a reason for the spline wear. All comments welcome by return.

bearfoil

5th Dec 2010, 13:41

I am intrigued by the Splines wear. It seems reasonable to assume that the TRENT is a well balanced and smooth running machine. I also think it possible to entertain other than lack of lubrication as a partial factor in the loss of Spline metal.

Under the great stress of Climb thrust, the engine is reliant on its internal balance for long service life.

Splines, though accomplishing a "Rigid" coupling, are subject to vibration (chaotic) and Harmonic (synchronous). Each wave upsets the face of Spline, Groove with opposite and energetic input. Hence the loss of metal from the "Crest" of the Spline, and the faces as well.

Under its ultimate Power loading, any impact that impinges on the face/groove of the Rigid coupling produces wear. Almost all of the Thrust from nozzle and Fan are used to propel the a/c, some is lost as friction, it is friction that may have done in the Rigid coupling. The "Tug O' War" between LPT and Fan is "Refereed" at the Thrust Bearing, any load impinges on the Splines, if there is very rapid loading/unloading in this couple, the joint beats itself into the wear rate that caused the AD's IMO

I still think that while very important, the oiling is not the entire answer. It may be that the extra one tonne of max Thrust is a bit too much for the system. That is a very big Supersonic Fan, any vibration and harmonic whether mechanical or 'acoustic' is a very big load.

Just some thoughts

bearfoil

Turbine D

5th Dec 2010, 13:51

Bearfoil and DERG

In the photograph of the fractured stub pipe in the area of the fracture, I think the surface having swirl marks on it is the result of subsequent forensic examination. That is to say, the swirls come from a radial cutting wheel under coolant spray (may account for the brownish color). The examiners were probably trying to get a better view of the fracture itself, and cut away an unaffected area to enable this. I am sure there are other unreleased photographs that show this component in its original state as found before analysis.

Turbine D

bearfoil

5th Dec 2010, 14:07

TurbineD

Point taken. However, the 'damage' is consonant with the offset of the 'miscreant drill'. I still think it possible that the 'smoothed' offset is wear induced, perhaps caused by an 'aspirator' affixed to the end of the Stub. An open and unadorned exit of an oil supply/scavenge doesn't fit with a supply that is highly engineered to 'mist' its lubricant.

I could see a rotating tip, an 'aspirator' to induce an aerosol mist into the bearing cavity.

The AD specifically mentions Vanes. Restrictor Vanes. The AD also addresses "clogging" vanes. If there was such a "fan" at the tip of this line, its loss would increase oil supply. If this increase in Oil Supply is too much for the scavenge system, the case would flood with oil. This unscavenged Oil would be noted at Flight's end by line people, or even spoken by a CEO: "There is Oil where it shouldn't be..." Alan Joyce.

If this "imagined" aspirator became "clogged" it would resist the Oil's flow, and perhaps, if out of balance, cause the wear that is evident on this terminus.

I think your point is well taken, but I also doubt any destructive testing would want to 'follow' an out of round (eccentric) fault.

conjecture.

bearfoil

barit1

5th Dec 2010, 14:10

DERG:
At TO the 972 would gulp a few gallons per SECOND in the Qantas 388 at full load. Makes ya just slaver your chops don't it!

Incredible. Do the sums for SFC, you'll find your number would make the Trent a very uncompetitive engine.

(Unless, perhaps, you're referring to total fuel flow for four Trents on the ship...)

CAAAD

5th Dec 2010, 14:23

DERG - Thank you for that. But spline wear seems to be a problem on all Trent 900 engines, hence the AD. Are you suggesting that they all suffer from oil leakage into the combustion system, causing the harmonious vibration?

bearfoil

5th Dec 2010, 14:35

CAAAD

You present as an engineer, not a comedian, and I among others very greatly respect your comments. Rather than waste your time on snark, what do you think of my previous post? I expect to learn from you, if you are serious.

Do you think it possible that what looks like a "Misaligned line bore" could actually be wear instead? I say this because there are no telltales, no "bit marks". Any cutting tool will leave a signature if all the bore is to face is the passage of clean oil, The "Offset" is remarkably smooth, suggestive not of Carbide, but wear instread. Thoughts?

regards,

bear

Turbine D

5th Dec 2010, 15:12

Bearfoil
I am with you on this. I think that shaft coupling spline wear on engines with such limited hours and cycles is very unusual. Splines are coated with wear resistant coatings to prevent premature wear. Today's modern high-bypass fan engines are designed to stay on wing for many cycles and hours before removal, teardown, inspection and component repair or replacement. Some stay on wing for as long as five years of operation accumulating many cycles quickly (shorter routes). Spline wear is not a problem that you normally think of or worry about. Engines are generally removed because of a deteriorating EGT margin. This is generally due to hot section degradation, particularly the combustor and turbine rotor blade tip seals. Obviously operating conditions and individual operators have a lot to do with on wing engine life.
This spline situation on the 900 is very odd indeed. Just some thoughts.

Turbine D

bearfoil

5th Dec 2010, 15:27

Turbine D

All things otherwise equal, the common (least obtuse) factor would be oiling. Oil can withstand very high mechanical friction, given tolerances close enough to prevent metal/metal contact. If so, the problem distills to lack of oil, or too large tolerances, or some combination. I think the oil is not at fault, so it is most likely wear, beyond limiting Lubrication values. This is to say, Mechanical forces sufficient to diminish Oil's filmic properties. The TRENT is a proven concept, so what's new? More and More Thrust?

I think not. I believe it may have to do with un-attenuated vibration and/or insufficient oiling. Now the Authority has identified Oiling properties as the root, so what follows on is more than likely mitigable circumstances: eg. Vibration.

The RR Bearing mechanism seems to be proprietary. Will the need to know the results of investigation trump Commercial Protections? I would think so.

"We know the problem, but it's a secret, and we fixed it." .....Won't "Fly" I think.

Edit: What are your thoughts on the "Stub Pipe? I would rule out flubbed manufacturing. First, the "Line Bore" mistake would snap any machining tool I'm familiar with. There is insufficient mass to counterbalance the "eccentric". The ledge on the bore is too smoothe to class as defect in manufacturing, I see it as wear induced. The "defect on the tip" is likewise not due to machining, the metal composition of the pipe would have left resistance marks, "chatter". It is too smoothe, suggesting a polish, and why would anyone polish an incision into the lip if the goal was inspection? The fractures are fresh, they are rough, and unsmoothed. The alignment of the smooth "Off-Bore" defects with the fracture location suggest a common axis of wear, suggesting a rotating mass in the bore (aspirator?), or a coupling that is misaligned. All the defects exhibited in the Photograph happened after the installation of the engine, and the beginning of service, IMO. IMO.

One other thing. If a borescope can be inserted into the Bearing cavity, and there are "Vanes" on the Stub Tip, no wear would be noticed. I think this is why the Authority in the AD required an assessment of "Clogging" at the Vanes?

bear :ok:

Turbine D

5th Dec 2010, 15:39

Bearfoil
Relative to the stub pipe, I inadvertently forgot to mention the most important question of a component failure analysis. Is the material used the correct material? And if it is, is it within specification compositional limits? To determine this, a sample must be extracted for spectrographic analysis as close to the fracture as possible without destroying the fracture surface itself to eliminate off-composition material as being a factor.

Relative to the off-center counter boring, I am having a hard time envisioning how this could happen at the component manufacturing stage. In simplistic terms, one centers the cylinder in relationship to the cutting tool, lock it down and begin the machining process to the required depth.
so I can't figure out why or how it got to the shape depicted in the photo.

Turbine D

bearfoil

5th Dec 2010, 15:44

Sampling of course, but at the weak point of the part? With potential for corrupting the failure's site? An artifact that suggests "Machining", rather than Sampling? I take your point of course, but again, I see a concentric with the "defect" (wear?) in the bore!!

For me, I try to imagine what is not present in the evidence that may have played a part in failure, so bear with me. The RR architecture is supposedly proprietary, so at this point, we may not see more.

If there was an "Aspirator" on the tip of the Stub, and it fouled, it would have created extra drag on the oil pump. The "Swirl Marks" on the tip may be an artifact of siezed ball bearings, having contributed heat of failure to the wear's face. If the Oil was under Pressure of delivery, the load would be absorbed by a ball bearing contact. Again, I think the Concentric orientation of the tip defect with the bore "Ledge" is telling.

bear

CAAAD

5th Dec 2010, 18:13

bearfoil - I choose my words carefully, and I try not to give offence and avoid sarcasm. Also I try not to be light hearted but it's a bit difficult when faced with some posts.

But to get to your point.

No, I don't think the offset counterbore is wear, the surface is too uniform. It appears to be a false cut during manufacture.

I do not understand the geometry of the component as depicted in the photo, and I have no idea of the mating parts and surrounding scenery. Hence I find myself unable to comment.

Oh, all right, then, the stub pipe could be an integral part of a housing casting, in which case the counterbore could have been done on a boring machine. An accidental offset of the spindle would have done the trick.

I honestly think we need more information such as a detailed GA or the relevant pages of the Overhaul Manual before we can get down to informed speculation.

I do not believe there is any fancy aspirator type device involved. The counterbore looks tailor made for a pair of O rings. I would not expect lubrication to be by means of a mist. Oil jets more likely.

As Iomapaseo often says, we should leave the real professionals, Investigators, RR and so on to get on with the job. I have no doubt that they will do a terrific job.

Trouble is, I find it impossible not to respond to some of the more extreme imaginings found on here.

Oh, and can we be a bit more careful with the vocabulary please, and only use terms that are recognised in the Trade.

bearfoil

5th Dec 2010, 19:06

CAAAD,

Recognize "Terms of the Trade"....hmmmm

I am unaware of restrictions relating to terminology, and I don't recognize you as a Mod. Are you one? I doubt it.

"Must respond to imaginings". Your responses to these seem dismissive, You are not opposed to imagination, are you?

You have couched yourself as a "Professional". May be a Continental thing, but in my experience, Professionals do not belittle others, since that is the surest sign of a non-professional.

The idea here is to "......have a little fun...". I would hope that does not mean "at the expense of others."

"Real Professionals". Here I find your comment woefully off target. How in Heaven's name can an anonymous forum have any deleterious affect on the "Work" of the "true" Professional?

"Leave the Professionals to it". Really? May I suggest that they are doing fine, with or without "Tech Log".

I come here to share, to have fun, and practice my writing. Most of all, I am here to learn. Without Imagination, I dare say, there would not be flight. Isn't flight the reason we are here?

respectfully, bearfoil

CAAAD

5th Dec 2010, 20:17

bearfoil - I'm sorry if I've caused offence. Just to clear the air a bit

I have never couched myself as a 'professional' anything. And not a Mod.

It is often easier to understand a point of view if it is phrased in conventional terminology.

And I repeated a point often made here , that we will not know the details of the investigation until the findings are made known, so excessive conjecture is not very productive.

But I thought my comments re the stub pipe fracture weren't too bad.

DERG

6th Dec 2010, 06:17

Please don't make this more complicated than it is. This failure was common in the early part of the 20th century. This is VERY basic mechanical engineering. A 20 yr old second year Mech Eng student can tackle this easily. RR are not noted for sharing information and that is the ONLY problem that second year Eng student would have.

BEAR your post of 5th Dec 2010 15:41 fits my theory. OK the metallurgy is complex but please remember they are seeking to make this engine's mass as LOW as possible.

Also remember that disc thingy?:ugh:(senior moment) that exploded out goes round in the opposite direction to the rest of the internals.

CAAD it is fun to theorise and we, well, I anyway, can do this cause 466 lives were not lost. All Trents? No..not all..but this T972 variant in this situation YES. Specific too.

TURBINE D "so I can't figure out why or how it got to the shape depicted in the photo" Are you serious? It was shoddy work.
What else can it be?

I trust the NTSB. I do not trust RR or Airbus in being open about events.

Please remember that product testing involved 466 people and Qantas was somewaht ignorant of the events going on elsewhere regarding this engine. You will note how the Germans have kept silent through all this apart from a very definite eary statement: "We see no reason to stop flying our 380." That was the day after the accident.

And again: this is a VERY basic engineering failure. OK we have a fancy oil bearing and some high end metallurgy and high energy transfers for total mass of engine..but that is all. We have all the tools to find out what happened.

The biggest problem are the PEOPLE involved. The politics. The cost. And the disgrace.

bearfoil

6th Dec 2010, 14:47

DERG

On page 70 there is a "Slice" through the TRENT and with it a graphic that shows the LP and IP rotating the same direction, it is the HP that contra rotates, as I view it. A bone to pick with an earlier drawing that shows trajectories out the case of The IPT. The trajectories begin above the axis of rotation. If that is accurate one assumes the Projectiles would have exited to port.

Ferpe's schematic might be the TRENT 700. If the oiling is similar on the 9, take note of the "coupling" at one end of the stub pipe shown by arrow. If it is a couple, the end presented as the stub pipe in the "pics" may be the penultimate opening of the delivery tube, this would indeed provide an explanation of what I see as "Wear" rather than manufacturing "Defect".

The TRENT 700 is 2000 pounds lighter than the GE carried on some 777 airframes, it is this lighter weight that was a selling point for Operators of the TRENT on this Boeing. DERG, light weight is quite important in this accident, as it was in BA038.

One of the contributing factors to the Fuel starvation in 038 was vibration on Thrust select on short final. It is "known" by the AAIB to have shaken loose "Migratory Ice", that impacted the FOHE, causing cavitation and spool down.

Here, with QF32, vibration seems to have been a factor; another would be mechanical stresses focused on this "Connection" feed to delivery. The arrowed oil tube is supplying the dual roller bearings at LPT, so it may not be the correct "Stub Pipe", in question.

DevX has responded emphatically re: "Drawing". My request would be of him to supply a picture (of the TRENT 900) isolating the "stub pipe" in question, to determine if indeed the end shown to the public is one half of a "Quick Couple".

Once again, I note tube architecture that suggests other than the delivery end of an oil supply system, and that the damage appears to be Wear, not "Bench Numpty".

Ever ready to occupy the end of the "Limb", I will say the loss of oiling was caused by the severing of the supply line from the delivery line. I have seen fluid couplings fail with that signature under seriously more docile environments than TRENT @ max chat. Standing to be corrected. Anybody?

bear

DERG

6th Dec 2010, 17:13

Bear...there is a guy called Page who I call a true vocational professional engineer....see:

Page (http://www.mech.unsw.edu.au/content/staff/Page.cfm?ss=4)

I see RR take total responsibility for these engines and Qantas pay money direct to RR per flight hour. The only thing Qantas engineers will know is how much turbine oil was being used when it returned home. They still don't know how much had to be added at destination ports.

Since 1995 I have watched how the unbiquitous MBA graduates have eaten away at engineering authority. When I was the tender age of 22 I could call a STOP at any stage until an issue was sorted.

My own is son is 22 and at university for his diploma. He was taught on the tools from the age of 15. He already has exercised the "STOP" option on his course much to the surprise of his tutors. Makes me, and I have to say his tutors, very happy!

The telemetry affixed to these machines really is a JOKE. All they are there for is to minimise RR costs. They ARE NOT there for the benefit of Qantas or the general public.

Yes Bear the T972 is much lighter than the GE equivalent and this is the reason Qantas bought it...so they get max revenue especially on the routes from California. They had no reason to doubt that RR knew WTF it was doing.

What i really want to know is WTF was done when this machine was up at the Lufthansa facility in Germany for the "C" check. I also want to know why SQ was changeing T970 engines like dirty underwear.

There is NO WAY that RR will meet Qantas in open litigation because we will see what a tin of worms RR has cultivated. For those of us who care about people more than our bonus this catastrophe has torn away our faith.

For those engineers who read this: if the company you work for is taking chances with anything then WALK AWAY. There are plenty of good companies around the world who DO care. Sell up and emigrate. The best guys I know all know work worldwide. Not always for the big players either.

Unlike avionics the mechanical engineering problems are often easily identified to a skilled engineer. Believe me there will be quite a few guys on the tools that knew this T972 was unhealthy. They had mortgages to pay and their supervisors should be no where near a commercial transport aircraft.

Qantas needs to employ a bunch of top notch mobile engineers to get maintenance in hand, rewrite the leasing contract and restructure the chain of command. The way 466 people were used as Guinea Pigs sickens me to the core.

DERG

6th Dec 2010, 17:15

Dept Eng Uni of N S Wales Australia

Diversification

6th Dec 2010, 23:19

Regarding the broken pipe, there are some statements in a patent taken in 2003 by RR. See US6516618B1
In the text also an oil-fire resulting from a break in the scavenge pipe is discussed.
There are also two drawings which may hint to where the counter-bore could be.

Regards

DERG

8th Dec 2010, 18:38

http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2010/SAFO10021.pdf

At this point the RR case has collapsed there are so many flaws in this Trent series it is unbelievable. All comments welcome.

bearfoil

8th Dec 2010, 18:55

I must respond. This SAFO bulletin referenced an OIL SPEC change, and related to subsequent coking on TRENT 700.

The tube in question was an oil vent tube, a design certified to withstand ignition by backflow into the scavenge system.

TRENT 900 Issues: Poor quality control of critical oil tubes manufacture. The fix is agreed to, no new issues have arisen, and I am ready to board Qantas out of SFO.

Poor Form: A very real lack of information targeted to passengers who actually care about the equipment they travel in.

The Bad joint turns out to be a connection after all, involving missed maintenance as well as quality issues.

A poor ATD (attention to detail) in performing mandated inspections following issuance of AD. "Oil Leak? What Oil Leak?"

Another missed opportunity to Sell Safety to the traveling public, instead of offering puerile excuses and "explanations" from twits who think kerosine is to light the Barbie.

bear happy landings

sooty655

8th Dec 2010, 18:55

DERG

If you read the SAFO, you would realise that it is aimed at ALL engine manufacturers and ALL operators. How it adds up to "the RR case has collapsed" isn't clear to me.

Perhaps you would care to give it a bit more thought before you try to explain. :ugh:

Turbine D

8th Dec 2010, 21:53

Diversification
Interesting post!
Did anyone notice in the drawings that the counter bore is actually displaced relative to the outside diameter of the part? Drawing inaccuracy or intentional? Look at Figure 1 in the patent carefully to see what I mean, at least on this particular design.

Turbine D

bearfoil

8th Dec 2010, 22:38

Turbine D re:
US PatOff 6516618

In the Patent description there is reference to a single scavenge line, where I believe the 972 has a "Gallery". Language describes an interesting mechanism for "Fail-Safe" re: Fire, since the Oil Pressure increases rapidly when Gas Path contents enter the scavenge line. This increase is referenced as "Constantly Monitored", thus allowing a manual cage of the engine, predating I would say even FADEC? I don't notice the offset in the drawing, is it the image on Page One?

The 972 failed pipe is I think a supply line, and the damage to the "Tip" (Which End?) might be either aspirator (Mister), or "external" coupling? It is not clear from released data, either written or pictorial.

Sorry, almost missed the "point"; if "Offset" I would not rule out a designed for "Eccentric" that augmented aspiration of the lubricating Oil. (Misting).

I still maintain that if a mfg. defect, there is patent "Wear", suggesting ongoing leakage, ("Top your Oil, Captain?") a result of missed or deferred Maintenance.

bearfoil

Turbine D

8th Dec 2010, 23:56

Bearfoil

Yes, I see what you mean, eccentric is a better word. Agreed to the rest of your post.

Turbine D

DERG

9th Dec 2010, 08:00

Thanks Sooty yes. No need to be rude.

I just cannot see the offset (eccentric) bore in the pipe being a design feature. If it was a design feature it was a serious error. No consultant/check engineer would sanction that design without due process. By that I mean a belt and braces dissection of how the pipe would react in situ. I just cannot see how that design would be purposefully offset like that. It is agin every principal known. It appears to be shoddy work.

The NTSB has cited this as a manufacturing flaw. If Rolls Royce claims this was a design feature they are committing hari kiri.

BEAR: These engines were on a full maintenance lease from the RR company. So the only stuff the Qant guys did was top up the oil and do a visual check that all is OK. When the A-380 got to a destination port you would expect another check of the turbine oil and maybe another top up. So as far as I can see, this sounds crazy I agree, that nobody really knew at RR just how much these engines were consuming oil. I really think it was that incompetence: a proper record was not made of the oil being consumed.

I would not take a ride on a RR equipped A-380 until we have a fully documented and approved published report.

The most disturbing aspect is why this aircraft had just passed a C check with the Lufthansa facility in Germany. Moreover, why could LHT make a very definitive statement that "they saw no reason to stop operation of their A-380". What did they know that Qantas did not?

All replies most welcome.