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Qantas A380 uncontained #2 engine failure

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Qantas A380 uncontained #2 engine failure

Old 3rd Dec 2010, 21:51
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Sober Lark

Qantas bashing has become a media past time in the last 10 years.

A Qantas aircraft can be delayed and it will get front page news,
even though every other airline has more delays. Go figure.

Yes, they cocked up on the 747 Landing overun a few years back,
had a few unexplained flight problems and the 2 big one's mentioned
above but they still got the aircraft on the ground in one piece as I have
said before.

And it seems that the flight crew had a lot to do with that being the case.
But they / the media don't acknowledge that.
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Old 3rd Dec 2010, 22:04
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McGinty

Therefore there is unfortunately no recording of the flight crew's handling of this incident, a recording which would have proved invaluable for future cockpit crew training. The period before over-writing on the CVR is stupidly short.
I am not sure what industry you are in...? However, as a commercial pilot, my understanding of a CVR is for accident understanding/investigation purposes, not training.

This incident/accident might prove a good debating point over why the CVR is there, and fortunately it has tended to my view, in that it is not to (cannot) be used.

We have 5 crew here, no criticism(s) implied, and an engineering issue leading to mechanical problems, and a safe outcome. I am not sure the CVR would add anything to the root causes / investigation.

If I have a similar incident, I would rather act iaw my training / skills, and not second guessing the CVR write-up.

If the crew are willing for their actions to be used in a training video, then I am sure they will willingly undertake the flight again, in the Sim I agree that the CRM interactions might be interesting, good for training, but I'd rather that be with the crews' consent.

Just my view...

NoD
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Old 3rd Dec 2010, 22:24
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CAAAD

Thank you for your patience, and your kind response.


"Burst" is what's called in the English language a euphemism. "Same as", "Proxy-word", or stand in.

It is used to pretty up a term that may startle, offend, or distract. Explosion is an accurate term, and I can see why a partisan would prefer "Burst". Boils burst, even superchargers burst, and bubbles certainly.

This engine exploded. The pressure within the case became so great, it exceeded maximum designed for limits, quite high, as we know. A five hundred pound Nickle Alloy disc was blown off its shaft with enough force to double back its drive arm, causing it to separate into three pieces and completely shred a Titanium container on its way through a wing and its spar. No data exists as to how much altitude it gained after exiting the a/c wing.

Have you taken note of the drive arm after the "burst"? This feature was blown 180 degrees from normal, with nothing for the "explosion" to work against except the pressure in the cavity. This may be a new world/old world thing, but nomenclature is the least of Rolls' problems. (imo)

all best, bearfoil
 
Old 4th Dec 2010, 00:35
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Great Link:

Plane Talking
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Old 4th Dec 2010, 00:56
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CAAAD

No problem in following your arguments

Again we agree on much and mostly what's left is how to address the rest. So I will adopt some of your wording and explain more of mine.

At the engine level specific requirements within the regs must be met and always take priority over nice to have minimization type regs. as such there is no direct regulatory link from the engine to an aircraft requirement associated with catastrophe. Thus it is better to use the wording "critical part or prime reliable" rather than likely catastrophic'. So all I really meant was that rotor disks are shall we say critical because the only thing standing between them and a very bad result is an aircraft level minimization reg (do the best you can and suffer the rest). So, to me at the engine level, once a design is seen to be susceptible to causing a rotor failure in a single point failure condition than that part of the design need be controlled to the same standards as the rotor disk itself. Now I really don't mean to extrapolate this to design features that add in multiple barrier or minimization conditions at the engine level (to me that's what 33.75 and its JAR-E equiv are all about) At this point I'm guessing that Rolls, GE and P&W thought they had done this adequately until the A380 incident (still awaiting final findings)

And we probably agree that most engine rules don't contain a robustness clause that considers "lessons learned" except for the minimization rule 33.75 and its JAR-E equiv.

Perhaps I'm missing something here, but the regulators ought to have some criteria along these lines to audit this rule against some standard of experience, else we will always be left with closing the barn door after an event under Continued Airworthiness or worse yet subcoming to the subjectivity of an investigating agencies recommendations



Lompaseo - Once again I am in general agreement with your comments, but the final paragraphs concerning criticality are a bit difficult.

A Critical Part is one the failure of which could cause Catastrophe. I do not believe the Requirements or Regulations provide for levels of criticality. Parts are either Critical or not,and the lifing and manufacturing processes are applied accordingly.

If the safety assessment indicates that a non-disc type part such as an oil pipe could fail in a manner likely to lead to Catastrophe a redesign would be necessary. Hence engines have few Critical parts other than discs or shafts.

I also have difficulty with your view that the current rules are sufficiently robust to be able to encompass 'lessons learned'. My experience indicates that if your really believe safety needs to be enhanced then the only certain fix is a change to the Rules. Tinkering with advisory material seldom works.

It has to be said that the whole arena of safety assessments is an absolute nightmare when it comes to agreeing compliance, since there are so many different ways in which the job can be done. This inevitably leads to inconsistency of approach between constructors and between regulators.

Perhaps it is time to stop assuming that everything on the aircraft is correct to drawing and adopt a more pragmatic approach that recognises human falibility, such as is the case I believe with CRM in operational affairs.

Trouble is, Regulators are not very imaginative when their fundamental assumptions are challenged.

Sorry this is a bit rambling, but it's quite interesting, isn't it?
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Old 4th Dec 2010, 01:50
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What would be the cost of fitting two extra cameras for the crew to have a visual on the engines at any time ?
Cameras are an inflight version of a walk around.
Cost of the hardware is peanuts. Design, integration and certification is the pricey part. For it to be useful you have to be able to properly cover most of the airframe.

A bang followed by explosive decompression leaves a pilot wondering the size and location of the hole, so non cabin portions of the fuselage should be covered. Cameras on the wing looking back at the fuselage could achieve this.

Day/night capable cameras are a reliable means of quickly communicating to the crew the overall state of wing or tail.
Night capable cameras would give the crew confidence to stay in their seats rather than peering past windows with torches.

Cameras pointing at landing wheels also a good idea.
IR/visible spectrum cameras with views of the hold also useful to help confirm presence and scale of smoke.

High definition cameras plumbed to a 12-17 inch HD monitor offers a worthwhile improvement to situational awareness in an incident.

This adds up to +14 cameras
A touch screen with thumbnails to select active picture and a simple exposure control are basic controls. For $500 per camera the pictures can be in a loop record (continuous recording) to a solid state recorder.
Much new information can be gained after the event by study of images, in particular of events that cannot be tested on the ground.


No one is suggesting channel hopping the cctv images should be prioritised ahead of seat of the pants, intuitive flying when the worst happens.



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Old 4th Dec 2010, 02:04
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The Australian Transportation Safety Board Preliminary Report contains two items which have so far not been commented on.

First, it seems that the cabin crew were unable to talk to the flight deck:

"The customer service manager (CSM) reported attempting to contact the flight crew, including through the use of the EMERGENCY contact selection on the cabin interphone system, which activated the flight deck warning horn. However, that selection had no associated ECAM message and the flight crew stated that they associated the emergency contact warning horn with the continuously-sounding warnings from the ECAM system and so cancelled the horn."
The pilots were too busy to answer the phone. There was no 'unable' about it....they had other things to do.

It therefore seems that, assuming the CSM has no way of actually entering the cockpit in these strengthened door days, there was no way for the cabin crew to inform the flight deck about any possible injuries to passengers from engine debris.
Sure there is.....

Therefore there is unfortunately no recording of the flight crew's handling of this incident, a recording which would have proved invaluable for future cockpit crew training. The period before over-writing on the CVR is stupidly short.
All that's needed to show how the crew handled the incident is recorded on the DFDR and QAR. All that they don't have is the words, and the background sounds. And whilst they may be of some use, they really come into their own when you don't have a crew to talk to, or aircraft to look at. The contents of a CVR would not be released under Australian law, so they would not be available for 'training'.

But, you are right in that 2 hours does seem short in this age of cheap chips.
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Old 4th Dec 2010, 02:50
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I've been following this thread with interest since the beginning from many perspectives of interest, not the least being that I'm a regular A380 passenger and have been since it's first week of commercial service.

Bearfoil you make many erudite and well informed points, but I really must question your description here:

This engine exploded. The pressure within the case became so great, it exceeded maximum designed for limits, quite high, as we know. A five hundred pound Nickle Alloy disc was blown off its shaft with enough force to double back its drive arm, causing it to separate into three pieces and completely shred a Titanium container on its way through a wing and its spar. No data exists as to how much altitude it gained after exiting the a/c wing.
The engine did not 'explode.' The turbine disc experienced considerable mechanical overload - caused by the overspeed - resulting in ductile overstress failure. Explosions are caused by the rapid expansion of high pressure gases - either through combustion or release of pressurised gas. That's not what happened here though, because of the magnitude of the energy involved, the damage resulting was similar to that caused by an explosion.
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Old 4th Dec 2010, 03:25
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Surely this can not be right, RR limiting A380 passengers to 80;

Qantas court blast over Rolls-Royce engine rules | Perth Now
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Old 4th Dec 2010, 04:12
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It could be right. I read that Qantas is no longer flying the A380 across the Pacific because RR has said only reduced thrust take-offs are allowed. A fully-loaded, fully-fuelled A380 to LAX cannot get off the ground on reduced thrust, I understand.
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Old 4th Dec 2010, 04:27
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212 writes:
caused by the overspeed
I hate when people do this... But is there a source for this?

I haven't heard anything solid about the IP turbine going overspeed - if you have, please share!



Cheers!
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Old 4th Dec 2010, 05:04
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More on that Mysterious Borescope ??

Quick Comment on the Borescope , The fact that a Borescope measures in a 3D fashion ( X Y And Z axis ) means that it uses PSeudo 3D imaging - - - - , The Everest system (as far as I have seen) operates in a 2D realm and uses Maths to produce a 3D measurement result .

(Witness the size of the Camera needed to film "Avatar" - - which is a special form of 3D presentation recording system . Now get that gear into a 4 mm Fiberscope! ).

A word also about the Australian publics current Low opinion of Qantas . - -
In Australia when we and our Friends fly overseas it takes a full 20 hours to Europe and 14 Hours or so to the USA - - - and its over water all the way !

I appreciate Trained Engineers - - - - , In dont have much time for "Risk Assesors" and neither do many other Australians it seems ,
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Old 4th Dec 2010, 05:22
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Rottenray, you make a good point! I read the report yesterday and now that I re-read it again I agree it is not stated as such. However, the ATSB do use the term 'disc burst' so I think my interpretation was tempered by that. Discs 'burst' through overload, so whether that overload was caused by overspeed beyond it's design limit, or being weakened by the fire and then failing at a lower limit becomes a little academic once the bits start flying out the side. This was more the point I was trying to make regarding the use of the word 'explosion.'

Apologies though for any misleading suggestion.
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Old 4th Dec 2010, 05:30
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LPC Ball Bearing

In Post 1375, the ball bearing carrying the fan load, is shown underneath the IPC. How are the stationary races anchored to the engine case? Is there a rearward traveling extension shaft coming from the 2 roller bearings near the fan? Any one have a diagram or links to other web pages showing more detailed drawings or photos of this engine type? thanks.
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Old 4th Dec 2010, 05:40
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Bearfoil has been questioned for stating a senario in which a spline lubrication problem is the cause, to wit:

bearfoil - I'm not sure that I understand the thrust of your latest thoughts.

Are you implying that the defective oil tube is in some way connected with the spline and other ADs.

I cannot for the life of me work out what you are saying. Perhaps it's a European thing. Would it be possible to do a translation for those of us in the Old World?
Back in 2003 there is an AD in which RR suggests that failure of spline lubrication can result in uncontained engine failure, in certain models of the RB 211 3-shaft style engine. RR identified the problem as excessive spline wear due to difficulties with the designed oil-air mist lubrication system for the splines.

RR did not say what might cause these difficulties to the oil-air mist, but it doesn't seem over-reaching to assume that problems with the oil tubing might result in too little oil in the mist.

I believe RR has said that spline failure might cause overspeed of the associated turbine stage, although they don't always say this explicitly. Here we seem to generally assume this would be due to loss of the load from the compressor driven by the particular stage.

Bearfoil has also described the oil-fire senario. We are all hampered by not having any good drawing details of this engine. But at least in that we are in good company-- Boeing had never seen any PW engine drawings until the engine problem just prior to the 747 rollout, despite having specified PW engines for more than two decades.

I quoted the Old/New World translation problem just to mention we have the same problem in reverse-- I'm still trying to figure out what the "abutments" of the splines are, in hopes I could understand how they "axially" locate the turbine, without any drawings. I am assuming these are what we call the "flanks" of the splines, but then in what way would they locate the turbine and keep it from moving rearwards...

OE
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Old 4th Dec 2010, 06:05
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I learned quite a lot from reading the accident report and the CVR transcript from one event where the pilots of a crippled United Airlines DC10 in the summer of 1989 were quite fortunate and very grateful as the event unfolded to have another experienced pilot aboard their stricken craft....suffering from multiple injuries from one of those pesky uncontained engine failures.
At my airline, though the all that was needed to show how the crew handled the emergency was recorded on the flight recorder, and there were surviving pieces of the aircraft to examine, as well as all cockpit crew, the transcript was handy for training discussion. We didn't have DC10 Captain Al Haynes to personally conduct a seminar like the DHL A300 Captain had attended sometime prior to his A300 attempted shootdown in Iraq; so we made due use of some of the CVR transcript.


There has been discussion here that the pilots were too busy to communicate with the FA's and I do not doubt that.... but I suppose that during a cabin visit by one of the pilots to assess conditions on the Qantas A380, a flight attendant or two probably intercepted the pilot and communicated with him.
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Old 4th Dec 2010, 07:14
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Trent 900 Build Standards

"A spokesman for Qantas said their (sic) were currently three builds or versions of the Trent 900, A, B and C. The incident on November 4 was in an A build engine, and all such builds have been removed from the Qantas fleet." - Ben Sandilands, Plane Talking website.

Does anybody know if Qantas is suggesting that they were not aware of these three build standards prior to Nov 4 ?
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Old 4th Dec 2010, 08:24
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The Nomenclature we assign to objects and events does not materially alter the events, or the objects.

"Disc Burst". Fair, but I see it as a large object "disintegrating" into smaller pieces, and then subject to release from high pressure environment, making the pieces "shrapnel"

"Case Burst", ok, not 'wrong' but the case "blew up" because it could not contain high Energy Gas and chaotic masses within.

"Explosion", Here, 212Man, is an example of your very definition of explosion.

"Explosions are caused by the release of high pressure Gases-Either through Combustion or release of Pressurized Gas". Your quote, and it fits well the circumstances as evidenced by the images and statements?

Language in the AD's suggest a possible failure of the Splines on the LP Shaft, the mechanism is unclear, no diagrams. If an oil fire, it is reasonable to assume high pressures in the IP LP shaft passage, which migrates aft to impinge on the aft side of the IP Wheel. The wheel is containing high pressure on its aft face, and with additional pressure in the cavity from the "fire", it is overstressed 'forward'. If this additional Heat/Pressure had heated the hub area of the Disc to plastic, any resistance to shear at its Shaft would have been asymmetrical, and subject to chaotic pressures in the IPLP cavity. The release of the wheel at the hub and fracturing at the radials may have been the first "Bang", followed by penetration of the Case and release of the Cavity contents to the airstream, the second "Bang"?

It is also possible the Cavity release was the first Bang; the disc "Burst" and the Cavity release may have been too close to separate audibly, and the second was the penetration of the wing.

In any case, this is simply conjecture, nothing more. I think we have the precise nomenclature sufficient to understand each other, I don't mind going with 'burst',
Knowing the word can be insufficient to capture the massive release of energy in the "Explosion".

bear
 
Old 4th Dec 2010, 09:06
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"Explosions are caused by the release of high pressure Gases-Either through Combustion or release of Pressurized Gas". Your quote, and it fits well the circumstances as evidenced by the images and statements?
Bear, the posters are correct to point out the engine did not "explode" in the classic "release of high pressure gas" way.

The failure of the disc will be down it exceeding its mechanical properties due to centrifugal/petal (i.e. spinning) forces. As stated, this is likely to be either due to overspeed or heat damage to the disk material.

To illustrate - imagine spinning a 1kg weight around with your arm on a piece of thin string at 1 rev per second. You can imagine that if you tried to spin it at 3 revs per second, the string might break as the forces needed to keep the 1kg weight spinning are higher than the strength of the string. This basically the same as the IP disc - the forces at 7000rpm (or whatever it spins at) are huge, and the disc is designed to be strong enough for "normal" spin speeds only, with some margin. If it was designed to survive e.g. 20,000rpm it would end up being far too heavy - so it isn't, and an overspeed will lead to the 'string breaking' in the IP disk.

Secondly, the disc material is key to its strength - hence if you were to set fire to the string even with the 1kg spinning at 1 rev per second, you can see that it would weaken to the point where it would break even under a normal 1rev/s speed. Obviously a metal disc doesn't burn under fire like a piece of string, but its mechnical strength can still be significantly changed - even at modest temps well under melting point to the point where it is no longer strong enough to spin at its normal speed of say 7000rpm.

Hence, there is no classic gas explosion, it is a material failure of the metal that leads to the exit of the disk in various pieces.

One final thought - this is speculation only, no evidence - it maybe that the first "bang" was the turbine/compressor becoming "disconnected". This would allow to turbine to rapidly accelerate (i.e. no longer working to turn the compressor so can spin as fast as it likes) and overspeed - hence burst and create the second "bang" soon after the first. Overspeed wouldn't take long to be achieved after initial "decoupling".

Last edited by JFZ90; 4th Dec 2010 at 09:38.
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Old 4th Dec 2010, 09:09
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Accident: Qantas A388 near Singapore on Nov 4th 2010, uncontained engine failure

Very good summary.

Concerning the crew performance, this was a text book example of excellent CRM

Not only to bring the ship down safely and to a halt under challenging conditions also the decision NOT to evac.

Great Job guys.
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