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Qantas A380 uncontained #2 engine failure

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Qantas A380 uncontained #2 engine failure

Old 4th Nov 2010, 12:30
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FOD

Admission upfront - I'm a UK national transport journalist.

I haven't seen anything here about whether ingestion of foreign objects from the runway might be a possible cause - is that a possibility or would you expect that to cause a problem immediately rather than the 10-15mins after take-off that it seems to have taken?
Foreign Object ingestion would usually manifest itself immediately depending on the object ingested however.
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Old 4th Nov 2010, 12:30
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Old Fella:
I completely agree that it was definitely uncontained and that is an indication of the severity of the engine failure. I hope the press are not too hard on good old Airbus or Quantas for that matter. It appears that the aircraft and the crew performed brilliantly under severe adverse circumstances – engine stuck on, holed wing, etc.

Ranger 1:
You are looking at two different engines!
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Old 4th Nov 2010, 12:32
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just as an aside to design, wouldnt it be sensible to have a contained area around the engine where fuel bays must have some form of Fuel tank inerting, in my case with the aircraft type I fly, this is foam.

For those that dont know, military aircraft have been lost due to FVE - Fuel vapour explosion - when large, hot pieces of metal have hit the fuel ullage where vapour naturally forms. The effects typically are catastrophic.

Other point to note is Hydrodynamic Ram effect. With the advent of modern high speed computing and CFD, isnt it time the regulators introduced mandatory protection in the form of baffles to protect from this in the engine area:

Hydrodynamic Ram - BAE Systems


ScienceDirect - International Journal of Impact Engineering : Numerical modelling of the hydrodynamic ram phenomenon

Hell, seeing as this pprune, I will do what all knobheads do and speculate up the jing yang. My uni dissertation background is vibrational analysis of high cycle fatigue components in hot sections of gas turbines. I now fly transport aircraft of the non civilian variety.

It looks like a hot section failure with subsequent disruption to flow causing surging (and the blackening round the cowling).

Its highly unlikely a catastrophic turbine blade failure would cause rupture like that of an entire disk.

Without looking at the cross-section of the disk under a microscope, the exact cause of the disk failure cannot be determined. but, going of previous examples, its not a design issue. Its could be a manufacturing issue, or it could have been something (damage causing propagation) that has been missed on an inspection major. These cracks propagate pretty quickly to pretty slowly. If you know anything about high cycle fatigue, you know it takes millions, potentially hundreds of millions of cycles to generate failure. Unfortunately, gas turbines operate under conditions where they are recieving vaying loading at the rotational frequency and multiples of the rotational frequency also. Then you get harmonics in the components. all you need is harmonic to adjust slightly due to an imbalance, or damage, and the 2 frequenencies interact. You get forcing every time a blade passes through an injector flow, or every time the disk rotates, or every time a blade passes a stator. Its hugely complex and is why gas turbine design often gets delayed. Despite all the CFD, FEA and computational design elements, you can have everything perfect, put the turbine together and then find something else is causing a vibration that requires a complete redesign of a component or a section. Then again, this is all complete speculation and will probably be proved to complete and utter horsesh!t.

How the engine vib sensors didnt get advance warning of this though is beyond me. If there was any single lesson I learned from my dissertation is this: Vibration is one of the best indications of impending engine failure I know.

Last edited by VinRouge; 4th Nov 2010 at 12:42.
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Old 4th Nov 2010, 12:40
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whats interesting in this photo is the fuel vane being found in debris

http://resources2.news.com.au/images...294-qantas.jpg
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Old 4th Nov 2010, 12:40
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Interested observer

Admission upfront - I'm a UK national transport journalist.
Now that's the way! Good.

I haven't seen anything here about whether ingestion of foreign objects from the runway might be a possible cause - is that a possibility or would you expect that to cause a problem immediately rather than the 10-15mins after take-off that it seems to have taken?
It's too early to say for sure but here's an engineer's guess. Theoretically possible, maybe, but likely, I should not think so. Anything ingested from the runway should have damaged the fan first, and I could see no sign of that. Once they've inspected the engine you'll have your answer I presume.
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Old 4th Nov 2010, 12:40
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It certainly looks like the entire HP Turbine blade mount went! A blade, albeit the front fan being rather large, is designed to be contained by the casing. I really don't think any engineer is going to be able to design an engine with competitive power to weight ratio that could contain something like a turbine mounting disc with the energy contained within.

Obviously, IF that was the cause, then the investigation needs to look at why it failed as the hours on these engines can't be all too long.

As to shutting down the engine, if the Fire disconnect push buttons failed to cut off the Hyd, Fuel and electrics then something needs a serious look at! If the failure of the engine was in the rear of the core, as the pictures suggest, then there is always the possibility of high speed spin from the main fan.

All conjecture as the only true cause and consequence will be from the official report.

Good job by the Flight Crew though, must have been an interesting day in ECAM world!!!!
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Old 4th Nov 2010, 12:41
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Looking at the picture in post #106 - is that fuel coming out or just smoke from the damaged engine? Looks too light in colour to be smoke, and it seems to come from the right of the #2 engine.
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Old 4th Nov 2010, 12:44
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Sand Man

Now how much are pilots worth in situations like this???? (side issue)
About $300 Million and 500 lives!

Awesome job by the crew. Would love to listen to the debrief! Well done Qantas, this could have been very very nasty. Even when Great skill is required, it really helps if Lady luck can smile on you. The wing punctures look very worrisome.
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Old 4th Nov 2010, 12:45
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whats interesting in this photo is the fuel vane being found in debris
Its a stator. It diverts the flow path onto the oncoming blades and also converts pressure to velocity, in a ratio depending on the radial distance. It has nothing to do with fuel.
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Old 4th Nov 2010, 12:46
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Admission upfront - I'm a UK national transport journalist.

I haven't seen anything here about whether ingestion of foreign objects from the runway might be a possible cause - is that a possibility or would you expect that to cause a problem immediately rather than the 10-15mins after take-off that it seems to have taken?

Thanks
Thompson, bird ingestion at MAN

YouTube - Thomson 263H Bird Strike In Manchester Airport

problems occur immediately.
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Old 4th Nov 2010, 12:47
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The Australian Broadcasting Network are now reporting that a teacher and student were injured when debris struck the roof if the school.
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Old 4th Nov 2010, 12:47
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One interesting fact is that max RPM for an engine is not on Tale Off but during the climb. I wonder if it is relevant?
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Old 4th Nov 2010, 12:49
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Video from inside A/C in this link, not so nice to see the upper surface of the wing

Aftonbladet: Sveriges nyhetskälla och mötesplats
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Old 4th Nov 2010, 12:51
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My mail says Eng#2 on that A/C has been carrying a Cat A Turbine Overspeed MEL since Tuesday.
someone posted this on the Dunnunda thread. Could anyone elaborate a little?
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Old 4th Nov 2010, 12:52
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Re: Use of stairs

Someone was asking earlier about use of pax stairs to get the passengers off the aircraft,

It's possible to have an 'evacuation' using stairs, however from the photos this appears to me to be a textbook QF 'precautionary disembarkation'.

The flight crew no doubt were in communication with fire services who advised them of the circumstances outside the a/c and the PIC having this information at hand would decide the best course of action.

A full evacuation using slides is a risky business often resulting in injury (eg broken bones) to pax and crew and therefore is a last resort. If you have ARFF in attendance and nothing is actually on fire then it is probably safer for the majority to expedite disembarkation via stairs rather than popping slides.

Having said that please note that QF cabin crew are trained that during precautionary disembarkation, it can become a full evac at any time. In which case any and all available doors with slides would be used. Correct any doors with stairs in position would continue to be used with stairs.

Also note in this case I highly doubt any of the CC would have used any of the LHS exits, as evidenced by the photos of No 1 still running.

Hope this helps. Sorry for the slight thread drift but I hate seeing the suggestion that by not using slides they did something 'wrong'
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Old 4th Nov 2010, 13:00
  #116 (permalink)  
 
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I haven't seen anything here about whether ingestion of foreign objects from the runway might be a possible cause - is that a possibility or would you expect that to cause a problem immediately rather than the 10-15mins after take-off that it seems to have taken? Thanks
It really depends what you mean by foreign objects. Any sizeable debris would not cause this sort of failure. To reach the turbine stage the debris would have to make it through multiple compressor and stator stages, through the combustor and past the turbine entry stator. That's massively unlikely to happen. I suppose you could get some sort of dust ingestion (think Volcanic ash) but even then the turbine disk would not fail if the blades around the disk were contaminated with dust.
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Old 4th Nov 2010, 13:00
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One interesting fact is that max RPM for an engine is not on Tale Off but during the climb. I wonder if it is relevant?
My understanding is that max RPM occurs in the latter stage of climb (ie above FL250). Where this event happened, the aircraft would have been about 4-6000 feet. The departures to the SE out of SIN of Runway 20C have a 4000 or above height restriction which is quite difficult for large widebody aircraft to achieve so it is probable that the maximum climb thrust would have been selected.

My mail says Eng#2 on that A/C has been carrying a Cat A Turbine Overspeed MEL since Tuesday.
This may have a bearing (no pun intended) on the investigation.
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Old 4th Nov 2010, 13:13
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My mail says Eng#2 on that A/C has been carrying a Cat A Turbine Overspeed MEL since Tuesday.
Does each stage have its own N value on the engine display?

How would they have known the extent of the overspeed in the cockpit or is this only available as a postflight debrief point?
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Old 4th Nov 2010, 13:15
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SQ have announced delays to all A380 services pending inspections on advice from RR and AB.

https://www.singaporeair.com/saa/Uti...up.jsp?msgId=1
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Old 4th Nov 2010, 13:20
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I hope that the jounalists don't take very much of the discussions above as fact.

The nuggets are

This failure condition is severe
It must not be allowed to occur again
Investigation will determine its causes
Corrective actions will follow immediately.

Design issues take up a lot of discussion, but are useless to discuss at the non-expert level.
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