Qantas A380 uncontained #2 engine failure
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It sounds as though you are an engineer?
Not on Airbus but the exact same systems
There are actually 2 small alternators/generators in each EEC/Fadec for redundancey and two control loops for engine throttle control.
As far as the fuel leaking on the ground from #2 we do not know if the electrical for the valve was damaged to shut off the fuel or physical damage to the valve and or tubing feeding the valve or if the tank was damaged. We will have to wait for the report or further information.
Needless to say it is going to take a lot more than a new engine and a roll of speed tape to get this aircraft back in the air.
Right now the redundancy and safety designed into the aircraft have come into play and we have a good ending for all on board. No doubt some design items will be re-examined.
Still looks like Rolls has an ugly baby
VFD
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Here's a thought for R-R control system designers:
If the IP shaft fails, as it seems wont to do, the N2 (IP) turbine accelerates damn fast, because all that gas stream energy is driving only the free turbine, and not the LP compressor.
Simultaneously, the LP compressor will DECELERATE quickly, because no driving torque is being supplied, but its blading is still trying to compress more air.
Now then - I'm guessing the N2 tachometer indication is derived at the cold end of the engine, as are N1 and N3. There is a normal relationship between N1, N2, and N3 that crews are familiar with. If N2 is suddenly out of whack, much slower than expected, an IP shaft uncoupling is a likely cause.
The big question: can this condition be detected quickly enough by the FADEC to shut off fuel before the IPT disassembles itself?
If the IP shaft fails, as it seems wont to do, the N2 (IP) turbine accelerates damn fast, because all that gas stream energy is driving only the free turbine, and not the LP compressor.
Simultaneously, the LP compressor will DECELERATE quickly, because no driving torque is being supplied, but its blading is still trying to compress more air.
Now then - I'm guessing the N2 tachometer indication is derived at the cold end of the engine, as are N1 and N3. There is a normal relationship between N1, N2, and N3 that crews are familiar with. If N2 is suddenly out of whack, much slower than expected, an IP shaft uncoupling is a likely cause.
The big question: can this condition be detected quickly enough by the FADEC to shut off fuel before the IPT disassembles itself?
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The big question: can this condition be detected quickly enough by the FADEC to shut off fuel before the IPT disassembles itself?
I think evidence points to a big no. Even the enertia of such a big engine will prevent a rapid shut down.
I think evidence points to a big no. Even the enertia of such a big engine will prevent a rapid shut down.
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Quote by VFD: ''There are actually 2 small alternators/generators in each EEC/Fadec for redundancey and two control loops for engine throttle control.''
There most certainly isn't anything like this on the Trent 900, however what it does have is a gearbox driven dedicated generator which supplies energy to the EEC via lanes A & B, or ''two control loops'' to use your terminology.
There most certainly isn't anything like this on the Trent 900, however what it does have is a gearbox driven dedicated generator which supplies energy to the EEC via lanes A & B, or ''two control loops'' to use your terminology.
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VFD
That would be a yes.
Not on Airbus but the exact same systems
There are actually 2 small alternators/generators in each EEC/Fadec for redundancey and two control loops for engine throttle control.
Not on Airbus but the exact same systems
There are actually 2 small alternators/generators in each EEC/Fadec for redundancey and two control loops for engine throttle control.
We will have to wait for the report or further information.
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catastrophic probability.
Hydroman400: 532: Sorry, I don't get it. 10^(-7) by 1/20 catastrophic gives 5*10^(-9) per engine . Now you have to multiply by the number of engines, 4, and you get 20*10^(-9) which is 2*10^(-8). Not nearly as good as 1*10^(-9). Per ChristiaanJ, it's still not certain what timespan the original 10^(-7) applies to.
DevX, VFD: Thanks for the EEC power details. I'm still not clear whether the [various] shutdown signals come over a data bus or on wire discretes. If they're on wire discretes, are they routed separately in the wing?
DevX, VFD: Thanks for the EEC power details. I'm still not clear whether the [various] shutdown signals come over a data bus or on wire discretes. If they're on wire discretes, are they routed separately in the wing?
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As far as I remember, on the types I have maintained all the fire handle shut down signals are on discrete wiring. I should add my only experience of A380s is assembling fuselage sections, however I do have maintenance experience on several types, both Boeings and Airbuses.
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Qantas to change engines on two A380s
The number three engine on an A380, registration VH-OQC, will be changed after an inspection in Sydney found abnormalities including an oil leak, say sources familiar with the matter. Another Qantas A380 currently grounded in Los Angeles will have one of its engines changed due to unspecified problems.
The abnormalities in the number three engine of VH-OQC could have potentially led to a repeat of Thursday's incident on QF32, sources say.
The abnormalities in the number three engine of VH-OQC could have potentially led to a repeat of Thursday's incident on QF32, sources say.
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"the probability of the disc being released, is (from memory) and causing a fatal accident, in the order of 10 to the power of -6."
10^(-6) . One in (only) a million. That seems very high. Is that per engine-life (bad enough) or per engine flight hour (really terrible) ?
10^(-6) . One in (only) a million. That seems very high. Is that per engine-life (bad enough) or per engine flight hour (really terrible) ?
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barit1, contractor25: 544:
But equally, IPT inertia will prevent it from accelerating all that quickly. My guess would be that that with the IP compressor inop and impeding flow into the HP compressor, the engine would flame out before the IPT disintegrates, but surely there must have been an FMEA on this submitted for cert. ?
But equally, IPT inertia will prevent it from accelerating all that quickly. My guess would be that that with the IP compressor inop and impeding flow into the HP compressor, the engine would flame out before the IPT disintegrates, but surely there must have been an FMEA on this submitted for cert. ?
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They said that this was the case on that How to Build a Jumbo Jet engine programme which was shown on BBC2 some months back.
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So half of the Qantas fleet require an engine change upon inspection.
None of the 11 Singapore aircraft - we have yet to hear of any of the 3 Lufthansa.
Would any resident mathematician/statistician like to work out the odds that this could be a simply random coincidence?
None of the 11 Singapore aircraft - we have yet to hear of any of the 3 Lufthansa.
Would any resident mathematician/statistician like to work out the odds that this could be a simply random coincidence?
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Castings in the debris
The images of the debris found shows engine castings do they not? Not just cowling pieces. This indicates to my mind enormous centrifugal force at the time of the failure and that they occurred in an area where containment did not meet the situation. Also one of the locals was holding a section of blade with inner and outer casing intact which appeared to be about 8 inches long.
The possibility of failure to detect faults prior to assembly seems much more likely than design problems. Nevertheless that is a serious quality control problem at best.
The possibility of failure to detect faults prior to assembly seems much more likely than design problems. Nevertheless that is a serious quality control problem at best.
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BillS (20:50):
A very rough calculation (discounting the possibility of 2 to 4 problem engines on 1 airframe and assuming all of LH's are OK) gave me 0.0246348
(or 2.46348% for the bean counters and around 40:1 for the punters).
When you include the possibility of 1 to 3 problem engines on one airframe, the probability, surprisingly, goes down to 0.0155793 (worse than 60:1) .
Excluding the 3 LH aiframes altogether gives us 0.0255406 (about 38:1)
A very rough calculation (discounting the possibility of 2 to 4 problem engines on 1 airframe and assuming all of LH's are OK) gave me 0.0246348
(or 2.46348% for the bean counters and around 40:1 for the punters).
When you include the possibility of 1 to 3 problem engines on one airframe, the probability, surprisingly, goes down to 0.0155793 (worse than 60:1) .
Excluding the 3 LH aiframes altogether gives us 0.0255406 (about 38:1)
Last edited by Gegenbeispiel; 6th Nov 2010 at 21:48.
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So half of the Qantas fleet require an engine change upon inspection.
None of the 11 Singapore aircraft - we have yet to hear of any of the 3 Lufthansa.
Would any resident mathematician/statistician like to work out the odds that this could be a simply random coincidence?
None of the 11 Singapore aircraft - we have yet to hear of any of the 3 Lufthansa.
Would any resident mathematician/statistician like to work out the odds that this could be a simply random coincidence?
NoD
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Originally Posted by interpreter
The possibility of failure to detect faults prior to assembly seems much more likely than design problems. Nevertheless that is a serious quality control problem at best.
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Quote:
So half of the Qantas fleet require an engine change upon inspection.
None of the 11 Singapore aircraft - we have yet to hear of any of the 3 Lufthansa.
Would any resident mathematician/statistician like to work out the odds that this could be a simply random coincidence?
So half of the Qantas fleet require an engine change upon inspection.
None of the 11 Singapore aircraft - we have yet to hear of any of the 3 Lufthansa.
Would any resident mathematician/statistician like to work out the odds that this could be a simply random coincidence?
Maybe you need to check the engine types... there might be a (significant?) difference
It may be that there is a particular Mark used by Qantas - that would be very significant if so.
A 2.7% chance of it being coincidental - is the converse that it is over 97% likely that it is not?
So quite likely it is either related to a particular engine Mark or alternatively related to a (Qantas) procedure.
(it could be the inspection procedure!)