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A380 engine failure - Qantas

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A380 engine failure - Qantas

Old 6th Nov 2010, 01:26
  #21 (permalink)  
 
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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
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Old 6th Nov 2010, 01:35
  #22 (permalink)  
bearfoil
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BarbiesBoyfriend

"Parsec Tonnes"?
 
Old 6th Nov 2010, 01:42
  #23 (permalink)  
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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?
 
Old 6th Nov 2010, 01:42
  #24 (permalink)  
 
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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
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Old 6th Nov 2010, 01:47
  #25 (permalink)  
bearfoil
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Parsec: Distance

Tonne: Weight.......... A play on Foot Pounds, a version you cite!!
 
Old 6th Nov 2010, 01:58
  #26 (permalink)  
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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....
 
Old 6th Nov 2010, 02:06
  #27 (permalink)  
bearfoil
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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
 
Old 6th Nov 2010, 02:13
  #28 (permalink)  
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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.
 
Old 6th Nov 2010, 15:06
  #29 (permalink)  
 
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Anyone want to speculate on repair costs?

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?
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Old 6th Nov 2010, 16:31
  #30 (permalink)  
 
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1/2 I w^2 = energy

or one half times moment of inertia times angular velocity squared

Moment of Inertia, Thin Disc
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Old 6th Nov 2010, 16:57
  #31 (permalink)  
 
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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.
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Old 6th Nov 2010, 17:01
  #32 (permalink)  
 
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G27

you have seconds to change quantas to qantas before they turn up..........
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Old 6th Nov 2010, 17:02
  #33 (permalink)  
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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.

bear
 
Old 7th Nov 2010, 01:44
  #34 (permalink)  
 
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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
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Old 7th Nov 2010, 02:48
  #35 (permalink)  
 
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China-Memphis v's Beijing - Memphis

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.
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Old 7th Nov 2010, 06:29
  #36 (permalink)  
 
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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).
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Old 7th Nov 2010, 07:41
  #37 (permalink)  
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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.
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Old 7th Nov 2010, 13:23
  #38 (permalink)  
 
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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
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Old 7th Nov 2010, 19:01
  #39 (permalink)  
 
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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.
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Old 7th Nov 2010, 22:17
  #40 (permalink)  
 
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Why is QF still grounded while LH & SQ are flying?

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
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