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QANTAS A380 Uncontained failure.

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QANTAS A380 Uncontained failure.

Old 6th Mar 2011, 21:03
  #621 (permalink)  
bearfoil
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108TD, 381AP

TRENT 700. Discussed at length in the BA038 Thread, the purported "cause" of Fuel "Starvation" in both powerplants, seven seconds apart, was Vibration. Although Boeing, Rolls and others could not demonstrate the actual trail of failure leading to Hull loss, it was reported that vibration played a role in "Dislodging" Line Ice into the FOHE head. At the Tubesheet, this ICE collected and deposited from the tubesheet face backward, until choking the 177 tubes from fuel delivery. The "Solution" (via AD) then, became to 'trim' the tubes back flush to the FOHE diaphragm. Since no ICE was demonstrated in test at Renton, It is completely appropriate to fix blame for this Hull Loss on vibration alone.

The later incident involving the TRENT on NorthwestAL over Montana produced a fix that had little to do with ICE accretion, but mainly directed the Pilot to descend, and Throttle back, at which time the "ICE" will have "melted" (though the ICE had never been replicated in test, right?)

What follows a retardation of cruise Thrust and loss of Altitude is the migration away from Vibration that may have been causing Fuel issues, absent ICE.

To my knowledge, no information exists in the public record that establishes Fuel Line ICE as the cause either of BA038 or Northwest accident/incidents. airfoilmod and one or two others were on about harmonics and resonant issues in that situation as well as here.

An absence of evidence is not always evidence of absence.

The linkage is apparent, in that fluids in the external plumbing were affected at high levels of Thrust, mechanical damage was evident, and "problems" with fluids supply/cycle/consumption continue........

Likewise a drop in RPM "repaired" the 'problem' almost immediately. Faster than ICE can melt? It could be reported that way, to be sure.

Unlike BA038, the testing appears to be conducted in revenue flight.
 
Old 6th Mar 2011, 23:58
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Bearfoil : "Yes, just those. Keep in mind, the QF32 #2 IPT failed at a Thrust value of 72,000 POT

Wrong: It failed when at a DCL1 power setting of 96.4% of full thrust = 69,400 lb thrust.

The 900 can produce 80,000 POT. Wrong: It is rated at up to 84,000 lb (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/09b47c27a9cfb982862573080054f9ea/$FILE/E00075EN.pdf) and has attained thrust on a test bed of 93,000 lb
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Old 7th Mar 2011, 08:14
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360 hits in in two days..not bad...you have a member here called... w w w does some posts over on Mr Hradecky's site.

Got one of mine deleted over there about saftey issues and regulation...makes ya wonder does it not?
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Old 7th Mar 2011, 15:20
  #624 (permalink)  
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erm... 72,000 POT, rated.

Noted. Your point is?? GE made 127,000 POT on stand. Max continuous is in discussion, No?
 
Old 8th Mar 2011, 00:55
  #625 (permalink)  
 
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Lots of rumours flying about re the repair job on the plane. Apparently nothing has happened and the parties are still fighting it out. Allegations Airbus is nervous about twisting of the frame between the wings.
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Old 8th Mar 2011, 18:03
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Torsional stiffness

Just as background to the information posted by sound asleep, the torsional stiffness of a hollow prism (such as a wing) would depend on the area enclosed by the structural cross-section of object, in addition to the thicknesses of the enclosing cross-section. Here this would normally be the vertical surfaces of the forward and aft main spars, and the horizontal upper and lower surfaces of the wing between these points.

[Note: To some extent the relatively thick vertical webs of the spars cannot be fully utilized in torsion, as the wing surfaces are not comparably thick; additionally, the square corners on this section add to stresses making these regions less efficient. But these complications are basically the same before and after the incident, and so can be ignored in visualizing the basic problem (if not ignored in analyzing it in detail).]

The problem now is that the forward spar is missing in action to some extent. A tear in a surface loaded in torsion (twisting) is a serious problem, as in general the surface must be continuous to satisfy the mathematical condition of enclosing an area. Discounting the damaged forward spar entirely, the area enclosed would be reduced, perhaps to 3/4 or less compared to the undamaged condition.

This would be so even though the forward spar only carried 5% of the load, as was posted sometime back, IIRC-- presumably the reference was to vertical load. And of course openings in shear surfaces can be reinforced, but this is not easy to calculate. And one can say, well, just plug the geometry, as damaged, into the analysis program. This too can be much more easily said than done, as explained following.

That is, every added node is a problem beyond a certain point. It is always necessary that the load matrix operate on the stiffness matrix in such a way the the output matrix of stresses can, first, actually converge to an answer; and, second, that the output stresses are actually correct values. I omit any references to this as I am speaking from the experience of having had to deal with large-matrix structural grid analyses that did not initially converge, even using very sophisticated programs. One's analysis costs can quickly rise if your repetoire of input tweaks fails. (Well, that's how I did it in my day.) OE
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Old 8th Mar 2011, 20:45
  #627 (permalink)  
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Old Engineer

Howdy, you've been missed.

Is it not nearly impossible to test an engineering solution in situ ??

I think the wing is complete toast.
The Port wing, that is. It is virtually impossible to warrant a repair as new, since falling short means a failure, and "overbuilding" produces such losses in efficiency and economy due to weight??

This is not a normal challenge, since the Burst damaged an airframe that had every (contractual) expectation of 'limitless' service life. There is no contractual obligation on the part of any of the three players to repair.

Qantas has no interest in flying a "bird in the sling", Airbus would quote astronomical costs for a one-off (and rightly so), and Rolls (although their Pride is not quantifiable), may not want to risk Corporate survival on a crap shoot. The Insuror(s) will always quote the low ball, but they (most likely) wouldn't push too hard for a rebuild, given the others' interests in coming out whole.

Anything further on the 'seventh note' in the seventh chord??
 
Old 8th Mar 2011, 21:05
  #628 (permalink)  
 
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I think the wing is complete toast.The Port wing, that is. It is virtually impossible to warrant a repair as new, since falling short means a failure, and "overbuilding" produces such losses in efficiency and economy due to weight??
Fit a new (identical to the original, same weight and warranted) wing?
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Old 8th Mar 2011, 21:17
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Absolutely. That makes a great solution. Who would quibble?

Last edited by bearfoil; 8th Mar 2011 at 23:16.
 
Old 8th Mar 2011, 22:36
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At last - the forum is back on topic!

I agree - new wing or a new acft.
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Old 9th Mar 2011, 02:34
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I agree - new wing or a new acft.
Try that with your auto insurrance carrier some day

In the long run the decision does involve considerations of meeting regulatons as well. Simply opting for feel-good decisions on the fly to suit what sounds best to the user may indeed increase the burden of risk on the insurrer. In the long run all operators will have to pony up increased premiums if the insurrer is forced to accept unanticipated repair risks.
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Old 9th Mar 2011, 03:01
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Try that with your auto insurrance carrier some day
Fit a new (identical to the original, same weight and warranted) wing?
The wing is going to be fixed in situ in Singapore,

The pontiffs of this thread may argue the merits of this but this is the reality.
I would suggest the only thrashing out being done is who is paying the bill.

As to much of the theory regarding engine faults and vibration the cause.
I suggest you steer away from conspiracy and think incompetence the cause.
The recent oil leaks are from engines off the shop floor. Nil further leaks found after fleet wide torque check of oil tubes.
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Old 15th Mar 2011, 18:01
  #633 (permalink)  
 
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Well BoltyMcBolt.Sir, in all the years I've been reading the stuff on the internet I've never seen a post stun so many others into silence so emphatically.

Those last three sentences of yours stunned me --no doubt.
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Old 16th Mar 2011, 14:15
  #634 (permalink)  
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flapping madly

The die is cast. The problem is well framed, in Regulatory action and in events of nature. The bottom line in revenue flight is to make money, and not kill too many people in its pursuit.

If, as Bolty implies, the entire TRENT issue folder is down to gremlins who cannot read a digital torque, then fair enough. Likewise if it is hungover bench monkeys with double vision who "counterbore" evil into the din.

We will see as events move along. Either the TRENT 900 can produce its touted power without shaking itself into bankruptcy, or it will fail. When 200 cycles loom nye, it will out what the Group has concocted so far as safety/profit.

It remains to be seen who values which side of the equation more.

"Safety is no Accident"

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Old 16th Mar 2011, 20:03
  #635 (permalink)  
 
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Was a torque wrench used during the installation of these hyd lines/B nuts ?
I doubt very much that one was used.
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Old 17th Mar 2011, 01:46
  #636 (permalink)  
 
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Old Engineer, et al

The surface tear can be analyzed the same as any other opening in a continuous diaphragm..the opening must be able to distribute the forces around the opening.

The affected members at the 'opening', may need reinforcement to distribute, without wholesale replacement.

With the skin or diaphragm, that is a mere function of the fastening in regards to continuous, so perhaps a different fastener schedule about the affected area.

This event was an impact, so as long as there hasnt been deflection (bending) in the members, there can be no justification for replacement of the wing structure.

others comments..no, no, and no, a new wing is NOT required...if above.

You dont replace your arm if you have a cut.
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Old 17th Mar 2011, 02:01
  #637 (permalink)  
 
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unmanned transport:
Was a torque wrench used during the installation of these hyd lines/B nuts ?
I doubt very much that one was used.
You may be interested to know that the B-nut fitting vendors acknowledge alternative tightening methods - other than the familiar torque system. I worked on an engine that used a wrench arc method - and it was quite successful, after a bit of training of the knucklebuster crews.
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Old 17th Mar 2011, 02:29
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Barit1

Before I first became a field engineer - forty years ago - I had to take a mechanical aptitude test and was then interviewed. His first and, as it turned out, only question was; "How much do you tighten a screw (or nut)?"

I thought about this for a moment and then gave the only answer I could think of;

"Enough."

I got the job.

Roger.
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Old 17th Mar 2011, 02:30
  #639 (permalink)  
 
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barit 1, the question remains, was a torque wrench with current calibration used ?

Even more questions, if a torque wrench was not used, was the engineer familiar with the 'wrench arc' method ?
If he/she was familiar with that method, was it used on each B-nut that was disturbed? Was a leak check performed after the nuts were torqued?
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Old 17th Mar 2011, 02:43
  #640 (permalink)  
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Bolty would know...trust me.
 

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