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Posted on 02/16/2006 2:01:08 PM PST by A.A. Cunningham
Airbus A380 test wing breaks just below ultimate load target
The wing of the Airbus A380 static test specimen suffered a structural failure below the ultimate load target during trials in Toulouse earlier this week, but Airbus is confident that it will not need to modify production aircraft.
The airframer has been running load trials on a full scale A380 static test specimen in Toulouse since late 2004 (pictured below). After completing “limit load” tests (ie the maximum loads likely to experienced by the aircraft during normal service), progressively greater loads have been applied to the specimen towards the required 1.5 times the limit load. Engineers develop finite element models (FEM) to calculate the load requirements.
“The failure occurred last Tuesday between 1.45 and 1.5 times the limit load at a point between the inboard and outboard engines,” says Airbus executive vice president engineering Alain Garcia. “This is within 3% of the 1.5 target, which shows the accuracy of the FEM.” He adds that the ultimate load trial is an “extremely severe test during which a wing deflection of 7.4m (24.3ft) was recorded”.
The European Aviation Safety Agency (EASA) says that the maximum loading conditions are defined in the A380 certification basis. “The aircraft structure is analysed and tested to demonstrate that the structure can withstand the maximum loads, including a factor of safety of 1.5. This process is ongoing and will be completed before type certification.”
However Garcia says that the failure of the wing below the 1.5 target will require “essentially no modifications” to production aircraft: “This static test airframe has the first set of wings built, and we have refined the structural design for subsequent aircraft due to increased weights etc. We will use this calibration of the FEM to prove the adequacy of the structure on production aircraft.”
EASA says that it is aware of the structural failure but "cannot make a statement about the specific failure as it has not been officially briefed by Airbus on what the cause was, and the certification process is ongoing".
Garcia says that the FEM calculations had already established that the A380’s wing had “no margin at ultimate load. We had a weight saving programme and ‘played the game’ to achieve ultimate load.” However in earlier briefings, Airbus structural engineers had stated that it planned to carry out “a residual strength and margin research test” in 2006 after completing ultimate load trials.
The results gleaned from the static testing will be extrapolated for the future aircraft developments over the next 40 to 50 years says Garcia. “It is normal to refine and strengthen the structure of new heavier or longer range variants,” he says.
MAX KINGSLEY-JONES / LONDON
No margin?
Not exactly: The required load (before breaking) "margin" was 1.50 times design loads, but they didn't quite get there.
Surprised the EU is going to regulate EVERYTHING (including outdoor sports, the number of eggs in a carton, and the size of wineglasses... but will "accept" a structural airplane test that came close but still DIDN'T meet specs.
I'd think they would have to repeat the test on a new wing.
That flexing (bending) under high stress DOES change flight characteristics, is the main reason for several flight crashes earlier in the 40, 50, 60's ..
Affect "front facing wings" like the X-29 (?) significantly.
That is what they did: Go past the "maxuimum expected load" to 1.50 times max expected and see if it stays together.
It didn't meet the requirement of 1.50 times max load, but broke at 1.47 maximum expected load.
>>Mmmm... C-17!
I've gotten a really good tour from a friend who's a pilot. Really an awesome aircraft.
We don't realize how important our having real military transport/logistics support really is, until you see stories like the recent one of the Belgian wheeled AFV's getting hijacked into some African he!!hole while being transported by a commercial freighter.
Fair question. Expect to drop the major part of 4 Franklins. I like the SA/DA capability, the stainless steel is totally cool. However, if you have big hands (like me) you gotta watch the webspace "bite" of these blowback pistols. Ouch! Just takes once to cure that mistake.
The evacuation test should be fine. Running away is a french specialty. They should pass with flying colors.
Seriously, though, the A340 crash in Canada showed that Airbus does design effective escape systems.
If it aint Boeing , I'm not going
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Check post #35. Per the regs, the 1.50 was a "must have" and Airbus tried to go with no margin over that. So they failed with "no margin" per spec.
I understand what you're saying, but there is more than one margin in play here.
Yep, they'll need to design, build, and test a whole new fuselage/wing assembly... Poor Airbus... heh.
I'm jealous!
Thanks for the info and the tip.
Saw that on a TV special. (Discover or History channel, can't remember which) It's pretty impressive when the wing finally goes! Ka BOOOOM!
Oh, I did see a Bursa Thunder (blued, not nickel/stainless) for $280 at Academy.
Thanks. That's what I thought. IOW, no big story here.
Yeah and they said it broke exactly where they thought it would and at the force it should ....
My understanding of what they said was they do the wing load test on all the new models ... I don't think they do it anymore on production airplanes ...
Now that I'm into aviation (just passed my private and going for my instrument) I read the NTSB Reporter and they also mentioned there was some corrosion at the rudder/body join??? I read where there was some aggresive rudder inputs from the F/O - that also exceded stress ....
Concur. Regardless of the spin, Airbus failed to meet the 1.50 goal.
Further, they decided to go with "design per computer" right to that limit.
I haven't followed the story over the years but I have seen nor long ago that they were looking at imperfections or cracks in the composites. Now you say corrosion.
That rudder input thing always struck me as bogus. If "aggressive" rudder inputs can rip the tail off THAT easily the ground would be littered with fallen planes.
Remember that the control surfaces must acutate or stop movement of a known mass at known velocities in the air. That deflecting the rudder of a plane in that particular plane's configuration, even sharply, can knock off the tail just doesn't pass the laugh test.
Ask your instructor what it would take to rip off the tail of a Cessna 150. It can be done easily BUT then extrapolate the speeds and forces involved to THAT JETLINER.
For all I know composites are fine but I suspect something was wrong with that particular plane.
I think it was the attaching bolts that failed. My instructor said you could rip the tail off by using heavy rudder inputs when turning to final if you do a heavy side-slip to get down ....
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