A380 wing structural failure < 1.5x Limit load

[Mitch Cronin]

http://www.flightinternational.com/Article...imate+load.html

Hey! Maybe they should put a 5th engine up in the tail and then they won't have to worry about trimming all the strength out of it to keep the weight down?

... It's a dud I tell ya! An oversized lemon of aircraft.... There's too much at stake.... who knows what compromises will worm their way into the beast? Weakened to the max in every nook and cranny in efforts to keep weight down... now it's still too heavy, and too weak! ....Note to self: Neverevereverever let your kids fly on this thing if it ever actually goes into service!

[Guest rattler]

I find the following quote from the article to be a little disturbing.

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.

[Kip Powick]

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.”

Perhaps this quote refutes what you have quoted????????

[Guest rattler]

Perhaps this quote refutes what you have quoted????????

perhaps but then:

However Garcia says that the failure of the wing below the 1.5 target will require “essentially no modifications” to production aircraft:

[Mitch Cronin]

It'll be interesting to see where this goes now... Do they wind up with a room full of NASA style rationalizers saying, "well, the "Ultimate Load" is 1.5 times the Limit Load after all... which is already the absolute maximum expected loads to be experienced in service... and we were only 3% shy at that, so that should be just fine."? ...

Will they just need to submit drawings of improvements, or will they yet have to prove the wings now in production will indeed meet that Ultimate Load for certification?

With the coin already spent on this megalodactyl, I wonder what it would take for it to be scrapped, or significantly redesigned, if they do run into serious design problems (if they haven't already!?)? ....Just seems like such a monstrous project, involving huge expenditures by so many, that the momentum to carry on regardless must be enormous! .....I find that line of thought somewhat troubling.

[ccairspace]

... It's a dud I tell ya! An oversized lemon of aircraft.... There's too much at stake.... who knows what compromises will worm their way into the beast? Weakened to the max in every nook and cranny in efforts to keep weight down... now it's still too heavy, and too weak! ....Note to self: Neverevereverever let your kids fly on this thing if it ever actually goes into service!

Speak up sir! Don't mumble into your moustache. Let it all out!

(Besides, as I've said before, some of us elderly types can't read print that small... )

ccairspace

[Mitch Cronin]

That's what makes keeping it small fun!

...but ok, if you insist:

I don't like this bird! I don't trust the wizards of Airbus to turn around and take their losses when things aren't right with this one!

I think they may have bet the whole farm on it and will make it work whether it should or not.

[Don Hudson]

Mitch;

The largest problem here is, none of us are, (I believe), aeronautical engineers so interpreting this information is risky. In fact, its a bit presumptuous for Flight Int'l to do so, but they are careful to stay away from predictions and let the Airbus staff speak for themselves.

I hear exactly what you're stating regarding "normalizing" a reduced standard, but this is certification stuff. Airbus said the test was "1.5x the ultimate limit". Since transport aircraft certified under the JARs are required to demonstrate a flaps-up positive g-load of 2.5 and negative load of 2.0, we might assume that an "ultimate load" is somewhere above 3.5g's, which, for transport category aircraft, is substantial. I think the remark from Airbus would mean that there was little "built-in" residual margin above their expected numbers, (minus 3%, so they say). This "steady" load would be different than an instantaneous spike. The Toronto DC8 that went in after the spoilers were pulled in the air hit with over 16g's and the wing stayed together, (until the fuel-air explosion).

The Airbus statement regarding "margin" probably could be taken by abject laymen such as myself to mean that the DC8, the B707, B727 and the B747 were "over-built". (I know for a fact that the 8 and the 727 were...I tried them out on more than one occasion....on touchdown, of course... However, I take NO responsibility for the A340 and A330 "second landing" when the main bogies unlock.)

[Mitch Cronin]

Hi Don,

I remember being told in a classroom somewhere, somewhen.... that meeting that "ultimate load" of one and a half times the "limit load" is a certification requirement for primary structure... Overbuilt? Maybe....?

...another wonder that occurs to me is:

What effect will fatigue have, over time, on a structure that is somewhat less "overbuilt"...?

I know fatigue testing is done, but I also know that the odd blue moon has shone, and occasionally an aircraft that passed all the tests has had some difficulty.

I guess at the root of my concern is all the money spent before difficulties showed up... so I imagine a huge, unstoppable steamroller driving it through to market.

Whatever.... I guess I should just shut up and watch... Ultimately, I'm sure they'll fly this bird however it ends up.

[plankspanker]

I remember being told in a classroom somewhere, somewhen.... that meeting that "ultimate load" of one and a half times the "limit load" is a certification requirement for primary structure... Overbuilt? Maybe....?

I was taught the same in college. Limit load is the absolute maximum expected loading in service. ie. getting bounced around in serious turbulence with a full payload or maneuvering at max G loadings etc.... and then just to be sure you prove the airframe to one and a half times that limit load amount to ensure a little, and this is the technical term "wiggle room".

[Guest rattler]

Of course when the "Limit Load" is exceeded things can go south.

Aircraft failure

Here is an article on the Boeing testing of the 777

Boeing 777 Limit Load Testing

[conehead]

Saw a picture recently of a C-130 that had a wing snap off during refueling. Pretty weird.