The A380 wing ?

[Hermano Lobo]

The A380 has just flown with passengers from Singapore to Sydney.

I remember a news item that during testing the wing failed at 1.47 struture test, it should have passed at 1.5 - Was this resolved ?

[Alternate Law]

Yes. No certification would be awarded unless the minimum requirements were acheived.

[barit1]

Remember, the max bending load on the wing is a function of ZFW (including any fuselage or CWT fuel).

Thus one possible solution for early series airplanes is to reduce ZFW by 2% (the amount of the ultimate test shortfall) - until the wing structure is upgraded and retested. It's a problem, certainly an economic one, but not insurmountable.

[Mudfoot]

As the break-point analysis is done, the CAD/CAM design & methods, and hence the structure, are revised for strengthing the area of breakage. Standard procedure nowadays. The authorities analyse and accept this.

Cheers, y'all.

[PBL]

To expand on Mudfoot's cryptic contribution:-

Airbus used the failed breakage test to calibrate the codes they used for the design. Using the established level of accuracy (say \alpha), they redesigned the structure at the breakpoint and validated the redesigned wing using the codes to a level of at least (1.5 + \alpha) times design load, and provided all this evidence to the certification authorities, which accepted it as equivalent to a wing test.

PBL

[old,not bold]

Not a contribution to this discussion; just thanks and congratulations to Mudfoot and PBL for explaining something, about which I knew nothing until I read those two posts, so succintly and clearly!

[chornedsnorkack]

So, for some reason, Airbus was not asked to build a second wing reinforced as planned, and actually break it at more than 150 % ultimate load.

If Airbus did not have to break a second wing, why did they have to break the first one, instead of simply showing analysis?

[old,not bold]

To demonstrate my new-found understanding, or otherwise, wouldn't that be because the test to destruction provided validated data that were not previously available?

[barit1]

ONB, you've basically got it. Although the static test was deemed a failure because it didn't make 150%, it was mostly successful because it provided plenty of data up to the 147% point.

These data, coupled with post-test reconstruction of the exact failure mode, give plenty of reason to believe that minor upgrades and modern analytic processes (and several tonnes of paperwork) will result in certification at the desired TOGW (ZFW actually) level.

And in service, it will be low-cycle fatigue (TO & landing cycles) that will be the telling criteria.

[lomapaseo]

When it comes to certification single tests like "jump this high" and you pass, ......a failed test with data if far more substantiating then just passing a high-jump test.

Unfortunately those with little scientific knowlege see things only as black and white like turning on and off a light switch, rather than the dawn of real understanding.