Static tests - when do you need to repeat them?

[NWSRG]

Folks,

With the static test approaching for the A380, I was wondering what the rules are regarding testing of different versions?

For example, once the A380 enters service, Airbus will probably try to engineer weight out of the structure, to enhance range, payload etc.

If they change some wing design detail, will the wing have to be retested?

Do Boeing have to retest the 777 wing with the changes introduced for the 772LR and 773ER?

Or for the A345/346, with a significantly bigger wing than the A343, did this structure have to go through a full destructive test?

Seems a rather expensive test, snapping a set of perfectly good wings! I'm sure the manufacturers don't like to overdo it!

[Genghis the Engineer]

Absolutely, they fight tooth and nail to keep load testing to an absolute minimum - it's a very expensive and time consuming occupation.

In this day and age, static testing is not an absolute, it's part of a wider strength analysis, and is mostly used to validate a complex combination of finite element analysis and supporting manual calculations. It will also almost certainly have been done based upon company predictions of the long term weight increase that derivatives of that aircraft will need.

Where part of that structure is modified later in life, proof of that is mostly by analysis, based upon the records that exist of previous analysis and testing. There are two ways in which this can be done - one (the complicated and expensive way) is to re-stress and, if necessary, re-test everything. The other (the cheaper and easier way) is to prove that the modified bit of structure is "no worse than before" from all relevant strength, inertial, flexural and resonant viewpoints. This goes on all the time, not so much from a lightening viewpoint, but usually as in-service problems, areas prone to fatigue, the need to add a new box of electronics somewhere goes on constantly through the life of the aeroplane.

G

[IBTheseus]

The A380 is to use some composite ribs as part of their weight reduction program. Presumably other parts in the wing may extend the use of composite materials.

Is there enough known about composite ribs so that this is a natural extension of composites, or is this cutting edge use?

What other large acft use composite ribs, particularly on the main wing?

Would this change the structural stress testing program to that of a new, convensional wing?