Originally Posted by
medod
Hopefully I have engaged my brain now.
So this *was* the ultimate load test, and the airframe gave way at 99% — in what must be a fairly unusual way? Is the object of this test to test the wings alone or the fuselage and wings as a unit? My introduction to the test was the 777 documentary way back and I’ve always assumed only the wings were being tested.
It must be a safe bet that Boeing didn’t expect the fuselage to fail, but is it possible that the failure is an artefact of the test?
It is almost impossible to run an ultimate load test on ' only' the wings or 'only' the fuselage except for some ' partial conditions ".. For example over 60 years ago, the 707 fuselage section was immersed in a large water tank and pressurized hundreds- or thousands of times- this the result of Comet disaster re fatigue of window frames. But when it comes to an ultimate test of factory production assembled wings at least part of the fuselage ( above the wingbox ) is involved. -This since to bend the wings up one has to hold something down and if a way was figured out to simply hold the assembled fuselage ONLY above the wing box, it would then call into question about how various loads were distributed, etc. So it is much more realistic ( not discussing regulations for the moment ) to include the whole fuselage (cockpit- above wingbox- fuselage section aft of wingbox - and tail section including aft pressure bulkhead, etc )
Most of the regulations- requirements - were/are the result of the comet disaster- and no doubt further enhanced by the Electra ' whirl mode' disasters. I'm sure a more qualified person than myself can- could expand on my overview above .
BTW then 767 ultimate load test on wings etc failed due to loads on the aft section and a missing stringer- circumferential near the rear door. result was a approx 10 degree twist of the aft section from normal visible later by the cocked from vertical vertical stabilizer section.