[rolph]

ok 1: the wings were bent in an extreme manner.

so you have a cylinder to a close approximation, with a hole in the side of it. Then you have two levers [wings] affixed to said cylinder, then you apply force to the levers, and distort the cylinder thus distorting the hole in the cylinder....

at this point i would invoke a toplogical parlour trick of making a quarter fall through a dime sized hole as an analogy.

https://prop-tricks.wonderhowto.com/how-to/do-large-coin-sma...

my hypothesis is that the entire airframe flexed causing the door frame to distort thus loosing its grip on the door panel, then FOOF! door goes away!

[rolph]

If you dont think this is the case then lets hear your critique, please tell me why you think this is not the case. then if there is time left i can change my most recent actions in this thread

..."The test is meant to push the plane beyond its limits. Engineers had the plane pressurized and on the ground. They loaded it up well beyond capacity and BENT ITS WINGS in an extreme manner, in a way almost certain to never happen in the real world."

[donarb]

That was my thought as well, especially since the carbon fiber wings flex so much more. That flex might induce more stress on the wing mounts which in turn deform the cylinder. The good thing is that these test fixtures are fitted with lots of sensors that record all of the stress.

[rolph]

In my experience there are strain guages installed all over the air frame for testing and for operation, so the strain history of the frame can be reviewed.

The thing to keep in mind, is the different goals in testing engineered products like this.

there is a thing called Mean Time Before Failure [MTBF] that usually involves sampling of a number of units to arrive at a maintenance and replacement interval.

there is also a need to find the maximim service limits of a product, for example the swash plates and rotor linkage of a helicopter has a threshhold requiring at instance replacement. so for example, if you shook the yoke of a heli quickly left and right beyond a point you will probably knock yourself out of the air, but you will also induce damage requireing immediate replacement.

and then, there is what happened with the airframe of topic. immediate catastrophe during testing. I suspect this wasnt the immediate goal, as the engineers projected it would hold up, and were suprised, luckily not injured.

then the last thing that is usually a pre-production test, is an intentional induction of failure. you have a good idea when its going to break, and you take it there and beyond to gawp at the failure mode and the pieces, and re- engineer it until catastrophe is far beyond extreme duty conditions.[ideally]