[hinckley buzzard]

Would it not be a routine procedure to take a critical element (like the wing) to the breaking point in tests? I'm no engineer, but I think I would want to know what the real limit is, and there's only one way to find out.

[Robert A Cook PE]

That is what they did: Go past the "maxuimum expected load" to 1.50 times max expected and see if it stays together.

It didn't meet the requirement of 1.50 times max load, but broke at 1.47 maximum expected load.