Originally Posted by Grunf
TightSlot:
It does go more or less along the lines I have already posted.
You do get a result based on the initial set of assumptions.
If you do not have the good result you change the assumptions.
One thing you can change is your model (FEM = finite element model - the "wire" model that in specialized software (FE) simulates the structure exposed to conditions it will see in flight).
The closer are your simulated results to tests the better it is. If you are close on the lower side that gives you few options:
1) Change the model so it can better represent the real conditions
2) Declare a weight penalty (ouch!) and pay the price
3) Reinforce the failed part of the structure and redo the test (tooooooo expensive)
Also a certain level of "convincing" and political approach is always present. All this rules can be interpreted in different way. What I quoted before from CFAR 25 is just a small portion of all that has to be satisfied in order for an aircraft to get its CofA (certificate of airworthiness).
it is up to a local CAA (regulatory body) to make that decision.
Therefore, it is not a straight yes or no answer.