I I
I would Suggest that the casing was tested to arrive at the 2700 hours
As riff raff quoted
Good manufacturing practice also would dictate that critical areas in a structural casting (like the attachment feet in the S-92 housing) would be areas where tensile test coupons are periodically cut from sample castings and checked for mechanical properties. This ensures that foundry processes used to produce the casting are being properly controlled.
There seems to be a flaw in either design \ material, or the loads \ vibrations analysis are way off, either way why should the 3 leg test be any better? as the original calcs seem to be adrift.