I'm curious about the testing that was done on this gearbox. I would guess that it was done on a test stand and not on an actual airframe tied to the ground. This being the case does is accurately show what the gearbox is experiencing in flight? After all, on a real helicopter it not only has to transmit the power, which is done on the test stand, but also support the weight af the entire machine as it is in flight. I doubt the test stand has the capability to simulate all this.
We see it all the time with engines that show a particular symptom on the wing but will not show it on the test cell. I'm sure nobody wants to take the chance on ruining an entire aircraft to test a gearbox failure, but at what point do we consider it an apples to apples test?
Max