resonance and balance
I want to come back to DERG´s last entry before he encountered the "Thunderstorm".
I too believe that since SchaefflerGroup / FAG as the bearing supplier has denied a failure of their bearing(s) as a primary cause, the case is down to the bottom where a closer look should be taken on resonance and to a lesser degree on balance.
Since it was mentioned in this thread repeatedly that vibrations are common in jet engines and balancing is a well controlable issue. Only conclusion left is resonance in parts of the engine ?? probably or more likely the shafts ?
Because the engine still eats its spline connections, the AD is not recalled yet, though softened to the extend that inspections for a new engine come first after 200 cycles and than it continues with 100 cycles. But what kind of ongoing field test is that with an engine supposed to last thousands of cycles ???