The "Tube" is not the problem
. It is the result. No matter the cause of the damage to the "Stub". Misbore or Vibration, Box movement (!), etc. The Support Structure is insufficient. In other words, the Core has mass issues, as DERG points out (as have I).
The Splines too, are not the problem. They are also a result.Oil problem? Certainly, but again, not the cause.
If the Splines were the only issue, There would be no AD, there would have been a revocation of the certificate. "Inspections only" certify that both Rolls and EASA were cognizant of the procuring cause. Again, Simply Certifying the "C" Mod as curative means that the source of the problem was KNOWN, and from the beginning. We do not know if the "C" is the complete answer, simply because QANTAS is not flying it, nor have the EASA certified the Engine as yet, UNDER THE ORIGINAL CERTIFICATE. Inspections are still required.
Think about that. This Engine has had two rebuilds since approval, and still the Engine is not released for its predicted service life. The Engine is still in TEST, can one see it any other way?? Either the engine itself with the C is complete, and needs no re-cert, or it is not, and its reliability is subject to doubt.
10 hours over water. That's the "good news". The bad? Ditch, Crash, loss of life.
Vibration, Resonance, lack of sufficient mass, destructive rapid wear. This engine had an oil fire on the stand, Remember? What happens when the Stub (IP) shaft is severed next time? At some point, the word Burst will have to be retired. It is insufficient to describe what may as yet prove out.