There is one piece of evidence to what is the root cause of the oil pipe cracking which has not been debated here. In the court filing that Qantas filed there is the following statement (from flightglobal
http://www.flightglobal.com/blogs/wings-down-under/2010/12/fixing-rolls-royces-disposable-a380-engines.html)
However, the extra thrust exposes the engine to 540 psi at P30, which causes the engine to experience "high severity", the affidavit says. Rolls-Royce's interim suggestion to Qantas has to been to derate the engines in order to "reduce the engine pressure ratio in the 'P30' area of the engine and therefore increase the life of the oil transfer tubes within the HP/IP support structure", the affidavit says.
This seems to indicate that the pressure causes movement of the structure where the stub oil pressure pipe enters into the bearing box. My conclusion is that on the A and B engines the support structure between HPT and IPT is simply not strong enough to stop the bearing box from moving at max thrust to such a level that it affects the pipes fatigue life. The solution is a strenghtend support structure. It is a big operation and explains why in the A version the problem was dectected but to late to fix it for production of the engine, the B mod is a reinforcement of the original structure and the C mod is a redesigned support structure that fixes the problem (but had to be extensively tested before applying it). The flight blogger concludes that the oil pipe needed strengthening, this is an easy fix and should not have required 3 different versions of the engine therefore I don't think this is the fix in the C mod. Further the crack is where the stub oil pipe meets the bearing box, if the box is moving a stronger pipe is not the fix, you need a more flexible and durable pipe but primarly a box that is not moving.
So what is the communities thought about this piece of evidence
?