Lonewolf 50
In my #1883, and in barit1's #1887, mention is made hypothetically that in hindsight (!), Qantas and perhaps Rolls would have been better off giving the 972 a miss.
The specificity of the AD's and the focus on Spline wear underscore something I see too in Turbine D's post relative to failChain. Either Roll's emphasis on the singular source of the problem (Stub Pipe manufacture) as being exclusive to the 972 is accurate, or some sort of wishful thinking.
Stub Pipe 6/7 is vulnerable to fracture due poor machining or wear (caused by vibration?).
The engine's are "identical" in design and construction throughout the inventory (900), one assumes the Oiling is consistent?
Vibration, assumedly, is not present on Install or early service life, but develops.
The AD directs inspections of Spline Wear "At the Abutment Face".
Is Spline Wear due lack of Lubrication? Does it make a difference, at this point?
People do guess at the cause of important problems, especially when involved in the Industry displaying same. Rolls serves no one, least of all themselves, by being so coy.
Cross-Type Modularity is a boon, but carries some important pitfalls. One size fits all, but also screws up as a Unit. Splines carry the very reason for the powerplant's existence, a problem of any kind with these portends other than a changeout of a stub pipe.
E IPT disintegration
D Stub Pipe failure, Oil Fire
C Vibration
B Spline Slop/Imbalance issues
A Choose one or more: Poor Lubrication, causing friction and rapid wear. Poor Design, Splines don't "Pocket" in the Abutment Face. Poor Metallurgy, Insufficient Ductility. Stretching too far the limit of "Lightweight/Power". Insufficient attention to "Production Rate" verse "Quality".
Early on, I figured this problem would cost about a Billion dollars. Exclusive of Marque Tarnish. Rolls needs "Marqued" improvement in Disclosure.IMO IMO.
bear