That is a very interesting set of comments. I've been intending to put up some information about splines, spline design matters, and my thoughts on vibration related to splines. I just wanted to find an example that backed up those thoughts, and I found it a couple of days ago. It was a 7th harmonic vibration in the particular example. A high harmonic is what I was thinking. As hard for me to find such a report as it was for them to find the 7th harmonic.
Looks like you have decoded the recent reports on Qantas actions and comments. I read a set of several over on Flight Global this afternoon. Apparently we both now believe that every 75 take-offs from LAX four engines are going to be scrapped (or very substantially rebuilt?). So this will have to take place back at the real factory, not at the two special RR-900 qualified shops out in the field, no?