WojtekSz
I couldn't let this pass without some comments:
1. The composite material may be more expensive, but the end product isn't. You have to look at the bigger picture. Here is a site that gives you a picture of the machining that is required (none). Also, think about what is all required to produce a hollow titanium fan blade and inspect it for all the things that could present a problem.
GE to Auction GE90 Fan Blade at Oshkosh
The GE90 composite fan blade was not a gamble, the technology was there to do it and it was done.
2. Balancing of the GE90 fan is easier, remember, no machining of the fan blade, only the simple disc and attachment slots.
3. Read the Oxford/Rolls Royce study again. From 4/9/02 - 9/30/03, 11 Trent 500 production engines failed pass-off testing for abnormal vibrations. These are known in the business as "hanger queens". In 17 months, you can barely afford to have one hangar queen, let alone 11. This is indicative of systemic problem that requires lots of attention.
4. The best phrase here is an acronym: K.I.S.S. It means "keep it simple, stupid".
5. Small vibrations are not as hard to detect as unknown vibrations.
6. Vibrations can be measured on an instrumented engine in a test cell. The problem is they may not be the same vibrations encountered in flight on the wing of the aircraft, but, it is a good start.
7. The advantage of a three spool engine is shorter length. Therefore a shorter nacelle can be used that normally produces less drag and better aerodynamic performance for most aircraft. However, the disadvantage is the SFC of a three spool engine is generally less than a longer two spool engine and it could turn out to be a wash. It has been reported the GP7200 engine has better SFC than the Trent 900 in the same nacelle, not a surprise.
8. Only the weak link in the chain.
9. Continuous improvement is important in any business and every organization making up the business including top management. This starts at the very top, water always flows down the staircase and rarely up.
10. Maybe going back to the Trent 500 days, there was some handwriting on the wall there, that was missed as the technology envelope was pushed.
11. A lesson learned on the A-340 that hit the wall on the ground in which they couldn't shut off the engine for 5 hours was thought to be a not repeatable incident.
