Originally Posted by
tdracer
GE/Pratt design practice is that if the LP shaft breaks, it'll move aft enough that the turbine blades will clash with the turbine nozzles in a controlled manner to bring the shaft to a stop. Otherwise the unloaded LP shaft will quickly overspeed (Rolls had issues with this on the RB211 about 35 years ago - cut the back off a 747 engine when the LP turbine came apart).
The issue with the GEnx fan shaft was related to use of the wrong anti-seize compound during assembly of the fan shaft - this caused stress corrosion which then failed the shaft.
Ah, I'd heard the initial thinking that it was hydrogen embrittlement caused by insufficient baking after a plating process...
As an engineer it's always frustrating when the people building your design don't build it in the way one has specified. Grrr.