Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for Rolls-Royce plc RB211 Trent 875-17, Trent 877-17, Trent 884-17, Trent 892-17, Trent 892B-17, and Trent 895-17 turbofan engines with high pressure (HP) compressor rotor rear stage 5 and 6 discs and cone shafts, part numbers (P/Ns) FK25230 and FK27899 installed. This proposed AD would require removing these parts at new reduced cycle limits. This proposed AD results from Rolls-Royce plc reducing the lives of these parts and changing the life calculating method to use ``Standard Duty Cycles'' with ``Multiple Flight Profile Monitoring'' and ``Flight Cycles'' with ``Heavy Flight Profile Monitoring''. We are proposing this AD to prevent stage 5 and 6 disc crack initiation and propagation that might lead to uncontained disc failure and damage to the airplane.