Airworthiness Directives; Rolls-Royce plc Model RB211 Turbofan Engines

This amendment adopts a new airworthiness directive (AD), that is applicable to Rolls-Royce plc (RR) model RB211-535E4-37, RB211- 535E4-B-37, and RB211-535E4-B-75 turbofan engines. This amendment requires removal from service of certain high pressure (HP) turbine discs before they reach newly established life limits. This amendment is prompted by the manufacturer's inspections and analysis of HP turbine discs that have accumulated high cycles. The actions specified by this AD are intended to prevent machining-induced cracking of the HP turbine disc which could cause an uncontained HP turbine disc failure and damage to the airplane.