Airworthiness Directives; Rolls-Royce plc Turbofan Engines

We are adopting a new airworthiness directive (AD) for certain Rolls-Royce plc (RR) RB211 Trent 768-60, 772-60, and 772B-60 turbofan engines. This AD requires modification of the engine by removing an electronic engine control (EEC) incorporating EEC software standard A14 or earlier and installing an EEC eligible for installation. This AD was prompted by an uncontained multiple turbine blade failure on an RR RB211 Trent 772B turbofan engine. We are issuing this AD to prevent failure of the intermediate-pressure (IP) turbine disk drive arm or burst of the high-pressure turbine disk, which could lead to uncontained engine failure and damage to the airplane.