Summary
We propose to adopt a new airworthiness directive (AD) for certain Rolls-Royce plc (RR) RB211 Trent 768-60, 772-60, and 772B-60 turbofan engines. This proposed AD was prompted by an uncontained multiple turbine blade failure on an RR RB211 Trent 772B turbofan engine. This proposed AD would require 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. We are proposing 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.