Airworthiness Directives; Rolls-Royce plc Turbofan Engines

We propose to supersede airworthiness directive (AD) 2015-17- 19 that applies to all Rolls-Royce plc (RR) RB211 Trent 768-60, 772-60, and 772B-60 turbofan engines. AD 2015-17-19 requires inspection of the fan case low-pressure (LP) fuel tubes and associated clips and the fuel oil heat exchanger (FOHE) mounts and associated hardware. Since we issued AD 2015-17-19, fractures on the LP fuel return tube at mid-span locations were found with resulting fuel leaks. This proposed AD would require a modification, which terminates the repetitive inspections. We are proposing this AD to prevent failure of the fan case LP fuel tubes, which could lead to an in-flight shutdown, loss of thrust control, and damage to the airplane.