Airworthiness Directives; Rolls-Royce plc Turbofan Engines
We are adopting a new airworthiness directive (AD) for all Rolls-Royce plc RB211-Trent 970-84, RB211-Trent 970B-84, RB211-Trent 972-84, RB211-Trent 972B-84, RB211-Trent 977-84, RB211-Trent 977B-84 and RB211-Trent 980-84 turbofan engines. This AD requires on-wing inspections of low-pressure turbine (LPT) disk seal fins and interstage seals when post-flight review indicates Engine Health Monitoring (EHM) vibratory maintenance-alert limits were exceeded in flight. The AD also requires in-shop inspections of the LPT disk seal fins and interstage seals to detect cracks or damage and, depending on the findings, accomplishment of corrective action. This AD is prompted by a Trent 900 engine experiencing LPT stage 2 disk interstage seal material loss and increased low-pressure rotor vibration while in flight. We are issuing this AD to prevent cracks in the LPT disk, which could result in uncontained engine failure and damage to the airplane.