Airworthiness Directives; Rolls-Royce Spey 555-15, -15H, -15N, and -15P Turbofan Engines

This amendment adopts a new airworthiness directive (AD), applicable to Rolls-Royce (RR) plc. Spey 555-15, -15H, -15N, and -15P turbofan engines, that requires modification of the low pressure (LP) turbine stage 2 nozzle guide vane (NGV) support ring seal assembly. This amendment is prompted by two instances of disk drive arm damage. In both cases, heavy damage to the stage 1 LP turbine-to-stage 2 LP turbine disk drive arm occurred as a result of an out-of-balance condition following the failure of a stage 2 LP turbine blade. The actions specified by this AD are intended to prevent damage to the disk drive arm which could result in loss of stage 1 LP turbine-to-stage 2 LP turbine disk drive, a turbine overspeed condition, and possible uncontained disk failure and damage to the airplane.