Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Rolls-Royce (RR) plc Spey 555-15, -15H, -15N, and -15P turbofan engines. This proposal would require modification of the low pressure (LP) turbine stage 2 nozzle guide vane (NGV) support ring seal assembly. This proposal 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 the proposed 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.