Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Pratt & Whitney Canada (P&WC) Model PW305 and PW305A turbofan engines. This proposal would require removing stage 4 low pressure turbine (LPT) disks from service before exceeding new, lower cyclic life limits. This proposal is prompted by the results of a spin pit test analysis which indicate that the stage 4 LPT disk does not have full published life. The actions specified by the proposed AD are intended to prevent LPT disk failure resulting from premature cracking of the LPT disks, which could result in an uncontained engine failure and damage to the airplane.