Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Pratt & Whitney (PW) JT8D series turbofan engines. This proposal would require recalculation of cyclic life limits for certain compressor and turbine disks installed on engines with hush kits (Stage III noise reduction systems) installed in accordance with PW Service Bulletin No. 5947, removal from service of disks that exceed the new, lower cyclic life limits, and replacement with serviceable parts. This proposal is prompted by reports that compressor and turbine disks have higher rotor speeds on engines with hush kits that result in lower cyclic lives. The actions specified by the proposed AD are intended to prevent compressor and turbine disk failure due to reduced cyclic lives, which could result in an uncontained engine failure and damage to the airplane.