Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Pratt & Whitney JT8D series turbofan engines, that currently requires inspections of low pressure turbine (LPT) blade sets for blade shroud crossnotch wear, and removal, if necessary. In addition, the current AD requires, as a terminating action to the inspections, installation of improved LPT containment hardware, and installation of an improved No. 6 bearing scavenge pump bracket bushing. This action would keep the compliance actions of the current AD intact but change the compliance time for full compliance from the current calendar end-date to December 31, 1998. This proposal is prompted by a report of a fourth stage hub manufacturing defect that led to the failure of the hub and subsequent release of LPT blades. The actions specified by the proposed AD are intended to prevent damage to the aircraft resulting from engine debris following an LPT blade, shaft, or hub failure.