Airworthiness Directives; AlliedSignal Inc. TFE731 Series Turbofan Engines

This amendment supersedes an existing airworthiness directive (AD), applicable to AlliedSignal Inc. (formerly Garrett Engine Division) TFE731 SeriesTurbofan Engines, that currently requires inspection of fan rotor disks within certain schedules. This amendment requires initial and repetitive eddy current inspections using an improved, more definitive procedure for detecting fan rotor disk dovetail slot cracks. Also, this amendment adds additional engine models and fan rotor disk part numbers and disallows fluorescent penetrant inspection (FPI) as an alternative inspection method for detecting fan rotor disk dovetail slot cracks. This amendment is prompted after additional analyses revealed that stress levels in the fan rotor disk dovetail slots for the applicable engine models are higher than initially calculated. The actions specified by this AD are intended to prevent uncontained failure of fan rotor disks due to fatigue cracking in the dovetail slots, which can result in inflight engine shutdowns, severe secondary damage, and fan rotor assembly separation from the engine.