Airworthiness Directives; General Electric Company CT58 Series Turboshaft Engines

This amendment adopts a new airworthiness directive (AD), applicable to General Electric Company CT58 series turboshaft engines, that requires removal from service of certain compressor rear shafts, initial and repetitive inspections of specific critical rotating parts, and replacement if found cracked, until those parts are removed from service and replaced with improved design parts. This amendment is prompted by a stage 2 turbine wheel incident in 1993 which resulted in an increased awareness of small features on critical rotating parts which could affect part life. The actions specified by this AD are intended to prevent fatigue cracking on specific critical rotating parts, which could result in failure of the part, causing an uncontained engine failure and damage to the aircraft.