Summary
The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to Honeywell International, Inc., (formerly AlliedSignal, Inc., Textron Lycoming, Avco Lycoming, and Lycoming) former military T53 series turboshaft engines (herein referred to as Lycoming) having certain part numbers of centrifugal compressor impellers installed. This proposal would require conducting a revised operating cycle count (prorate) and initial and repetitive inspections for cracks of those compressor impellers. This proposal is prompted by a report of a military surplus helicopter that experienced low-cycle fatigue failure of the centrifugal compressor impeller, resulting in an uncontained engine failure. The actions specified by the proposed AD are intended to prevent centrifugal compressor impeller failure, which can result in an uncontained engine failure, in-flight engine shutdown, or damage to the helicopter.