Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for certain GEAE CT7-8A turboshaft engines. That AD currently requires initial and repetitive inspections of the electrical chip detectors for the No. 3 bearing. This proposed AD would require removing certain GEAE CT7-8A turboshaft engines within 6,200 cycles- since-new. This proposed AD results from investigation for the root causes of two failures of the No. 3 bearing. We are proposing this AD to prevent failure of the No. 3 bearing due to contamination by Aluminum Oxide, which could result in a possible dual in-flight shutdown of the engines.