FAA 2023–21–07

Supersedes AD 2018–03–13 that required initial and repetitive visual inspections and fluorescent penetrant inspections (FPIs) of the main propeller shaft. This AD was prompted by an in-flight failure of a main propeller shaft on a GE Model CT7–9B engine, resulting in the loss of the propeller. This AD requires initial and repetitive visual inspections, FPIs, and ultrasonic inspections of the main propeller shaft. Depending on the results of these inspections, this AD requires replacement of the main propeller shaft. As an optional terminating action, this AD requires revising the airworthiness limitations section of the existing maintenance manual and the operator's existing approved maintenance program or inspection program, as applicable, to incorporate the tasks and reduced inspection thresholds for the main propeller shaft.