Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for RRC models 250-C30R/3, -C30R/3M, -C47B, and -C47M turboshaft engines. That AD currently requires initial and repetitive electrical signal inspections of the hydromechanical unit (HMU) Power Lever Angle (PLA) potentiometer. This proposed AD would continue to require those inspections and would add replacement of the existing HMU with a new design HMU as a mandatory terminating action to the repetitive inspection requirements. This proposed AD results from the manufacturer releasing a redesigned HMU that has a dual-element potentiometer. We are proposing this AD to prevent uncommanded and sudden changes in engine power.