Airworthiness Directives; Short Brothers Model SD3-30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Short Brothers Model SD3-30, SD3-60, SD3-SHERPA, and SD3-60 SHERPA series airplanes. This amendment requires revising the Airplane Flight Manual (AFM) to modify the limitation that prohibits positioning the power levers below the flight idle stop during flight, and to provide a statement of the consequences of positioning the power levers below the flight idle stop during flight. This amendment is prompted by incidents and accidents involving airplanes equipped with turboprop engines in which the ground propeller beta range was used improperly during flight. The actions specified by this AD are intended to prevent loss of airplane controllability, or engine overspeed and consequent loss of engine power caused by the power levers being positioned below the flight idle stop while the airplane is in flight.