Airworthiness Directives; Pilatus Aircraft LTD Models PC-6/B1-H2, PC-6/B2-H2, PC-6/B2-H4, and PC-12 Airplanes

This amendment adopts a new airworthiness directive (AD) that applies to certain Pilatus Aircraft LTD (Pilatus) Models PC-6/B1-H2, PC-6/B2-H2, PC-6/B2-H4 airplanes and all Pilatus Model PC-12 airplanes. This AD requires amending the Limitations Section of either the airplane flight manual (AFM) or the pilot's operating handbook (POH) to prohibit the positioning of the power levers below the flight idle stop while the airplane is in flight. This AFM amendment will include a statement of consequences if the limitation is not followed. This AD results from numerous incidents and five documented accidents involving airplanes equipped with turboprop engines where the propeller beta was improperly utilized during flight. The actions specified by this AD are intended to prevent loss of airplane control or engine overspeed with consequent loss of engine power caused by the power levers being positioned below the flight idle stop while the airplane is in flight.