Airworthiness Directives; Pilatus Aircraft Ltd. Models PC-6, PC- 6/A, PC-6/B, and PC-6/C Series Airplanes

This amendment adopts a new airworthiness directive (AD) that applies to certain Pilatus Aircraft Ltd. (Pilatus) Models PC-6, PC-6/A, PC-6/B, and PC-6/C series airplanes equipped with turbo-prop engines. This AD requires modifying the fuel system to improve the venting between the collector tank, the main wing tanks, and the engine. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. The actions specified by this AD are intended to prevent engine fuel starvation during maximum climb and descent caused by poor fuel tank venting with low fuel levels, which could result in a loss of engine power during critical phases of flight.