Airworthiness Directives; Pilatus Aircraft Ltd. Models PC-12 and PC-12/45 Airplanes

This document adopts a new airworthiness directive (AD) that applies to all Pilatus Aircraft Ltd. (Pilatus) Models PC-12 and PC-12/ 45 airplanes that are equipped with pneumatic deicing boots. This AD requires you to revise the Airplane Flight Manual (AFM) to include requirements for activation of the airframe pneumatic deicing boots. This AD is the result of reports of in-flight incidents and an accident (on airplanes other than the affected Pilatus airplanes) that occurred in icing conditions where the airframe pneumatic deicing boots were not activated. The Pilatus Models PC-12 and PC-12/45 airplanes have a similar type design (as it relates to airframe pneumatic ice boots) to the incident and accident airplanes. The actions specified by this AD are intended to assure that flightcrews activate the pneumatic wing and tail deicing boots at the first signs of ice accumulation. This action will prevent reduced controllability of the aircraft due to adverse aerodynamic effects of ice adhering to the airplane prior to the first deicing cycle.