Airworthiness Directives; Harbin Aircraft Manufacturing Corporation Model Y12 IV Airplanes

This document adopts a new airworthiness directive (AD) that applies to all Harbin Aircraft Manufacturing Corporation (Harbin) Model Y12 IV airplanes. This AD requires you to revise the Airplane Flight Manual (AFM) to include requirements for activating the airframe pneumatic deicing boots. This AD is the result of reports of in-flight incidents and an accident that occurred in icing conditions where the airframe pneumatic deicing boots were not activated. The actions specified by this AD are intended to assure that flightcrews have the information necessary to activate the pneumatic wing and tail deicing boots at the first signs of ice accumulation. Without this information, flightcrews could experience reduced controllability of the aircraft due to adverse aerodynamic effects of ice adhering to the airplane prior to the first deicing cycle.