Airworthiness Directives; McDonnell Douglas Models DC-3 and DC-4 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain McDonnell Douglas Models DC-3 and DC-4 series airplanes that requires an inspection to determine the type of airframe pneumatic deicing boots installed. This amendment also requires revising the Airplane Flight Manual (AFM) to include requirements for activation of the pneumatic deicing boots for those airplanes equipped with "modern" boots. This amendment is prompted by reports of inflight 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 ensure 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.