Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to certain Fokker Model F27 Mark 100, 200, 300, 400, 500, 600, and 700 series airplanes and Model F27 Mark 050 series airplanes, that would have required revising the Airplane Flight Manual (AFM) to include requirements for activation of the airframe pneumatic deicing boots. That proposal was 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 that proposed AD are intended to ensure that flightcrews activate the pneumatic wing and tail deicing boots at the first signs of ice accumulation. This new proposed action revises the proposed rule by specifying that, at the first signs of ice accumulation, ``heavy'' automatic cycling mode must be used during operation of the deicing boots. The actions specified by this new proposed AD are intended to prevent reduced controllability of the aircraft due to adverse aerodynamic effects of ice adhering to the airplane prior to the first deicing cycle.