Summary
This document revises an earlier proposed airworthiness directive (AD) for Bell Helicopter Textron Canada Limited (Bell) Model 427 helicopters that would have required modifying each auxiliary fin (fin) by relocating the upper tuning weights to a lower position. That proposal was prompted by several incidents of main rotor blades contacting the top of the fin that have resulted in an upper tuning weight (weight) becoming loose. This action revises the proposed rule by requiring a different modification of the auxiliary fin and revising the Limitations section of the Rotorcraft Flight Manual (RFM) to reduce the never-exceed speed (Vne) for a tail rotor pedal stop failure. The actions specified by this proposed AD are intended to prevent a main rotor blade from striking a fin, loss of a tuning weight, impact with a tail or main rotor blade, and subsequent loss of control of the helicopter.