Summary
This document proposes adopting a new airworthiness directive (AD) for Enstrom Helicopter Corporation (Enstrom) Model F-28A, F-28C, F-28F, TH-28, 280, 280C, 280F, 280FX, 480, and 480B helicopters. The AD would require determining the installation dates for each main rotor push-pull control rod (push-pull rod), inspecting the push-pull rods for corrosion, replacing any push-pull rod which has corrosion that is severe enough to cause pitting, or has visible moisture inside the rod, and repairing each push-pull rod that has corrosion but no pitting. This proposal is prompted by one reported incident in which the helicopter pilot encountered severe in flight vibration due to the failure of a push-pull rod, requiring an emergency landing. The actions specified by the proposed AD are intended to detect corrosion and prevent failure of a push-pull rod, and subsequent loss of control of the helicopter.