Summary
This document proposes to supersede Airworthiness Directive (AD) 94-04-17, which currently requires the following on Twin Commander Aircraft Corporation (Twin Commander) 500, 520, 560, 680, 681, 685, 690, 695, and 720 series airplanes: inspecting (one-time) the flap system for cables with broken wires or pulleys with worn cable clips, replacing any damaged parts, and replacing the master pulley and cable with new parts of improved design. The proposed AD would require inspecting all flap system cable grooves for the correct width, inspecting all flap system pulleys for rubbing on the support brackets, inspecting all flap pulley cable assemblies for frayed wires, and reworking or replacing any parts with discrepancies. The proposed AD results from several reports of worn and frayed flap system cables attributed to flap pulley grooves that are too narrow. The actions specified by the proposed AD are intended to prevent failure of a flap system cable caused by fatigue, which could result in loss of control of the airplane.