AD FAA-2010-0410

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2010-05-51, which was sent previously to all known U.S. owners and operators of ECF Model EC120B helicopters by individual letters. This AD requires, at specified intervals, inspecting the main rotor head rotor hub (rotor hub) for a crack. If you find scoring, paint flaking or left-over identification plate adhesive, the AD requires sanding the area until the primer coat becomes visible and inspecting the rotor hub for a crack. If you find a crack, the AD requires, before further flight, replacing the rotor hub with an airworthy rotor hub. This amendment is prompted by a mandatory continuing airworthiness information (MCAI) AD issued by the European Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Community. The MCAI AD states that ECF has been informed of an emergency landing due to excessive vibrations originating from the main rotor. After an investigation, it was determined that the main rotor head rotor hub (rotor hub) had failed in the attachment area of one of the three drag damper fittings. The actions specified by the AD are intended to prevent failure of a hub, excessive vibrations, loss of a main rotor blade, and subsequent loss of control of the helicopter.