Airworthiness Directives; MD Helicopters, Inc. Model MD900 Helicopters

This document publishes in the Federal Register an amendment adopting Emergency Airworthiness Directive (AD) 2010-18-52 which was sent previously to all known owners and operators of MD Helicopters, Inc. (MDHI) Model MD900 helicopters by individual letters. This AD requires visually inspecting the main rotor hub (hub) for a crack. If a crack is found, this AD requires, before further flight, replacing the unairworthy hub with an airworthy hub. Additionally, if a cracked hub is found, this AD requires reporting the finding to the Los Angeles Aircraft Certification Office within 10 days of finding the crack. This AD is prompted by two reports of cracks detected in the hub in the area near the flex beam bolt hole locations during maintenance on two MDHI Model MD900 helicopters. The actions specified by this AD are intended to detect a crack in the hub and prevent failure of the hub and subsequent loss of control of the helicopter.