The FAA is adopting a new Airworthiness Directive that supersedes an existing airworthiness directive for the MD Helicopters MD900. It requires a visual inspection and, if necessary, an eddy-current inspection of the main rotor lower hub assembly (lower hub) for a crack. If a crack exists, the AD requires replacing the lower hub with an airworthy lower hub before further flight. It also requires long-term recurring inspections unlike the superseded AD. The AD seeks to detect a crack in the lower hub and prevent failure of the lower hub and subsequent loss of control of the helicopter.