Airworthiness Directives; Sikorsky Aircraft Corporation Model S-92A Helicopters

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2009-23-51, which was sent previously to all known U.S. owners and operators of Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters by individual letters. This AD requires cleaning and inspecting each main gearbox (MGB) assembly mounting foot pad and rib for a crack and corrosion. If you do not find a crack, the AD requires applying a corrosion preventive compound. If you find a crack, the AD requires replacing the MGB before further flight. If you find corrosion, bubbled paint, or paint discoloration, the AD also requires you to repair the MGB before further flight. This amendment is prompted by reports of cracks in the MGB mounting foot pads and foot ribs. This condition, if not detected, could result in loss of the MGB and subsequent loss of control of the helicopter.