AD FAA-2010-1136

This amendment supersedes an existing airworthiness directive (AD) for Sikorsky Model S-92A helicopters that currently 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 requires you to repair the MGB before further flight. This amendment retains the current requirements and expands the applicability to include another part-numbered MGB assembly and MGB housing. This amendment is prompted by the need to expand the applicability to include another MGB assembly and MGB housing that is prone to the same cracks and corrosion as the MGB listed in the current AD. The actions specified by this AD are intended to prevent the loss of the MGB and subsequent loss of control of the helicopter.