Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to all Boeing Model 747 series airplanes. This action requires, for certain airplanes, revising the Airplane Flight Manual (AFM) to advise the flightcrew of limitations on dry (no fuel) operation of the override/jettison pumps of the center wing fuel tank. This action also requires repetitive inspections for wear or damage of the inlet check valves and inlet adapters of the override/jettison pumps, and replacement of the check valves and pumps with new or serviceable parts, if necessary. Such replacement terminates the AFM revision. This amendment is prompted by a report that inlet adapters of override/jettison pumps were found to be worn excessively, which allowed contact to occur between the inlet check valve and the inducer. The actions specified in this AD are intended to ensure that the flightcrew is advised of the hazards of dry operation of the override/ jettison pumps of the center wing fuel tank, and to detect and correct wear or damage to the inlet check valves and inlet adapters of the override/jettison pumps; such conditions, if not corrected, could result in a fire or explosion in the fuel tank during dry operation.