Action
Final rule.
Summary
We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 777-200, -200LR, -300, and -300ER series airplanes. This AD was prompted by fuel system reviews conducted by the manufacturer. This AD requires doing an inspection to identify the part number of the motor-operated valve (MOV) actuators of the main and center fuel tanks; replacing certain MOV actuators with new MOV actuators; and measuring the electrical resistance of the bond from the adapter plate to the airplane structure, and doing corrective actions if necessary. We are issuing this AD to prevent electrical current from flowing through an MOV actuator into a fuel tank, which could create a potential ignition source inside the fuel tank. This condition, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.