Airworthiness Directives; The Boeing Company Model 777-200, -200LR, -300, and -300ER Series Airplanes

摘要

We are revising an earlier proposed airworthiness directive (AD) for certain Model 777-200, -200LR, -300, and -300ER series airplanes. The original NPRM would have required 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. The original NPRM also would have required revising the Airworthiness Limitations section of the Instructions for Continued Airworthiness. The original NPRM resulted from fuel system reviews conducted by the manufacturer. This action revises the original NPRM by adding airplanes to the applicability. This action also revises the original NPRM by removing the requirement for revising the Airworthiness Limitations section of the Instructions for Continued Airworthiness. We are proposing this supplemental NPRM 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 w