Summary
We propose to adopt a new airworthiness directive (AD) for certain Model 747-400 and -400D series airplanes. This proposed AD would require a general visual inspection to determine the routing of the wire bundles in the number two and number three engine pylons near the leading edge, and related investigative and corrective actions, if necessary. For certain airplanes, this proposed AD would also require certain concurrent actions. This proposed AD results from a report of a fuel leak from the drain line of the number two engine pylon. We are proposing this AD to detect and correct chafing of the main fuel feed tube and the alternating current motor-driven hydraulic pump wire bundle, which could lead to arcing from the exposed wire to the fuel feed tube, and could result in a fire or explosion.