Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to all Boeing Model 737-100, -200, -300, -400, and - 500 series airplanes, that currently requires removal of the fuel boost pump wiring in the conduits of the wing and center fuel tanks; an inspection to detect damage of the wiring, and corrective action, if necessary; and eventual installation of Teflon sleeving over the electrical cable. That AD was prompted by reports of severe wear of the fuel boost pump wiring due to chafing between the wiring and the surrounding conduit inside the fuel tank; pin-hole-sized holes in the conduit that appear to be the result of arc-through of the conduit; and exposure of the main tank boost pump wire conductor inside a conduit and signs of arcing to the wall of the conduit. This amendment expands the inspection requirement to include additional airplanes. The actions specified by this AD are intended to detect and correct chafing and electrical arcing between the fuel boost pump wiring and the surrounding conduit, which, if not corrected, could result in arc- through of the conduit, and consequent fire or explosion of the fuel tank.