Airworthiness Directives; The Boeing Company Model 757 Airplanes

We are superseding an existing airworthiness directive (AD) for the products listed above. That AD currently requires sealing the fasteners on the front and rear spars inside the left and right main fuel tanks and on the rear spar and lower panel of the center fuel tank. That AD also requires inspections of the wire bundle support installations to verify if certain clamps are installed and if Teflon sleeving covers the wire bundles inside the left and right equipment cooling system bays, on the left and right rear spars, and on the left and right front spars; and corrective actions if necessary. This new AD also requires sealing the additional fasteners on the rear spar inside the left and right main fuel tanks. This AD was prompted by a fuel system review conducted by the manufacturer. We have received reports from the manufacturer that additional fasteners in the main fuel tanks must be sealed for lightning strike protection. We are issuing this AD to detect and correct improper wire bundle support installation and sleeving and to prevent improperly sealed fasteners in the main and center fuel tanks from becoming an ignition source, in the event of a fault current or lightning strike, which could result in a fuel tank explosion and consequent loss of the airplane.