Airworthiness Directives; The Boeing Company Model 777 Airplanes

We are adopting a new airworthiness directive (AD) for certain Model 777 airplanes. This AD requires inspecting the bolt, nut, and downstop of the slat track assembly to determine if the bolt, nut, or stops are missing and to determine if the thread protrusion of the bolt from the nut is within specified limits and parts are correctly installed, and related investigative and corrective actions if necessary. For certain airplanes, this AD also requires inspecting the slat cans at the outboard slat number 3 and 12 outboard main track locations for holes and wear damage, and corrective actions if necessary; and replacing the downstop hardware for the outboard slats number 3 and 12 outboard and inboard main track locations. This AD results from a report of a hole in the inboard main track slat can for outboard slat number 12 on a Model 777 airplane. The hole was caused when the bolt securing the downstop migrated out of the fitting and contacted the slat can. We are issuing this AD to detect and correct damage to the outboard slat main track slat cans, which can allow fuel leakage into the fixed wing leading edge in excess of the capacity of the draining system. Excess fuel leakage could result in an uncontained fire.