Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 777-200 series airplanes. This proposal would require the application of sealant to the front spar and upper surface of the wing center section to ensure the integrity of the secondary fuel barrier. This proposal is prompted by reports from the airplane manufacturer that the sealant was inadvertently not applied to portions of the wing center section on certain Boeing Model 777-200 series airplanes. The actions specified by the proposed AD are intended to prevent fuel or fuel vapors from entering the cargo and passenger compartments in the event of a failure of the primary seal or development of a crack in the wing center section structure. Leakage of fuel or fuel vapors into the cargo and passenger compartments could be hazardous to personnel, and could cause a fire in those compartments.