Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 757 airplanes. This proposed AD would require inspecting for discrepancies and insufficient coverage of the secondary fuel barrier, determining the thickness of the secondary fuel barrier, and corrective actions if necessary. This proposed AD was prompted by reports that inspections of the wing center section revealed defective, misapplied, or missing secondary fuel vapor barrier on the center fuel tank. We are proposing this AD to detect and correct defective surfaces and insufficient thickness of secondary fuel barrier, which could allow fuel leaks or fumes into the pressurized cabin, and allow fuel or fuel vapors to come in contact with an ignition source, which could result in a fire or an explosion.