The Federal Aviation Administration (FAA) has proposed a new airworthiness directive (AD) for certain 747-400F series aircraft, addressing the findings of a report that suggests cap seals were not applied to certain fasteners during production. A consultation window is open until May 28, 2024, with the FAA proposing the remedial action of applying cap seals to certain fastener collars inside the fuel tanks.
The FAA has determined ‘that the actions identified in this proposed AD are necessary to reduce the potential of ignition sources inside fuel tanks which in combination with flammable fuel vapors, could result in fuel tank explosion or fire’.
Although an earlier AD (issued in 2022) aimed to address the ‘application of cap seals to certain fasteners in the fuel tank on airplanes having line numbers 645 through 1363 inclusive’, Boeing subsequently discovered that the design change ‘omitted application of the cap seals on eight fasteners,’ explains the FAA. In the event of a lightning strike or high-powered short circuit, the aircraft could therefore be susceptible to an ignition source in the fuel tank.
FAA proposes new AD for certain 747-400Fs
