Summary
The FAA is revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 757 airplanes. The original NPRM would have required, for certain airplanes, reworking the spar bonding path and reapplying sealant; and, for certain other airplanes, testing the electrical bond between the engine fuel feed hose and the wing front spar and, if applicable, reworking the spar bonding path and reapplying sealant. The original NPRM also would have required, for all airplanes, an inspection to ensure the electrical bonding jumper is installed between the engine fuel feed tube and the adjacent wing station. The original NPRM resulted from fuel system reviews conducted by the manufacturer. This action revises the original NPRM by requiring operators that may have installed an incorrect O-ring to install the correct part and do a re-test. We are proposing this supplemental NPRM to prevent arcing or sparking at the interface between the bulkhead fittings of the engine fuel feed tube and the front spar during a lightning strike, which could provide a possible ignition source for the fuel vapor inside the fuel tank and result in a fuel tank explosion.