Summary
The FAA is revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 747 and 767 airplanes. The original NPRM would have required reworking the electrical bonding between the airplane structure and the pump housing of the outboard boost pumps in the main fuel tank of certain Boeing Model 747 airplanes, and between the airplane structure and the pump housing of the override/jettison pumps in the left and right wing center auxiliary fuel tanks of certain Boeing Model 767 airplanes. The original NPRM would also have required related investigative actions and corrective actions if necessary. The original NPRM resulted from fuel system reviews conducted by the manufacturer. This action revises the original NPRM by adding an inspection requirement for certain Model 747 airplanes, and by specifying cold-working the fastener holes for certain other Model 747 airplanes. We are proposing this supplemental NPRM to prevent insufficient electrical bonding, which could result in a potential of ignition sources inside the fuel tanks, and which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.