Summary
The FAA is revising an earlier NPRM for an airworthiness directive (AD) that applies to all Airbus Model A318, A319, A320, and A321 airplanes. The original NPRM would have superseded an existing AD that currently requires inspecting to determine the part number and serial number of the fuel tank boost pumps and, for airplanes with affected pumps, revising the airplane flight manual (AFM) and the FAA- approved maintenance program. The existing AD also provides for optional terminating action for compliance with the revisions to the AFM and the maintenance program. The original NPRM proposed to require modifying or replacing the fuel tank boost pumps, which would terminate the AFM limitations and the maintenance program revisions. The original NPRM resulted from a report that a fuel tank boost pump failed in service, due to a detached screw of the boost pump housing that created a short circuit between the stator and rotor of the boost pump motor and tripped a circuit breaker. This new action revises the original NPRM by excluding certain modified airplanes from the applicability, requiring the AFM/maintenance program revisions on additional airplanes, and requiring modification or replacement of additional fuel tank boost pumps. We are proposing this supplemental NPRM to prevent electrical arcing in the fuel tank boost pump motor, which, in the presence of a combustible air-fuel mixture in the pump, could result in an explosion and loss of the airplane.