Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to all Boeing Model 747-400, -400D, and - 400F series airplanes. The existing AD currently requires revising the airplane flight manual (AFM) to require the flightcrew to maintain certain minimum fuel levels in the center fuel tanks, and to prohibit the use of the horizontal stabilizer fuel tank. This proposed AD would require installing new integrated display software in the integrated display units and electronic flight instrument system/engine indication and crew alerting system interface units (EIUs) of the flight deck. This proposed AD also would require revising the AFM to include procedures to prevent dry operation of the center wing and horizontal stabilizer fuel tanks; for maintaining minimum fuel levels; and for de- fueling fuel tanks. For certain airplanes, the proposed AD also requires removing G13 pin ground wires of a certain wire integration unit of the EIUs at certain connectorlocations. This proposed AD results from fuel system reviews conducted by the manufacturer. We are proposing this AD to reduce the potential for ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane.