Airworthiness Directives; Boeing Model 747-400, 747-400D, and 747-400F Series Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to all Boeing Model 747-400, -400D, and -400F series airplanes. That 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 new AD requires installing new integrated display system (IDS) software; and also requires 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, this new AD also requires removing certain program pin ground wires of the IDS. This AD results from fuel system reviews conducted by the manufacturer. We are issuing 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.