AD FAA-2009-0556

We are adopting a new airworthiness directive (AD) for certain Boeing Model 747-400 and -400F series airplanes. This AD requires modifying certain thrust reverser control system wiring to the flap control unit (FCU). This AD results from a report of automatic retraction of the leading edge flaps during takeoff due to indications transmitted to the FCU from the thrust reverser control system. We are issuing this AD to prevent automatic retraction of the leading edge flaps during takeoff, which could result in reduced climb performance and consequent collision with terrain and obstacles or forced landing of the airplane.