AD FAA-2009-0794

We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747- 200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes. This AD was prompted by reports of cracks in the main entry door number 1 upper main sill outer chord, along the bend radius of the chord on several airplanes. This AD requires a general visual inspection to identify any existing structural repair manual (SRM) repairs of the upper main sill outer chord of the left and right side main entry door number 1, repetitive detailed inspections for cracks in the upper main sill of the door(s); and related investigative and corrective actions, if necessary. This AD also requires repetitive inspections for airplanes on which a certain repair is done, and corrective actions if necessary, and reduces certain compliance times. We are issuing this AD to detect and correct cracks in the main entry door number 1 upper main sill outer chord, along the bend radius of the chord, which could result in loss of structural integrity of the airplane.