Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for certain 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 fatigue cracks in the station 320 crown frame and in window post number 3. This AD requires repetitive inspections for cracks and missing fasteners of the station 320 crown frame, cracks in the web and flange surfaces of the forward segment of window post number 3, and missing fasteners and cracks of the window upper sill; post-modification inspections for cracks of the window upper sill; a one-time fastener rework; and related investigative and corrective actions if necessary. We are issuing this AD to detect and correct fatigue cracking and missing fasteners of the station 320 crown frame, cracking of the window post number 3, and cracking of the window upper sill, which could result in an in-flight decompression and a loss of structural integrity of the fuselage.