Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-100B SUD, 747-200B, 747-300, 747-400, and 747-400D series airplanes. This AD was prompted by an evaluation by the design approval holder (DAH) indicating that the upper deck tension ties are subject to widespread fatigue damage (WFD). This AD requires repetitive inspections for cracking in the upper deck tension ties, and related investigative and corrective actions if necessary; tension tie replacement; and post-replacement repetitive inspections for cracking in the upper deck tension ties, and related investigative and corrective actions if necessary. We are issuing this AD to detect and correct fatigue cracking of the upper deck tension ties. Severed or disconnected tension ties at multiple locations could result in rapid decompression and loss of structural integrity of the airplane.