Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 747-100B SUD, 747-200B, 747-300, 747- 400, 747-400D series airplanes. This proposed 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 proposed AD would require 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 proposing 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.