Airworthiness Directives; The Boeing Company Model 747-200F, 747-200C, 747-400, 747-400D, and 747-400F Series Airplanes

摘要

The FAA is superseding an existing airworthiness directive (AD), which applies to all Model 747-200F, 747-200C, 747-400, 747-400D, and 747-400F series airplanes. That AD currently requires repetitive inspections for cracking of certain fuselage internal structure (i.e., Sections 42 and 46 fuselage frames, upper deck floor beams, electronic bay access door cutout, nose wheel well, and main entry doors and door cutouts), and repair if necessary. This new AD requires additional repetitive inspections for cracking of certain fuselage structure (i.e., Section 41 fuselage frames where they connect to upper deck floor beams, and Section 41 fuselage frames between stringers (S-8 and S-12)), and related investigative/corrective actions if necessary. This AD also reduces the inspection threshold and repetitive inspection intervals for certain airplanes. This AD results from fatigue tests and analysis that identified additional areas of the fuselage where fatigue cracks can occur. We are issuing this AD to prevent the loss of structural integrity of the fuselage, which could result in rapid depressurization of the airplane.