Airworthiness Directives; The Boeing Company Model 747-100, -200B, and -200F Series Airplanes

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Model 747-100, 747-200B, and -200F series airplanes. That AD currently requires inspections to detect cracking in the upper row of fasteners holes of the skin lap joints in the fuselage lower lobe, and repair if necessary. This new AD reduces the maximum interval of the post-modification inspections. This AD results from reports of fatigue cracking on modified airplanes. We are issuing this AD to detect and correct fatigue cracking in the longitudinal lap joints of the fuselage lower lobe, which could lead to the rapid decompression of the airplane and the inability of the structure to carry fail-safe loads.