Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100, - 200, and -300 series airplanes. This proposal would require repetitive inspections to detect cracking of certain lower lobe fuselage frames, and repair, if necessary. This proposal is prompted by reports indicating that fatigue cracks were found in lower lobe frames on the left side of the fuselage. The actions specified by the proposed AD are intended to detect and correct fatigue cracking of certain lower lobe fuselage frames, which could lead to fatigue cracks in the fuselage skin, and consequent rapid decompression of the airplane.