Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-400F series airplanes. This proposal would require repetitive detailed and general visual inspections of the external fuselage skin for cracks; various inspections of the affected area where cracks are found to determine the extent of the damage; and repair of cracks. This action is necessary to detect and correct fatigue cracks in the fuselage skin and frame shear tie assemblies, which could propagate and result in possible in-flight decompression of the airplane. This action is intended to address the identified unsafe condition.