Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-400 and -400D series airplanes. This proposal would require an inspection to detect missing fasteners in the section 42 skin and internal doubler at the cutout for the ground exhaust valve of the electrical equipment; modification and rework of the doubler; repetitive inspections of the skin for cracks; and corrective actions if necessary; as applicable. This action is necessary to detect and correct fatigue cracks in the section 42 skin at the cutout for the ground exhaust valve of the electrical equipment, which could result in rapid decompression of the airplane. This action is intended to address the identified unsafe condition.