Airworthiness Directives; Boeing Model 747-100B SUD, 747-200B, 747-300, 747-400, and 747-400D Series Airplanes

摘要

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 747-100B SUD, 747-300, 747-400, and 747-400D series airplanes; and Model 747-200B series airplanes having a stretched upper deck. This proposed AD would require repetitively inspecting for cracking or discrepancies of the fasteners in the tension ties, shear webs, and frames at body stations 1120 through 1220, and related investigative and corrective actions if necessary. This proposed AD results from new reports of severed tension ties, as well as numerous reports of cracked tension ties, broken fasteners, and cracks in the frame, shear web, and shear ties adjacent to tension ties for the upper deck. We are proposing this AD to detect and correct cracking of the tension ties, shear webs, and frames of the upper deck, which could result in rapid decompression of the airplane.