Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 747-100, 747-100B, 747-100B SUD, 747- 200B, 747-200C, 747-300, 747-400, 747-400D, and 747SR series airplanes. For certain airplanes, the original NPRM would have required a material type inspection to determine if the lower forward corner reveal of the number 3 main entry doors (MEDs) is a casting. If the reveals are castings, the original NPRM would have required repetitive inspections of the reveals for cracking, and corrective action if necessary. If the reveals are not castings, the original NPRM would have required a detailed inspection of the reveals for a sharp edge and repetitive inspections of the reveals for cracking, and corrective action if necessary. For certain other airplanes, the original NPRM would have required only a detailed inspection of the reveals for a sharp edge and repetitive inspections of the reveals for cracking, and corrective action if necessary. For certainother airplanes, the original NPRM would have required repetitive inspections of the reveals for cracking only, and corrective action if necessary. The original NPRM resulted from reports of cracking and/or a sharp edge in the lower forward corner reveal of the number 3 MEDs. This action revises the original NPRM by reducing the compliance times for doing certain inspections and allowing a certain replacement as an optional action for the material type inspection for certain airplanes. We are proposing this supplemental NPRM to detect and correct fatigue cracking of the lower forward corner reveal of the number 3 MEDs, which could lead to the door escape slide departing the airplane when the door is opened and the slide is deployed, and consequent injuries to passengers and crew using the door escape slide during an emergency evacuation.