Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 747-200F, 747-300, 747-400, and 747-400D series airplanes. This proposed AD would require a detailed inspection to detect missing fasteners from the shear clip at a certain stub frame to auxiliary sill joint, and applicable related investigative and corrective actions. This proposed AD results from reports of missing fasteners from the shear clip of the stub frame to auxiliary sill joint and cracking of the adjacent exterior skin and internal doubler. We are proposing this AD to ensure that fasteners are installed in the shear clip of the stub frame to auxiliary sill joint. Missing fasteners could result in cracks in the adjacent exterior skin and internal doubler, which can propagate and result in loss of structural integrity and sudden in-flight decompression of the airplane.