Summary
We propose to adopt a new airworthiness directive (AD) for all Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747- 200F, 747-300, 747-400, 747-400D, 747-400F, and 747SR series airplanes. This proposed AD would require repetitive inspections for cracks or fractures of the forward end attachment and the forward lower flange of the flap tracks of the trailing edge flaps, and corrective actions if necessary. For certain airplanes, this proposed AD would also require modifying the fail-safe links of the main carriage. This proposed AD results from a detailed structural analysis of the flap attach structural and fail-safe components, accomplished as a result of a dynamic stability and control analysis, which could not demonstrate continued safe flight and landing of the airplane after the loss of a trailing edge flap. We are proposing this AD to detect and correct cracks or fractures of the primary structural and fail-safe load paths of the inboard and outboard trailing edge flaps, which could result in the loss of a flap during takeoff or landing, reducing flightcrew ability to maintain the safe flight and landing of the airplane.