Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 747-200B, 747-300, 747-400, 747-400D, and 747- 400F series airplanes. This proposed AD would require repetitive inspections of the left- and right-hand flipper door assemblies of the engine core cowls for migrated pins and damaged flipper doors, and corrective actions if necessary. Modification of the hinge assemblies terminates the repetitive inspections. This proposed AD results from two reports of missing flipper doors for the engine core cowls. We are proposing this AD to detect and correct migrated hinge pins and damaged flipper doors, which could allow the flipper door to fall off, resulting in the potential for an engine fire to propagate into the flammable leakage zone of the strut and for the amount of fire extinguishing agent reaching the fire to be diluted, and subsequent uncontained fire in the engine strut.