Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 747-400 and 747-400F series airplanes. This proposed AD was prompted by an evaluation that determined fatigue cracks could develop in the underwing longerons. This proposed AD would require repetitive inspections of the underwing longerons and certain fuselage skins for any crack, and applicable on- condition actions. The FAA is proposing this AD to address the unsafe condition on these products.