Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for certain Boeing Model 747 series airplanes. That AD currently requires repetitive inspections to detect cracks in various areas of the fuselage internal structure, and repair if necessary. This proposed AD would require repetitive inspections of additional areas of the fuselage internal structure, and related investigative/corrective actions if necessary. This proposed AD also would remove certain requirements from the existing AD. This proposed AD is prompted by the results of fatigue testing of the fuselage structure of a Boeing Model 747SR series airplane. We are proposing this AD to prevent the loss of the structural integrity of the fuselage, which could result in rapid depressurization of the airplane.