Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to certain Boeing Model 747 series airplanes. The existing AD currently requires repetitive inspections to detect cracks in various areas of the fuselage internal structure, and related investigative/corrective actions if necessary. This proposed AD would require additional repetitive inspections for cracking of certain fuselage structure, and related investigative/corrective actions if necessary. This proposed AD results from fatigue tests and analysis by Boeing that identified areas of the fuselage where fatigue cracks can occur. 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.