AD FAA-2009-0477

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 747 series airplanes. That AD currently requires repetitive inspections to detect cracks in various areas of the fuselage internal structure, and related investigative/corrective actions if necessary. This new AD requires additional repetitive inspections for cracking of certain fuselage structure, and related investigative/corrective actions if necessary. This AD results from fatigue tests and analysis by Boeing that identified areas of the fuselage where fatigue cracks can occur. We are issuing this AD to prevent the loss of the structural integrity of the fuselage, which could result in rapid depressurization of the airplane.