Airworthiness Directives; Boeing Model 747-100 Series Airplanes

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100 series airplanes. This action requires repetitive inspections to detect cracking of the outer chord of the Body Station (BS) 1480 upper and lower bulkhead and longeron splice fitting, and repair, if necessary. Alternatively, this action requires other repetitive inspections to detect cracking of the BS 1480 upper and lower bulkhead, bulkhead outer chord, web, skin, splice components, and lower bulkhead/stringer interface; and modification of the skin splice plate, the outer chord splice fitting, and the stringer interface of the lower bulkhead, if necessary. This amendment is prompted by a report indicating that fatigue cracking was found in the outer chord of the BS 1480 bulkhead at the overwing longeron splice, and that the longeron splice fitting was completely severed. The actions specified in this AD are intended to detect and correct fatigue cracking of the BS 1480 bulkhead outer chord and longeron splice fitting, which could result in reduced structural integrity of the fuselage and the inability to carry limit load.