Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747-100 series airplanes, that currently requires repetitive inspections to detect cracking of the outer chord of the body station (BS) 1480 upper and lower bulkhead and longeron splice fitting; repair, if necessary; and modification of the skin splice plate, the outer chord splice fitting, and the stringer interface of the lower bulkhead, if necessary. This amendment revises the applicability of the existing AD to add additional airplanes, requires accomplishment of previously optional inspections and clarifies those inspections, extends certain compliance times, and requires additional work in certain areas. This amendment is prompted by reports that fatigue cracking has been found in the outer chord of the BS 1480 bulkhead at the overwing longeron splice on airplanes not subject to the existing AD. The actions specified by this AD are intended to detect and correct fatigue cracking of the skin, splice fittings, bulkhead web, and outer chord of the BS 1480 upper and lower bulkhead and longeron splice fitting, which could result in reduced structural integrity of the fuselage and the inability to carry limit load.