Airworthiness Directives; Boeing Model 747 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to all Boeing Model 747 series airplanes, that requires repetitive inspections to detect cracking of the forward and aft inner chords and the splice fitting of the forward inner chord of the station 2598 bulkhead, and repair, if necessary. This amendment is prompted by reports of fatigue cracking found in those areas. The actions specified by this AD are intended to detect and correct such cracking, which could result in reduced structural capability of the bulkhead and the inability of the structure to carry horizontal stabilizer flight loads.