Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200F, 747-200C, 747-300, 747SR, and 747SP Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing transport category airplanes listed above. This AD requires an initial inspection to identify all H-11 steel bolts on the outer chord of the body station (BS) 2360 aft pressure bulkhead between stringers 12L and 12R, follow-on repetitive inspections to identify all remaining H-11 steel bolts on the entire outer chord of the BS 2360 aft pressure bulkhead, and follow-on and corrective actions if necessary. This AD also requires eventual replacement of all H-11 steel bolts with Inconel bolts. This action is necessary to prevent broken bolts, which could result in progressive failure of the remaining bolts and consequent structural damage, rapid depressurization, and loss of control of the airplane. This action is intended to address the identified unsafe condition.