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

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 at certain stringer fastener locations; and repair, if necessary. For certain airplanes, that AD requires a modification in certain areas where reports indicate that cracking was prevalent. This modification terminates the repetitive inspections only for those areas, and is also an option for other airplanes affected by the existing AD. This new AD requires an additional inspection of areas that may have Alodine-coated rivets installed, and repair if necessary. This AD results from a report of cracking discovered in a skin lap joint that was previously inspected using the eddy current method. We are issuing this AD to prevent rapid decompression of the airplane due to disbonding and subsequent cracking of the skin panels.