AD FAA-2009-0684

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Model 747-200C and -200F series airplanes. That AD currently requires repetitive inspections to find fatigue cracking in the floor panel attachment fastener holes of the upper chord of certain upper deck floor beams in Section 41 (i.e., body station 520 and forward), and repair if necessary. The existing AD also provides optional modifications, which extend the threshold for initiating certain repetitive inspections. This new AD requires additional repetitive inspections to find fatigue cracking in the floor panel attachment fastener holes of the upper chord of certain other upper deck floor beams in Section 41 and Section 42 (i.e., aft of body station 520); repetitive inspections to find fatigue cracking in the permanent fastener holes of the upper chord of certain upper deck floor beams in Section 41; and related investigative and corrective actions. This new AD also provides a new optional modification, which terminates certain repetitive inspections. This AD results from new reports of cracking in the upper chord of the upper deck floor beams in Sections 41 and 42, and new analysis that shows the permanent fastener holes of the upper chord of certain upper deck floor beams in Section 41 are also susceptible to fatigue cracking. We are issuing this AD to detect and correct cracking in the upper chord of the upper deck floor beams. Such cracking could extend and sever the floor beams, which could result in rapid decompression and loss of controllability of the airplane.