Action
Final rule.
Summary
We are adopting a new airworthiness directive (AD) for all The Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747- 200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP series airplanes. This AD was prompted by a report of incidents involving fatigue cracking in transport category airplanes that are approaching or have exceeded their design service objective and a structural reevaluation by the manufacturer that identified additional structural elements that qualify as structural significant items (SSIs). This AD requires revising the maintenance or inspection program, as applicable, to include inspections that will give no less than the required damage tolerance rating (DTR) for certain SSI, performing repetitive inspections to detect cracks of all SSIs, and repairing cracked structures if necessary. Additionally, this AD requires all cracks involving an SSI or related structure in close vicinity to the SSI to be reported to Boeing. We are issuing this AD to address the unsafe condition on these products.