Airworthiness Directives; Airbus Airplanes

We are adopting a new airworthiness directive (AD) for certain Airbus Model A300 B4-600R series airplanes; Model A300 B4-603, B4-620, and B4-622 airplanes; Model A300 C4-605R Variant F airplanes; and Model A300 F4-605R airplanes. This AD was prompted by a determination that the top stringer joints at rib 18 are an area of uniform stress distribution, which indicates that cracks may develop in adjacent stringers at the same time. This AD requires an inspection of the upper wing skin and top stringer joints, and modification of the stringer joint couplings if necessary. We are issuing this AD to address the unsafe condition on these products.