AD FAA-2015-1421

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 767-300 and -300F series airplanes. This AD was prompted by reports of fatigue cracking on airplanes with Aviation Partners Boeing winglets installed. This AD requires high frequency eddy current (HFEC) inspections for cracking of the lower outboard wing skin, and repair or modification if necessary. This AD also requires one of three follow-on actions: Repeating the HFEC inspections, modifying certain internal stringers and oversizing and plugging the existing fastener holes of the lower wing, or modifying the external doubler/tripler and doing repetitive post-modification inspections. We are issuing this AD to address the unsafe condition on these products.