AD 2006-13-15 71 FR 36984

We are adopting a new airworthiness directive (AD) for all Mitsubishi Heavy Industries MU-2B series airplanes. This AD requires you to do the following: Remove and visually inspect the wing attach barrel nuts, bolts, and retainers for cracks, corrosion, and fractures; replace any cracked, corroded, or fractured parts; inspect reusable wing attach barrel nuts and bolts for deformation and irregularities in the threads; check the minimum breakaway torque of reused wing attach barrel nuts; replace any deformed or irregular parts; and install new or reusable parts and torque to the correct value. This AD results from a recent safety evaluation that used a data-driven approach to evaluate the design, operation, and maintenance of the MU-2B series airplanes in order to determine their safety and define what steps, if any, are necessary for their safe operation. Part of that evaluation was the identification of unsafe conditions that exist or could develop on the affected type design airplanes. We are issuing this AD to detect and correct cracks, corrosion, fractures, and incorrect torque values in the wing attach barrel nuts, which could result in failure of the wing barrel nuts and/or associated wing attachment hardware. This failure could lead to in-flight separation of the outer wing from the center wing section and result in loss of controlled flight.