Incident Overview
During the final approach phase of a flight, the airplane experienced a sudden and uncommanded roll to the left immediately after the pilot selected the 35-degree flap setting. The pilot responded by applying full opposite aileron input, which successfully countered the roll, allowing the aircraft to land without further incident.
Examination Findings
A post-incident examination of the left wing flaps was conducted. While the wing flaps were found to be fully extended in the aft direction, the inboard trailing edge of the left outboard flap had been forced upward approximately 3 inches. The cause was traced to the inboard aft flap track roller bearing assembly, including its attaching bolt and washer, which had pulled through the skin of the flap track hinge bracket.
Analysis by Beech
Beech performed an analysis of the failed components. It was found that the outer roller of the roller bearing assembly was loose and could be shifted axially. A circular wear pattern matching the diameter of the outer roller flange was observed on the portion of the flap track hinge bracket that had pulled out. Beech concluded that the bearing outer roller had shifted on the roller element bearing, allowing the outer roller flange to wear against the side of the flap hinge bracket until the bearing assembly was pulled out. The failed flap track hinge bracket and bearing assembly are contained within the interior of the flap structure.