Accident Sequence
During cruise flight, the airplane unexpectedly began a shallow left turn that the pilot was unable to counteract. The pilot moved the yoke to the left and right, but the left bank angle remained unaffected. The unintended left turn continued, with the bank angle becoming increasingly steeper, for three complete turns. At the completion of the third turn, the airplane's pitch was vertically nose-down, and the airplane impacted trees and terrain.
Investigation Findings
Examination of the aileron control cable circuit revealed that the inboard end of the right aileron upper cable was missing its eye splice and thimble. The cable exhibited an approximately 90-degree bend at the location corresponding to the eye, consistent with residual deformation associated with an eye loop. The cable separation did not show any kinking or heavy rubbing.
Sleeve Nonconformity
The remaining sleeve (nicropress) on the right aileron upper cable did not conform to the manufacturer's specified crimp dimensions. Tooling markings on the sleeve were not consistent with the use of the specified installation tool. In a properly installed eye splice, the cable should fracture before pulling out of its corresponding sleeve. The aileron cables had a specified limit load of 2,000 pounds. The remaining eye splice on the right aileron upper cable pulled out of its sleeve at 476 pounds. In contrast, the other five eye splices tested held more than 1,600 pounds before failure occurred in the cable.
Maintenance Records
A review of the aircraft's maintenance logbooks did not reveal any specific mention of aileron control cable replacement. However, given the variability in the appearance and characteristics of the other aileron cable sleeves, it is likely that the nonconforming sleeves were not of original manufacture.