Piper PA-32R-301T N4184X incident near Mount Pleasant, Texas

Probable cause

The failure of an aileron control cable due to a seized idler pulley bearing.

NTSB analysis

The pilot reported that he was in level flight with the autopilot engaged when the airplane began an uncommanded roll. The pilot disengaged the autopilot and found that the airplane’s ailerons were inoperative. The pilot made a successful landing using the rudder for directional and roll control. A postaccident examination of the airplane revealed that the right aileron primary control cable was severed where it contacted an idler pulley. That pulley would not rotate due to an out-of-tolerance idler pulley outer bearing that restricted the rotation of the pulley. It is likely that the control cable sliding against the seized pulley caused the cable to wear through. The airplane manufacturer issued a maintenance alert following this incident that highlighted the importance of proper and recurring inspections of the flight control cables and pulleys.

Text from the NTSB. Open the NTSB docket for CEN10IA453 for the full record.