Narrative:

Commercial rating cross country flight. Trim wheel began spinning to a nose high attitude on its own. I corrected it to maintain correct altitude. It started spinning to a nose high attitude again; only this time it was stuck. I was forced to apply intense strong pressure on yoke to maintain airspeed and altitude. At this point I concluded that there must be a flight control malfunction with the trim system.as this issue began getting worse; further flight under these conditions [would] not be in my best interest for safety. I was also concerned that another flight control system may malfunction or fail. I spotted a wide gravel road where I could safely land. I notified center of the issues; reported mayday. Upon safely landing I contacted an airliner who forwarded my coordinates to center who then contacted the [local] sheriff's office. I believe the autopilot system malfunctioned. If I were in this situation again I would have tried turning off the autopilot system; reset the avionics switch and or pull the autopilot circuit breaker and see if those actions solved the problem.

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Original NASA ASRS Text

Title: C172 pilot reported experiencing runaway nose up trim which required strong counter pressure on the yoke to maintain altitude and airspeed. A precautionary landing on a road was completed without incident.

Narrative: Commercial rating cross country flight. Trim wheel began spinning to a nose high attitude on its own. I corrected it to maintain correct altitude. It started spinning to a nose high attitude again; only this time it was stuck. I was forced to apply intense strong pressure on yoke to maintain airspeed and altitude. At this point I concluded that there must be a flight control malfunction with the trim system.As this issue began getting worse; further flight under these conditions [would] not be in my best interest for safety. I was also concerned that another flight control system may malfunction or fail. I spotted a wide gravel road where I could safely land. I notified Center of the issues; reported Mayday. Upon safely landing I contacted an airliner who forwarded my coordinates to Center who then contacted the [local] Sheriff's Office. I believe the autopilot system malfunctioned. If I were in this situation again I would have tried turning OFF the autopilot system; reset the avionics switch and or pull the autopilot circuit breaker and see if those actions solved the problem.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.