Narrative:

I was on the first hour of a 4 hour flight. The cloud tops were forecast to be at 5;000 and I had filed for 6;000. I found the tops to be at over 7;000 and getting higher. Most of the traffic (including me) were asking for higher altitudes to stay out of the very bumpy cumulous clouds. The flight conditions were VMC but it was turbulent in the clouds. There was no precipitation or thunderstorm activity; it was just turbulent. I was cleared up to 10;000 and climbed to that altitude; however I was just a few hundred feet shy of getting on top and the controller could not give me higher at the moment so I entered the top of a white puffy cumulous cloud and had a couple of pretty good bumps. The autopilot was engaged and as I came out of the cloud; the controller was calling me asking why I was flying south when my as filed course was west northwest. I noted that the autopilot was flying off the desired track and so I disengaged the autopilot. However; I had trouble holding heading. As I flew on; it was clear that there was something amiss as I had to hold right aileron (at about 10 or 11 o'clock on the control wheel) to keep it flying on a straight heading. I immediately informed the controller that something was wrong (possibly with my aileron after my encounter with turbulence) and I asked for vectors to the nearest airport. He was very helpful and vectored me to a close-by airport; and once I had it in sight cleared me for the visual approach as I was in VFR conditions below 4;000. I took a couple of turns around the airport and was having difficulty with any left turns as it over-banked in that direction. I came in on a long stabilized final approach and landed safely. Having to get back to work; I left the plane with the FBO and flew home on the airlines. The FBO will give it a test flight this week to determine what the issue is. Yesterday and today three separate a&P's inspected the plane and found that the plane did not sustain any physical damage from the turbulence and they see nothing visibly wrong. Speculation is a stuck servo from the autopilot. Thank god for ATC assistance; it is very lonely up there when something goes wrong with your airplane or the weather!

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Original NASA ASRS Text

Title: PA32 pilot was alerted by ATC of a large heading deviation while on an IFR clearance and experiencing turbulence in the cloud tops. The pilot then noticed a strong left turning tendency; and needed to add significant opposite control input to maintain course. With ATC assistant flight was diverted to the nearest airport and landed safely.

Narrative: I was on the first hour of a 4 hour flight. The cloud tops were forecast to be at 5;000 and I had filed for 6;000. I found the tops to be at over 7;000 and getting higher. Most of the traffic (including me) were asking for higher altitudes to stay out of the very bumpy cumulous clouds. The flight conditions were VMC but it was turbulent in the clouds. There was no precipitation or thunderstorm activity; it was just turbulent. I was cleared up to 10;000 and climbed to that altitude; however I was just a few hundred feet shy of getting on top and the Controller could not give me higher at the moment so I entered the top of a white puffy cumulous cloud and had a couple of pretty good bumps. The autopilot was engaged and as I came out of the cloud; the Controller was calling me asking why I was flying south when my as filed course was west northwest. I noted that the autopilot was flying off the desired track and so I disengaged the autopilot. However; I had trouble holding heading. As I flew on; it was clear that there was something amiss as I had to hold right aileron (at about 10 or 11 o'clock on the control wheel) to keep it flying on a straight heading. I immediately informed the Controller that something was wrong (possibly with my aileron after my encounter with turbulence) and I asked for vectors to the nearest airport. He was very helpful and vectored me to a close-by airport; and once I had it in sight cleared me for the visual approach as I was in VFR conditions below 4;000. I took a couple of turns around the airport and was having difficulty with any left turns as it over-banked in that direction. I came in on a long stabilized final approach and landed safely. Having to get back to work; I left the plane with the FBO and flew home on the airlines. The FBO will give it a test flight this week to determine what the issue is. Yesterday and today three separate A&P's inspected the plane and found that the plane did not sustain any physical damage from the turbulence and they see nothing visibly wrong. Speculation is a stuck servo from the autopilot. Thank god for ATC assistance; it is very lonely up there when something goes wrong with your airplane or the weather!

Data retrieved from NASA's ASRS site as of July 2013 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.