Vans Aircraft Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Private
Flight Crew Last 90 Days 25; Flight Crew Total 1620; Flight Crew Type 575
Distraction; Time Pressure; Troubleshooting; Workload
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Excursion Runway
Aircraft Aircraft Damaged; Flight Crew Overcame Equipment Problem; Flight Crew Regained Aircraft Control; Flight Crew Rejected Takeoff; General Flight Cancelled / Delayed
Aircraft
Before take-off; I performed my normal pre-takeoff checks; and everything was perfect; including a brake check; flight controls free and correct; auto pilot off; and trim set for takeoff. I also had a passenger who is an experienced RV pilot that I frequently fly with him; either in his airplane or mine.  I was cleared for takeoff on Runway XX by the Control Tower. My normal takeoff procedure is to do a soft field takeoff; where I have the control stick full aft as I start to feed in power. As the airplane starts to roll and increases speed; the nose wheel comes off the ground; and I relax aft pressure on the stick and hold the nose wheel off the ground until the airplane flies itself off the ground. On the day this occurred; I was in takeoff attitude; with the nose wheel off the ground; and was accelerating down the runway. I started to feel forward pressure on the stick; which became heavier and heavier. I glanced down at the trim indicator and it showed a full nose down trim indication. I immediately pulled power to idle to abort the takeoff and was now focused on keeping the airplane under directional control and getting it stopped. As I applied braking to stop the airplane; I realized that I was getting close to the south end of Runway XX. I applied heavy braking being careful not to skid the tires and risk a blow-out. When I reached near the end of Runway XX; I felt that I was still moving too fast to safely make the 90 degree left turn onto Taxiway Alpha. I elected to taxi straight ahead and get the airplane stopped or go off the runway pavement and into the grass. I was not able to get the airplane stopped; so I went off the runway pavement and approximately 20 ft. into the grass. I made an immediate 180 degree turn back onto the runway pavement; made a right turn toward Taxiway Alpha and exited the runway onto Taxiway Alpha. After clearing the runway; I called the Control Tower and advised them that I had aborted my takeoff and that I had a malfunction with my trim and that I was going to troubleshoot the malfunction while I was in the run-up area for Runway XY; and I would call them back with my intentions. My airplane is equipped with electric pitch and roll trim; which is activated by a hat switch located on each control stick grip.  After troubleshooting the system; we determined that I had experienced a runaway trim condition. I called the Control Tower and informed them that I wanted to taxi back to my hangar. They gave me the taxi clearance and I taxied to my hangar. The airplane is grounded until I can get a satisfactory understanding and repair to the electric trim system. There was no personal injury to me or my passenger and there was no damage to airport property. The main gear fairings were scraped on the bottom presumably when the aircraft transitioned from concrete to the grass.
A light sport aircraft pilot reported runaway trim during takeoff resulting in a runway excursion.