On September 18, 2009, about 1810 eastern daylight time, a Mooney M20K, N999DJ, was substantially damaged after veering off the runway while landing at Farmville Regional Airport (FVX), Farmville, Virginia. The certificated commercial pilot and the passenger were not injured. Visual meteorological conditions prevailed. An instrument flight rules flight plan had been filed for the flight, from Enterprise Municipal Airport (EDN), Enterprise, Alabama, to Farmville. The personal flight was conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 91. According to the pilot, the airplane was rolling out after landing on runway 21 and the engine surged. Prior to the surge, it was "loping" at 500 to 600 rpm with the throttle at idle. When the engine surged, the pilot had already applied left rudder, as he was "anticipating the left turn onto the taxiway." The airplane then left the runway, onto sod, and continued in a left turn "through the taxiway" until it impacted a hedge row. The airplane was powered by a Continental TSIO-360-LB1 engine. In response to a query about how or if the engine could have accelerated during the rollout, an air safety investigator from the manufacturer responded, "Concerning your question about the Mooney engine accelerating on rollout for no reason: If the throttle valve is closed, no air can reach the engine unless the throttle valve is opened, and it must be opened manually from the cockpit." FAA-H-8083-25, The Pilot’s Handbook of Aeronautical Knowledge, states, "the fuel/air control unit…meters fuel based on the mixture control setting, and sends it to the fuel manifold valve at a rate controlled by the throttle." According to a Federal Aviation Administration (FAA) inspector, the airplane veered off the left side of the runway, went across a shallow ditch, and hit one of the VASI (Visual Approach Slope Indicator) stanchions, before continuing to veer to the left. It then struck a hedgerow, reversed direction and came to a stop facing back toward the runway. There was no evidence of braking or skidding in the grass. An examination of the cockpit revealed that the throttle control was in the fully out position, and a preliminary inspection of the engine, throttle and propeller controls revealed no anomalies. A review of the airplane’s logbooks revealed no prior history relating to engine surges. A photograph of the airplane after the accident revealed only one of the two propeller blades, which was twisted at the blade tip. On September 25, 2009, two additional FAA inspectors removed the cowling and examined the engine. They confirmed that the throttle linkage operated smoothly between the fully open and fully closed positions. There was no evidence of any throttle linkage sticking or binding. The fuel control for the turbocharger was also checked, with no mechanical anomalies noted and no evidence of leakage. In addition, the propeller pitch control was moved from the fully in to the fully out position smoothly, and without binding. Runway 21 was 4,400 feet long and 75 feet wide. The only taxiway, a left turn to the parking apron, was about 2,800 feet from the runway threshold, and 1,700 feet beyond the approximate point where the airplane departed the runway. Runway 21 did not have a parallel taxiway, and to take off from that runway would require a back taxi on runway 3, and a course reversal at one of two teardrop-shaped turnabouts. One of the turnabouts was located at the approach end of runway 21, and another was located about 200 hundred feet beyond the point where the airplane departed the runway, or about 1,500 feet prior to the taxiway that joined the parking apron. Both turnabouts were on the left side of runway 21. Winds at the time, as reported by the pilot, were from 210 degrees true at 3 knots.