On June 1, 2010, about 1255 eastern daylight time, an experimental, amateur-built Vans RV-9A, N858JK, was substantially damaged during a forced landing, after experiencing a loss of engine power while on approach to the Hanover County Municipal Airport (OFP), Ashland, Virginia. The certificated private pilot sustained minor injuries. Visual meteorological conditions prevailed and no flight plan had been filed for the personal flight conducted under the provisions of 14 Code of Federal Regulations Part 91. The pilot/builder reported that he was in the process of conducting the airplane's 40-hour Phase 1 test flights. He departed OFP and landed at the Tappahannock-Essex County Airport (XSA), Tappahannock, Virginia, without incident. Shortly after takeoff from XSA, the airplane experienced a momentary sudden reduction in rpm, and the pilot elected to fly to OFP. While en route, the engine experienced additional sudden intermittent power reductions from 2,350 to 2,100 rpm. The pilot was able to restore power either by applying full throttle or the application of carburetor heat. The airplane was at an altitude of 1,300 feet, approximately 2.5 miles south of OFP, when the engine rpm decreased again. The pilot applied carburetor heat without any affect, and the engine subsequently ceased producing power completely. The pilot attempted to lose altitude and perform a forced landing on runway 34, a 5,402-foot-long, 100-foot-wide, asphalt runway; however, the airplane overshot the runway, touched down in the grass north of the runway and nosed over. The airplane sustained substantial damage to the vertical stabilizer and fuselage. The airplane was equipped with an ECI O-320 series engine, which had been operated for about 22 hours since new. Examination of the airplane and engine by a Federal Aviation Administration inspector (FAA), with assistance from representatives of the engine manufacturer did not reveal any mechanical malfunctions which would have resulted in a loss of engine power. It was noted that the spark plugs removed from the engine were dark, consistent with a rich mixture. The pilot reported 261 hours of total flight experience, which included approximately 30 hours in the same make and model as the accident airplane. A weather observation taken at OFP, about the time of the accident reported, wind from 210 degrees at 10 knots, gusting to 19 knots; visibility 10 statute miles; scattered clouds at 3,400 feet, temperature 30 degrees Celsius (C), dew point 20 degrees C; altimeter 29.93 inches of mercury. Review of an FAA carburetor icing envelope chart revealed that the reported temperature and dew point at the time of the accident was within the "serious icing (glide power)" area of the chart.