On August 4, 2016, about 1813 eastern daylight time, an experimental amateur-built Arion Lightning, N270J, sustained substantial damage during a forced landing to a field near the New Garden Airport (N57), Toughkenamon, Pennsylvania. The sport pilot/builder, who was also the registered owner and operator, sustained minor injuries. Visual meteorological conditions prevailed for the personal flight conducted under the provisions of 14 Code of Federal Regulations Part 91. No flight plan was filed for the local flight that depart N57 about 1705. The pilot stated that he had flown for about an hour before he returned to the airport. While on the downwind leg of the traffic pattern, he reduced engine power, extended the flaps to 20°, turned on the electric fuel pump and the carburetor heat, and adjusted the mixture. The pilot said this was his normal procedure to land. When turning onto the base leg, he reduced engine power to idle and the engine suddenly stopped producing power. The pilot tried to re-start the engine several times, but realized he was not going to make the runway and attempted to land in a field. The airplane struck a power line and landed hard resulting in substantial damage to the wings, firewall, and fuselage. A postaccident examination of the engine by a Federal Aviation Administration (FAA) inspector confirmed compression and valve train continuity for each cylinder when the engine crankshaft was rotated. The engine-driven fuel pump also turned. The airframe fuel filter was examined and absent of debris. The carburetor was removed from the engine and disassembled. The bowl and jets were clear and absent of debris. The carburetor floats were undamaged, and the fuel needle valve was clear of debris and had a positive cutoff of fuel. The altitude compensation bellows were undamaged and functioned properly. The ignition cut-off switch and the left and right distributor caps were undamaged and functioned when tested. The spark plugs exhibited "normal" wear. No preimpact mechanical deficiencies were noted that would have precluded normal operation of the engine at the time of impact. The airplane was equipped with a Dynon SkyView SV-D1000 display and data was downloaded at the NTSB Recorder Laboratory, Washington D.C. A review of the data revealed that after the pilot departed, he headed west and climbed to 7,300 ft, before turning back to the airport at 1739. When the airplane turned on a left downwind to land, the engine rpm decreased rapidly from 2,300 rpm to 1,300 rpm. Engine rpm decreased at a slower rate to 700 rpm for the next 25 seconds before dropping to zero at 1812. The airplane impacted terrain at 1813. A review of engine parameters for the last few minutes of the flight were consistent with a loss of engine power as reported by the pilot. A review of the airplane maintenance logbook indicated that the pilot performed the last condition inspection on July 6, 2016. The airplane and engine had both accrued about 372 total hours at the time of the accident. The pilot held a private pilot certificate for airplane single-engine land, a sport pilot certificate, and a repairman certificate (experimental aircraft builder). He was operating as a sport pilot at the time of the accident and had a valid Pennsylvania driver's license as required by the FAA. The pilot reported a total of 883 total of hours, of which, 315 hours, were in the accident airplane. Weather at the Chester County G.O. Carlson Airport, about 10 miles northwest of the accident site, at 1835, was reported as calm wind, visibility 10 miles, and clear skies.