On August 20, 2017, at 1200 eastern daylight time, a Bell 47G-2A, N9526, was substantially damaged during a hard landing at St Marys, Pennsylvania. The student pilot was not injured. The helicopter was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a local, solo-instructional flight. Day, visual meteorological conditions prevailed at the time, and no flight plan was filed. The flight originated at St Marys Municipal Airport (OYM), St Marys, Pennsylvania about 1000.The pilot reported that he arrived at OYM and performed his preflight inspection. He determined that the fuel tanks contained between 25 and 30 gallons of fuel, and then he added 12 gallons before the flight. He departed the airport and flew for about 2 hours when the helicopter "ran out of fuel." He performed an autorotation to a level, grassy lot and the helicopter landed hard. He exited the helicopter and was met by first responders. The pilot reported there were no preimpact mechanical malfunctions or anomalies that would have precluded normal operation of the helicopter. An inspector with the Federal Aviation Administration reported that the helicopter came to rest upright in a grassy lot, about 2.6 miles west of OYM. The fuselage was structurally damaged. The landing gear skids were spread and forced up, against the fuselage. The main rotor blades were bent. There was no fire. The inspector examined the fuel system and determined that both fuel tanks were intact and undamaged. The fuel lines remained in place and there were no fuel leaks. He estimated that both fuel tanks contained 1 gallon or less of fuel, which was the unusable fuel quantity for each tank. The pilot also reported that he used an average fuel burn for estimating his fuel status, with no adjustment for pressure, temperature, or other performance metrics.