On December 6, 2011, at 1630 Pacific standard time, N2466D, a Piper PA 38-112, lost engine power during approach to Yolo County Airport, Davis, California. Mazzei Flying Service was operating the airplane under the provisions of Title 14 Code of Federal Regulations Part 91. The private pilot was not injured; the airplane sustained substantial damage. Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that he was conducting a cross-country flight in preparation for his commercial pilot certificate. The pilot reported departing with 26 gallons of fuel. He originally departed at 1415, conducted a touch-and-go landing at Sacramento International Airport, Sacramento, California, and was on the final approach leg to his second airport of intended landing when a loss of engine power occured. The pilot force-landed the airplane in a field and it nosed over. The airplane came to rest inverted. Initial responders reported that fuel seepage was present from the left wing tank and the exact fuel quantity in the tank at the time of the accident could not be determined. There was no fuel seepage from the right fuel tank. Residual fuel was found in each tank when the airplane was recovered the following morning. The engine was later test run. No operational anomalies were noted. In a conversation with the owner of the flight school, he reported that the pilot was unable to confirm how much fuel was in the airplane upon departure. Due to weight and balance requirements, the pilot had not filled the tanks to capacity and he estimated the amount of fuel onboard. He did not have a means of verifying the exact fuel quantity. Following the loss of engine power, the pilot switched fuel tanks, but could not recall to which fuel tank the fuel selector was positioned. When the airplane came to rest, the pilot positioned the fuel selector in the "Off" position.