On August 18, 2010, about 1800 Pacific daylight time, a Cessna 177A, N30559, made an off-field forced landing near Manson, Washington. Skylarks Flying Club was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The airline transport pilot and one passenger sustained minor injuries, and two passengers were not injured. The airplane sustained substantial damage to the airframe from impact forces. The cross-country personal flight departed Cle Elum Municipal Airport, Cle Elum, Washington, at 1710, with a planned destination of Chelan, Washington. Visual meteorological conditions (VFR) prevailed, and a VFR flight plan had been filed. The pilot reported that he planned a round trip flight from Chelan to Cle Elum. His preflight planning determined that it would take about 40 minutes in both directions at 6,500 feet to Chelan, and 5,500 feet on the return. He planned for 1 hour on the return as he wanted to fly over Lake Chelan prior to landing at Chelan. He planned on a burn rate of 7.3 gallons per hour (gph) on the outbound leg, and 7.4 gph on the return trip. This was computed using a lean mixture at 2,300 revolutions per minute (rpm), although he would always fly at 2,200 rpm, and plan the flight time accordingly (slightly lower burn rate). He computed that he needed 12.3 gallons for the flight, plus 3.5 gallons to meet reserve requirements (30 minutes day VFR). In his written statement, the pilot indicated that he conducted a preflight, which included a visual inspection of the fuel tanks. He estimated the tanks to be 3/4 full, and noted approximately the same readings on the cockpit fuel gages. As the fuel capacity of the airplane was 48 gallons, he estimated that he had between 30-36 gallons, which was enough for the planned flights. He was certain that the fuel tank filler caps were placed correctly upon completion of the visual inspection. He noted no defects or problems with the airplane. He departed, activated his flight plan en route, and completed an uneventful flight to Cle Elum. The pilot stated that he conducted a visual walk-around of the airplane at Cle Elum, and noted no defects. He departed, and activated his flight plan en route; the flight was uneventful until over Lake Chelan. Approaching the lake, he descended the airplane to approximately 600 feet above ground level (agl), and proceeded up the lake for a short distance. He reversed course and went toward the Chelan Airport. Abeam Manson, Washington, the engine began to run rough. He initiated a climb, and then the engine stopped. The pilot stated that he established the airplane in a power off glide at 80 miles per hour (mph), and selected a field for a landing. He confirmed that the fuel valve and fuel selector were in the correct position, and the auxiliary fuel pump was on. The engine would not restart, and he placed flaps to 20 degrees down as he configured the airplane for the approach. After the glide path was established, the engine briefly restarted. This event caused his aim point to be further away, putting him potentially into a berm towards the north end of the field. He elected to turn to the left knowing that the airplane would lose more altitude, but it would provide for a better landing area. The airplane touched down wings level very near or at stall speed for the configuration. The airplane sustained substantial damage upon landing in the rough terrain. In the data blocks in the pilot/operator report, the pilot indicated that 12 gallons of fuel was on board the airplane at the last takeoff, which was Cle Elum. The pilot indicated that there must have been a fuel leak, as the tanks were reported as dry after the off airport landing. He stated that the fuel gauges were reading nearly empty on the right side, and approximately 1/4 on the left side prior to landing. In a post accident interview with a Federal Aviation Administration inspector, the pilot indicated that he did not have a calibrated device for measuring the amount of fuel in the tanks. He also did not check the fuel level at Cle Elum prior to departure. The FAA inspector asked the pilot if he had any idea how the airplane ran out of the fuel, and the pilot did not.