On September 8, 2005, about 1845 Pacific daylight time, a North American AT-6D, N3617F, registered to Gaillard Aviation Corp. and doing business as American Warbirds as a 14 CFR Part 91 revenue sightseeing flight, experienced a loss of engine power shortly after takeoff from the Chehalis-Centralia Airport, Chehalis, Washington. The aircraft subsequently touched down hard on the remaining runway which damaged the landing gear. Visual meteorological conditions prevailed at the time and no flight plan was filed for the local flight. The aircraft was substantially damaged during the subsequent gear-up landing. The Airline Transport Pilot and his passenger were not injured. In a written statement, the pilot reported that he had been conducting revenue sightseeing and instructional flights throughout the day. This was the 11th ride of the day for the purpose of sightseeing. The pilot stated that during the pre-takeoff check, he recorded on the manifest that he switched the fuel selector to the fullest fuel tank, but failed to physically perform the action of switching the fuel selector. During the takeoff initial climb at about 100 feet above ground level, the engine began to lose power. The landing gear was already retracted and the pilot called for his passenger to extend the landing gear. The pilot switched the fuel selector to the fullest fuel tank and pumped the manual fuel pump. At the same time as the aircraft touched down hard on the remaining runway, the engine regained power and the pilot continued the takeoff. The landing gear was left in the extended position and was soon determined that the right main landing gear torque link was damaged and the wheel was 90 degrees to the direction of flight. After discussing the situation with the ground crew, the pilot elected to land the aircraft with the landing gear retracted. During the gear-up landing, the aircraft slid off the runway surface into a muddy area, colliding with a runway taxi light and raised manhole cover.