On June 18, 1995, at 1932 central daylight time, a Stewart Pitts S-1S, N901S, was substantially damaged during a forced landing near Cleburne, Texas. The private pilot was seriously injured. The aircraft was being operated by the owner/builder under Title 14 CFR Part 91. The flight originated from the Aero Country Airport near McKinney, Texas, at 1900. Visual meteorological conditions prevailed for the personal cross country flight and a flight plan was not filed. On the enclosed Pilot/Operator Report, the pilot stated that there were 8 gallons of fuel in the tank during a preflight at McKinney. The pilot stated that this engine consumed 8 gallons per hour during cross country flights. Approximately 30 minutes after departure, the engine "coughed." The pilot pumped the wobble fuel pump and the engine "cleared." Subsequently the engine "stopped," and the pilot executed a forced landing to a field. Following the "hard" landing, the airplane nosed over coming to rest inverted. Examination of the airplane by the Federal Aviation Administration inspector revealed that "less than 1/2 a cup of fuel was found in the aircraft's fuel system." No evidence of fuel spillage was found. The engine manufacturer operator's manual indicates the following fuel burn rates for this engine: Normal Rated (2700 RPM, 200 HP) 16.1 Gal./Hr. 75% Rated (2450 RPM, 150 HP) 12.3 Gal./Hr. 65% Rated (2350 RPM, 130 HP) 9.5 Gal./Hr. The 32 minutes of flight time reported by the pilot did not include fuel used for start up, taxi, and runup.