On July 24, 1995, at 1130 mountain daylight time, a Cessna 175, N9304B, impacted the ground while maneuvering near Silvercliff, Colorado. The commercial pilot and passenger received serious injuries and the aircraft sustained substantial damage. Visual meteorological conditions prevailed and no flight plan was filed for this local area 14 CFR Part 91 observation flight which departed Westcliffe, Colorado at 1045. According to the pilot, the purpose of the flight was to "view the valley." At the time of the accident, the weather reported by the pilot was clear skies with light and variable winds, and a temperature of 80 degrees Fahrenheit. The pilot stated that the engine lost power at 100 feet above ground level. He said that switching fuel tanks, turning on boost pump and advancing the mixture did not change the power loss and he made a forced landing on hilly terrain covered with trees at an elevation of about 9,000 feet above mean sea level. During examination of the aircraft by an FAA inspector following the accident, he noted that there was no fuel present in any tank, in the lines, strainer, carburetor, fuel pump, nor were there any fuel stains on the ground. The aircraft recovery people verified that they found no evidence of fuel, and during an engine examination, following recovery of the aircraft, no evidence of fuel was found by this investigator. The engine examination provided no evidence of failure or malfunction. According to the pilot, he had approximately 20 gallons of fuel on board at the time the flight originated, about 45 minutes prior to the accident, and he stated that the left tank gauge indicated about 1/2 full at the time the engine lost power. Verification of the fuel measuring system accuracy could not be accomplished following the accident due to aircraft damage. According to the aircraft manual, the fuel system consists of two 26 gallon aluminum tanks. Each tank useable capacity is 21.5 gallons. The fuel selector provides the pilot with options of off, right tank, left tank, or both. Based on operating data from the aircraft manual, takeoff weight was approximately 1,865 pounds, 485 pounds below maximum, and fuel burn at 9,000 feet in normal cruise, lean mixture, averaged about eight gallons per hour.