On March 2, 2001, at 1545 central standard time, a Cessna 182P single-engine airplane, N4721K, was substantially damaged during a forced landing following a loss of engine power near Tuttle, Oklahoma. The private pilot, sole occupant of the airplane, was not injured. The airplane was registered to and operated by Kremmling Flying, Inc., of Kremmling, Colorado. Visual meteorological conditions prevailed and a visual flight rules flight plan was filed for the 14 Code of Federal Regulations Part 91 personal flight. The airplane departed Kremmling, Colorado, at 1045 mountain standard time, and was destined for the University of Oklahoma Westheimer Airport near Norman, Oklahoma. The pilot stated that prior to takeoff, both fuel tanks were topped off. Approximately 15 miles from the intended destination, at 3,500 feet msl, the engine RPM began to decrease. The pilot pulled the carburetor heat ON, and the "RPMs picked back up." Approximately 10 seconds later, the engine RPM started to decrease again. The pilot adjusted the mixture control, applied full propeller RPM, and repositioned the fuel selector, in an attempt to regain engine power; however, no change in engine power was noted. The pilot contacted the Westheimer control tower and declared an emergency. With the propeller windmilling, the pilot executed a forced landing to a field. During the touchdown, the nose landing gear contacted a "drainage terrace," and the airplane nosed over and came to rest inverted. According to an FAA inspector, who responded to the accident site, after the airplane was turned upright, the right fuel tank was found empty, and the left fuel tank contained residual fuel. The right fuel cap was found unlocked and hanging out of the fuel cell by its retaining chain. The pilot reported that the airplane was equipped with long-range 88-gallon capacity fuel tanks and had an endurance of approximately 6 hours and 45 minutes of flight time. The pilot stated that some of the fuel may have been syphoned out of the fuel tank due to a loose fuel cap.