On April 3, 1997, about 1615 central standard time, a Cessna 210M, N761VX, registered to Air Carriers Inc,, crashed during a forced landing following loss of engine power in the vicinity of Troy, Alabama, while on a Title 14 CFR Part 135 business flight. Visual meteorological conditions prevailed. The commercial-rated pilot was not injured. The aircraft was substantially damaged. The flight originated from Dothan, Alabama. The pilot reported experiencing a partial loss of engine power while en route from Dothan, Alabama, to Bessemer, Alabama at 4,500 feet in visual meteorological conditions. The pilot performed an emergency landing under partial power at the Happy Valley Community Airpark, an ultralight airfield. The aircraft's landing roll exceeded the runway length, struck tree stumps and dirt piles, flipped on its back and came to rest at the end of the runway. The engine was transported to Teledyne Continental Motors in Mobile, Alabama. The engine was placed in a test cell. The engine start up was immediate and the engine ran smoothly at all rpm's. The propeller was removed and disassembled. The examination revealed the No. 2 blade hub was not attached to the phenolic link on the piston assembly, and was broken into three pieces. The three pitch change brackets with phenolic links were forwarded to the NTSB Materials Laboratory Division for further analysis. Examination of the No. 2 blade hub was conducted with an electron microscope after ultrasonic cleaning with soap and water revealed features typical of tensile overstress with no preexisting features. No stress raiser such as a gouge mark or pore was found on the surface in the area of the fractures. For additional information see NTSB Metallurgist's Factual Report No. 97-150. The three pitch change brackets with phenolic links were released to Mr. Scott Grant, FAA, FSDO-09, on October 6, 1997.