On August 19, 2003, at 2015 central daylight time a Piper PA-28-140, N8496R, registered to and operated by the private pilot collided with the ground following a partial loss of one propeller blade while in cruise flight in Winchester, Tennessee. The personal flight was operated under the provisions of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed and no flight plan was filed. The pilot and passenger received minor injuries and the airplane sustained substantial damage. The flight originated in Collegedale, Tennessee on August 19, 2003, at 1945. The flight was enroute to Maury Regional Airport, Columbia, Tennessee. According to the pilot while in cruise flight at 4500 feet mean sea level, the airplane began shaking violently. The pilot saw smoke coming from under the dashboard. The pilot shut down the engine and saw part of one propeller blade missing. The pilot attempted to radio contact Memphis approach control to declare an emergency, but there was no response. The pilot executed a forced landing into a field approximately 12 miles east of Winchester, Tennessee. A review of the engine logbook showed that the leading edge of the propeller had a nick, and was filled during an annual inspection on March 8, 2002. Examination of the downed airplane revealed that the propeller was fractured 17.5 inches from the hub center. The National Transportation Safety Board Materials Laboratory examination of the propeller reported fracture features typical of fatigue. The fatigue features originated from a nick on the flat face approximately 0 .8 inch away from the leading edge of the propeller. Examination of the propeller blade showed paint from the flat face extended into the nick. According to a representative from the Sensenich Propeller Manufacturing Company, the repair manual does not specify a minimum size for damage requiring repair. The representative suggested that any visible damage to the propeller should be blended. The nick was of sufficient size that it would have been visible to the naked eye. The shape of the nick boundary indicates that it was not blended. Examination of the downed airplane revealed that the nose wheel was separated. The right wingtip was damaged. The motor mount broke and the engine was canted downward.