HISTORY OF FLIGHT On October 14, 2003, about 1540 central daylight time, a Yakovliev YAK55M, N55YA, registered to a private owner, operating as a 14 CFR Part 91 personal flight, received substantial damage during a forced landing in a cornfield in the vicinity of Troy, Alabama. Visual meteorological conditions prevailed and no flight plan was filed. The private pilot reported no injuries. The flight originated from Tallahassee, Florida, on October 14, 2003, at 1540 eastern daylight time. The pilot stated he was 8 miles south of Troy, Alabama, at 3,000 feet in cruise flight, when he felt an instantaneous onset of a severe vibration. He reduced power and looked at the instrument panel. He did not observe an illumination of the engine chip detector light. He increased power to see what manifold pressure that he could maintain. The airplane would not maintain cruise flight. He observed a field to his front and initiated a forced landing to the field. He completed an engine shut down and started slipping the airplane to the harvested cornfield. The airplane touched down and rolled about 200 feet when the airplane collided with a berm. The berm decelerated the airplane and launched it back into the air. The airplane touched down again about 150 feet past the berm and rolled about 250 to 300 feet. Once the airplane had stopped he observed the propeller rotating at about 200 to 300 rpm even though the engine was not running. He exited the airplane and secured the propeller with a bungee cord. PERSONNEL INFORMATION Review of information on file with the FAA Airman's Certification Division, Oklahoma City, Oklahoma, revealed the pilot was issued a private pilot certificate on June 30, 2000, with ratings for airplane single engine land. The certificate was issued on the basis of and valid only when accompanied by a Canada pilot license. All limitations and restrictions on the Canada pilot license apply. The pilot holds a third class Canada medical certificate issued on May 7, 2003, with no restrictions. The pilot entered on the NTSB Pilot/Operator Aircraft Accident Report that he had accumulated 1,200 total flight hours with 22 hours in the YAK55M, and his last biennial flight review was July 10, 2003. AIRCRAFT INFORMATION Review of the airplane logbooks revealed the engine and original propeller were installed on May 23, 1993. The propeller was replaced on June 6, 1995, at 1.2 hours, and on July 1, 1997, at 330.0 hours. The last recorded annual inspection was conducted on April 4, 2003. The total time on the engine and airframe at the time of the inspection was 752 hours. The airplane has flown 28 hours since the annual inspection, and had accumulated 780 total hours at the time of the accident. METEOROLOGICAL INFORMATION The closest weather reporting facility was Troy Municipal Airport, Troy, Alabama, located 8 miles west of the accident site at an elevation of 397 feet msl. The Troy Municipal Airport weather observation at 1453 was, wind 250 degrees at 10 knots, visibility 10 miles, few clouds at 4,500 feet, temperature 81-degress Fahrenheit, dew point temperature 64-degrees Fahrenheit, and altimeter 29.78. WRECKAGE AND IMPACT INFORMATION The airplane was transported to Griffin, Georgia, for further examination. Examination of the airframe revealed wrinkling and crush damage forward and aft of the right wing attach points. Removal of the lower fuselage cabin floor revealed one rib and one stringer were buckled. Examination of the propeller assembly revealed the propeller hub was intact and all three propeller blades did not sustain any damage. The propeller turned freely without any restriction. The engine assembly was in place and all engine mounts, and all engine bolts were tight and secure. The engine was disassembled and revealed the propeller shaft had a planar fracture, perpendicular to the axis of the shaft. In addition, all of the connecting rods on the master and articulated rod assembly were broken and battered. The propeller shaft, crankshaft with connecting rods, and 9 cylinder assemblies were forwarded to the NTSB Materials Laboratory for further examination. Examination of the propeller shaft revealed it failed due to torsional overstress. All of the connecting rods were fractured. Post separation damage obliterated the fracture features and no determination of the failure modes could be determined. MEDICAL AND PATHOLOGICAL INFORMATION The pilot was not injured and toxicology specimens were not requested from the pilot. ADDITIONAL INFORMATION The propeller shaft, master and articulated rod assembly, and nine engine cylinders were released to Atlanta Air Recovery, Griffin, Georgia, on July 27, 2004.