On June 15, 1994, about 1230 eastern daylight time, a Robinson R- 22, N8029Z, lost total engine power while in cruise flight. An emergency landing was made and the helicopter was substantially damaged during the landing. The pilot was not injured. Visual meteorological conditions prevailed at the time and location of the accident. The business flight was conducted under 14 CFR Part 91. The pilot stated that the helicopter was about 500 feet above the ground when he noticed a rapid rise in the oil temperature, cylinder head temperature, and manifold pressure. He stated that the revolutions per minute (RPM) were decreasing. He stated he started to make an emergency descent and at 100 feet above the ground the engine lost total power. The pilot stated, "I initiated auto rotation at that point. Irregular terrain at the landing site caused the main rotor blades to flex down and contact the tail boom." Examination of the helicopter at the accident site revealed the tail boom was severed about 33 inches in front of the tail rotor gear box. Fuel was found throughout the fuel system. According to the pilot, the engine was to receive a major overhaul in about 46 hours. The engine was examined by the owner/operator without the permission or supervision of the National Transportation Safety Board. According to the owner of the helicopter, metal shavings were found throughout the engine and the number four piston lands and rings were broken. The failure mode of the engine was not determined.