On July 10, 2004, at approximately 1030 mountain daylight time, a Whitlock Rotorway Exec 162F, N518W, piloted by a private pilot, sustained substantial damage when it impacted terrain during an autorotation 3 miles north of Meeker Airport (EEO), Meeker, Colorado. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The private pilot and his passenger were not injured. The flight originated at Meeker, Colorado, at 1027 and was en route to Craig, Colorado. According to the report submitted by the pilot, approximately 3 minutes after departing Meeker, he heard a "loud squealing noise" from the engine and rotor rpm began to decrease. The pilot initiated an autorotation at 1,200 feet agl and positioned the helicopter to land in a nearby field. The pilot stated that several feet off the ground he heard a "growling noise" and the helicopter "yawed to the right," approximately 70 degrees. The helicopter landed on the left skid and subsequently rolled onto its side. The main rotor, landing skids and tail boom bent during the impact. According to the pilot, post accident examination revealed that the supercharger on the engine had failed.