On March 10, 2005, approximately 1220 Pacific standard time, an experimental Garner RotorWay Exec 162F, N20539, collided with the terrain during an emergency autorotation near Coos Bay, Oregon. The commercial pilot, who was the sole occupant, received minor injuries, and the aircraft, which is owned and operated by the pilot, was destroyed by the post-crash fire. The 14 CFR Part 91 personal pleasure flight, which departed North Bend Municipal Airport, North Bend, Oregon, about 10 minutes prior to the accident, was being operated in visual meteorological conditions. No flight plan had been filed for the intended flight to Norway, Oregon. According to the pilot, while in cruise flight, he detected a burning rubber smell and heard "strange loud noises" just as both the engine and rotor rpm began to fluctuate. Soon thereafter, the engine began to lose power, and the pilot elected to make an autorotational landing. He headed for a nearby opening, which turned out to be a cemetery, and as he touched down among the gravestones with zero forward speed, the aircraft rolled over onto its right side. Immediately after it rolled to the side, flames appeared in the cockpit, but the pilot was able to escape out of the left side of the helicopter. A post-accident teardown inspection of the engine and drive assembly revealed that the upper main drive pulley bearing, a double ball bearing assembly, had partially disintegrated, leading to the decoupling of the main rotor shaft drive from the engine output drive shaft. The upper ball bearings were loose in the assembly, and their retaining cage had been destroyed. All of the subject bearings displayed excessive wear, flat spots, and significant thermal damage. Although there was very little grease remaining in the assembly, and the lower drive belt sheave grease passage set screw was found backed half way out, it could not be positively determined whether a lack of lubrication initiated the sequence of events leading to the failure of the bearing assembly, or whether the grease had been consumed by the heat generated by an internal failure resulting from other factors. According to the pilot/builder of the helicopter, he had adhered to the required 25 hour grease service intervals since the aircraft had been built, approximately 115 hours prior to the accident.