On September 3, 2004, about 1930 Pacific daylight time, a Hughes 369D helicopter, N505ST, was substantially damaged after impacting terrain following a forced landing near Cottage Grove, Oregon. The certificated private pilot and his two passengers were not injured. Visual meteorological conditions prevailed for the personal flight, which was conducted in accordance with 14 CFR Part 91, and a flight plan was not filed. The helicopter departed the Hobby Field Airport (77S), Creswell, Oregon, at 1830. According to the Pilot/Operator Aircraft Accident Report (NTSB form 6120.1/2), the pilot reported that while flying at an altitude of 1,000 feet AGL, "...the engine had a sudden power loss and the collective became very heavy." The pilot further reported that after he put the collective full down and began an autorotation, he looked down and observed a "split" in the rotor rpm and the N2 needle. The pilot stated he was over a steep side slope (60%) with trees at the bottom, when he saw a rock pit and made a decision to attempt a landing there. The pilot said he checked the rotor speed again, which was still at the bottom of the green, and the collective was still heavy. The pilot reported that he continued the autorotation at 60 knots, and at 30 feet AGL he pulled back on the cyclic to slow down to about 30 knots, at which point the helicopter made contact with the ground. The pilot stated that after the helicopter impacted the ground the left side skid separated, the helicopter fell over on its left side skidding to a stop, and the main rotor blades severed the tail boom. Two Federal Aviation Administration (FAA) airworthiness inspectors visited the accident site to conduct a post accident examination of the helicopter. The inspectors reported that flight continuity to all flight controls had been established, and that the aircraft had approximately 200 pounds of fuel on board. The inspectors further reported the fuel and bleed air lines did not leak after the engine was motored, the fuel nozzle had a good spray pattern, and there was "good fire" to the igniter. The inspectors stated that all five main rotor blades had been accounted for. On September 28, 2004, a subsequent examination of the aircraft's engine was conducted by representatives of the FAA and Rolls-Royce Corporation. The N1 drive train rotated free and continuous by the N1 tachometer drive pad utilizing a one-quarter inch drive ratchet. The N2 drive train rotated free and continuous by the N2 tachometer drive pad utilizing a one-quarter inch drive ratchet. Both engine gearbox magnetic indicating plugs were found void of material, and the engine did not exhibit any visual external damage. All engine pneumatic and oil lines were found at least finger tight and no fractured lines were found. No evidence of pre-impact failed components was found during the examination, which would have led to the reported power loss.