On June 25, 1995, approximately 0930 Pacific daylight time, a Sagerser Rotorway Executive helicopter, N336CS, was substantially damaged during a hard landing following a precautionary autorotation to a grass field near Enumclaw, Washington. The 75 year old airline transport pilot received minor injuries. Visual meteorological conditions prevailed and no flight plan had been filed. The flight, which was personal, was to have been operated under 14CFR91 and originated from the Flying H private airstrip, Enumclaw, Washington, approximately 10 minutes before the accident. The pilot reported that shortly after takeoff, and while climbing through 300-400 feet above ground, the engine surged. He stated that he reduced collective and executed an autorotation landing to a grass field. During the flare the helicopter touched down hard and with some forward velocity. The pilot reported approximately 55 hours in the aircraft over the previous year and a half and indicated he had not flown the aircraft for about a month. During a telephone conversation with an FAA inspector, the pilot reported that the power was increasing so he shut off the magnetos, then tried to unsuccessfully restart the engine. The reason for the power surge was not determined.