On April 18, 1998, at 1030 hours Pacific daylight time, a Porat RAF-200 gyroplane, N313EP, crashed into an open field near Hollister, California. The aircraft was destroyed and the pilot/owner, the sole occupant, was not injured. Visual meteorological conditions prevailed and no flight plan was filed. The local personal flight originated at 1015. The pilot reported that he had been flying the gyroplane for approximately 15 minutes and was on a wide base leg back to the airport about 500 feet agl when he felt a strong vibration from the main rotor. He stated that the engine sounded normal and opined that the vibration might have been caused by an uncoordinated turn. He further stated that he "spent too much time trying to find out the source of the vibration and forgot to fly the [aircraft]." The pilot reported that he was about 200 feet agl over a housing area, with trees and powerlines in his direct flight path, and didn't feel that he had enough time to recover any altitude. He decided to slow [himself] down by landing in an area of bushes that were approximately 6 feet high. The aircraft then collided with terrain about 1 mile from the airport. The pilot holds a private pilot certificate with single and multiengine land ratings. The pilot purchased the gyroplane kit and put it together himself. He reported that he had received approximately 9 hours of dual instruction in helicopters, all in the accident aircraft. This was the pilot's second solo flight in the accident aircraft.