On January 12, 1998, at 1030 hours Hawaiian standard time, a Daniel RAF-2000, N90606, experimental gyrocopter, crashed into a field near Wahiawa, Oahu, Hawaii. Visual meteorological conditions prevailed at the time of the solo flight, and no flight plan was filed. The gyrocopter was owned, operated, and built by the pilot. The accident occurred during the pilot's approach to an agricultural airstrip near the Dillingham Airfield, Oahu. The homebuilt aircraft was substantially damaged and the student pilot was not injured. The flight originated from Oahu about 0915. According to the pilot, the accident occurred during the first day of flight testing his gyrocopter following the installation of a new, more powerful engine. The pilot reported that because of a strong left turning tendency noted during an earlier flight, he adjusted the rudder trim tab and the trim springs. Approaching the airstrip on a subsequent flight, however, he lost directional control upon application of full engine power to arrest a descent. The gyrocopter turned 90 degrees left, and it crashed into a sugar cane field. The Federal Aviation Administration (FAA) coordinator reported that its examination of the pilot's personal flight record logbook indicated the pilot had last received dual flight instruction on November 25, 1996. The pilot's last 90-day solo flying endorsement was signed by his certified flight instructor (CFI) on April 4, 1997. The FAA coordinator further indicated that the CFI's supervision over his student's flight training had been inadequate because, in part, the CFI was aware his student continued solo flying without having received the requisite current solo flying logbook endorsement and dual flight instruction.