On April 13, 1998, at 1845 central daylight time, a Froberg Rotorway Executive experimental helicopter, N71RF, owned and operated by a private individual as a Title 14 CFR Part 91 personal flight, was destroyed after a forced landing following an in-flight fire near Sand Springs, Oklahoma. Visual meteorological conditions prevailed, and a flight plan was not filed. The private pilot, sole occupant of the helicopter, was not injured. The flight originated from West Port, Oklahoma, approximately 6 minutes prior to the accident. The pilot reported in the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2) that he was flying the helicopter to the William R. Pogue Municipal Airport, Sand Springs, Oklahoma, for fuel. Approximately 6 minutes after takeoff, the pilot observed smoke entering the cockpit from the right side and noted a loss of oil pressure. He executed an autorotation to a field of tall dry grass and exited the helicopter. He further reported that after exiting the aircraft, he observed a fire underneath the helicopter. The aircraft was then consumed by the fire within a few minutes. The pilot reported to the FAA inspector that "there was an oil leak and oil was dripping on the exhaust pipe." Examination of the aircraft wreckage by the FAA inspector revealed that it was destroyed by the fire. According to the FAA inspector, the pilot had purchased the Froberg Rotorway Executive helicopter about a year prior to the accident. The pilot had flown the aircraft about 30 hours since purchasing it and had not registered it. No maintenance had been performed on the helicopter in the last 20 hours.