On April 24, 2014, at 1248 eastern daylight time, an experimental amateur-built Brecher Rotorway Exec 162F, N43691, impacted terrain during a hard landing to a field near Richwood, Ohio. The pilot stated that he performed a precautionary autorotation when a caution annunciator light illuminated. The helicopter was destroyed by post impact fire. A pilot, who was the helicopter builder/owner, and a flight instructor sustained serious injuries. The helicopter was registered to and operated by the pilot under the provisions of 14 CFR Part 91 as an instructional flight. Visual meteorological conditions prevailed for the flight that was not operating on a flight plan. The flight originated from Delaware Municipal Airport - Jim Moore Field (DLZ), Delaware, Ohio, at 1215 and was destined to Mount Victory, Ohio. The flight instructor stated that he performed an autorotation after he saw a caution light illuminate on the instrument panel and heard a noise during cruise flight at 800 feet above ground level. He said that he did not know if there was a loss of engine power. The flight instructor had not previously performed an autorotation in a Rotorway Exec 162F. Examination of the engine revealed that engine case contained holes consistent with post-crash fire damage. All of the engine pistons were connected to the crank shaft. All of the piston rings were intact. The piston domes did not display melting or damage consistent with valve contact. The piston domes had the following writing: "L2490 STO" and "2C150". All of the spark plug's center and ground electrodes were intact. The intake and exhaust valves were not fractured. The engine FADEC and engine accessories were destroyed by fire. Examination of the main rotor chain drive revealed that the chain was resting on around and within the teeth of both sprockets. About half of the larger sprocket was consumed by post-crash fire. The surrounding structure did not exhibit any witness marks consistent with impact from the chain. Examination of the flight control system confirmed flight control continuity. Impact and post-crash fire damage precluded functional testing of the helicopter. An aircraft logbook entry showed that the helicopter was issued a special airworthiness certificate on December 18, 2006. The last logbook entry was dated April 21, 2013, and had a total time in service of 56.2 hours. A National Transportation Safety Board Pilot/Operator Aircraft Accident/Incident Report was not received from the helicopter owner.