On July 27, 2002, about 1315 mountain standard time, a Robinson R22 Beta, N232DR, experienced a hard landing while attempting a practice autorotation in a field near Prescott, Arizona. Guidance Helicopters Inc. owned and operated the helicopter under 14 CFR Part 91. The certified flight instructor (CFI) and student pilot were not injured; the helicopter sustained substantial damage. Day visual meteorological conditions prevailed, and a flight plan was not filed. The local instructional flight originated from Ernest A. Love Field Airport (PRC), Prescott, Arizona, about 1240. In a written statement, the CFI reported that the purpose of the flight was for the student to practice maneuvers for his upcoming check ride. After completing several maneuvers at the airport, they flew to a familiar practice area and the student performed an uneventful practice straight-in autorotation. On the second attempt, they experienced light turbulence and lost about 100 feet of altitude prior to the autorotation entry. They decided to proceed with the maneuver because they still had sufficient altitude and airspeed. About 200 feet above ground level (agl), the main rotor rpm gauge showed a drop and the warning horn sounded momentarily. The student lowered the collective and the helicopter began a high sink rate. The CFI initiated a power recovery in an effort to counteract the sink rate about 100 to 150 feet above ground level (agl). The helicopter continued to sink and the rotor rpm remained low. A few feet above the ground, with the helicopter still sinking, the CFI decided to level the helicopter and brace for impact. The skids contacted the forward sloping terrain in a straight and flat attitude. The helicopter experienced a forward, left roll, and came to rest on its left side. In a written statement, the student pilot reported that during the practice autorotation the sink rate increased and the main rotor rpm dropped slightly. He lowered the collective and began to flare about 40 feet agl. The CFI increased power and the low rotor rpm horn came back on about 4 to 6 feet agl. The helicopter touched down on the uneven terrain and rolled on its left side. Both the CFI and student pilot walked away from the wreckage to the nearest road. The CFI and student pilot thought the abnormally high sink rate could have been a result of the adverse wind conditions in the area. During the accident the helicopter incurred damage to the fuselage, tail boom, main rotor, and drive train. A routine aviation weather report (METAR) for PRC, about 10 miles away on a bearing of 035 degrees, reported winds at 5 knots, gusting to 17 knots.