On May 20, 2005, at 1500 eastern standard time, a Brantly B-2B, N2274U, collided with the terrain during a practice autorotation in Lakeview, Michigan. Neither the certified flight instructor (CFI) nor the private rated dual student were injured. The helicopter was substantially damaged. The 14 Code of Federal Regulation Part 91 instructional flight was operating in visual meteorological conditions without a flight plan. The flight originated in Lakeview, Michigan. The purpose of the flight was for the private pilot, who held single-engine land and single-engine sea ratings, to practice autorotations in preparation for a rotorcraft rating. He stated the accident occurred during the third autorotation of the flight. The student reported that during the autorotation the airspeed decreased below 40 miles per hour and the rotor rpm decayed. He stated the CFI took control of the throttle and rolled it on and off about three times, but they were too slow and low. He stated the helicopter impacted the ground "hard." The student reported that he did not notice a mechanical failure/malfunction with the helicopter, reporting that they just got too slow and the rotor rpm decayed. He continued to report, "I learned later that when practicing autorotations, I should not roll the throttle to idle, because there is a governor that keeps it at about 2,000 rpm when the collective is lowered." He stated his CFI never said anything to him about not rolling the throttle to idle. The CFI stated the engine quit during the simulated engine failure. He stated they made a full touchdown autorotation into a soft field and the left skid dug into the terrain causing the helicopter roll over. The last annual inspection on the helicopter was completed on May 10, 2005. During this inspection the idle rpm was found to be set at 1,080 rpm. The idle rpm was adjusted to 850 rpm.