On June 28, 2003, at 1550 mountain standard time, a Robinson R22 Beta, N332MD, landed hard and rolled over during a practice autorotation near Prescott Love Field (PRC), Prescott, Arizona. Guidance Helicopters, Inc., was operating the helicopter under the provisions of 14 CFR Part 91. The pilot and check pilot were not injured; the helicopter sustained substantial damage. The flight departed Prescott about 1515 for the purpose of conducting a private pilot practical flight test with a designated pilot examiner. Visual meteorological conditions prevailed and no flight plan had been filed. In a written statement, the pilot reported the purpose of the flight was for his private pilot helicopter rating. He held a private pilot certificate with a single engine land airplane rating and was seeking a private helicopter add-on rating. After the pilot completed a series of maneuvers, the check pilot requested an autorotation. The entry and descent were normal and the pilot began a flare about 100 feet above ground level (agl). At 15 feet agl, a power recovery was initiated, which resulted in a nose right yaw, and a left pedal correction was applied. The low rotor rpm horn sounded. The check pilot came onto the controls and "assumed the aircraft." Shortly thereafter, the pilot added additional throttle and down collective. The helicopter bounced 3 feet and the rear portion of the left skid impacted the ground. The helicopter came to rest on its left side. The check pilot submitted a written statement. He reported that the pilot was very well prepared for the flight test and demonstrated above average skills during the normal procedure portion of the flight test. During the autorotation, the entry and descent were smooth. He flared at the proper altitude and applied power to recover; the engine rpm and rotor rpm needles were "in the green." The pilot then began to cushion the descent with collective. During this cushion, the low rotor rpm horn activated. The check pilot expected the pilot to lower the collective slightly and roll on additional throttle; instead, the pilot lowered the collective "almost all the way down." The check pilot told the pilot "I have the controls," and they were close to the ground. The helicopter entered a right turn and the check pilot intended to "let the aircraft continue into a slow right turn and milk whatever power we had to fly out of it." At this time, the check pilot felt the right pedal move against his foot, and the helicopter settled to the ground at an angle. After bouncing once, it touched down on the left skid, and rolled over. After the accident, the check pilot asked the pilot if he had been rolling the throttle off as he was pulling the collective up during the cushion portion of the autorotation. The pilot reported in the past, he had been over speeding the engine so he would slightly reduce the throttle to compensate. In this case, he had decreased the throttle "at the wrong time," and was too aggressive on the recovery. The pilot applied left pedal when he was attempting to align the helicopter with a track. No mechanical discrepancies were noted with the helicopter prior to the accident. Federal Aviation Administration (FAA) records for the designated pilot examiner (check pilot) were reviewed by the Safety Board investigator-in-charge (IIC). The records indicated his designation was valid through June 30, 2003, in Robinson R22, and Bell 206/407 series helicopters. The density altitude was calculated using a Safety Board computer program. It was 8,393 feet mean sea level (msl) at the time of the accident. Field elevation at Prescott is 5,045 feet msl.