On August 27, 2005, about 1445 mountain daylight time, a Robinson R22 Beta helicopter, N3825, sustained substantial damage subsequent to a hard landing following a practice autorotation at the Boise Air Terminal, Boise, Idaho. The helicopter is owned by Silver State Helicopters of North Las Vegas, and was being operated as a visual flight rules (VFR) instructional flight under Title 14 CFR Part 91, when the accident occurred. The certified flight instructor, and student pilot receiving helicopter training, were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight. The flight originated from Boise, Idaho, approximately one hour prior to the accident. In a written statement dated August 27, 2005, and subsequent telephone conversation with the NTSB IIC, the instructor pilot reported he and the student pilot were practicing power recovery autorotations at the Boise airport. During the tenth practice autorotation, with the student pilot on the controls, the instructor noted a lower than normal main rotor RPM (approximately 94 percent) and elected to take the controls in an effort to make the necessary inputs to recover from the maneuver. The instructor pilot reported that during the transition (approximately 60 feet agl), there was a "struggle" for the controls and corrective action was delayed resulting in a hard landing and substantial damage to the helicopter. The instructor pilot stated that he does not recall verbalizing the transfer of control to the student pilot.