On November 27, 2006, about 1130 Pacific standard time, a Robinson R22B, N7198N, touched down hard during a practice autorotation about 0.5 miles northwest of the Redding Municipal Airport, Redding, California. The helicopter was operated by Air Shasta Rotor & Wing, LLC, Redding, and it was substantially damaged. Neither the certificated flight instructor (CFI) nor the student pilot was injured. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight was performed under the provisions of 14 CFR Part 91, and it originated from Redding about 1115. On November 28, the CFI verbally reported to the National Transportation Safety Board investigator that the helicopter was functioning normally during the flight. He was monitoring his student's flying, and he instructed his student to perform a practice autorotation. The CFI stated that his student did not perform the maneuver correctly; he initiated the landing flare about 40 feet above ground level (agl). The CFI additionally indicated that despite his effort to perform a normal touchdown and/or recovery, the helicopter's low rotor warning horn sounded and the respective annunciator light illuminated. Thereafter, the helicopter contacted the ground, bounced, and came to rest after making two complete rotations about its vertical axis. During this event the tail boom and vertical stabilizer bent. In the CFI's completed "Aircraft Accident Report," he reiterated that during the flight he had not experienced any mechanical malfunction or failure with the helicopter. According to the CFI, when the helicopter was about 10 feet above ground level he took over the controls, raised the collective, and rolled on the throttle to perform a power recovery. The CFI and the student had about 285 and 15 hours of helicopter flying experience, respectively. Also, the CFI had given a total of 38 hours of rotorcraft instruction, of which 15 hours were given in the Robinson R22.