On October 29, 2005, at 1211 eastern standard time, a Robinson R22 Beta, N8176B, was substantially damaged during a hard landing and subsequent rollover at Doylestown Airport (DYL), Doylestown, Pennsylvania. The certificated flight instructor incurred minor injuries, and the certificated student pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which was conducted under 14 CFR Part 91. According to the flight instructor, he and the student pilot were practicing hovering autorotations. They began by performing two or three autorotations about 1 foot above the ground, then climbed the helicopter to about 3 feet above the ground. The flight instructor recalled that the student pilot "cut the throttle," and the helicopter descended. He could not recall whether he or the student pilot was moving the collective pitch control. The helicopter impacted the ground hard, on the rear portion of the left skid and then "started into a dynamic rollover." When asked, the flight instructor stated that the helicopter was performing "fine" at the time of the accident. A Federal Aviation Administration inspector examined the helicopter following the accident, and noted no mechanical abnormalities. The weather reported at Doylestown Airport, at 1154, included winds from 350 degrees at 12 knots, an overcast ceiling at 6,000 feet, and 10 statute miles visibility.