On November 27, 1993, about 1200 hours eastern standard time, N8380J, a Robinson R-22 helicopter, operated by Bruce Woollett, Owls Head, Maine, was substantially damaged during landing at the Knox County Regional Airport, Rockland, Maine. The pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed and a flight plan was not filed. The personal flight departed from the Knox County Regional Airport and was conducted under 14 CFR 91. The pilot stated that he was practicing autorotations to landing. During the second autorotation, the pilot lowered the collective and "... reduced power slightly." The low rotor RPM warning activated, so the pilot lowered the collective to restore RPM. As he performed this, the right skid of the helicopter "hit the soft ground in a slight right drift, resulting in a rollover." No mechanical malfunctions were reported. According to a FAA aviation safety inspector, the rollover caused substantial damage to the rotorblades, mast, and tail.