On July 14, 2000, at 0945 hours Pacific daylight time, a Robinson R-22 Beta, N169CW, landed hard and the main rotor severed the tail boom during an autorotation to the ground near Lake Piru, California. The flight instructor and the commercial pilot were not injured. The helicopter sustained substantial damage. The purpose of the instructional flight was a preparation for a flight instructor check ride. The helicopter, operated by Group Three Aviation, was being flown under 14 CFR Part 91 when the accident occurred. Visual meteorological conditions prevailed and a flight plan was not filed for the local area flight. The flight originated at 0810. According to the flight instructor, they were practicing full touchdown autorotations and had completed one prior to this attempt. The flight instructor stated that in the prior autorotation the student had placed the cyclic too far forward, and during this attempt the cyclic was moved too far back, and the main rotor came into contact with the tailboom assembly. According to the operator, upon ground contact, the tail boom leveled resulting in tail boom contact with the main rotor in the plain of rotation. The tail boom was severed upon impact with the main rotor.