On August 29, 1996, at 2200 hours Pacific daylight time, a Bell 47-G5, N57RA, was substantially damaged during a hard landing at the Riverside Municipal Airport, Riverside, California. Visual meteorological conditions prevailed for the local area personal flight and the commercial pilot was not injured. The pilot reported that he was regaining night flying proficiency and was practicing a night autorotation landing from 3,000 feet without use of the aircraft's landing light. There was a full moon and the ground was visible. During the autorotation flare, he misjudged the aircraft's height above the surface, flared too high, and the helicopter dropped the last 4 or 5 feet. The aircraft landed hard with little energy in the main rotor and the rotor severed the tail boom. The pilot reported that he had no other night flying time in the previous 90 days, and that there were no mechanical malfunctions involved. He also said that the landing light was operational had he chosen to use it.