On October 14, 2003, at 1000 central daylight time, a Bell 47G-3B-1, N90463, experienced a hard landing while practicing an autorotation at the Schaumburg Regional Airport (06C), Schaumburg, Illinois. The certified flight instructor (CFI) and the commercial rated pilot who was receiving flight instruction were not injured. The helicopter was substantially damaged. The 14 CFR Part 91 local instructional flight was operating in visual meteorological conditions. The flight originated at 06C. The commercial rated pilot reported that he was in training preparation for his CFI check ride, and was practicing 90 degree and 180 degree full touchdown autorotations with the CFI. Four autorotations went without incident. The commercial pilot decided to complete one more autorotation before a full-stop. The commercial pilot stated that he was flying a right traffic pattern and landing in a grass area on the northeast corner of the airport parallel to runway 29. The commercial pilot reported that he entered the autorotation at 700 feet agl at 60 knots. He made a right 180 degree turn and lined up with his touchdown point. He stated that he checked his rotor RPM, airspeed, and heading. The commercial pilot reported that he flared approximately 50 feet above ground level (agl), and leveled the helicopter at 10 feet agl. During the final 3 feet, the helicopter yawed to the left, a correction was made, and the helicopter landed. The CFI stated that the commercial pilot entered the maneuver, executed the 180 degree turn and continued the decent until reaching 50 to 60 agl, where the commercial pilot initiated the flare. The CFI reported that immediately after the flare, the helicopter began to yaw to the left. The CFI stated that he instructed the commercial pilot to correct the yaw and align the helicopter straight with the ground. The CFI reported that he "came on the cyclic" to assure a straight track was achieved. A hard landing was encountered, resulting in the main rotor blades striking the tail rotor drive shaft and tailboom.