On January 11, 1996, about 0930 eastern standard time, a Bell 206B, N33HF, registered to Heliflight Inc., operating as a 14 CFR Part 141 instructional flight, experienced a hard landing during an autorotation at Pompano Air Park, Pompano Beach, Florida. Visual meteorological conditions prevailed and no flight plan was filed. The airline transport pilot-in-command /certified flight instructor and airline transport pilot receiving instruction reported no injuries. The flight originated from Fort Lauderdale Executive Airport about 15 minutes before the accident. The flight instructor stated the student pilot was making a straight in autorotation to a taxiway. During the autorotation the student pilot informed him the rotor rpm was low. a visual check of the rotor rpm revealed it was in the low to mid green area. The student pilot started the deceleration at 50 feet, made an initial collective pitch pull at about 15 to 20 feet, and then lowered the collective to the full down position. The helicopter was at about 5 to 10 feet in a nose-high attitude when the student pilot pulled in nearly full up collective. The flight instructor attempted to level the helicopter, but it would not level due to low rotor rpm, caused by the premature collective pitch pull by the student pilot. The helicopter collided with the ground in a nose-high attitude on the heels of the skids. The nose of the helicopter pitched down and the main rotor blades collided with the tailboom assembly. The student pilot stated he entered the autorotation as instructed by the flight instructor. A few seconds later he informed the flight instructor that the rotor rpm was in the low green. The instructor responded, "everything is ok." The student pilot verified that he had the collective pitch in the full down position. He could feel the flight instructor on the flight controls with him during the deceleration, initial pitch, and cushioning pitch. He thought he managed to land the helicopter smoothly with a very gentle touchdown. Examination of the helicopter by an airframe and powerplant mechanic with inspection authority was conducted. The inspection, revealed the helicopter touched down on the aft portion of the skids, and the tailboom assembly pitched upward. One main rotor blade struck the tailboom and severed the tail rotor driveshaft. The rotating disk of the main rotor swashplate assembly struck the transmission cowling on the aft left side of the main rotor pylon damaging the air inlet cowling.