On March 19, 2005, about 1515 eastern standard time, a Robinson R44 helicopter, N1ZP, registered to a private individual, was landed hard at Homestead General Aviation Airport, Homestead, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 instructional, local flight, from Kendall-Tamiami Executive Airport, Miami, Florida. The helicopter was substantially damaged and the certified flight instructor (CFI), and student pilot were not injured. The flight originated about 1355, from Kendall-Tamiami Executive Airport. The certified flight instructor stated that the student had performed 11 previous straight-in autorotative landings with a power recovery. On another practice autorotative landing, the student initiated the maneuver from an altitude of approximately 500 feet, at an indicated airspeed of between 65-75 knots. He maintained 65 knots during the descent, and when the flight was approximately 75 feet above ground level (agl), he flared. The autorotation continued, and when the flight was approximately 20 feet agl at an indicated airspeed of approximately 20 knots, the student added power, but the helicopter yawed to the left. The CFI got on the controls and when the flight was approximately 10 feet agl, and at an indicated airspeed between 10 and 20 knots, he pulled collective but the helicopter impacted on grass right skid low. The helicopter then pivoted 90 degrees to the right, and rolled onto its right side. The installed emergency locator transmitter (ELT) activated. The student pilot reported that after takeoff, the flight proceeded to the Homestead General Aviation Airport; where, before the occurrence, he had performed approximately 10 uneventful practice autorotative landings with power recovery. He departed to perform another practice autorotative landing and when the flight was on the downwind leg abeam runway 36, he applied carburetor heat, checked for annunciation lights, and the intended touchdown area. He announced his intentions on the common traffic advisory frequency (CTAF), turned base and final, slowed to approximately 70 knots, questioned if the CFI was ready, counted to three, and entered the maneuver at approximately 500 feet. He applied right anti-torque pedal input, aft cyclic control, and maintained approximately 65 to 70 knots during the descent keeping the main rotor rpm at approximately 100 percent. He flared when the flight was approximately 50 to 60 feet, slowed to a walking speed, continued descending, leveled the helicopter, and applied throttle input to recover to a hover. He looked back in the cockpit and noted the CFI grab the controls. The helicopter contacted the grass and rolled onto its right side. He further reported that he did not hear the low rotor warning horn, could not recall if the helicopter yawed when he applied power to recover, and was surprised to see the CFI grab the controls. Postaccident, the carburetor bowl was drained which revealed large particles; however, the inlet screen was clean. The engine was removed from the helicopter, placed in a test stand with a test club, and with NTSB oversight, started and operated to 2,000 to 2,100 rpm at full throttle (specification with test club installed); no discrepancies were noted during the engine run. The helicopter minus the engine was released to Christopher Dannecker, of CTC Services Aviation (LAD, Inc.), on April 14, 2005. The engine was also released to Christopher Dannecker on April 20, 2005.