On January 5, 1999, about 1604 Pacific standard time, a Robinson R-22, N605HA, registered to and operated by Hillsboro Aviation, was substantially damaged after a hard landing at the Hillsboro Airport, Hillsboro, Oregon. The aircraft was being operated as a 14 CFR Part 91 training flight. Visual meteorological conditions prevailed, and no flight plan was filed for the local training flight. The student pilot, the sole occupant, was uninjured. The flight originated from the Hillsboro Airport approximately 35 minutes prior to the accident. There was no fire, and no report of an ELT actuating. The pilot stated that he was practicing set downs (landings) on the compass rose and the last set down was "a little bit harder than the others, but not too hard." He then stated that the helicopter momentarily became airborne and then collided with the ground. The tail rotor struck the ground first, followed by the main skids. An FAA inspector from the Portland, Oregon, Flight Standards District Office inspected the helicopter after the accident and reported that there was no evidence found to indicate a mechanical failure or malfunction.