On August 6, 1997, about 1220 eastern standard time, a Robinson R-22 Beta, N717GT, was substantially damaged during a hard landing at the Windham Airport, Willimantic, Connecticut. The certificated flight instructor and the pre-solo foreign student were uninjured. Visual meteorological conditions prevailed and no flight plan was filed for the instructional flight conducted under 14 CFR 91. The flight originated from the Ellington Airport, Ellington, Connecticut, about 1138. The flight instructor stated that they flew to Windham Airport to practice approaches and hovering. Upon completion of their maneuvers and while hovering at 10 feet, the instructor asked the foreign student to return to Ellington Airport to practice auto rotations. According to the instructor, the student moved the throttle to idle and the helicopter impacted the ground before he could recover control of the helicopter. The student pilot was a foreign national with limited ability to speak and understand English. His previous two flights were with another instructor, who had the student pilot practice hovering auto rotations. When interviewed after the accident, the student stated that he mistakenly thought the new instructor requested an auto rotation from their present location. The student adjusted the throttle and it slipped to the idle position. Neither the instructor nor the student reported mechanical problems with the helicopter.