On January 11, 2002, approximately 1131 Pacific standard time, a Robinson R22 Beta helicopter, N7185A, being operated by Classic Helicopter Corporation of Seattle, Washington, on a 14 CFR 91 instructional flight, was substantially damaged when it inadvertently contacted the ground and rolled over during an in-ground-effect hover demonstration in a vacant lot in a practice area in Renton, Washington. The certificated flight instructor (a commercial pilot) and a dual student receiving an introductory helicopter flight lesson received minor injuries. Visual meteorological conditions, with calm winds, were reported at Renton at 1053, and the local flight, which departed King County International Airport/Boeing Field, Seattle, Washington, about 1105, was not on a flight plan. The dual student reported that at the time of the accident, they were hovering at 4 to 5 feet. The dual student reported that the instructor had a hold of the cyclic, and that "I had a loose grip on it and we tipped back." The student stated that "We went straight up in the air for ten to fifteen feet and immediately banked left, almost up side down." The instructor reported that prior to flight, she gave the student a safety briefing in accordance with Special Federal Aviation Regulation (SFAR) No. 73, consisting of a discussion on the use of controls and transfer of controls, low G condition and mast bumping, RPM management, and safe altitude and airspeed pertaining to energy management. She stated that after demonstrating hovering flight to the student, she had the student take hold of the cyclic control with her. She stated that while maintaining control of the collective and pedals, she verified cyclic control transfer with the student and let her hand loose around the cyclic grip. The instructor reported that the helicopter then began to drift slightly sideways, forward and backward. She stated that she then took the cyclic control back and stabilized the hover. She stated that she then briefly described hovering flight to the student again, then had him take hold of the cyclic with her again as she kept control of the collective and pedals. She stated that after verifying cyclic control transfer with the student, she again let her hand loose around the cyclic grip. She reported that the helicopter then started to move forward. She stated that the student "reacted by applying gradual aft cyclic at first, then quickly applied more aft cyclic." She stated that, "Before full correction could be applied, the aircraft hit the ground. The helicopter then lifted back up a little, and started spinning to the right before falling on its side." The operator's accident report to the NTSB indicated that no mechanical malfunction or failure was involved in the accident.