On July 22, 2005, at 1030 eastern daylight time, a Robinson R22, N8041J, was substantially damaged while hovering at Boire Field Airport (ASH), Nashua, New Hampshire. The certificated flight instructor and student pilot were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which was conducted under 14 CFR Part 91. According to the flight instructor, the purpose of the flight was to give the student an introductory flight. They departed the airport at 0950, and 20 minutes later, returned for "hover work" in an area located on the north portion of the airport. After completing the hover work, they air taxied to runway 32. After arriving at runway 32, the instructor placed the helicopter in a hover 4-foot above the ground, abeam taxiway bravo. Then while waiting to cross, the instructor had the student try to hold the helicopter steady in the hover while he also kept his hands on the controls. The student then "pulled the controls" from his hands, and moments later, he realized that the student had let go of the controls. The helicopter then "rolled hard left, very fast" and the instructor could not regain control. The main rotor blades then struck the ground. Examination of the helicopter by the FAA inspector revealed no evidence of any preimpact malfunctions. During an interview with the student, he stated that when they arrived back at the airport, the instructor stopped the helicopter about 10-feet in the air while they were "waiting for planes to land." He then gave him the "stick." The student stated that this made him very "uncomfortable" and he did not know what to do. Shortly thereafter, the helicopter started drifting sideways to the left and the accident occurred. The flight instructor held a commercial pilot certificate with a rating for rotorcraft helicopter. His most recent application for an FAA second-class medical certificate was dated April 12, 2005. He reported 3,200 total hours of flight experience. The helicopter was manufactured in 2001, and the most recent annual inspection was completed on June 24, 2005. At the time of the accident, the helicopter had accrued 6,214.7 total hours of operation. The weather reported at the airport, at 1045, included winds from 320 degrees at 5 knots.