On December 28, 1994, at 1400 eastern standard time, a homebuilt, experimental, Scorpion II, helicopter, N65662, was destroyed during a forced landing, at Cronish Flat, New Hampshire. The student pilot, Curtis Wyman, was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the flight which operated under 14 CFR Part 91. The helicopter was on approach to a landing in an open field, when a vibration, which the pilot described as severe, developed. The pilot attempted to make an autorotation; however, he was unable to maintain directional control of the helicopter. It rotated 180 degrees, and struck the ground while traveling backwards. Examination of the helicopter revealed that the lower blade surface had separated, from the tip to within 30 inches of the hub. The aluminum blades were constructed by the owner as part of the kit. They had 50.9 hours on them since being built.