On April 19, 2008, about 1600 eastern daylight time, a Let Blanik L-13 glider, N90870, was substantially damaged when it impacted terrain while landing at the Dansville Municipal Airport (DSV), Dansville, New York. The certificated flight instructor (CFI) and the certificated private pilot were not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the local instructional flight conducted under 14 Code of Federal Regulations Part 91. The flight instructor was conducting a familiarization flight with the private pilot, who had not flown in a glider for about 3 years. According to the CFI, the glider was towed to an altitude of the 2,000 feet and released. The private pilot was flying and subsequently entered the traffic pattern for the grass landing area adjacent to runway 14, a 3,500-foot-long, by 100-foot-wide, asphalt runway. The turn from the base leg to the final approach course was performed at an altitude of approximately 700 feet above ground level (agl). The CFI stated that the private pilot was "a little reluctant" to remove the dive brakes and he removed them at 600 feet agl. He further stated: "At this point in the flight the runway touchdown point appeared ok, so we continued. As we approached approximately 200 [feet] agl we began to sink, so I was forced to take over the controls. We encountered a wind gradient which substantially reduced the glide ratio of the aircraft, which resulted in landing short of the desired touchdown point. The left-hand wind struck a tree which ground-looped the aircraft and we came to a full stop facing the opposite direction of landing...." The glider came to rest about 100 feet prior to the runway and sustained substantial damage to its left wing and fuselage. The private pilot stated that she felt the glider was "too high" until she turned onto the final approach path and realized it was "too low." The CFI reported 7,679 hours of total flight experience which included 145 hours in gliders. The private pilot reported 300 hours of total flight experience, all in gliders. Neither pilot reported any mechanical malfunctions of the glider during the accident flight. A weather observation taken at DSV, at 1554, reported: wind from 140 degrees at 15 knots, visibility 10 statute miles, clear skies, temperature 29 degrees Celsius (C), dew point 2 degrees C, altimeter 29.82 inches of mercury.