On June 8, 1997, about 1605 eastern daylight time, a Schweizer SGS 135, a glider, N17976, was substantially damaged during an uncontrolled descent into a river, while maneuvering on final approach to the Pepperell Airport (MA09), Pepperell, Massachusetts. The certificated private pilot sustained serious injuries. Visual meteorological conditions prevailed for the personal flight that originated at MA09, about 1530. No flight plan had been filed for the flight conducted under 14 CFR Part 91. In the NTSB Form 6120.1/2, the pilot stated that she had intended to fly a local flight and return to MA09. After 30 minutes of flying, she entered a left traffic pattern for landing on runway 24, at MA09. She further stated: "...I was high on my turn to final, I assessed traffic, and proceeded to complete a 360 [degree] turn to lose excess altitude. As I turned onto final, the second time, the left wing of the glider stalled and induced a spin to the left from about 300 ft. AGL. The glider crashed into the Nashua River..." The winds at an airport, 6 miles northeast of MA09, were reported from 150 degrees at 10 knots. The pilot had accumulated 109 hours of total flying experience, of which 70 hours were as pilot in command, and 3 1/2 hours in make and model.