According to the glider pilot, the purpose of the flight was to release from the tow about 300 ft above ground level, return to the airport, and land on the departure runway in the opposite direction, which would simulate the response to a "rope-break" emergency during the initial climb. After departure from runway 27 and release from the tow, the pilot completed a 270° turn (to his right) on the north side of the runway and had a 90°, left base-to-final turn remaining to return to the runway. While still on the base leg, the glider encountered an 11-knot wind from the south that gusted to 18 knots, and the pilot surmised that he must have encountered "wind shear" as he "lost all elevator control" and impacted terrain.Postaccident examination of the flight control system did not reveal any anomalies and the pilot reported that there were no preimpact mechanical malfunctions or failures with the glider that would have precluded normal operation.