On August 17, 2014, about 1520 central daylight time, a Let L-23 Super Blanik glider, N266SE, was substantially damaged when it impacted trees and terrain while maneuvering for landing at Merkel Field Sylacauga Municipal Airport (SCD), Sylacauga, Alabama. The student pilot was seriously injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local instructional flight, which was operated under the provisions of Title 14 Code of Federal Regulations Part 91. The pilot stated that she conducted a preflight inspection of the glider and added ballast for the solo flight. She described the tow as "normal," and after about 30 minutes of flight, elected to return to the airport. Her last recollection was turning the glider at an altitude of about 1,800 feet and airspeed of 45 knots to allow room for another glider in the pattern to land. She then "vaguely" remembered the glider entering an aerodynamic stall. She recalled impacting a tree, and subsequently egressing the glider. She stated that the glider performed normally throughout the flight, with no mechanical malfunctions or anomalies. In a statement to a Federal Aviation Administration (FAA) inspector, the pilot stated that she felt nauseated on the morning of the accident, and had also taken an over-the-counter decongestant around 0800. She further stated that she was not properly hydrated before or during the flight, which may have contributed to her general condition. The pilot's flight instructor was flying with another student at the time of the accident. He did not witness the accident, but recalled seeing the accident glider in the traffic pattern for runway 27 at an altitude about 1,800 feet, and felt that it was "in a good position" to land behind his glider. A witness reported to the FAA inspector who responded to the scene that he observed the accident glider approach SCD from the north. He watched the glider enter a steep right bank followed by a stall. The glider recovered before subsequently entering a right spin. The witness observed the glider complete two full rotations in a near-vertical attitude before it disappeared from view behind a tree line. A second witness recounted that the accident glider was on the right downwind leg of the traffic pattern for runway 27 when it stalled and entered a spin. After about one half rotation, it appeared to recover before entering a second spin to the right. He stated that the glider completed two rotations before disappearing from view. The glider came to rest in a near-vertical position in trees approximately 1 mile north of runway 27 at SCD, and sustained substantial damage to the forward cabin area and wings. The pilot held a student pilot certificate, and reported 33 total hours of flight experience, of which 3 hours were in the accident glider make and model. According to FAA airworthiness records, the glider was manufactured in 1993. Its most recent annual inspection was completed in April 2014. The 1535 weather observation at Thomas C Russell Field Airport (ALX), Alexander City, Alabama, located about 23 miles southeast of the accident site, included wind from 200 degrees at 10 knots with gusts to 15 knots, 10 miles visibility, clear skies, and an altimeter setting of 30.01. Remarks noted distant lightning in all quadrants.