On May 21, 1993, at 1637 eastern daylight time, a Schweizer SGS 233A glider, N17870, registered to the Triple Cities Soaring Society, was substantially damaged during landing at Binghamton Regional Airport, Johnson City, New York. The pilot and passenger received minor injuries. Visual meteorological conditions prevailed and a flight plan was not filed. The personal flight departed from Endicott, New York, and was conducted under 14 CFR 91. According to FAA inspector Anthony James, the glider was cleared to land on runway 34 by Binghamton Tower. About one half mile from the runway, the glider was observed to bank to the right and pitch down. It impacted a sloped bank of rocks near the threshold of runway 34 and then slid into a tree. Inspector James examined the wreckage, confirmed control cable continuity, and reported that the "spoilers were up." He also stated that no mechanical malfunctions were reported by the pilot. According to the certified flight instructor (CFI), the private pilot seated in the rear seat was at the controls of the glider up until the last ten seconds of flight. The flight departed with a towplane takeoff from an airstrip located 11 miles from the Binghamton Regional Airport. The glider was towed up to 3000 feet above mean sea level. The CFI stated that he delayed the order to release from the towplane so that ". . . the angles looked good for a very conservative approach . . . " He stated that the glider was ". . . less than the runway's length out from the runway . . . " at the time of release. The CFI stated that during the initial portion of the straight in approach to runway 34, the glider encountered a "fairly severe sink" and the private pilot corrected "appropriately". It still appeared to the CFI that the glider would be able to "land beyond the numbers". The glider then encountered "very severe sinking air". After observing rapidly rising terrain and powerlines near the threshold of the runway, the CFI took control of the glider and turned toward a small scrub covered field because " . . . that seemed to be our only option." The right wing impacted the ground, followed by the nose of the glider. No mechanical malfunctions were reported by either pilot.