On December 11, 1994, at 1400 hours Pacific standard time, a Grob G-103 glider, N3950A, collided with some trees near Tehachapi, California. The pilot was conducting a local visual flight rules instructional flight. The glider, operated by Skylark North, Tehachapi, California, sustained substantial damage. Neither the certificated commercial pilot/certified flight instructor (CFI) nor the certificated private/student glider pilot was injured. Visual meteorological conditions prevailed. The flight originated at Mountain Valley Airport, Tehachapi, California, at 1330 hours. The CFI reported this accident to the National Transportation Safety Board on December 12, 1994. He said the flight encountered a severe downdraft while maneuvering over a ridge on a southeast/northwest course about 100 feet above the ground. The glider's right wing struck some trees. The CFI landed the glider at Mountain Valley Airport without further incident. Examination of the glider revealed that the right wing sustained structural damage. The CFI submitted the required Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1/2. He repeated his telephone statement in the report. He said that the accident occurred on the second pass over the ridge line. The first pass was uneventful. When the glider encountered the downdraft, the airspeed was inadequate to climb successfully over the impending tree line. The CFI also said that the glider did not experience any mechanical malfunctions or failures.