Incident Overview
A student glider pilot, observed by his Certified Flight Instructor (CFI) from the ground, executed a base turn from the downwind leg that was made at too low an altitude and too late relative to his position in the landing pattern. This maneuver prevented the glider from arriving at the runway with sufficient altitude and airspeed for a safe landing.
Contributing Factor
A contributing factor to the low and slow condition on final approach was the pilot's failure to realize that the spoilers were still deployed. The spoilers, when extended, increase drag and reduce lift, exacerbating the energy deficit caused by the poorly timed turn.
Outcome
The glider subsequently collided with an airport perimeter fence short of the runway. The impact caused substantial damage to the aircraft.
Probable Cause
The probable cause of the accident was the student pilot's premature and excessively low base turn, combined with his failure to retract the spoilers, resulting in insufficient altitude and airspeed to reach the runway.