The pilot, who was also the holder of a Private Pilot Licence, was conducting his first gliding flight for the day. The glider was aero-towed to 1100 feet above the aerodrome, but only weak lift was encountered in the area. The pilot elected to return for landing and commenced a normal circuit. On the downwind leg strong sink was encountered and the base turn was conducted at about 300 feet above the ground. Indicated airspeed at the time was reported to be about 55 knots. The pilot subsequently advised that the roll into the turn was normal, but he was unable to level the wings again, even with full opposite aileron. The aircraft continued descending in a wing-low attitude and struck the ground about 250 metres before the threshold of the strip. Investigation revealed no evidence of any pre-impact defect or malfunction of the controls, and atmospheric conditions at the time were reported as being stable. When the sink was encountered on the downwind leg, the pilot had modified his circuit by flying closer to the strip. As a result, the angle of bank required for the base turn was steeper than normal. It was considered probable that the aircraft had stalled during this turn onto base, with insufficient height remaining to allow the pilot to recover control.
