What happened
During a flight intended for a biennial flight review, a flight instructor and a pilot departed in a motor glider under windy conditions. The instructor had advised the pilot to fly conservatively due to the wind. During the flight, the crew performed soaring maneuvers in the vicinity of the airport using a power-off configuration.
Upon returning to the airport, the flight instructor elected to perform a landing in the power-off configuration. During the approach, the pilot delayed the turn to base leg. While turning base, the pilot became uncomfortable with the approach and transferred control of the aircraft to the flight instructor.
As the instructor turned the aircraft directly toward the airport, the crew encountered very heavy sinking air. The instructor attempted to land on the grass short of the asphalt runway; however, the aircraft could not maintain sufficient lift to clear the trees bordering the airfield. The motor glider descended through the trees, resulting in a large section of the right wing being sheared off. The aircraft came to rest on its right side, partially inverted.
At the time of the accident, the winds were from 220 degrees at 16 knots, gusting to 23 knots, with the active runway being 24.
The investigation
An examination of the motor glider revealed no mechanical deficiencies. Investigators found that the speed brake handle was in the fully extended position. Specifically, the right speed brake was extended while the left speed brake remained retracted.