History of the Flight
The pilot, flying a Schleicher ASH 26 E glider registered D-KWAY, took off without assistance at around 12:07 from Serres-la-Batie Montsaleon for a local flight north of the aerodrome. After switching off the engine and retracting the propeller, he gained approximately 650 m in altitude by spiraling in a thermal. Around 12:20, he exited the spiral and headed towards Saint-Apôtre mountain, then flew along the south slopes. Having lost nearly 600 m of altitude and finding no updrafts, he turned towards Aspres-sur-Buëch aerodrome, which he believed he could reach given the glider's altitude and lift-to-drag ratio. He decided to use the engine to gain altitude and continue the flight. At 12:29, when at a height of 260 m and 2,850 m from the runway, he deployed the propeller and attempted to start the engine, but without success. The glider continued to lose height and struck trees a few dozen meters from the threshold of runway 10 at Aspres-sur-Buëch, then finished its run on the ground.
Additional Information
Pilot Experience
The 62-year-old pilot held a sailplane pilot license (SPL) with ratings for powered glider, TMG, aerobatic, winch, tow, and self-launch. He was a glider and motor glider instructor, with 5,039 glider flight hours (887 on type) and approximately 4,000 airplane flight hours. He had flown 106 h 21 min in the previous three months, including 66 h 08 min on type. He was the owner of D-KWAY.
Meteorological Information
Estimated conditions at the accident site: wind from 270° at 10 kt with gusts of 20 kt, CAVOK, temperature 35°C, QNH 1014 hPa.
Site and Wreckage Information
The wreckage was located 30 m from the threshold of runway 10 at Aspres-sur-Buëch and 85 m to the right of the runway edge. The glider had collided with several trees before coming to rest on the ground. The propeller was deployed and intact.
Pilot's Statement
The pilot reported purchasing D-KWAY in April 2013, a glider with an extendable propeller for self-launching. He stated that he was aware the propeller could deploy without the engine starting and had experienced this situation before. He knew the performance impact of a deployed non-operating propeller. Given his height, he decided to approach Aspres-sur-Buëch. He tried to start the engine, which had cooled since takeoff, but after several unsuccessful attempts, he continued the approach and attempted to land with the propeller extended. At low height, realizing he would not reach the runway, he prepared for a forced landing straight ahead, pulling on the stick to increase pitch before colliding with trees. In hindsight, he believed he could have landed on the runway had he not extended the propeller.
Use of Engine in Flight
The ASH 26 E is a single-seat self-launching glider with a combustion engine and propeller on a retractable pylon aft of the wings. The flight manual includes procedures for deploying the propeller and starting the engine, and specifies a minimum safe height of about 300 m. It notes that powered sailplane engines are not as reliable as certified airplane engines and that pilots must be prepared for failure.
Conclusions
The scenario: at sufficient height and distance to land, the pilot attempted to start the engine, which failed. The extended propeller reduced the lift-to-drag ratio from 40 to 10, making it impossible to reach the runway. Given the time needed to retract the propeller and the low height, the pilot prioritized holding the flight path. Contributing factors include overconfidence in engine reliability and insufficient knowledge of the effects of propeller deployment on lift-to-drag ratio.