What happened
On August 26, 2013, at approximately 16:45, an Alexander Schleicher ASK13 glider, registration D-05 and 37, was conducting a training flight near the private airfield of Seyne. The flight, which included an instructor in the rear seat and a student pilot, began with a winch launch at an altitude of approximately 1,200 meters. After releasing the cable at 1,600 meters, the instructor performed several spirals near the village of Seyne but struggled to gain altitude.
Seeking better conditions, the instructor directed the aircraft toward the Paré ridge to perform ridge soaring. After several maneuvers along the ridge, the crew attempted a figure-eight pattern along the southwest face of the terrain. During a left turn, the aircraft encountered a sudden downdraft, causing a sharp descent and a heavy left bank. The instructor applied nose-down elevator to prevent the glider from entering a spin and attempted to maneuver toward the valley. However, the left wing struck the treetops, and the glider came to rest 25 meters further into the trees, resulting in heavy damage to the aircraft. No injuries were reported.
The investigation
The investigation examined the flight sequence, meteorological conditions, and the experience of the crew. The instructor, who held a private pilot license for airplanes with approximately 4,300 total flight hours and 1,227 glider hours, had completed five flights earlier that day. He noted that while thermal activity was poor, he believed conditions for ridge soaring were suitable. The student pilot was on their second flight and was only handling the controls during straight flight phases.
Meteorological data at the time indicated variable winds, with a 7-knot wind from 070° and an 8-knot wind from 270° at a distance of 2,200 meters. The investigation also reviewed the pilot's manual, which notes that ridge soaring is typically only effective with winds exceeding 12 to 15 knots.
Findings
- The instructor decided to proceed with ridge soaring despite unfavorable aerological conditions.
- During a maneuver at ridge altitude, likely at a low airspeed, the instructor lost control of the aircraft due to a sudden downdraft.
- The proximity to the terrain and the low slope of the ridge prevented the instructor from successfully maneuvering the glider away from the obstacle.