What happened
On August 23, 2016, at approximately 17:15 local time, a Schleicher KA6 glider, registration F-CECN, was engaged in ridge soaring near Seillans, France. The flight began with a towed takeoff from the Fayence aerodrome at 17:00, with the pilot releasing from the tow cable at an altitude of roughly 1,100 meters east of Seillans.
While performing ridge soaring maneuvers, the pilot noticed the aircraft was losing altitude. Upon checking the flight instruments, the pilot determined the airspeed had dropped to approximately 80 km/h. Although the stall speed for this aircraft is 60 km/h, the local club regulations required a minimum flight speed of 90 km/h for ridge soaring. In an attempt to clear the terrain, the pilot initiated a left turn toward the valley; however, the glider struck trees before impacting the ground. The aircraft was destroyed, and there were no fatalities.
The investigation
The investigation examined the pilot's experience, the meteorological conditions, and the flight dynamics at the time of the accident. The pilot, who had held a glider license since April 2015, had a total of 82 flight hours, with 30 hours specifically on this aircraft type.
Meteorological analysis revealed that while surface conditions at the aerodrome showed a southeast wind of 5 to 10 knots, the conditions at the accident site involved a wind from 155° at 7 knots. A sea breeze at the surface and in the lower layers was overlaid by a northwesterly flow at higher altitudes. This opposing wind structure prevented convection from rising above 1,500 meters and was capable of generating downdrafts on the lee side of the slopes.
Findings
- The primary cause of the accident was the pilot's insufficient monitoring of airspeed and flight conditions relative to the terrain.
- This lack of surveillance led to a delayed decision-making process when attempting to maneuver away from the rising terrain.