What happened
On August 30, 2018, a Rolladen-Schneider LS8-18 glider, registration F-CVVS, was performing ridge soaring maneuvers near the Pic de Morgon in the Massif des Écrins. The pilot had originally departed from Sisteron Vaumeilh earlier that day but decided to return to base due to increasing cloud cover and diminishing thermal lift.
While flying near the terrain at approximately 1,420 meters, the pilot attempted to maintain altitude by performing "eight" pattern maneuvers. During a right-hand turn, the pilot increased the bank angle and pulled back on the control column to prevent the aircraft from drifting too close to the rising terrain. This maneuver caused the glider to stall and enter a right-hand spin. The aircraft struck trees at a low altitude, resulting in the destruction of the glider and one minor injury to the pilot, who was able to exit the wreckage without difficulty.
The investigation
The BEA examined the wreckage and recovered data from the onboard LX7007 flight computer. Although the sampling rate of the GPS data was too low to precisely estimate the airspeed at the moment of the stall, the investigation established that the aircraft's mass and center of gravity were within manufacturer limits.
The investigation also reviewed meteorological conditions, noting that valley breezes had weakened, leaving the north face of the mountain likely without sufficient lift. Witnesses on the ground observed the glider performing low-altitude maneuvers before the sudden, steepening bank and subsequent spin into the forest. The investigation also noted that the pilot's recovery attempts—specifically using only left aileron input—were insufficient given the low altitude and the nature of the stall.
Findings
- The primary cause of the accident was the pilot's focus on maintaining altitude and avoiding terrain, which led to a failure to monitor airspeed.
- The stall occurred as a result of increasing the angle of attack and bank angle simultaneously during a turn near the relief.
- The resulting asymmetric stall triggered a spin that the pilot could not recover from before impacting the vegetation.