Cat. 2 investigation report: simplified-format report, adapted to the circumstances of the occurrence and the investigation stakes.
While the pilot was slope soaring below the Soleil-Bœuf ridge, he performed a first spiral by making a left turn facing the slope.
He then approached the slope and started new "figure-of-eight” manoeuvres while still under the ridge. He again aborted this manoeuvre and made a turn, this time to the right, facing the slope. The high rate of climb and the altitude gained during the second turn may have led the pilot to believe that he had encountered uplift at this point relative to the spur. He may have continued the turn and made a spiral, as he had done previously, obliging him to turn facing the slope.
In this case, it is probable that the pilot then miscalculated the path for exiting the turn by underestimating the effects of the wind and the specific aerological conditions around the spur, which carried the glider off course, towards the terrain during the turn. To avoid a collision with the terrain, the pilot may have been forced to tighten the turn by significantly increasing the bank while probably simultaneously pulling back on the elevator control. During this manoeuvre, the glider probably stalled as a result of the increased load factor and then entered a spin. The height available at the time was not sufficient for the pilot to be able to regain control of the glider before hitting the ground.
Performing spirals while flying below the ridge line and at an insufficient lateral distance from the terrain probably did not allow the pilot to retreat towards the valley and thereby avoid a collision with the terrain.