What happened
On June 7, 2001, at 16:15, a single-seat Centrair C 101 A glider, registration F-CHDS, was involved in a collision with trees near the locality of Les Ramiettes, Presles. The flight originated from Grenoble Le Versoud, departing at 12:53.
After approximately one hour and fifteen minutes of flight, the pilot reached the Ramavoula point area. While attempting to utilize a thermal with a climb rate of 1 m/s, the pilot entered a left-hand spiral at an indicated airspeed of 100 km/h. As the aircraft reached the ridge line, the vertical speed became negative. In an attempt to reposition the aircraft toward the east to intercept a developing cumulus cloud, the pilot initiated a change in the direction of the spiral.
During this maneuver, the pilot encountered a ridge that had not been identified or assessed. To clear the terrain, the pilot increased speed and executed a pull-up maneuver. During this sequence, the left wing of the aircraft struck the treetops, leading to a crash on the ground. There were no fatalities reported, though the aircraft sustained heavy damage.
The investigation
The investigation relied on information provided by the pilot. Environmental conditions at the time of the accident included visibility exceeding 10 km, a light wind from 040° at 10 knots, and few clouds at 5,000 feet. The investigation examined the pilot's flight path, which was reconstructed using onboard GPS data.
Findings
- The pilot had previously flown over the area but had no prior experience flying at the level of this specific ridge.
- The pilot noted that the lighting conditions provided very little contrast.
- The primary cause of the accident was the incomplete perception of the environment, which prevented the pilot from noting the presence and contours of the ridge during the turn.