What happened
On March 3, 2015, a pilot operating an Alexander Schleicher ASW27 glider, registration F-CLCC, departed from the Château Arnoux Saint-Auban airfield for a circuit flight. After approximately two and a half hours of flight, the pilot was following a ridgeline toward the Denjuan summit. While performing several turns within a thermal to gain altitude, the pilot became disoriented and inadvertently turned east, crossing the ridgeline.
This maneuver placed the aircraft on the leeward side of the terrain, where it encountered intense downdors. In an attempt to recover altitude, the pilot performed several maneuvers but eventually determined that a forced landing was necessary. The pilot targeted a snowy slope on the eastern side of the Caduc peak. During the descent, the glider struck the treetops, which tore the wings from the fuselage. The fuselage continued through the trees before impacting the snowy ground. The pilot, who was uninjured, spent the night in the cockpit until rescue teams located and recovered him the following morning.
The investigation
Investigators reconstructed the flight path using FLARM data from other gliders in the area and GNSS data from a portable receiver carried by the pilot. The examination of the wreckage at 1,890 meters altitude revealed that the wings had been stripped from the fuselage upon impact with the trees, and the fuselage had broken at the mid-section of the tail boom.
Meteorological analysis showed variable winds between south-west and north-west at low altitudes, with stronger north-westerly winds at 3,000 meters. The investigation also noted that while the pilot's distress beacon was detected by commercial aircraft, the signal's location was imprecise, and the onset of darkness prevented immediate visual contact by search helicopters.