What happened
On Saturday, July 25, 1998, at 14:20, a Grob G103 C "Twin 3 Acro", registered F-CGXE, was involved in an accident near Saint-Geniez in the Alpes-de-Haute-Provence region. The pilot was conducting a local flight with one passenger for an introductory flight, having launched from the Sisteron airfield via a tow from Mont de Hongrie.
While utilizing thermal lift, the pilot followed the ridge toward Saint-Geniez. As the thermals began to dissipate, the pilot attempted to transition to ridge soaring. However, the aircraft lost altitude during this maneuver. In an attempt to navigate through a mountain pass, the pilot was forced to deviate to the right toward the valley due to insufficient clearance. While attempting to clear a section of terrain, the aircraft struck a tree, resulting in one injury to the pilot and heavy damage to the glider.
The investigation
The investigation focused on the flight path and the pilot's maneuvers in relation to the terrain and available lift. The investigation established that the pilot was operating in CAVOK conditions with light winds from the west-southwest. The sequence of events showed that the loss of altitude during the transition from thermal to ridge soaring necessitated a change in flight path to avoid terrain, which ultimately led to the collision.