What happened
On Thursday, April 16, 1998, at approximately 14:00, a mid-air collision occurred near Melve, France, involving two gliders. The first aircraft, a Schempp Hirth Duo Discus registered F-CHTC, was performing a right-hand spiral maneuver in a thermal near the Tête du Boursier at an altitude of approximately 1,250 meters. During this maneuver, the LS 3 glider, registered D-7732, was flying in a straight line on a westward heading along the mountain ridge between Malaup and Tête du Boursier.
The left wing of the LS 3 struck the right wing of the F-CHTC, tearing away approximately four meters of the Duo Discus's wing structure. Following the impact, the instructor on board the F-CHTC took control and attempted an emergency landing; however, the aircraft struck a line of trees and overturned in a field. The LS 3 entered a spiral descent and crashed approximately 100 meters below the Tête du Boursier peak. The collision resulted in two fatalities and one serious injury.
The investigation
The investigation examined the flight paths, weather conditions, and visibility at the time of the accident. Meteorological conditions at the site were reported as having a 10-knot wind from 180 degrees, visibility exceeding 10 km, and scattered cumulus clouds at 2,500 meters. Investigators noted that both gliders were equipped with reflective devices.
Witness testimony from another glider pilot following the LS 3 indicated that sunlight conditions were problematic. The witness stated that light rays made horizontal vision difficult, to the point that the collision was not seen as it occurred. The investigation also determined that the occupants of the F-CHTC did not attempt to bail out because the remaining altitude was too low to allow for a safe evacuation.
Findings
- The primary cause of the collision was visual non-perception of the other aircraft.
- Glare and lighting conditions likely hindered the pilot of the LS 3 from detecting the approaching F-CHTC.