What happened
On March 31, 2002, at approximately 14:40, a mid-air collision occurred between two gliders operating near Nibles, France. The aircraft involved were a Schempp Hirth Discus CS, registered D-0585, and a Rolladen Schneider LS4, registered D-3575.
Both aircraft had departed from Sisteron aerodrome roughly one hour prior to the accident. At the time of the collision, the gliders were flying at an altitude of approximately 1,800 meters within the same sector. The pilots were engaged in circuit maneuvers, utilizing two separate thermal updrafts; one pilot was spiraling to the left while the other was spiraling to the right. Each thermal contained approximately ten other gliders. Immediately preceding the impact, the pilot of the D-0585 executed a 30-degree left bank, while the pilot of the D-3575 performed a 20-degree right bank.
Following the impact, both aircraft were destroyed. However, both pilots successfully egressed from their respective cockpits and deployed their emergency parachutes to land safely.
The investigation
The investigation focused on the visibility and communication between the two pilots. It was established that the pilots had not established any radio contact prior to the collision. Furthermore, the pilots reported that they had not visually detected one another before the impact. Investigators noted that the pilot of the D-0585 was wearing sunglasses with closed protective sides. Both aircraft were equipped with reflective strips on their wings to increase visibility.