Nimbus 4DLM strikes a rock face out of a ridge turn

Both pilots of a Nimbus 4DLM were fatally injured when the glider flew into a rock face during a right turn in the Queyras massif near Vars; aircraft destroyed. After about three hours of mountain soaring — over an hour above 3,000 m without supplemental oxygen — the crew turned toward the valley, facing crests higher than the glider and probably without a clear horizon. Control was most likely lost in the turn, perhaps a stall, from too low to recover. Possible mild hypoxia, the heavy Open-class glider, and unclear sharing of control between the two pilots were contributing factors.

1. Alpine cross-country, Queyras: After aerotow from Aspres-sur-Buëch at 12:57, the Nimbus 4DLM (open class, 26.5 m wingspan) flew a ~3 h alpine circuit; the two-pilot crew shared the flying.
2. Heavy open-class in complex air: The Nimbus 4DLM is a large, heavy, high-inertia glider taking ~7 s to roll ±45°, versus ~4 s for a 15 m single-seater; aileron authority is limited. The ridge has complex, violent aerology.
3. Possible moderate hypoxia: Both occupants spent over 2 h above 2500 m and over 1 h above 3000 m without supplemental oxygen; hypoxia effects can appear from around 1500 m, with possible cognitive degradation.
4. Two-pilot role-sharing unclear: Who was at the controls when control was lost could not be determined, nor the interactions between the two pilots; guidance calls for explicit role definition on two-pilot flights.
5. Right turn into higher crests: At 3,060 m / 250 m AGL, the crew turned right toward the valley. The view ahead was bounded by crests reaching 3,200-3,350 m, higher than the glider; turn-entry speed was 119-143 km/h.
6. Loss of control near the rock face: Control was probably lost during or after the turn, in disturbed ridge airflow at low height with little clearance to the rock. Given the glider's inertia, recovery was not possible.
7. Frontal impact with rock face: The glider hit the rock face frontally with significant energy, then fell down the slope. The wreckage was found two days later; the aircraft was destroyed, both occupants fatally injured.