Incident du HBV Diamant lors du championnat suisse de vol à voile près de Trimbach
Le 24 mai 1972, un HBV Diamant a connu un incident près de Trimbach, France, lors du championnat suisse de vol à voile. Le pilote, participant à une course triangulaire de 145 km, a eu du mal à trouver des ascendances et a décidé d'effectuer un atterrissage en campagne. En manœuvrant pour l'atterrissage, le planeur a décroché et s'est écrasé, entraînant des blessures graves pour le pilote et la destruction de l'appareil. L'enquête a confirmé que l'accident a été causé par une vitesse du planeur tombant en dessous du minimum requis lors du virage d'atterrissage.
- Cross-country task flight: During a competition cross-country task, the pilot flew the HBV Diamant after aerotow launch from Grenchen and was returning from the first turnpoint.
- Unable to find lift: On the return leg near Barmelweid, the pilot had difficulty finding usable updrafts and began losing height.
- Continued flight low: Hoping to find lift near Trimbach, the pilot continued south of the Dottenberg toward the southwest, progressively losing more altitude.
- Insufficient height for airfield: The remaining altitude became insufficient to reach Olten airfield, forcing the pilot to plan an outlanding on a relatively small, high-grass field near Trimbach.
- Outlanding setup: The pilot selected a grass field at Grossfeld, flew two full circles to inspect it, and extended the landing gear to commit to the outlanding.
- Stall in landing turn: While turning in a relatively steep right-hand turn onto final approach, the glider’s airspeed dropped below minimum and it abruptly stalled, possibly influenced by strong gusts.
- Crash - serious injury: The glider entered a steep dive with about 45° bank and impacted the ground roughly 15 m short of the chosen field, seriously injuring the pilot and destroying the aircraft.