Collision entre l'hélicoptère Bell 47 G3 et le planeur B-4 près du col de Sanetsch entraîne trois décès

Le 15 juillet 1978, à 12h25, un hélicoptère et un planeur sont entrés en collision frontale à environ 3 km au nord-nord-ouest du col du Sanetsch. L'hélicoptère HB-XFA avait décollé de Gruyères à 11h55, tandis que le planeur HB-1259 avait quitté Saanen à 10h50. Les deux pilotes ainsi que la passagère de l'hélicoptère ont été tués, et les aéronefs ont été complètement détruits. L'enquête a révélé que les pilotes n'avaient pas remarqué l'autre aéronef à temps, ce qui a conduit à l'accident. Il est recommandé d'améliorer la visibilité et la conscience situationnelle des pilotes dans ces espaces aériens.

1. Aerotow to cruise: The glider HB-1259 was aerotowed from Saanen at 10:50 and released after about five minutes near the south slope of Eggli to begin an alpine soaring flight.
2. High-traffic glider zone: The flight took place within an active alpine glider zone near Sanetschpass, designated as a danger area with concentrated soaring activity.
3. Poor mutual visibility: Flight tests later showed that a B-4 glider is very hard to see from a Bell 47 and that the helicopter is not audible from the glider, making see-and-avoid difficult.
4. Converging flight paths: Around 12:25 the glider, circling north-northwest of Sanetschpass, and the helicopter flying toward Valais approached each other on nearly opposite headings at similar altitude without visual acquisition.
5. No effective avoidance: Neither pilot initiated an avoidance maneuver, indicating that the opposing aircraft was not seen in time to react.
6. Rotor strikes glider: The helicopter’s main rotor disc intersected the glider’s fuselage at about a 55° bank angle, cutting the B-4 longitudinally through the cockpit and right wing root and fatally striking the glider pilot.
7. Crash - fatal: Both the disintegrated glider and the damaged helicopter fell onto the snow-covered scree slope at Lapi di Bou NNW of Sanetschpass, destroying both aircraft and killing all three occupants.