Colisión del Ka 4 Rhönlerche II con árboles durante vuelo de entrenamiento en Bettlachstock, Suiza

El 26 de junio de 1964, un planeador Ka 4 Rhönlerche II, pilotado por un estudiante, colisionó con árboles durante un vuelo de entrenamiento cerca de Bettlachstock, Suiza. El vuelo, que se originó en el aeródromo de Granges, tenía como objetivo practicar el vuelo de ladera a lo largo de las montañas del Jura. El piloto estudiante, al ejecutar un giro, no logró mantener una distancia adecuada de la pendiente, resultando en una colisión inevitable. El planeador sufrió daños significativos, pero el piloto salió ileso. El incidente se atribuyó a la falta de atención del piloto durante la maniobra.

1. Ridge soaring flight: The student pilot departed Granges airfield in a Rhönlerche II for a ridge-soaring training flight along the Jura with a planned maximum duration of 75 minutes and specified speed and altitude constraints.
2. Low experience level: The pilot was a student with only 9 hours 38 minutes and 83 flights of total glider experience, all on the Rhönlerche II, and was still completing the altitude-gain flights required for his license.
3. Weak, irregular lift: While ridge soaring near Bettlachstock, the glider encountered weak and irregular lift averaging about 1 m/s, and had descended roughly 120 m in the preceding six minutes, likely keeping the pilot close to the slope.
4. Prolonged right turn: At about 1305 while flying along the Jura with the ridge on his left, the pilot initiated a right turn at about 78 km/h and 45° bank to reverse direction along the slope but allowed the turn to continue too long toward the terrain.
5. Late turn termination: The pilot, inattentive to his position relative to the slope, failed to stop the turn in time to re-establish safe separation from the hillside.
6. Collision with trees: With insufficient lateral clearance remaining, the glider could no longer avoid terrain and struck the tops of trees on the steep, forested south face of the Bettlachstock.
7. Crash - no injury: After contacting the trees the glider fell into the forest, was about 80% destroyed, and the pilot escaped uninjured.