Ka 4 Rhönlerche II Kollision mit Bäumen während Trainingsflug bei Bettlachstock, Schweiz

Am 26. Juni 1964 kollidierte ein Ka 4 Rhönlerche II Segelflugzeug, gesteuert von einem Schüler, während eines Trainingsflugs in der Nähe von Bettlachstock, Schweiz, mit Bäumen. Der Flug, der vom Flugplatz Granges startete, hatte das Ziel, Hangflüge entlang der Juraberge zu üben. Der Schülerpilot konnte beim Ausführen einer Kurve den ausreichenden Abstand zum Hang nicht halten, was zu einer unvermeidbaren Kollision führte. Das Segelflugzeug wurde erheblich beschädigt, aber der Pilot blieb unverletzt. Der Vorfall wurde auf die Unaufmerksamkeit des Piloten während des Manövers zurückgeführt.

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.