Unfall der Ka 4 Rhönlerche II während eines Schulungsflugs auf dem Flugplatz Olten

Am 23. Mai 1970 endete ein Schulungsflug mit einer Alexander Schleicher Ka 4 Rhönlerche II auf dem Flugplatz Olten in der Schweiz in einem Unfall. Das Segelflugzeug, gesteuert von einem Fluglehrer mit einem Schüler, erlebte einen Strömungsabriss während einer Kurve in geringer Höhe nach einem simulierten Seilriss. Der Fluglehrer versuchte, das Flugzeug abzufangen, aber es schlug auf den Boden auf, bevor das Manöver abgeschlossen war. Der Schüler erlitt leichte Verletzungen, während der Fluglehrer unverletzt blieb. Das Segelflugzeug wurde erheblich beschädigt, und es gab geringfügige Drittschäden.

1. Aerotow initial climb: The instructor and student began an aerotow training flight from grass runway 23 at Olten airfield and climbed out normally behind the towplane.
2. Low-altitude simulated break: As briefed, the instructor released the tow rope at about 15 m above ground near the end of the runway to simulate a cable break.
3. Very low height: The simulated cable break and subsequent maneuver were initiated at only about 15 m above ground, leaving minimal height margin for turns or recovery.
4. Obstacle proximity: Trees located roughly 120 m south of the departure path reduced lateral obstacle clearance and pressured the instructor to fly a very tight turn.
5. Tight low turn initiated: The instructor took control, banked right slightly, then began a left turn back with bank increasing to about 50° or more to tighten the turn away from the trees.
6. Stall in steep turn: During the steep, low-altitude turn the glider apparently dropped below minimum speed, became sluggish to control inputs, and stalled before the instructor could level the wings.
7. Crash - minor injury: Still in a partially banked attitude with a shallow nose-down flight path, the glider struck the ground before completing the turn, heavily damaging the aircraft and causing minor injury to the student.