Ka 4 Rhönlerche II accident during training flight at Olten airfield
On May 23, 1970, a training flight involving an Alexander Schleicher Ka 4 Rhönlerche II at Olten Airfield in Switzerland ended in an accident. The glider, piloted by an instructor with a student, experienced a stall during a low-altitude turn following a simulated cable break. The instructor attempted to recover, but the aircraft impacted the ground before completing the maneuver. The student sustained minor injuries, while the instructor was unharmed. The glider suffered significant damage, and there was minor third-party damage.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.