Ka 4 Rhönlerche II ground impact during low-altitude turn at Grenchen airfield
On April 17, 1970, an Alexander Schleicher Ka 4 Rhönlerche II experienced a ground impact at Grenchen Airfield, Switzerland. During a winch launch, the instructor initiated a cable break exercise at approximately 70 meters altitude. The student pilot's delayed response led to a loss of altitude, prompting the instructor to take control. While attempting a right turn to avoid an off-airfield landing, the aircraft stalled and struck the ground with its right wing. Both occupants sustained minor injuries, and the glider was heavily damaged.
- Winch launch climb: During a winch launch at Grenchen, the Rhönlerche II was climbing normally with instructor and student on board.
- Simulated cable break: At about 70 m above ground, the instructor intentionally released the winch cable to conduct a cable-break exercise.
- Delayed pitch response: The student reacted only hesitantly by pushing the stick forward, resulting in inadequate nose-down input and low airspeed.
- Low-speed left turn: Following the instructor’s command to head slightly left, the student initiated a left turn using only rudder at insufficient speed, causing rapid height loss.
- Instructor’s low turnback: The instructor took over, pushed strongly to regain speed, then in tree-top height initiated a steep right turnback to avoid an off-airfield landing.
- Stall in steep turn: In the steep low-altitude turn with an aft center of gravity, the glider entered an over‑stalled condition and responded poorly to control inputs.
- Crash - minor injury: The right wingtip struck the ground and the glider impacted hard, rotating about 180° on its yaw axis, causing serious airframe damage and minor injuries to both occupants.