Ka 4 Rhönlerche II incident during aerotow at Birrfeld airfield, Switzerland
On August 9, 1968, a Ka 4 Rhönlerche II experienced an incident at Birrfeld Airfield in Switzerland. Shortly after takeoff, the tow plane experienced an engine failure due to fuel exhaustion, necessitating a safe off-field landing. The glider, piloted by a student, attempted to return to the airfield but crashed during a low-altitude maneuver. The student pilot was unharmed, but the glider sustained damage. The investigation confirmed that the engine failure was due to fuel exhaustion.
- Aerotow initial climb: During an aerotow departure from Birrfeld, the glider was climbing behind the tow plane at about 50 m above ground in a slight left turn.
- Towplane engine failure: The tow plane’s engine suddenly stopped due to fuel exhaustion, forcing an immediate termination of the tow at low altitude.
- Low student experience: The glider was flown solo by a relatively inexperienced student with only eight prior solo flights and limited total gliding time.
- Turn back toward field: After release, the student turned about 200° left intending to return to the airfield, then decided instead to land parallel to the nearby road when it became clear the road could not be safely overflown.
- Tightened low-altitude turn: With insufficient height remaining for a normal turn, the student pulled back on the stick while applying right rudder to tighten the final turn toward the intended landing direction.
- Stall and spin entry: The glider was over‑controlled into a low-speed, uncoordinated condition, entered a stall with spin tendency, and dropped out of the turn from about 5 m above ground.
- Crash - no injury: The glider impacted the field and was substantially damaged, but the student pilot was uninjured.