Ka 4 Rhönlerche II Strömungsabriss nach Windenstartfehler auf Schweizer Militärflugplatz

Am 21. März 1964 erlebte eine Alexander Schleicher Ka 4 Rhönlerche II einen Windenstartfehler auf einem Militärflugplatz in der Schweiz. Das Segelflugzeug, gesteuert von einem Fluglehrer und einem Schüler, erlitt während des Aufstiegs einen Seilriss. Trotz der Verfügbarkeit einer langen Startbahn versuchte der Fluglehrer, zum Startpunkt zurückzukehren. Das Segelflugzeug überzog und geriet aus etwa 15-20 Metern in einen Trudeln, wobei es auf die Startbahn aufschlug. Beide Insassen blieben unverletzt, aber das Flugzeug erlitt Schäden am linken Flügel und an der Nase.

1. Winch launch climb: During a dual-instruction winch launch from a military airfield, the Rhönlerche began its initial climb with the student in front and the instructor in the rear seat.
2. Cable break in climb: After the glider had covered about 200–300 m and reached roughly 50–60 m height, the winch cable’s weak link failed and the cable broke.
3. Adequate landing area ahead: Despite approximately 800 m of hard-surface runway and a further 1000 m of flat grass available straight ahead, the crew did not plan for a straight-ahead landing after the cable break.
4. Student recovers, proposes turn: The student correctly lowered the nose to stabilize the glider after the cable break and then proposed a turn back toward the launch point, which the instructor accepted.
5. Instructor steepens low turn: When the student initiated a left turn that seemed too shallow, the instructor took over and increased the bank angle without increasing airspeed at low altitude.
6. Stall and wing drop: After about 100–120° of heading change, the glider became too slow and stalled, dropping over the left wing from an estimated 15–20 m height.
7. Crash - no injury: The glider struck the hard runway first with the left wingtip and then the nose, sustaining damage to the left wing and forward fuselage, while both occupants remained uninjured.