Collision en vol entre Ka 4 Rhönlerche II et Grunau Baby II près de Siblingen, Suisse

Le 1er avril 1961, une collision en vol s'est produite entre un Alexander Schleicher Ka 4 Rhönlerche II et un Edmund Schneider Grunau Baby II près de Siblingen, Suisse. Les deux planeurs volaient en conditions de portance de pente lorsque le Rhönlerche II est entré en collision avec le Grunau Baby II, entraînant des dommages significatifs aux deux appareils. Malgré la collision, les deux pilotes ont pu atterrir en toute sécurité sans blessures. L'enquête a conclu que les actions du pilote du Rhönlerche II ont contribué à la collision en perdant de vue le Grunau Baby II lors d'un virage à droite.

1. Ridge soaring flight: After aerotow launches from Schaffhausen-Neunkirch, the Rhönlerche HB-669 was ridge soaring along the Siblinger Schlossranden behind and below the Grunau Baby HB-170 in smooth hang lift.
2. Close trail position: As both gliders flew south toward the Randenturm at about 1100 m MSL, the Rhönlerche pilot allowed his aircraft to close to roughly 50 m behind and 20–30 m below the Grunau Baby, a small separation given his limited experience.
3. Right turn by lead: Near the Randenturm, the Grunau Baby, slightly left and above, initiated a right turn, contrary to the Rhönlerche pilot’s expectation of a left turn at the end of the ridge.
4. Follower mirrors turn: The Rhönlerche pilot immediately initiated a right turn as well, from a position slightly right-behind and below the Grunau Baby, and in doing so lost visual contact with the other glider.
5. Converging flight paths: While the Rhönlerche pilot had the Grunau Baby out of sight, the two gliders’ right turns caused their flight paths to converge laterally, rapidly reducing the remaining separation.
6. Late evasive maneuver: Both pilots suddenly reacquired sight of the other aircraft only moments before impact, and although the Rhönlerche pilot steepened his bank and pushed down, the collision could no longer be avoided.
7. Mid-air collision: The left wingtip of the Rhönlerche penetrated the nose of the Grunau Baby, causing serious structural damage to both gliders, but both pilots maintained control and landed safely without injury, one returning to Schaffhausen and the other outlanding near Hinterranden.