Mid-air collision between Ka 4 Rhönlerche II and Grunau Baby II near Siblingen, Switzerland

On April 1, 1961, a mid-air collision occurred between an Alexander Schleicher Ka 4 Rhönlerche II and an Edmund Schneider Grunau Baby II near Siblingen, Switzerland. Both gliders were flying in ridge lift conditions when the Rhönlerche II collided with the Grunau Baby II, resulting in significant damage to both aircraft. Despite the collision, both pilots were able to land safely without injuries. The investigation concluded that the Rhönlerche II pilot's actions contributed to the collision by losing sight of the Grunau Baby II during a right turn.

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.