Kollision in der Luft zwischen Ka 2 B und S 18 nahe Siblingen, Schweiz

Am 16. Mai 1965 kam es zu einer Kollision in der Luft zwischen einer Alexander Schleicher Ka 2 B und einem Spalinger S 18 II A nahe Siblingen, Schweiz. Beide Segelflugzeuge waren mit Thermikflügen beschäftigt, als sie aufgrund unzureichender Luftraumüberwachung kollidierten. Trotz erheblicher Schäden am rechten Flügel der S 18 gelang es dem Piloten, sicher in der Nähe des Flugplatzes Schaffhausen zu landen. Auch die Ka 2 B landete sicher, ohne dass Verletzungen gemeldet wurden. Der Vorfall wurde auf unzureichende Luftraumbeobachtung durch den Piloten der S 18 zurückgeführt.

1. Aerotow — thermaling: After an aerotow launch at 16:56, the S-18 HB-315 released near the Siblinger Schlossranden and began thermaling in weak, broken lift over the west side of the ridge.
2. Weak broken lift: The S-18 was operating in marginal, irregular lift with alternating strong climb and sink, requiring frequent corrections and making height-keeping and separation more difficult.
3. Instrument-focused flying: Concerned with the irregular up- and downdrafts, the S-18 pilot spent considerable time looking at the instruments and outside toward the ridge and horizon rather than systematically scanning for traffic above.
4. Inadequate lookout above: Although he had previously seen the Ka-2b about 50 m higher, the S-18 pilot continued circling without considering that the other glider might also be thermaling above in the same core and did not check the airspace above.
5. Converging thermaling paths: Both gliders flew roughly a full circle in the same area with only 20–50 m vertical separation, and the fluctuating lift reduced their height separation until the S-18’s right wingtip struck the Ka-2b’s fuselage around 17:05.
6. Damaged glider flown back: After feeling the impact, the S-18 pilot rolled out of the turn, confirmed the aircraft was still controllable despite significant damage to the right wing, and headed toward Schaffhausen airfield.
7. Outlanding - damage: Due to increased sink from the wing damage, the S-18 could not quite reach the runway and made a safe outlanding in a field about 50 m short of the Schaffhausen strip, with substantial wing damage but no injuries.