Collision en vol entre Ka 2 B et S 18 près de Siblingen, Suisse

Le 16 mai 1965, une collision en vol s'est produite entre un Alexander Schleicher Ka 2 B et un Spalinger S 18 II A près de Siblingen, Suisse. Les deux planeurs étaient engagés dans des opérations de vol en thermique lorsqu'ils sont entrés en collision en raison d'une surveillance insuffisante de l'espace aérien. Malgré des dommages importants à l'aile droite du S 18, le pilote a réussi à atterrir en toute sécurité près de l'aérodrome de Schaffhausen. Le Ka 2 B a également atterri sans problème et aucun blessé n'a été signalé. L'incident a été attribué à une observation inadéquate de l'espace aérien par le pilote du S 18.

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.