Collision d'un SZD-12A avec un arbre lors d'une approche à basse altitude près de l'aérodrome de Courtelary

Le 9 juillet 1973, un SZD SZD-12A Mucha 100A a percuté un arbre lors d'une approche à basse altitude près de l'aérodrome de Courtelary, en Suisse. Le pilote, qui n'a pas été blessé, a tenté d'atterrir dans un champ après avoir rencontré des courants descendants. Malgré les efforts pour gagner de l'altitude, le planeur a heurté un arbre et s'est immobilisé dans le lit de la rivière. L'appareil a subi des dommages importants, mais aucune blessure n'a été signalée. Le rapport final a identifié l'accident comme résultant d'une approche à une altitude trop basse.

1. Aerotow local soaring: The pilot aerotowed from Courtelary runway 07 and released near the ridge north of Cortébert at about 700 m QFE for a local soaring flight.
2. Weak lift conditions: After release the pilot found no usable lift near the ridge and then only weak 0.5–1 m/s climbs over Courtelary, indicating marginal soaring conditions.
3. Low circuit altitude: The pilot remained in the circuit area over Courtelary at altitudes down to about 250 m QFE and repeatedly flew left-hand turns in final approach instead of committing to a standard landing pattern as required.
4. Encountering strong sink: While turning left over Courtelary and briefly gaining 50–60 m, the glider then encountered descending air of about 3–4 m/s when on a northerly heading.
5. Continued low turns: The pilot continued the left turn through to a southerly heading to try to return to the aerodrome despite the strong sink and already low height.
6. Forced field landing: Realizing he could no longer reach the runway due to continued sink and insufficient altitude, the pilot elected to attempt a landing in a field parallel to the Suze north of the aerodrome and initiated a low-altitude turn onto the field axis.
7. Crash - no injury: During the low-altitude turn toward the field the left wingtip struck a tree on the north bank of the Suze, and the glider crashed into the riverbed and pivoted, sustaining serious damage while the pilot was uninjured.