Collision du Piper PA-18 avec des arbres lors d'un remorquage près de Dt-de-Valerette

Le 22 juillet 1961, un Piper PA-18 Super Cub remorquant un SZD-9 Bocian a rencontré des courants descendants près de Dt-de-Valerette, Suisse. Le pilote de remorquage a largué le câble, mais l'avion a percuté des arbres et s'est écrasé dans une clairière. Le pilote a subi des blessures légères et l'avion a été gravement endommagé. Le pilote du planeur a réussi à larguer le câble de remorquage et à s'éloigner en toute sécurité. Le rapport officiel a conclu que l'incident était dû à l'entrée de l'avion remorqueur dans un courant descendant à une altitude insuffisante.

1. Aerotow ridge flight: During an aerotow from Bex, the Piper towing the Bocian glider climbed toward Monthey and then followed the northwest slope of Dt-de-Valerette in ridge lift at low height above terrain.
2. Inexperienced tow in mountains: The tow pilot, although current and qualified, was towing a glider in mountainous terrain for the first time and had no personal soaring experience, while the glider pilot gave only vague routing instructions.
3. Low height near slope: While following the contours around the hamlet of Les Giètes, the tow plane flew relatively close to the terrain, only about 80–100 m above ground, below the recommended 150 m minimum for towed trains near slopes.
4. Entered downdraft zone: After leaving the northwest ascending slope and crossing the crest near Les Giètes onto the east face of Dt-de-Valerette, the tow plane’s lift zone rapidly changed to a strong downdraft, with the variometer dropping to about –4 m/s.
5. Tow cable released: Recognizing the rapidly rising terrain and loss of lift, the tow pilot released the tow cable almost simultaneously with the glider pilot releasing on his side to try to escape the slope.
6. Collision with trees: Still at low speed near stall and with insufficient maneuvering margin, the tow plane struck and decapitated two fir trees shortly after cable release and continued uncontrolled toward the ground.
7. Crash - minor injury: The tow plane crashed in a sloping clearing about 180 m beyond the trees, sliding and pivoting before coming to rest, resulting in minor injuries to the pilot and substantial destruction of the aircraft.