Accident du planeur SZD-51-1 lors d'un lancement par treuil à Croix-de-Coeur, Suisse

Le 6 août 1988, un planeur SZD-51-1 a été impliqué dans un accident lors d'un lancement par treuil à Croix-de-Coeur, Suisse. Le planeur, piloté par un pilote suisse, a rencontré des difficultés pendant la phase d'accélération en raison d'un vent arrière fort et d'une piste irrégulière. Le planeur a dévié de sa trajectoire et n'a pas pu atteindre la vitesse de décollage, entraînant une collision avec le terrain. Le pilote a subi de graves blessures et l'appareil a été gravement endommagé. Les conclusions officielles ont confirmé que les conditions de vent et l'état de la piste ont influencé l'accident.

1. Winch launch ground roll: During a test winch launch from the Croix-de-Coeur mountain landing site, the SZD-51-1 began its ground acceleration on a short, uneven, slightly downhill natural strip with a significant tailwind.
2. Glider yaws off axis: As the glider accelerated and passed over a bump where the slope changed, the off-axis winch cable routed via a pulley to the right of the runway caused the glider to yaw suddenly about 20–25° to the right.
3. High tailwind component: A tailwind of about 20 km/h reduced the effective airspeed gained during the limited usable ground run, making it harder to reach takeoff speed.
4. Degraded short runway: Only about the first 100 m of the 200 m natural strip were marginally usable, with the remainder increasingly rough and eroded, limiting acceleration and increasing drag and shocks.
5. Right-side pulley position: The winch cable was routed through a pulley positioned 13 m to the right of the runway axis, contrary to the flight manual requirement that the cable not pass to the right when using the central hook, creating a lateral pull on the glider.
6. Pilot continues launch: Believing liftoff was imminent after the yaw, the pilot chose not to release the winch cable and then, being violently shaken on the rough ground, was unable to operate the release and lost directional control.
7. Crash - serious injury: Still below flying speed and deflected off the strip, the glider was heavily braked by rough terrain, the cable broke, and the aircraft came to rest badly damaged in grass to the right of the runway, with the pilot seriously injured.