Atterrissage dur du Calif A21 à l'aéroport de Sion entraîne des blessures graves pour l'instructeur

Le 18 avril 1985, un planeur Caproni Vizzola Calif A-21S a été impliqué dans un atterrissage dur à l'aéroport de Sion, en Suisse. Le vol était un exercice d'entraînement à distance mené par un instructeur et un pilote. Lors de l'approche finale, l'instructeur a rétracté les aérofreins et ajusté les volets, entraînant une augmentation soudaine du taux de descente et un impact violent avec le sol. L'instructeur a subi des blessures graves, tandis que le pilote est resté indemne. Le planeur a été détruit lors de l'incident.

1. Final approach landing: During final approach to land on runway 26, the instructor was flying the Calif A21 glider with the student in a distance-training flight.
2. Unfamiliar with type: The instructor had not flown this particular glider type for about eight months and was using the approach to refamiliarize himself with its flap/airbrake system.
3. Unusual flap-airbrake design: The Calif A21’s combined flap/airbrake control required passing through a negative flap (flaps up) position when changing between positive flap and airbrake, causing a brief loss of lift near the ground.
4. Airbrakes set half: About 250 m before the threshold, with indicated airspeed around 120 km/h, the instructor extended the airbrakes to half travel, which immediately increased the descent rate.
5. Late configuration change: Perceiving the approach as too short, the instructor attempted to lengthen the glide by retracting the airbrakes and selecting positive flap, which necessarily drove the flaps briefly through the negative position close to the ground.
6. Sudden sink near ground: The transient negative flap position, combined with low height and turbulence, caused a sharp increase in sink and the glider was forced onto the ground just short of the runway.
7. Crash - serious injury: The glider impacted the ground hard and stopped almost immediately about 12 m before the runway threshold, seriously injuring the instructor while the other pilot was unhurt and the aircraft was destroyed.