Aterrizaje duro del Calif A21 en el aeropuerto de Sion resulta en lesiones graves para el instructor
El 18 de abril de 1985, un planeador Caproni Vizzola Calif A-21S estuvo involucrado en un aterrizaje duro en el aeropuerto de Sion, Suiza. El vuelo era un ejercicio de entrenamiento de distancia realizado por un instructor y un piloto. Durante la aproximación final, el instructor retrajo los aerofrenos y ajustó los flaps, lo que provocó un aumento repentino en la tasa de descenso y un impacto fuerte con el suelo. El instructor sufrió lesiones graves, mientras que el piloto resultó ileso. El planeador fue destruido en el incidente.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.