Accidente de un SZD-9 Bocian durante el lanzamiento por torno en el aeródromo de Samedan resultando en dos muertes

El 4 de julio de 1971, un SZD-9 Bocian se estrelló durante un lanzamiento por torno en el aeródromo de Samedan en Suiza. El planeador biplaza, pilotado por un instructor de vuelo y un aprendiz, experimentó un lanzamiento empinado e inestable. El cable del torno se soltó a una altitud de 70 a 100 metros, lo que provocó una pérdida de sustentación y un giro posterior. La aeronave impactó la pista, resultando en la destrucción del planeador y la muerte inmediata de ambos ocupantes. La investigación confirmó que la causa fue una combinación de velocidad insuficiente, ángulo de lanzamiento empinado y control inadecuado después de la liberación del cable.

1. Winch launch climb: The Bocian HB-648 began a winch launch from the grass runway at Samedan with the trainee in front and instructor in the rear, initial ground roll and liftoff appearing normal.
2. Excessively steep climb: At about 10–15 m above ground the glider was pitched into a very steep climb, causing a noticeable reduction in airspeed and oscillations about the longitudinal and vertical axes.
3. Limited winch experience: Both pilots had very little recent winch-launch experience, with the instructor’s last winch launch eight years earlier and the trainee’s only winch launches two years prior on a different type.
4. Cable auto-release: Around 70–100 m above ground, during a brief heading deviation and correction, the winch cable likely auto-released from the CG hook due to increased cable angle while the glider remained in a steep attitude.
5. Insufficient nose-down input: After cable release the crew apparently did not promptly and sufficiently lower the nose, so the glider continued at a high pitch attitude as the winch pull disappeared and airspeed decayed below stall speed.
6. Stall and right spin: With airspeed below minimum and right rudder likely still applied from the heading correction, the glider stalled and entered a right spin from low altitude.
7. Crash - fatal: After about one spin turn the Bocian impacted the hard-surface runway in a steep nose-down right rotation, destroying the glider and killing both occupants on impact.