Accidente de ASW 20 durante intento de aterrizaje en campo cerca de Sumiswald, Suiza

El 7 de junio de 1978, un Alexander Schleicher ASW 20 se estrelló durante un vuelo de competición cerca de Sumiswald, Suiza. El piloto, que participaba en los Campeonatos Suizos de Vuelo a Vela, intentó un aterrizaje en campo tras encontrar condiciones de ascenso débiles. El planeador entró en pérdida y se estrelló, resultando en lesiones fatales para el piloto. La investigación oficial atribuyó el accidente a la falta del piloto para mantener la velocidad mínima, con factores contribuyentes que incluyen una decisión tardía de aterrizar y ajustes de trimado incorrectos.

1. Cross-country task: The pilot launched by aerotow from Grenchen at 14:38 for a competition cross-country task and flew normally until reaching the Sumiswald area.
2. Weak lift conditions: In the Sumiswald area the glider encountered generally weak thermals with sink around 0.75 m/s, forcing continuous descent and leading to low altitude.
3. Late landing decision: Despite being low and repeatedly circling in weak lift near Sumiswald, the pilot delayed committing to an outlanding, reducing options for a proper landing pattern.
4. Low final approach: The pilot initiated an outlanding approach over the Chleinegg/Oberlinde area at an estimated 20–25 m above ground, with landing flap setting 5 selected and the trim set tail-heavy.
5. Improper trim setting: The longitudinal trim was set markedly tail-heavy instead of nose-heavy for landing, making it easier to fly below the minimum safe speed in flap 5.
6. Stall on approach: On short final in flap 5 with tail-heavy trim, the glider’s airspeed dropped below the minimum, the flow at the tailplane likely separated, and the aircraft abruptly rolled and pitched into a steep, turning descent.
7. Crash - fatal: The glider impacted the ground in a steep right-turn attitude near Oberlinde, was destroyed, and the pilot sustained fatal injuries shortly after hospital admission.