ASW 20 crash during outlanding attempt near Sumiswald, Switzerland
On June 7, 1978, an Alexander Schleicher ASW 20 crashed during a competition flight near Sumiswald, Switzerland. The pilot, participating in the Swiss Gliding Championships, attempted an outlanding after encountering weak lift conditions. The glider stalled and crashed, resulting in the pilot's fatal injuries. The official investigation attributed the accident to the pilot's failure to maintain minimum airspeed, with contributing factors including a late decision to land and improper trim settings.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.