L-13 Blanik-Absturz bei Muottas Muragl nach Strömungsabriss in turbulenten Bedingungen
Am 2. August 1974 stürzte ein Aero Vodochody L-13 Blanik bei Muottas Muragl, Schweiz, während eines Trainingsflugs ab. Das Segelflugzeug, gesteuert von zwei erfahrenen Piloten, erlitt einen Strömungsabriss, nachdem die Mindestfluggeschwindigkeit in der Nähe des Kamms nicht gehalten wurde. In der Gegend wurden turbulente Bedingungen gemeldet, die möglicherweise zu dem Vorfall beigetragen haben. Der Absturz führte zum Tod des Piloten im Vordersitz und zu schweren Verletzungen des Piloten im Hintersitz. Das Flugzeug wurde beim Aufprall zerstört.
- Ridge training flight: During a dual training flight after a winch launch from Samedan, the Blanik was flown in ridge lift along the Muottas Muragl slope at low height.
- Very low ridge height: Witnesses observed the glider flying along the Muottas Muragl slope in very low proximity to the terrain, estimated around 20–30 m above ground.
- Turbulent wind conditions: The accident area lay near the upper boundary of the Malojawind with known wind shear and strong turbulence, later confirmed by a helicopter pilot who experienced severe turbulence on approach to the site.
- Speed near minimum: In the weak ridge lift the front-seat pilot tended to fly slowly, around the speed for minimum sink (about 68–80 km/h), close to the aircraft’s stall speed, prompting the instructor to call for more speed several times.
- Minimum speed exceeded: While flying close to the slope in turbulent air, the glider’s airspeed dropped below the minimum safe flying speed, leading to an aerodynamic stall.
- Abrupt nose drop: The Blanik suddenly pitched nose-down and entered a steep, near-vertical descent, described by witnesses as a vertical fall or vertical right spin toward the slope.
- Crash - fatal: At about 14:36 local time the glider impacted the Muottas Muragl slope in a steep nose-down attitude and was destroyed, killing the front-seat pilot and seriously injuring the rear-seat pilot.