Colisión en el aire involucrando Bonanza 35, Piper PA-18 y planeador Mucha Standard en el aeródromo de Zweisimmen
El 31 de julio de 1974, ocurrió una colisión en el aire en el aeródromo de Zweisimmen, Suiza, involucrando un Beechcraft Bonanza 35, un Piper PA-18 y un planeador Mucha Standard. El Bonanza 35, en un vuelo VFR desde Zúrich, colisionó con el Piper PA-18, que remolcaba el planeador Mucha Standard poco después del despegue. El piloto del Bonanza resultó fatalmente herido, mientras que el piloto del avión remolcador sufrió heridas graves. El piloto del planeador Mucha Standard logró soltar la cuerda de remolque y aterrizó de manera segura sin daños. Ambas aeronaves motorizadas fueron destruidas en el incidente.
- Aerotow takeoff roll: The Mucha Standard glider HB-658, behind towplane HB-OUH, began its aerotow takeoff from the hard-surface runway with the start helper giving the launch signal.
- Misjudged approaching Bonanza: Before authorizing the tow launch, the start helper saw the Bonanza west of Betelried but, based on its height and track, incorrectly assumed it was not intending to land and thus did not delay the launch.
- Bonanza low over runway: While the tow combination was starting and climbing, the Bonanza HB-EBF flew along the runway centerline at about 80 m above ground with gear down and little or no flap, on what was effectively a landing approach.
- Converging flight paths: As the towplane and glider climbed through about 15 m above ground, the Bonanza, slightly left of the towline and descending, closed rapidly from behind, with witnesses noting an increase in its engine power shortly before overtaking.
- Glider releases towline: At the moment of collision, the glider pilot released the towline and continued independently to land on the remaining runway.
- Mid-air collision: The Bonanza collided with the climbing towplane at about 15 m above ground, both powered aircraft crashed onto the runway with one fatal and one serious injury, while the glider landed safely without damage.