Colisión en el aire entre Ka 4 y Piper J3C-65 en el Aeropuerto de Sion

El 26 de agosto de 1966, ocurrió una colisión en el aire en el Aeropuerto de Sion que involucró a un Piper J3C-65 y un Alexander Schleicher Ka 4 Rhönlerche II. El incidente ocurrió cuando el Ka 4, pilotado por un estudiante, regresaba para aterrizar tras un vuelo infructuoso. Simultáneamente, el Piper, con un instructor y un estudiante a bordo, se preparaba para el despegue. Las aeronaves colisionaron aproximadamente a 15 a 20 metros sobre la pista, resultando en la destrucción de ambas. El instructor y un estudiante resultaron fatalmente heridos, mientras que el otro estudiante sufrió heridas graves.

1. Aerotow — local soaring: In late afternoon the student in Greif I HB-579 launched on aerotow from Sion for a planned duration flight but was unable to find sufficient lift and eventually returned toward the airfield to land.
2. Mixed traffic operations: At Sion the grass runway 26 was being used simultaneously by gliders and powered aircraft under a complex mixed-traffic arrangement where glider circuits could intersect powered aircraft approaches and departures.
3. Piper preparing departure: While the glider was returning to land, the instructor took the front seat of Piper J-3C HB-OAV after his student’s previous flight and taxied to the threshold of the grass runway 26 to depart again with the student on board.
4. Piper initiates takeoff: The instructor in HB-OAV commenced a takeoff run on the grass runway 26 at the same time that glider HB-579 was on short final to land, placing both aircraft on converging, vertically overlapping flight paths.
5. Priority not yielded: Contrary to rules giving landing aircraft and gliders priority, the Piper instructor continued the takeoff instead of holding clear of the approach path of the landing glider.
6. Converging flight paths: The glider on final and the Piper climbing after liftoff reached the same area about 400 m beyond the runway 26 grass threshold at roughly 15–20 m above ground with insufficient separation to avoid each other.
7. Mid-air collision: The glider HB-579 and Piper HB-OAV collided about 15–20 m above the grass runway 26 at Sion, then crashed between the two parallel runways, destroying both aircraft and causing serious injuries to all three occupants, two of whom later died.