What happened
On May 10, 2024, at approximately 10:56 AM, a serious near-collision took place in the airspace above Schänert Airfield (LSZX) in Switzerland. The incident involved two separate flight operations occurring simultaneously at an altitude of roughly 720 meters.
One aircraft, a Diamond HK 36 TTC with registration HB-2328, was performing a powered flight in a descent. At the same time, a second operation was underway consisting of a tow formation: a Schempp Hirth Duo Discus glider, registered D-9195, being pulled by a tow aircraft. This second formation was in a climbing phase of flight. The two groups of aircraft experienced a dangerous close approach while operating under Visual Flight Rules (VFR).
A third aircraft, a Robin DR 400/180 R registered HB-EXU, was also present at the airfield performing a private flight under VFR, though it was not directly involved in the near-collision.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) launched an investigation into the event to determine the circumstances surrounding the close proximity of the two aircraft. The investigation focused on the flight paths and altitudes of the descending powered aircraft and the ascending glider tow formation to establish how the near-collision occurred at the 720-meter altitude mark.