What happened
On March 4, 2023, at approximately 11:33 AM, a Pelikan U4M motor glider, registration HB-TBX, was conducting a VFR flight from Speck-Fehraltorf to Locarno. While flying at an altitude of approximately 6,200 ft AMSL near the Chnügrat ridge, the pilot of the aircraft suddenly spotted a paraglider appearing below the engine cowling.
The paraglider, flying a Skywalk Arak, had launched from the Gumen mountain station shortly before the encounter. The two aircraft reached a closest point of approach with a horizontal distance of roughly 17 meters and a vertical separation of only 6 meters. Although the pilot of the HB-TBX attempted a left-hand evasive maneuver following an acoustic alert from a PowerFlarm device, the aircraft ultimately flew over the paraglider. The paraglider pilot was reportedly looking away from the approaching aircraft at the time of the encounter.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the flight paths, meteorological conditions, and the functionality of the collision warning systems used by both parties. The investigation noted that the Gumen area is a high-traffic zone for paragliders, a fact officially noted on Swiss aeronautical charts.
Investigators reviewed the PowerFlarm equipment on the HB-TBX, noting it lacked an obstacle database, though it was capable of detecting other aircraft. For the paraglider, the investigation found that the "Flarm Aware" feature on the Flymaster Live DS device was not activated, meaning the paraglider did not receive traffic warnings despite being visible to other Flarm receivers. The investigation also found that the incident was not immediately reported to the required emergency notification center (REGA) as mandated by Swiss regulations.
Findings
- The primary cause of the near-collision was that the pilot of the HB-TBB did not detect the paraglider until it was too late to perform an effective evasive maneuver.
- The visibility of the paraglider was significantly hindered by the structural design of the Pelikan U4M, specifically the engine cowling, which obscured the lower field of view for the pilot.
- The paraglider pilot was likely not monitoring the airspace directly above them at the moment of the encounter.
- While the aircraft's collision warning system provided an acoustic alert, the lack of an obstacle database meant the system was only capable of detecting other transponder-equipped aircraft, not stationary objects.
Safety action
To prevent similar dangerous approaches, pilots are advised to avoid high-traffic paragliding areas whenever possible by flying wide detours around known launch sites. Furthermore, the investigation emphasizes that the effectiveness of "sense and avoid" technology depends on the professional installation, regular updates, and correct configuration of all collision warning software and hardware.