What happened
On October 12, 2013, a SAAB MFI 15, registration SE-FIO, departed from Sundbro airfield, north of Uppsala, on a VFR flight toward Johannisberg. During the flight, a paraglider was being winched at Härkeberga, a location situated along the aircraft's intended route.
As the paraglider reached an altitude of approximately 350 meters, the pilot observed the aircraft approaching head-on at a slightly lower altitude. The aircraft passed beneath the paraglider without making contact. The paraglider pilot estimated a vertical separation of roughly 50 meters and a lateral distance to the winch line of between 1 and 3 meters. The pilot of the SAAB M15 did not perceive the encounter.
The investigation
The Swedish Accident Investigation Authority (SHK) examined the circumstances surrounding the near-miss. The investigation focused on the visibility conditions, the availability of aeronautical data, and the potential physical consequences of a collision.
To assess the risks, the SHK commissioned a technical study to simulate a hypothetical collision between the aircraft and the winch line. The simulation, which included various parameters such as different aircraft weights and line tensions, concluded that while a collision would likely cause minor damage to the wing, the line would likely break, and the aircraft would not enter an uncontrollable state.
Findings
- The primary cause of the incident was that the flight maps used by the pilot lacked information regarding paragliding activities at Härkeberga, preventing the flight from being planned and executed safely.
- A contributing factor was reduced visibility caused by backlight conditions during the flight.
- The aircraft and the paraglider were operating in uncontrolled airspace, and neither was at an altitude that required contact with controlled airspace.