What happened
On February 20, 2018, two Swiss Air Force Boeing F/A-18C fighter jets, registered as J-5015 and J-5018, were conducting a navigation exercise over Switzerland. The mission, ordered by the Chief Air Defence, involved identifying a foreign state aircraft flying through the G5 airway. Following the identification, the two jets performed a pre-planned flight pattern at approximately 2,400 ft AMSL, traveling at ground speeds of roughly 355 knots.
Simultaneously, a commercial Airbus Helicopters AS 350 B3, registration HB-ZAN, was performing cargo transport duties between Pfäffikon SZ and Ufenau Island on Lake Zurich. The helicopter pilot was utilizing a 50-meter sling load to move materials.
As the helicopter pilot accelerated away from Ufenau Island, he was alerted by ground personnel to the approach of the two jets. The pilot observed the Boeing F/A-18C aircraft crossing his flight path from west to east at a distance of between 250 m and 500 m horizontally and approximately 100 m vertically. The encounter is classified as an ICAO Category B airprox.
The investigation
SUST examined radar data from the military FLORAKO system, flight records from the helicopter's Flarm collision warning system, and crew statements. The investigation established that the helicopter was flying at a low altitude, which likely placed it below the radar coverage of the FLORAKO system. Consequently, the tactical control center was unable to provide traffic advisories to the fighter pilots.
While the helicopter was equipped with an active transponder and a Flarm system, the fighter jets' onboard radars did not detect the aircraft. The investigation noted that even if the radar had detected the helicopter, the information would only appear on the cockpit instrument panel rather than the Head-Up Display (HUD) without manual pilot intervention, which is impractical during high-speed flight.
Findings
- The primary cause of the near-collision was the lack of compatible collision warning systems on the military aircraft.
- The helicopter was flying too low to be detected by the military's primary radar surveillance system.
- Diffuse haze and cloud cover (1,200 to 1,500 ft AGL) reduced the visual detectability of the helicopter.
- The high speed of the fighter jets left a very narrow window for any potential evasive maneuvers.
Safety action
This incident highlights a recurring safety deficit. Previous investigations (Reports No. 2157 and No. 2270) had already recommended that the Federal Office of Civil Aviation (FOCA) and the Air Force ensure that military aircraft operating primarily in civilian airspace are equipped with collision warning systems compatible with civilian standards. The SUST noted that the consistent implementation of this recommendation would likely have prevented this encounter.