What happened
On May 15, 2019, a near-collision occurred approximately 2 km southwest of Altendorf, Switzerland, at the boundary of Class G and Class E airspace. A Mooney M20J, registration HB-DIH, was performing a descent and turn toward Wangen-Lachen airport at an altitude of roughly 2,000 ft AGL. Simultaneously, a formation of two F/A-18 fighter jets, registrations J-5236 and J-5025, was transiting the area at a high ground speed of approximately 430 kt.
While the fighter jet leader received a traffic warning from military air traffic control and attempted to maneuver downward, the aircraft came within a horizontal distance of about 100 m and a vertical separation of only 15 m. The closing speed between the aircraft was approximately 1,000 km/h.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined radar records, GPS flight tracks, radio communications, and pilot statements. The investigation focused on the effectiveness of the "see and avoid" principle in mixed-use airspace. The investigation found that while the fighter jet leader established visual contact and attempted an evasive maneuver, the extreme speed of the military aircraft made a more effective avoidance maneuver impossible once the aircraft were visually identified.
Findings
- The Mooney M20J was flying in a descending turn into the same airspace occupied by the fighter jets.
- The fighter jets were operating at extremely high speeds, which significantly limited the window for effective collision avoidance.
- The crew of HB-DIH did not receive a warning from their onboard collision warning system, nor were they able to hear the military air traffic control warning issued to the fighter jets.
- The near-miss was caused by the combination of the light aircraft's flight path and the high velocity of the military formation, which rendered the "see and avoid" principle insufficient for preventing the close approach.