What happened
On September 29, 2018, an Airbus A319, registration HB-IPT, was on final approach to Zurich Airport (LSZH) following a flight from Berlin Tegel. While flying at approximately 3,000 ft AMSL near Stadlerberg, the flight crew observed an object ahead that initially appeared to be a group of birds. Upon closer inspection, the crew identified the object as a large, silver-colored drone, notably larger than typical commercial models.
Due to the high closing speed of the aircraft, the crew was unable to perform an evasive maneuver. The drone passed directly above the aircraft at a vertical separation of only about 10 meters. The crew immediately notified air traffic control of the near-collision. While the controller was able to warn following aircraft on the same approach, the drone could not be located by subsequent traffic. Despite efforts by the airport authority and local police, the drone and its operator were not identified.
The investigation
The SUST investigation examined the circumstances of the near-miss and reviewed a significant trend of drone-related incidents in the Zurich airspace. The investigation noted that the drone lacked a transponder, meaning it was invisible to both the aircraft's Traffic Alert and Collision Avoidance System (TCAS) and the air traffic control radar.
Investigators also reviewed the technical challenges of drone detection. Studies indicate that visual identification of drones from a cockpit is extremely difficult, especially at high approach speeds. Furthermore, the investigation highlighted that unlike bird strikes, collisions with drones—which possess high structural stiffness due to metals and composites—can cause much more severe damage to primary aircraft structures, including engines and windshields.
Findings
- The primary cause of the near-miss was the inability to use "detect and avoid" technology, as the drone was not equipped with a transponder.
- The "see and avoid" method proved ineffective because the drone was only identified at a very late stage, leaving no time for an evasive maneuver.
- The drone was operating in a flight path commonly used by aircraft on the ILS 14 approach.
- There is a documented increase in dangerous drone encounters in the Zurich controlled airspace, with several other near-misses involving various aircraft types recorded in 2018 alone.