What happened
On October 13, 2019, a serious airprox incident occurred approximately 18 NM northwest of Zurich Airport. A British Airways Airbus A20N, registration G-TTND, was operating flight BAW14R on an instrument approach to Zurich under radar control. Simultaneously, a private Rockwell Commander 112, registration HB-NCB, was flying under visual flight rules (VFR) from Locarno toward Donaueschingen.
While the air traffic controller was managing the descent of the commercial airliner, the radar display revealed an unidentified aircraft climbing toward the flight path of the Airbus. The ground-based conflict warning system triggered an alert, prompting the controller to immediately instruct the crew of G-TTND to turn right to a heading of 120 degrees. The two aircraft crossed paths with a horizontal separation of only 1.2 NM and a vertical separation of 425 ft, well below the required minimums of 3 NM or 1000 ft.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) conducted an inquiry involving radar and radio recordings, as well as interviews with the flight crews and air traffic controllers. The investigation focused on the movements of both aircraft and the airspace structure in the Zurich Terminal Area (TMA). The inquiry also examined the history of airspace violations in Switzerland and the effectiveness of existing safety measures.
Findings
- The primary cause of the near-collision was that the pilot of the HB-NCB entered the controlled airspace of the Zurich TMA without authorization from air traffic control.
- The pilot of the private aircraft was climbing through 5,000 ft, which placed the aircraft within the controlled sector while the commercial flight was being cleared to descend.
- A significant contributing factor was the limited vertical separation of only 500 ft between the lower boundary of the Class C airspace and the adjacent Class E airspace, which increased the risk of unauthorized incursions.
Safety action
SUST issued safety recommendation No. 574, urging the Federal Office of Civil Aviation (FOCA) to implement measures to reduce the risk of dangerous approaches resulting from airspace violations. This includes addressing the ongoing safety deficit where general aviation aircraft enter controlled airspace without clearance, a phenomenon that occurs hundreds of times annually in Switzerland.