What happened
On January 14, 2015, an incident involving a loss of separation occurred within the Warsaw Flight Information Region (FIR EPWW). An Airbus A3HD was climbing through FL 280, en route to FL 320, while communicating with the General Air Traffic (GAT) ACC controller. Simultaneously, a formation of four F-16 military aircraft was climbing from FL 300 to FL 310 on a heading of 270 degrees, communicating with the Operational Air Traffic (OAT) ACC controller.
During the climb, the radar system triggered a CONFLICT ALERT on the GAT ACC display. In response, the GAT controller instructed the Airbus A320 crew to execute a 15-degree left turn and to level off at FL 300. The OAT controller, after establishing contact with the F-16 formation at FL 300, instructed the pilots to turn to a heading of 180 degrees and continue climbing to FL 310. Despite these interventions, the minimum separation between the aircraft was recorded at 6 NM horizontally and 1,700 feet vertically, failing to meet the required separation standards of 10 NM horizontally or 2,000 feet vertically.
The investigation
The investigation examined the operational environment and the technical interface used by air traffic controllers. Investigators noted that the controllers involved were returning to duty following recent time off. The investigation also reviewed the workload and technical limitations of the radar display and communication systems.
Key technical issues identified included:
- The radar display used identical pink colors for both GAT tracks and military aircraft tracks, making the screen difficult to read during high-traffic periods.
- High traffic density and the use of multiple frequencies (up to six different frequencies in a single sector) increased controller workload.
- The lack of an established Letter of Agreement (LoA) between the OAT and military authorities regarding procedures for exiting active zones or handling special situations.
- Communication difficulties arising from the need to manually switch radio transmitters as aircraft moved between different coverage areas.
Findings
- The primary cause of the incident was errors in Air Traffic Management (ATM) operations.
- The separation infringement occurred while the F-16 formation was already in the process of executing a turn to a heading of 270 degrees.
- The OAT controller had initially permitted a westward heading due to an urgent request from the flight lead regarding low fuel, but later ordered a southward heading upon recognizing the conflict with the Airbus A320.
- Technical limitations, such as illegible radar indicators during intense operations and the lack of visual distinction between different aircraft tracks, contributed to increased controller workload.