What happened
On the date of the incident, two aircraft operating in the Barcelona terminal area experienced a near-mid-air collision risk. The first aircraft, an Airbus A320, was climbing through the terminal area following a standard departure. The second aircraft, an Airbus A321, was also climbing on a separate departure route.
Due to a controller error, the aircraft were assigned departure tracks that intersected. The Airbus A321 was instructed to fly a path that crossed the path of the Airbus A320. As the aircraft progressed, the distance between them closed rapidly, leading to a loss of separation. The Airbus A320 crew received a warning, and the aircraft eventually reached a point of separation violation, prompting the Airbus A321 crew to take evasive action following a TCAS resolution advisory.
Why did it happen
The investigation determined that the primary cause was an air traffic controller error. The controller issued instructions that resulted in the aircraft-controlled tracks intersecting, failing to maintain the required separation between the two departing flights.
Furthermore, the controller's attention was divided. At the time of the incident, the controller was managing a potential conflict between two other aircraft in a different sector of the terminal area. This distraction contributed to the failure to identify the converging tracks of the Airbus A320 and A32'1.
Additionally, the air traffic control system's Short Term Conflict Alert (STCA) was not effective in this instance because the conflict was developing in a manner that did not trigger the alert before the separation was lost. The investigation also noted that the-inhibition of certain-conflict alerts in the sector due to the management of other traffic contributed to the situation.
How was it prevented
The investigation recommended improvements to air traffic controller training, specifically regarding workload management and conflict detection in high-density environments. The investigation also highlighted the need for reviewing the configuration of conflict alert systems to ensure they remain effective during periods of high traffic density and complex conflict management.