What happened
On February 8, 2012, at 08:30 local time, two aircraft approaching runway 25R at Barcelona Airport experienced TCAS Resolution Advisory (RA) warnings. The first aircraft, a Brussels Airlines AIRBUS A-319 with registration OO-SSR, was established on the localizer and descending. The second aircraft, an Iberia AIRBUS A-330-214 with registration EC-HAG, was performing a radar vector approach.
At the time of the incident, a third aircraft, a Delta Airlines Boeing 777, was also in the sequence. The air traffic controller had originally planned a landing sequence of the Boeing 777, followed by the Iberia flight, and finally the Brussels Airlines flight. However, due to the Boeing 777 delaying its turn, the controller determined that the required wake turbulence separation could not be maintained for the Iberia flight to follow the heavy aircraft. To resolve this, the controller changed the sequence, instructing the Iberia flight to turn left to position it behind the Brussels Airlines flight.
This maneuver placed the two aircraft on converging paths at the same altitude. The Iberia flight performed a wider turn than anticipated, leading to a reduction in horizontal separation to 2.2 NM. Shortly thereafter, both aircraft received TCAS RA warnings. The Brussels Airlines crew received a descent instruction, while the Iberia crew received a climb instruction. The minimum separation reached during the event was 1.4 NM horizontally and 400 ft vertically.
The investigation
Investigators examined the flight paths, air traffic control (ATC) instructions, and communication protocols. Analysis of the Quality Assurance Recording (QAR) data from the EC-HAG confirmed that the aircraft's turn was executed with a lower bank angle than a standard turn, which contributed to the decreased separation.
The investigation also reviewed the operational status of the Short Term Conflict Alert (STCA) system. It was found that the STCA was inhibited below FL195 in the Barcelona TMA to reduce nuisance warnings, meaning the system was not active during the conflict. Furthermore, investigators analyzed the language used by the controller, noting that while the Brussels Airlines crew was addressed in English, the Iberia crew was addressed in Spanish, preventing the first crew from fully understanding the instructions being given to the second aircraft.
Findings
- The primary cause of the incident was a miscalculation by the air traffic controller when attempting to adjust flight paths to reorder the landing sequence.
- The decision to instruct the Iberia flight to turn left placed it on an intercept course with the Brussels Airlines flight at the same altitude.
- The controller failed to account for the fact that the Brussels Airlines flight was descending to an altitude that would intercept the Iberia flight's path.
- A contributing factor was deficient ATC communication, specifically the use of different languages (English and Spanish) for different crews, which prevented a shared situational awareness.
- The controller failed to provide necessary traffic information or respond to the Brussels Airlines crew following the TCAS alert.
Safety action
- It is recommended that AENA emphasize the importance of using English phraseology during controller training when managing crews that speak different languages.
- It is recommended that AENA reinforce training regarding effective vectoring, spacing, and speed control techniques for controllers.