What happened
On a flight from Montreal to Paris, an Air Canada Boeing 747, registration C-GAGN, was rerouted to a new oceanic track. This change placed the aircraft on a converging course with an Air France Airbus A340, registration F-GLZL, which was traveling from Houston to Paris. Both aircraft were cruising at flight level 370.
As the two aircraft approached the BANCS intersection, the radar controller at the Gander Area Control Centre was unaware of the developing conflict. Approximately 90 seconds before the near-miss, the controller contacted the Air Canada crew to advise them of upcoming changes to radar service, unaware that the aircraft were only 9 nautical miles apart and on intersecting paths.
At 0212 UTC, the crew of the Air Canada aircraft received a TCAS Resolution Advisory (RA) and immediately began a climb to flight level 380. Shortly after, the Air France crew also received a TCAS RA and initiated a descent. The two aircraft eventually closed to within 400 feet of vertical separation and 1.9 miles of horizontal separation. The Air Canada crew later reported that the aircraft were directly overhead the Air France plane and a collision was imminent.
The investigation
The investigation focused on why the radar controller failed to identify the conflict. Investigators examined the flight progress strips, which were posted under different fixes, meaning there was no single visual indicator of the proximity of the two aircraft. The investigation also reviewed the division of labor between the radar and data controllers, noting that the task design encouraged independent work rather than collaborative problem-solving.
Furthermore, the investigation looked into the lack of automated conflict alert tools and the absence of specific training regarding advanced radar monitoring techniques. It was noted that while the controller used a Predict Track Line tool regularly, it did not trigger an alert for this specific intersection.
Findings
- The radar controller failed to recognize the traffic conflict and did not apply required separation criteria.
- The lack of an automated conflict alert tool and the absence of a flight progress strip at the specific fix where the conflict occurred contributed to the oversight.
- The flight progress strips for the Air Canada aircraft lacked the required manual markings to alert the controller to the need for special attention.
- The division of responsibilities between the radar and data controllers did not promote effective team-based separation planning.
- There was no secondary technological or human defense available to catch the error once the controller missed the developing conflict.
- The TCAS RAs provided the only warning and the only successful resolution to the conflict.