What happened
On a night flight near Gander, Newfoundland, a Boeing 767 operating as Martinair 806 and a Boeing 747 operating as Air France 055 were traveling eastbound at flight level 330. The two aircraft were on converging tracks that brought them within approximately three miles of each other.
As the aircraft approached a collision course, the crews of both planes received and reacted to Traffic Collision Avoidance System (TCAS) resolution advisories. The Martinair 806 crew initiated a climb while the Air France 055 crew performed a rapid descent. The aircraft eventually crossed with roughly 1,200 feet of vertical separation and only 1/4 mile of lateral separation, failing to meet the required separation standards of 2,000 feet vertically or five miles laterally. There were no injuries among the 502 passengers and crew on board the two aircraft.
The investigation
The investigation focused on the actions of the Gander area control centre (ACC) controller. It was established that the controller had recently changed his route for Air France 055, directing it to proceed direct to St. John's, which altered its heading by about 20° toward the path of the Martinair 806.
Investigators found that a controller from the Moncton ACC had attempted to warn the Gander controller via a hotline call that the two aircraft were getting close; however, the Gander controller interrupted the warning and did not process the critical information. Furthermore, the controller had not established a range bearing line to monitor the distance between the converging aircraft and had not selected controller jurisdiction symbols on his radar display.
Findings
- The controller was inattentive to the radar display and the traffic situation, failing to detect the developing conflict.
- A critical warning from the Moncton ACC was missed because the controller cut off the incoming communication.
- The re-routing of Air France 055 was performed without verifying if the new heading would create a conflict with other traffic.
- TCAS equipment on both aircraft and the rapid response of the flight crews prevented a mid-air collision.
- The radar data processing system lacked an operational conflict alert function that could have alerted the controller to the risk.