What happened
In the early hours of the morning, an Air Transat flight, TSC 234, departed Mirabel Airport for Charles de Gaulle Airport, France. While climbing through the Quebec sector, the aircraft was cleared by the Lévis controller to FL 290 and a direct heading to the MIILS waypoint. Simultaneously, Inter-Canadien flight ICN 1647 was cruising at FL 200, approaching the Quebec VOR to intercept air route V98.
As the two aircraft approached the same airspace, they entered a collision course. At approximately 00:16:37 UTC, the Traffic Alert and Collision Avoidance System (TCAS) on both aircraft issued a Resolution Advisory (RA). The crews of both aircraft immediately executed vertical avoidance manoeuvres. During these maneuvers, the aircraft were separated by only 300 feet vertically and 2.25 miles horizontally, failing to meet the required separation of 1,000 feet vertically or 3 miles horizontally. The flight crews were able to visually identify each other during the avoidance process.
The investigation
The investigation focused on the air traffic control environment and the separation failure. It was established that the Quebec controller was managing the airspace alone, as his colleague was on break. At the time of the incident, the controller was preoccupied with coordinating a medical evacuation flight arrival at the Quebec Airport.
Furthermore, the investigation found that while the controller was responsible for maintaining separation, the aircraft's radio communications had been handed off to the Lévis sector. The controller's calculations regarding the aircraft's climb rate were also inaccurate; he had assumed a climb of 1,000 feet per minute, but the actual rate was lower due to high external temperatures and the heavy weight of the aircraft.
Findings
- The Quebec sector controller failed to maintain the minimum required separation between the two aircraft.
- The controller's attention was diverted by the coordination of a medical evacuation flight arrival.
- The controller was working alone in the radio and data position due to a colleague's break.
- A lack of direct radio communication with the aircraft contributed to the loss of separation.
- The controller was not fully accustomed to managing overflights at the newly increased altitude limit of FL 280, which had been implemented during his absence from the position.