What happened
On a Sunday morning in the Nuvilik sector of the Montreal Area Control Centre, a CL-600-2B16 (registration N8MC) departed Iqaluit, Northwest Territories, bound for Seattle. During the climb, the aircraft was subject to a revised route and an altitude restriction designed to maintain separation from a Boeing 747-400, registration G-BNLK, which was transiting the area at FL 350.
As the N8MC climbed, the Nuvilik radio controller—a trainee being monitored by an instructor—issued a new route and an instruction to remain at or below FL 330 until reaching a specific waypoint. However, the pilot reported that the aircraft had already passed the intended waypoint. Shortly thereafter, the altitude restriction was cancelled. This led to a situation where the two aircraft came within approximately 9 nautical miles laterally and 1,500 feet vertically, violating the required separation of 20 nm or 2,000 feet.
The investigation
The investigation focused on the actions of the Montreal ACC controllers and the technical errors made during the flight's progression. It was established that the Nuvilik data controller attempted to use a radar display to plot the new route using the range bearing line function. During this process, the controller entered the wrong coordinates for the second point of the route, inputting 65N 080W instead of 63N 080W. This error created a visual representation of the track that was much further north than the actual path.
Because of this incorrect display, the data controller mistakenly believed the N8MC was positioned well to the north of the heavy traffic, leading him to inform the supervisor that the altitude restriction could be lifted. The investigation also noted that the trainee radio controller was preoccupied with other traffic in a different part of the sector, and the on-the-job instructor did not intervene to verify the aircraft's exact position when uncertainty arose.