What happened
On a flight from Toluca, Mexico, a Skyservice Cessna Citation 650, registration C-FJJC, was descending to 6,000 feet toward Montreal International Airport. Simultaneously, an Air Canada Boeing 767, registration C-GAUP, departed runway 28 at Dorval, climbing toward a cleared altitude of 17,000 feet.
During the climb, the pilot of the Boeing 767 observed a traffic alert from the aircraft's collision avoidance system. The pilot subsequently halted the climb at 5,200 feet to avoid the Cessna Citation 650, which was positioned directly ahead. The two aircraft passed each other with a vertical separation of 1,400 feet and a horizontal distance of approximately 0.25 miles.
The investigation
The investigation focused on the actions of the Montreal Area Control Centre (ACC) controllers. The departure controller, responsible for the terminal departure sector, had cleared the Boeing 767 to climb through airspace assigned to the terminal south sector without coordinating with the controller in charge of that sector. While the departure controller was aware of the inbound C-FJJC earlier in the flight, he did not recall its presence when issuing the climb clearance.
At the same time, the terminal south controller had advised the pilot of the C-FJJC of nearby traffic, assuming the Boeing 767 would level off at 5,000 feet per standard procedures. Because no coordination occurred between the two sectors, the terminal south controller took no action to ensure separation. The investigation also noted that the radar target for the C-FJJC was temporarily partially obscured by another aircraft's data block on the controller's display during the period the clearance was issued.
Findings
- The departure controller issued a climb clearance through another controller's assigned airspace without coordination.
- The departure controller failed to recall the presence of the inbound aircraft when authorizing the climb.
- The departure controller did not monitor the Boeign 767's climb with enough vigilance to detect the conflict.
- The terminal south controller assumed the departing aircraft would follow standard altitude restrictions and therefore did not intervene.
- Local operating procedures allowed for the use of ad hoc separation methods that lacked necessary safety defenses against human error.