What happened
At approximately 2130 local time, a conflict was identified between a Korean Airlines Boeing 747-20 and a British Airways Boeing 747-400 flying at flight level 330. The two aircraft were on intersecting paths approximately 63 nautical miles east of Saskatoon, Saskatchewan. The Prince Albert sector controller realized the collision risk when the aircraft were only about 10 nautical miles from the crossing point.
To resolve the situation, the controller instructed the Korean Airlines crew to turn left and descend to flight level 310, while directing the British Airways crew to turn right. During the maneuvering, the vertical separation between the two aircraft dropped to just 700 feet, and the lateral distance reached a minimum of 7.9 nautical miles. Although the required 5 nautical mile separation was technically maintained, the aircraft had reached the crossing point without any planned separation, leaving safety unassured.
The investigation
The investigation examined the controller's workload and the procedures used for conflict prediction. At the time of the incident, the controller was managing 12 aircraft flight data strips. It was noted that the controller had not completed the conflict prediction sequence for the British Airways flight because his attention had been diverted to a hand-off for another aircraft and to re-programming radar display preferences following a software upgrade.
Furthermore, the investigation looked into the practice of grouping all flight progress strips under a single "Saskatoon" header on the data board. This method required the controller to manually search through all strips to identify potential conflicts, rather than using specific fix designator headers. The investigation also noted that the controller did not use the specific, imperative phraseology required for safety alerts, which likely contributed to a 23-second delay in the Korean Airlines crew beginning their descent.
Findings
- The controller failed to monitor flight progress strips with enough detail to identify the impending conflict.
- The controller did not adequately utilize the conflict prediction tools available on the radar situational display.
- The lack of automatic conflict detection software in the Winnipeg area control centre meant there was no automated alert for the developing risk.
- The practice of consolidating flight progress strips under a single header increased the difficulty of detecting potential crossing points.
- The use of non-imperative language and the failure to provide immediate traffic information to the crews delayed the necessary corrective maneuvers.