What happened
On an evening flight in northern Saskatchewan, two aircraft were approaching La Ronge under instrument flight rules (IFR) within minutes of each other. The first, a Beech 1900D operated by Transwest Air (registration TW203), was traveling from Stony Rapids. The second, a Hawker Sidley HS 748 operated by West Wind (registration WEW780), was arriving from Points North Landing. Because the La Ronge area lacked low-level radar service at the time, controllers relied on procedural separation.
At approximately 2031 UTC, the crew of WEW780 contacted Winnipeg air traffic control, reporting a departure time of 0003 UTC. This was an error; the aircraft had actually departed at 2003 UTC. The controller on duty did not identify this discrepancy, which would have placed the departure over three hours in the future. Consequently, the flight progress strips were not properly sequenced, and a separation plan for the two approaching aircraft was never established.
As the aircraft progressed, a descent clearance was issued to TW203 that would have taken it through the altitude occupied by WEW780. The conflict was only identified when WEW780 requested its own descent clearance. The radar controller immediately intervened, instructing TW203 to halt its descent at 16,000 feet, which restored the required minimum separation.
The investigation
Investigators examined the operations at the Winnipeg Area Control Centre's north low sector. They found that the controller handling the radar and data positions was in the middle of a position handover briefing when the error occurred. The investigation focused on why the incorrect departure time was not caught and why the potential conflict between the two aircraft was not detected during the transition of duties.
Findings
- The crew of WEW780 provided an incorrect departure time, which the controller recorded without verification.
- The second controller used this erroneous time to calculate an arrival time, resulting in an unrealistic arrival estimate that placed the aircraft strip out of order.
- The controllers failed to re-sequence the arrival strip for WEW780 after receiving a revised estimate, which prevented the detection of the impending conflict.
- High workload, significant background noise, and frequent interruptions during the handover process contributed to a loss of situational awareness.
- The Nav Canada transfer-of-position checklist was found to be too broad, relying on controller analysis rather than specific, step-by-step instructions, making it vulnerable to error during high-traffic periods.