What happened
At approximately 2300 PDT, a sequence of events at Vancouver International Airport resulted in a loss of instrument flight rules (IFR) separation between two medium-sized passenger aircraft. The incident involved a WestJet B 737 700 (Flight 628) and a WestJet B 737-800 (Flight 2057), alongside a Jazz Airlines de Havilland DHC8-311 (Flight 269).
While the airport was managing departures and arrivals on Runway 26L, the airport controller issued a takeoff clearance to the Jazz Airlines aircraft using the incorrect flight number, inadvertently assigning it the call sign of the WestJet B 737 700. This error caused confusion on the runway. Although the flight crew of the WestJet B 737 700 attempted to alert the controller to the mistake, their wording was vague, which delayed the controller's realization of the error.
As the controller worked to resolve the sequencing confusion, a third aircraft, the WestJet B 737-800, was approaching for landing. To manage the conflict, the controller directed the arriving aircraft to perform a missed approach. However, the instructions provided for the missed approach did not ensure the necessary separation. Consequently, the two WestJet aircraft came within approximately 2000 feet of lateral spacing before IFR separation was eventually restored.
The investigation
The investigation examined the controller's communications, decision-making processes, and the impact of fatigue. Investigators analyzed the use of non-standard phraseology, such as the failure to repeat departure sequence numbers and the omission of departure intersections in clearances. The investigation also reviewed the controller's situational awareness and the adequacy of the airport's supervision during the night shift, noting that no supervisor was on duty at the time of the occurrence.
Findings
- The primary cause was the airport controller's loss of situational awareness, which led to an operational decision that resulted in the loss of IFR separation.
- A call-sign mix-up by the controller initiated the sequence of events, and the subsequent lack of clarity from the flight crew delayed the correction of the error.
- The controller failed to provide missed-approach instructions that would have guaranteed the required separation for the arriving aircraft.
- The controller was likely experiencing the effects of fatigue, which hindered their ability to recognize the developing situation and take timely corrective action.
- The use of non-standard phraseology during multiple departures increased the risk of sequencing errors.
Safety action
Following the incident, NAV CANADA implemented a temporary prohibition on intersection departures at Vancouver International Airport, a policy that has since been made permanent. Additionally, management is working to revise missed-approach procedures to ensure greater safety margins for aircraft performing late-stage missed approaches.