What happened
During an approach to Runway 09 at Victoria International Airport, a Boeing 737-200 operated by Westjet experienced a sudden loss of communication with air traffic control. While the aircraft was being vectored toward a localizer intercept point, the Victoria terminal controller attempted several transmissions to provide instructions, but received no response for approximately one minute. During this period of silence, the aircraft continued on its heading, which led it into an area with a higher minimum vectoring altitude (MVA).
The communication gap occurred because the frequency being used by the controller (133.85 MHz) was taken offline for maintenance. Although the technical error was corrected within 61 seconds, the lack of contact prevented the controller from providing essential instructions regarding terrain and the approach path. Once the frequency was restored, the crew responded to the controller and performed a turn to re-intercept the localizer.
The investigation
The investigation established that the radio frequency was removed from service prematurely due to a misunderstanding between technical staff. A voice communication between a technical operations coordinator and an electronic systems technologist was misinterpreted, leading the technologist to believe the frequency was ready for maintenance. Additionally, a required Notice to Airmen (NOTAM) intended to warn of the outage had been delayed due to an error in the notification protocol.
Investigators also examined the controller's vectoring technique, known as a "short gate" procedure. This method involves vectoring aircraft closer to the runway than standard arrival routes suggest. While intended to increase efficiency, the investigation found this specific procedure was not in accordance with Nav Canada's Manual of Operations. Furthermore, the controller had descended the aircraft to a lower MVA before providing the necessary clearance or instructions to avoid high ground.
Findings
- A misunderstanding during technical coordination led to the premature removal of an active communication frequency.
- The controller descended the aircraft to a lower MVA before issuing the ILS approach clearance or providing instructions to avoid high terrain.
- A previous Operations Bulletin that would have required alternate instructions for such vectors had expired four days prior to the event.
- The "short gate" vectoring procedure used during the approach deviated from established manual instructions.
- A delay in the NOTAM issuance meant controllers were not alerted to the planned equipment maintenance via their operational information display system.