What happened
On a day characterized by instrument meteorological conditions (IMC) and light snow, two aircraft were approaching Kuujjuaq Airport, Quebec, on intersecting flight paths. The first, a First Air Boeing 737-248C (registration C-FNVT), was performing an RNAV approach for Runway 25. Simultaneously, an Air Creebec de Havilland DHC8-102 (registration C-GYWX) was conducting an RNAV approach for Runway 31.
As the aircraft approached the airport in uncontrolled airspace, the flight service station was managing four different IFR arrivals. While the crew of C-FNVT was configuring for its approach, the aircraft's airborne collision avoidance system (ACAS) indicated the presence of another plane. Shortly after, the Boeing 737-248C initiated a missed approach to ensure safety. During the maneuver, the two aircraft came within 2.0 nautical miles laterally and only 200 feet vertically of each other. Neither crew established visual contact due to the cloud cover. Both aircraft eventually landed safely without further incident.
The investigation
The investigation examined the communication environment, the functionality of onboard safety equipment, and the airport's operational status. It was established that the Kuujjuaq Flight Service Station was experiencing high workload and frequency congestion. The specialist was managing multiple inbound aircraft, and much of the available airtime was consumed by verbal communications and the need to repeat information in both official languages.
Investigators also looked into the status of the aircraft's collision avoidance systems. While the Boeing 737-248C had a functioning ACAS, the system on the DHC8-102 was not operational during the flight due to an intermittent fault. Furthermore, the investigation reviewed the airport's runway status, noting that a construction project had partially closed Runway 25, with an exception made only for specific jet traffic, which added to the complexity of the traffic situation.
Findings
- The primary cause of the collision risk was the convergence of the two aircraft at the same altitude in IMC without visual contact.
- The crew of the DHC8-102 was unaware of the proximity of the Boeing 737-248C because its ACAS was not functioning.
- High levels of frequency congestion prevented the crews from developing an effective separation plan.
- The lack of standardized arrival routes and the close proximity of approach fixes for different runways increased the risk of intersecting flight paths.
- The partial closure of Runway 25 contributed to increased communication workload and frequency congestion.