What happened
On a recent departure from Vancouver International Airport, an Air Canada Airbus A3 320, registration ACA1118, departed Runway 08R at 1640 Pacific daylight time. The departure controller instructed the aircraft to execute a left turn to 360° once it reached 3000 feet. Simultaneously, a Cessna 172M was conducting visual flight rules aerial work at 5000 feet in the same vicinity.
As the Airbus A320 climbed, the separation between the two aircraft decreased to 0.7 nautical miles laterally and 700 feet vertically. At 1642:52, the crew of ACA1118 received a traffic alert and a collision-avoidance system resolution advisory (RA) to climb due to the approaching Cessna 172M. While the flight paths were ultimately diverging—preventing a collision—the safety of both aircraft was compromised.
The investigation
The investigation examined the flight paths, air traffic control (ATC) procedures, and the performance of the aircraft involved. Investigators found that the controller used a specific altitude as the primary parameter for initiating the turn, rather than a geographical fix like the non-directional beacon (NDB).
Furthermore, the investigation looked into the discrepancy between the Air Canada noise-abatement profiles and the standard published procedures. It was noted that the controller's plan relied on the aircraft reaching 3000 feet at a specific point to maintain lateral spacing, a plan that failed when the aircraft's performance deviated from expectations.
Findings
- The pilot of ACA1118 did not follow the published vertical noise-abatement procedure, resulting in a flight path inconsistent with the controller's expectations.
- The pilot was delayed in responding to the instruction to turn left, which significantly shifted the aircraft's flight path toward the Cessna 172M.
- The departure controller's decision to use altitude as the trigger for the turn, rather than a geographical landmark, failed to provide sufficient lateral separation.
- The controller did not use imperative phraseology to convey the urgency of the situation, and subsequent small heading changes were insufficient to correct the developing conflict given the Airbus A320's high speed and wide turn radius.
- A lack of coordination between stakeholders led to the use of inconsistent noise-abatement profiles, increasing the complexity and risk for ATC controllers.