Lack of coordination led to risk of collision between two aircraft near Sudbury, ON
On 14 October 2016, Porter Airlines Flight 533 was on an instrument flight rules (IFR) flight to the Sudbury Airport (CYSB), Ontario.
It was to arrive from the south with an estimated time of arrival at 1005 Eastern Daylight Time. Soon after, the North Bay controller cleared Flight 533 for a visual approach to Runway 04, Jazz Aviation LP Flight 604 took off under visual flight rules (VFR) on Runway 22, heading south towards its destination.
Runway 22 was the active runway at Sudbury and reciprocal to Runway 04. Approximately three minutes later, when both aircraft were 9.5 nautical miles southwest of the Sudbury Airport, the traffic alert and collision avoidance systems (TCAS) in the flight crews' respective aircraft issued a resolution advisory to take specific action to avoid a collision.
Both flight crews took evasive action. Radar data indicated that the two aircraft came within 0.4 nautical miles of each other at the same altitude.
The investigation found that the North Bay controllers' practice of clearing incoming IFR aircraft for an approach without regard for the active runway at the Sudbury airport created a situation wherein IFR traffic was counter to the flow of, and therefore more likely to come into conflict with, VFR traffic operating at the airport.
Further, air traffic control approved the VFR departure of Flight 604 without a coordinated plan to prevent conflict between the aircraft and incoming IFR traffic.
Flight 604 was not fully aware of the traffic situation at the airport when it taxied to Runway 22, as the Sudbury flight service station's taxi departure advisory did not include information about inbound opposite direction traffic.
The risk of collision occurred after Flight 604 made its left turn to fly away from the airport towards its destination.
This turn was not apparent to North Bay air traffic control, as the display was set at scale that was too large to detect heading changes right after they occur.
Unaware of Flight 604's exact position, the controller suggested that it turn right, essentially bringing it back toward the approach path of Runway 04 and in conflict with Flight 533.
Following the TCAS resolution advisory, the flight crew from both Flight 604 and 533 initially maneuvered their respective aircraft contrary to the TCAS commands. As result, the vertical separation between the two aircraft was reduced. ■