ATC Issues Led To Loss Of Separation

An equipment issue and an overwhelmed air traffic controller led to a close call over the B.C. Interior in January of 2019 according to a Transportation Safety Board report. A WestJet Encore Q400 and a Piaggio business aircraft were on a collision course at 22,000 feet before their TCAS systems lit up and the crews on both aircraft were able to take appropriate action. The Encore plane immediately descended and the Piaggio crew had eyes on the airliner and ensured safe separation. They passed less than a mile laterally and 1,000 feet vertically. The business aircraft continued to Kamloops and the Q400 to Nanaimo after the scare.

The two aircraft were being worked by the same controller at Vancouver Centre and the software in the flight data processors had recently been upgraded but the system hadn’t been purged of all previous data. This led to a disparity error between the flight plan data and the actual path of the Piaggio. “The controller was not familiar with such disparity errors and in his attempts to resolve the discrepancy for the Piaggio, did not identify the potential conflict between the Westjet Encore and Piaggio flight plans,” the report said. Redundant systems failed to trigger and the audible alarm warning of a potential conflict had apparently been turned down and the controller didn’t hear it. The controller was also under an increased workload at the time. NavCanada has taken several steps to ensure similar errors do not happen again.