April 9, 2020

Computer Glitch, Heavy ATC Workload Led to Near-Miss – TSB


The Transportation Safety Board released an investigation report last week into an incident that occurred in the skies above and to the west of Kelowna, British Columbia on January 3, 2019, that led to the loss of separation between a Bombardier Q400 operated by WestJet and an American-registered Piaggio P180 operated by Rainbow Sandals Retail Inc. of California.

On converging flight paths at the same altitude, the crew of the Q400, on an IFR flight from Calgary (CYYC) to Nanaimo, B.C. (CYCD) at light level 220, or 22,000 feet ASL, responded to a Traffic Collision Avoidance System (TCAS) alert by descending. The crew of the P180, on an IFR flight from Spokane, Washington (KGEG) to Kamloops, B.C. (CYKA), and also equipped with a TCAS, maintained their cruising altitude of flight level 220. The aircraft came within 1,000 feet and 0.9 nautical miles of each other.

The investigators focused on the flight-tracking computer system used by the Vancouver Area Control Centre (ACC), which had received a software upgrade hours earlier. The investigation revealed that flight data for an earlier flight, including its transponder code, had not been properly purged from the system after its reboot, leading to confusion by the controller assigned to the occurrence airspace sector.

Issues related to controller workload and supervision were also identified in the lengthy, 38-page report.

The report, which is appended below, also summarizes safety actions taken by Nav Canada since the occurrence.

Image credits: Nav Canada with TSB annotations.