What happened
Two Aerospatiale ATR-42-300 aircraft, operating as flights OEL 1967 and OEL 1968 for Canadian Regional Airlines, were involved in a near-collision at Timmins airport, Ontario. The inbound flight, OEL 1967, was arriving from Sudbury and was cleared for an ILS arc approach to runway 03. Simultaneously, the outbound flight, OEL 1968, departed runway 28 and was climbing through 4,000 feet towards 17,000 feet.
As the two aircraft converged head-on within cloud cover, their Traffic Alert and Collision Avoidance System (TCAS) units issued Resolution Advisories (RA). The crew of OEL 1967 climbed 500 feet, while the crew of OEL 1968 descended 500 feet. These evasive maneuvers successfully prevented a collision. There were no injuries and no damage to either aircraft.
The investigation
The investigation focused on the air traffic control procedures at the Toronto Area Control Centre (ACC) and the technical functionality of the aircraft's TCAS equipment. Because Timmins lacks a control tower and radar coverage, the ACC controller relied on procedural separation.
Investigators found that the controller's separation plan was based on the assumption that the inbound aircraft would fly northeast toward runway 21, away from the departing traffic. However, the inbound aircraft was actually intercepting the localizer for runway 03, placing it on a direct collision course with the outbound aircraft. Additionally, it was noted that the crew of OEL 1968 did not hear the TCAS aural alert because the audio signals were not routed through the crew's headsets, forcing them to rely solely on visual indicators on the vertical speed indicator.