Short staffing and a deviation from standard procedure on the part of air traffic controllers at Montreal’s Pierre Elliott Trudeau Airport resulted in a close call between two planes, according to an investigative report from the Transportation Safety Board of Canada (TSB).
The incident, which took place on May 16, 2018, was deemed a “loss of separation” by the TSB. In air traffic control jargon, the term signifies that an aircraft has breached the minimum distance required from another aircraft, risking a chance of the two colliding.
The TSB found the planes — an Air Transat Airbus A310 from Toronto and a privately owned Cessna 421 light twin-engine aircraft from Trois-Rivières — were both coming in to land at Trudeau Airport.
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“The Airbus was coming from the west and was to fly north of the airport to land on Runway 24R, while the Cessna was inbound from the northeast and was to land on Runway 24L,” the report states.
“A loss of separation between the two aircraft occurred when both aircraft were approximately 18 nautical miles northeast of the airport. At the closest point, the two aircraft came within 500 feet vertically and 1.7 nautical miles laterally of each other.”
The board explains that aircraft should be separated by at least 1,000 feet vertically, or three nautical miles laterally.
The loss of separation, according to the TSB, was partially caused by the low number of air traffic controllers — three staff and a supervisor were on duty at the time, instead of seven staff and a supervisor.
“As a result, six sectors of airspace normally divided among the controllers needed to be combined and controlled by just three,” the TSB states.
The TSB’s investigation also found that, as the Cessna approached from the northeast, control responsibility was not transferred to the next sector according to standard procedure.
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That meant the controller-in-training responsible for the receiving sector was not initially made aware of the plane until it had entered his airspace.
“Also during this time, the instructor, who was both the shift supervisor and responsible for the trainee, was distracted by other tasks and wasn’t able to accurately monitor the developing situation.”
Once the controller-in-training noticed the Cessna on his display, he was able to re-establish the required separation, and both aircraft were able to land safely, according to the TSB.
The TSB did not recommend any safety action be taken in order to avoid another near-collision.
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