‘Drift’ in training contributed to near-miss at Calgary International Airport: TSB

Transportation Safety Board of Canada signage is pictured outside TSB offices in Ottawa, Monday, May 1, 2023. THE CANADIAN PRESS/Sean Kilpatrick

The Transportation Safety Board of Canada (TSB) says a near-miss collision between an aircraft and a pair of tow vehicles at Calgary International Airport was due to poor training.

At 11 a.m. on Oct. 6, 2023, two aircraft tugs at the south side of the airport were called to reposition an aircraft on a different runway.

To do this, the drivers needed to use taxiways at the facility to reach it, at which point they inadvertently drove onto an active runway where a Jazz Aviation DHC-8-402, operating as flight JZA7124, was beginning its take-off roll.

When the aircraft’s crew noticed the two vehicles, they decided to continue with takeoff, lifting off and passing over the tugs at an elevation of about 350 feet.

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The TSB, which was called to analyze the safety issues connected to the incident, determined that “a lack of recurrent training and oversight was an underlying factor.”

“In this occurrence, the tug driver misinterpreted the ground controller instructions and entered the active runway. This misunderstanding stemmed from differing mental models: the ground controller expected the driver to follow the intended taxi route, while the driver, who was positioned near the holding line, believed entering the runway was the only way to proceed,” the TSB said in a news release Tuesday.

In its final report, the TSB said the lead tug driver stopped too close to the runway, without enough room to turn around the vehicle even thought regulations stated that was needed.

The agency said this was likely due to a “drift” from defined procedures.

“The driver’s action was likely a practice that logically arose from the fact that an instruction to hold short of a runway is almost always followed by an instruction to continue on that route onto the runway and not to turn around. Additionally, the driver had never turned around on a taxiway before and believed this was not allowed,” the TSB said.

Furthermore, crossing onto the runway and immediately head back to another taxiway was “more reasonable to him,” the TSB said.

The ground controller’s belief was that the tug drivers were to follow any of the instructions provided to them.

The TSB said this “authority gradient” gave the tug driver the impression that they were not comfortable asking for a clarification of the instructions, especially those believed to be “unclear and erroneous.”

Meanwhile, the TSB said the flight crew should have aborted take-off because of the presence of the ground vehicles, but that instruction likely was not heard by the crew.

“During periods of high workload, individuals focus most of their attention on the most critical tasks and, as a result, filter or ignore sensory input that they deem less relevant or important,” the TSB wrote.

“When the tower controller was alerted to the vehicles on the runway, the abort take-off instruction given to the flight crew of flight JZA7124 was not heard by the flight crew.”

As a result of this, Nav Canada added correct phraseology for air traffic controllers to reduce the risk during these situations.