What happened
On 06 October 2023, shortly before 1100 Mountain Daylight Time, two airport tow vehicles (tugs) operated by Airport Terminal Services were maneuvering at Calgary International Airport (CYY/YYC) in Alberta. The drivers intended to move from Apron 1 to the southern side of the airport to reposition an aircraft located on Runway 26.
Initially, the ground controller directed the lead tug driver to travel south via taxiways C, C1, and Y, with instructions to hold short of Runway 26. This instruction was later modified, directing the driver to enter Taxiway C2 to yield to an aircraft taxiing in the opposite direction. This amended instruction also included a requirement to hold short of Runway 17R, which the driver acknowledged via readback.
After the opposing aircraft had cleared the area, the ground controller instructed the lead driver to continue on Taxiway C and hold short of Runway 26. Despite this instruction, at 1104, both tugs entered Runway 17R. Simultaneously, a De Havilland Aircraft of Canada Limited DHC-8-402, operating as Jazz Aviation flight JZA7124, was performing its takeoff roll on the same runway. The flight crew observed the two tugs as the aircraft approached its decision speed (V1), but they chose to continue the takeoff. The aircraft cleared the tugs by approximately 3,700 feet laterally before passing over them at an altitude of 350 feet above ground level while exiting the runway at Taxiway U.
The investigation
TSB investigators examined the communications between the ground controller and the tug drivers, as well as the sequence of taxiway movements and the instructions provided during the incident. The investigation focused on the discrepancy between the instructions to hold short of Runway 17R and the actual movement of the vehicles onto the active runway.