What happened
On the morning of 23 August 2021, a high-risk runway incursion occurred at Arvidsjaur Airport involving a Cessna 208B and a ground service vehicle. The incident began when an air traffic controller authorized a ground vehicle to enter the runway to perform routine bird control and runway inspections. During this period, the pilot of the Cessna 208B was preparing for departure.
After completing the inspection tasks, the driver of the vehicle began crossing the runway back toward the taxiway. As the vehicle reached the centerline, the driver noticed the aircraft approaching. The driver continued toward the southern edge of the runway, while the aircraft commenced its takeoff roll. The pilot did not observe any obstructions on the runway surface during the initial roll, but upon rotation, the vehicle was spotted to the right of the aircraft. The lateral separation between the two was estimated at only 11 meters, representing a significant collision risk.
The investigation
The investigation focused on the actions of the air traffic controller and the visibility of the ground vehicle. It was established that the controller had issued takeoff clearance while simultaneously reviewing new codes for reporting surface conditions. Because of this distraction, the Flight Progress Board was not checked before the clearance was granted.
While the controller was managing two separate radio frequencies—one for air traffic and one for ground communication—the controller was the only individual monitoring both. The investigation also examined the visibility of the vehicle, noting that while the runway was flat and unobstructed, the intensity of the vehicle's warning lights was insufficient. Furthermore, the investigation looked into the communication protocols and the application of the sterile concept at the tower.
Findings
- The primary cause of the incident was that essential checks to ensure the runway was clear were not completed prior to the issuance of takeoff clearance.
- The air traffic controller's attention was diverted by reviewing new surface condition reporting codes, leading to a failure to verify the Flight Progress Board.
- The limited light intensity of the ground vehicle's warning lights reduced the likelihood of the vehicle being detected by both the tower and the aircraft pilot.
- The driver of the vehicle was not monitoring the tower's air traffic frequency, which could have provided better situational awareness.
Safety action
Following the investigation, the following recommendations were made to the Swedish Transport Agency:
- Evaluate the necessity of implementing the Sterile concept within the national ATS regulations.
- Review methods for ensuring adequate situational awareness for ground personnel, such as the practice of monitoring tower air traffic frequencies at Swedish airports.