Description

On 15 October 2022, a Boeing 737-8 (C-GEOJ) operated by Air Canada on a scheduled passenger flight from Edmonton to Toronto as ACA174 was on final approach to runway 15R at destination in night visual meteorological conditions (VMC). The aircraft was instructed to go around when at approximately 200 feet agl because Air Traffic Control (ATC) had observed an airport authority maintenance vehicle, the first of two, entering the runway just beyond its threshold. The aircraft promptly commenced the go-around and remained above 150 feet agl whilst doing so.

Investigation

An Investigation was carried out by the Canadian Transportation Safety Board (TSB). Relevant information was used to create a ‘laboratory report’ in support of the investigation but it was not used. The vehicle driver involved had been a full-time airport authority employee for in excess of 5 years. The driver held a valid Airside Vehicle Operator’s Permit in the appropriate category, which allowed access to taxiways and runways. Both the controllers involved - tower and ground - were seated next to each other and had a good view of the thresholds of both runways in use at the time - 15L and 15R.

What Happened

Three airport authority employees had been instructed to complete runway painting tasks on the part of intersecting runway 05/23 to the west of runway 15R as part of regular runway maintenance. A NOTAM had been issued advising that runway 05/23 would be closed to allow this work to be completed. The three employees were to travel to the site from the Airport Maintenance Unit in a two-vehicle convoy, led by a vehicle occupied only by its driver and towing a trailer on which the required equipment had been loaded. Although use of northern service road would have allowed the convoy to reach their work without the need for either a taxi clearance or a runway crossing clearance, it was decided that they would use a more direct route via taxiway ‘J’ to cross runway 15R. That route required both taxi and runway crossing clearances but was “frequently used” by the drivers of both vehicles and many of their similarly authorised colleagues.

After a wait of almost ten minutes to obtain the necessary taxi clearance from the GND controller, the convoy lead driver received instructions to join taxiway ‘J’ and proceed to the holding point for runway 15R which was correctly read back. As the lead vehicle subsequently approached this holding point, the driver slowed down “almost to a full stop” before continuing onto the runway in the displaced threshold area despite the absence of a clearance. The driver of the second vehicle did not follow. Some of the airport’s runway access points have controllable red stop bars installed, but this access was not one of them and airport policy was that these stop bars were not normally activated outside low visibility conditions.

Shortly before this, the tower controller had cleared a Boeing 737-8 to land on runway 15R and whilst watching the aircraft on approach saw the maintenance vehicle entering the runway. The controller immediately instructed the aircraft to go around. He then asked the ground controller whether he had authorised the vehicle to cross the runway and it was confirmed that he had not. The ground controller then instructed all maintenance and inspection vehicles on his frequency to temporarily hold position whilst he assessed the situation. Having determined that it was safe to do so, he then resumed normal surface movement control. The route taken by the convoy compared to the longer route clear of the aircraft manoeuvring area is shown on the illustration below.

The route taken by the vehicle contrary to airport operator instructions (in blue) with the runway surface where the incursion occurred shown in red. [Reproduced from the Official Report]

Why It Happened

The instructions relating to the use of the driver’s category of permit were noted to require that drivers “shall use service and outer perimeter roads to reach field locations when these roads are available." No records of any enforcement action regarding non-compliance with these instructions were found during the Investigation.

The associated Driver Category Manual was found to state unequivocally that drivers holding this permit must “use service and outer perimeter roads to reach field locations when these roads are available." Its introductory text included a prominent statement (boxed in red and accompanied by a large “!”) that “the Manoeuvring Area must not be used as a shortcut to other areas of the airport”.

It was also established that presentations used during the training of drivers with airside access privileges did not include mention of the directives relating to the use of service roads to avoid unnecessary access to the manoeuvring area. It was not possible to “determine whether these directives were consistently discussed during practical training”.  

With reference to crossing an active runway, it was noted that although directives in the Driver Category Manual required drivers to “visually check that there is no conflicting traffic," there were “no procedures specific to runway crossings” required by airport traffic directives or introduced in the training materials.

It was noted that an earlier TSB Investigation into a vehicle / aircraft collision at Toronto at night had noted similar non-use of a route clear of the aircraft manoeuvring area as required by the relevant driver directives. It was also noted that in response to this earlier event, the airport operator had stated that it had “initiated a review of the entire Airside Vehicle Operator Permit programme” but that the Airport Traffic Directives in October 2022 were unchanged from those last issued four months before the 2019 collision.

The Investigation concluded by formally documenting the following Findings:

Causes and Contributing Factors 

1. The occurrence driver’s attention was split between his driving duties and the planning of the upcoming painting tasks that he would be supervising. As a result, he was paying less attention to monitoring the route for hazards.
2. Because the driver had crossed Runway 15R at the displaced threshold many times without stopping, the mental model he developed did not include stopping at the holding position, even though he read back the instruction to stop.
3. Although contrary to the Greater Toronto Airports Authority’s Airport Traffic Directives, drivers normally used the manoeuvring areas as opposed to the North Service Road because these areas are perceived to be quicker given the typical runway operations on the east/west runways.
4. Given the driver’s split attention, the visual cues that were available to designate the holding position were not salient enough to alter his mental model and stop him from entering the runway. The result was a runway incursion and a risk of collision with the aircraft on approach.

Risk (factors not directly relevant to this event but which may be identified in future similar events)

1. If airport vehicle drivers are not given specific procedures to follow when crossing runways, there is an increased risk of runway incursions or collisions.

The Final Report of the investigation was authorised for release on 6 December 2023 and officially released on 20 December 2023. No Safety Recommendations were made and the Investigation was “not aware” of any Safety Action taken (by the Airport Operator) following the investigated event.

Related Articles

• Runway Incursion
• Runway Crossing Incursions
• Runway Holding Position
• Runway Holding Point Lighting
• Stopbars (SKYclip)
• Airside driving (SKYclip)
• Vehicle Driver Airside Safety Check List
• Runway Maintenance
• DH8C, Toronto Canada, 2019