What happened
On 29 October 2020, a maintenance vehicle involved in wildlife dispersal operations entered Runway 02C/20C at Changi Airport without proper authorization. The incident began when an Air Traffic Control (ATC) controller, who was undergoing on-the-job training, contacted the driver of vehicle Rover 391 to prepare for wildlife dispersal scheduled for later that afternoon.
At approximately 1332LT, the driver contacted the controller via radio to report readiness. Although the controller had instructed the driver to "stand by" for a later entry time, the driver interpreted the communication as a clearance to proceed. The driver subsequently drove the maintenance vehicle onto the runway. Upon realizing the error, the controller notified the driver that clearance had not been granted, and the vehicle promptly vacated the active runway. No aircraft were departing or arriving at the time of the incursion.
The investigation
The investigation examined the communication protocols, the functionality of airfield safety systems, and the driver's adherence to traffic signals. Investigators looked into why the driver proceeded despite red traffic lights and why the Microwave Barrier Detectors (MBDs), designed to sense unauthorized runway entries, failed to trigger an alert. The probe also reviewed the use of remote controls for raising drop arm barriers and the role of the vehicle's co-worker during the event.
Findings
- The driver entered the runway after misinterpreting the radio instruction and failed to verify the red traffic light signal before proceeding.
- The communication between the controller and the driver utilized non-standard radio telephony phraseology.
- The MBD system failed to detect the incursion because its detection zone was obstructed by marker boards placed by the aerodrome operator.
- The use of a remote control to raise drop arm barriers allowed the vehicle to bypass the safety interlock between the barriers and the traffic lights.
- The vehicle's co-worker was distracted by mobile phone usage and did not monitor the radio or traffic signals to assist the driver.