Sequence of Events
On 29 October 2020 at approximately 1321 LT, the Changi Tower Runway Controller (an on-the-job trainee, referred to as the OJT Controller, supervised by an OJT Instructor) contacted the driver of a maintenance vehicle (call sign Rover 391) on radio frequency 121.9 MHz. The driver was instructed to prepare for wildlife dispersal at 1335 LT on Runway 02C/20C. The driver acknowledged. The vehicle, which also carried a co-worker, was positioned on roadway Hotel Charlie (HC) before a set of drop arm barriers.
Shortly after the acknowledgment, the co-worker raised the drop arm barriers using a remote control. The driver drove past the barriers and stopped before a set of red/green traffic lights that were showing red. The co-worker then lowered the barriers. At approximately 1330 LT, the OJT Controller asked the driver to monitor frequency 118.25 MHz. The driver switched to that frequency and reduced the volume on the previous radio.
At about 1332 LT, the driver reported on 118.25 MHz that he was ready for wildlife dispersal. The OJT Controller, having planned the entry for 1335 LT, instructed: "Rover 39, Singapore Tower, stand by to enter Runway 20C." The driver read back: "39, entering Runway 20C for wildlife dispersal" and drove toward the runway. The co-worker could not recall the instruction but remembered the readback.
The driver stated he heard a clearance to enter. He did not check the traffic light color. The OJT Controller, suspecting the traffic lights might have turned green, checked the control panel and found they still showed red. The OJT Instructor prompted her to stop the driver. She repeated: "Rover 39, stand by to enter Runway 20C." The driver responded "39, copied" but continued toward the runway. When the OJT Instructor saw the vehicle enter the runway, she transmitted that the driver had only been told to "stand by." The driver acknowledged and vacated the runway.
Safety Features
Two microwave barrier detectors (MBDs) installed 25 m apart along roadway HC failed to detect the incursion. Post-occurrence tests revealed that the MBD nearer the flashing red lights was affected by marker boards erected by the aerodrome operator to cordon off a construction site.
Personnel Information
The driver had 4 years of experience as a maintenance vehicle driver at Changi Aerodrome and held a Category 1 Airfield Driving Permit since 2012. The OJT Controller had no valid ATC rating, had passed simulator training, and had been undergoing on-the-job training since September 2020. The OJT Instructor had obtained the Changi Aerodrome rating in 2006 and had been an instructor since 2009.
Meteorological Conditions
The incident occurred in daylight with no precipitation.