What happened
On 3 October 2013, at Changi Airport, an aerodrome maintenance vehicle, identified as Rover 39, entered Runway 02/20C to remove a bird carcass. The vehicle moved onto the runway at 1125 hours after a communication exchange with air traffic control. Shortly thereafter, at 1126 hours, a Boeing B777-312ER, registration 9V-SWG, was cleared to land on the same runway.
As the aircraft touched down, the flight crew spotted the maintenance vehicle on the eastern edge of the runway. The pilot flying immediately disconnected the auto-braking system and applied manual braking to decelerate rapidly, while the pilot monitoring maneuvered the aircraft slightly to the right to increase lateral separation. The aircraft's left wing passed over the top of the vehicle as it rolled past. The vehicle eventually vacated the runway via a service road, and the aircraft exited via a taxiway. There were no injuries and no damage to the aircraft.
The investigation
The investigation focused on the breakdown in communication and surveillance. It was established that a supervisor (Controller 3) initiated contact with the vehicle to expedite the task, unaware that another controller had already instructed the vehicle to stand by. The vehicle's occupant, who did not hold the required airfield driving permit for radio communications, responded to the instruction in a way that the crew interpreted as clearance to enter the runway. Furthermore, the investigation found that the air traffic controller in charge of arrivals did not notice the vehicle during a visual scan and did not consult the Advanced-Surface Movement Guidance and Control System (A-SMGCS).
Findings
- The runway incursion was caused by miscommunication between the controller and the vehicle crew, where the vehicle crew interpreted a partial message as authorization to enter the runway.
- The vehicle's co-worker, who was not qualified for radio-telephony duties, provided an improper readback that was not corrected by the controller.
- The controller in charge of arrivals failed to detect the vehicle visually and did not utilize the A-SMGCS for verification.
- While the A-SMGCS triggered a visual runway incursion warning, the controllers did not notice it, and the aural warning was likely inaudible due to low speaker volume settings.
Safety action
Following the incident, several measures were implemented, including:
- Prohibiting personnel without a Category 1 ADP from performing radio communications.
- Implementing mandatory checks of A-SMGCS aural warning functionality at the start of every shift.
- Instructing controllers to use standard phraseology and to explicitly use "Hold short" instructions when necessary.
- Planning the installation of microwave barrier detectors at runway entrances to trigger alarms for unauthorized entries.