What happened
During a scheduled maintenance period at Seletar Airport on 7 April 2018, a runway incursion occurred involving a maintenance vehicle. The runway had been closed starting late on 6 April for various works, including airfield lighting and runway marking painting.
As the maintenance work concluded in the early hours of 7 April, a driver operating Mobile 75 attempted to return to the Assembly Point after visiting an equipment store. Although the maintenance teams had been instructed to use a specific taxiway for entering and exiting the runway, the driver of Mobile 75 used a different taxiway to take a shorter route. Crucially, the driver was unaware that the runway had already been reopened to traffic. At approximately 05:40LT, a driver from another team, operating Mobile 36, informed the Air Traffic Control Tower that all maintenance parties had cleared the runway. This communication was made without the explicit permission of the Runway Entry/Exit Point Officer (REPO), leading the Tower to reopen the runway. Shortly thereafter, Mobile 75 crossed the active runway, resulting in the incursion.
The investigation
The investigation examined the coordination between the aerodrome operator, the REPO, and the various maintenance contractors. Investigators looked into the radio communication protocols used during the transition from closed to open runway status. The probe also scrutinized the movement of vehicles between the equipment store and the assembly point, as well as the specific instructions provided to the maintenance crews regarding entry and exit points.
Findings
- The primary cause of the incursion was that the driver of Mobile 75 entered the runway via an unauthorized taxiway without realizing the runway had been reopened.
- A breakdown in communication occurred when the driver of Mobile 36 informed the Tower that the runway was clear without first obtaining authorization from the REPO.
- The REPO failed to verify the exact location of all maintenance vehicles before the runway was returned to service.
- The aerodrome operator's procedures for runway closure were not strictly followed, and there were ambiguities regarding the specific duties of the REPO and the lead contractor.
- The lack of a strict "stop bar" enforcement policy meant that vehicles could cross the runway without a definitive signal from the Tower.
Safety action
Following the incident, the aerodrome operator implemented several safety improvements:
- The airport adopted a stricter policy where red stop bar lights signify that no vehicle may cross the runway under any circumstances.
- Procedures were updated to ensure only personnel with a Category One Airfield Driving Permit (ADP) can serve as the REPO.
- The roles and responsibilities of all maintenance personnel have been formally documented.
- A new master list was developed to help the REPO track the entry and exit of every vehicle.
- The equipment store was relocated to prevent the need for vehicles to cross the runway when returning tools.
- A mobile tracking system was implemented for vehicles equipped with radio communication to allow the REPO to monitor their real-time locations.