What happened
On the night of 29 May 2009, a Boeing 757-28A, registration C-GTBB, was operating a passenger charter flight from Sharm-el-Sheikh to Dublin Airport. During the landing on Runway 10, the aircraft encountered poor visibility due to fog. As the aircraft decelerated along the runway, the flight crew observed a ride-on grass mower traveling along the runway surface, approximately 18.5 meters from the centerline. The aircraft's wingtip passed directly over the vehicle during the rollout. There were no injuries and no damage to the aircraft, but the incident posed a significant safety risk.
The investigation
The AAIU investigation focused on the movements of ground vehicles and the communication protocols in place during the grass-cutting operations. The investigation established that several vehicles were active on the airfield to address grass growth near runway lighting. While one tractor was equipped with airfield radio, the ride-on mower in question lacked the ability to monitor Air Traffic Control (ATC) frequencies.
Investigators examined the coordination between the maintenance supervisor and the vehicle operators. It was found that while the supervisor had instructed the mower to vacate the runway due to deteriorating visibility, the driver of the mower was unaware of the approaching aircraft. Furthermore, the investigation looked into the capabilities of the Surface Movement Radar (SMR) and the Advanced Surface Movements Guidance and $Control System (ASMGCS), noting that the system was still under testing and its display was not available in the control tower at the time.
Findings
Several critical factors contributed to the near-collision:
- The driver of the ride-on mower failed to vacate the runway after receiving instructions to clear the area.
- The maintenance supervisor assumed all vehicles had cleared the runway without receiving direct confirmation from the mower operator or visually verifying the runway was empty.
- The ride-on mower was not equipped with an airfield radio, preventing the driver from hearing ATC instructions regarding arriving aircraft.
- The maintenance supervisor did not specifically warn the mower driver that an aircraft was on approach.
- The use of the active runway as a transit route for maintenance vehicles was identified as poor practice.
- Limited visibility and the restricted performance of the available ground surveillance radar prevented the controller from detecting the conflict.
Safety action
The AAIU issued a safety recommendation to the Dublin Airport Authority (DAA) to review the training programs and the frequency of refresher training for all personnel authorized to drive vehicles within the maneuvering area. The recommendation emphasizes the importance of incorporating international standards for the prevention of runway incursions into these training modules.