What happened
On 29 August 2006, a DHC-6 Twin Otter, registration G-BVVK, was stationary at the Y1 holding point at Glasgow Airport. The aircraft had arrived from Campbeltown Airport and was part of a scheduled commercial passenger flight. While waiting at the holding point, the commander engaged in a training discussion with the co-pilot, using paper to illustrate specific points. This distraction caused the commander to lose track of time and develop a false perception of how long the aircraft had been stationary.
At the same time, an Embraer EMB-145EU, registration G-EMBV, landed on the active Runway 23. Believing the Embraer had already passed the intersection, the commander of the G-BVVK began to taxi forward to cross the runway, following an ATC clearance to cross after the landing aircraft. As the aircraft approached the edge of the runway, the commander spotted the G-EMBV to his left, just as it was about to touch down. The commander immediately applied power reversers, bringing the aircraft back toward the Y1 holding point and preventing an incursion.
The crew of the G-EMBV observed the G-BVVK just before touchdown but assumed it was stationary and continued their normal landing roll.
The investigation
The investigation examined the functionality of the Runway Incursion Monitoring and Conflict Alerting Sub-system (RIMCAS) in use at the time. It was established that the controller had selected the 'Visual' mode for Runway 05/23. Because Runway 09/27 was only being used as a taxiway, the 'Cross Runway' mode was not active.
Under the 'Visual' mode settings, the monitored area did not extend to the space between the holding points and the runway edge. Consequently, when the G-BVVK moved forward and crossed the Y1 holding point, the RIMCAS did not trigger an alert. The investigation also found that the controller's perception of the system's coverage was inconsistent with its actual technical limitations during visual operations.
Findings
- The runway incursion was caused by the G-BVVK flight crew diverting their attention from monitoring external activity to discussing training matters.
- The commander's focus on training notes led to a loss of situational awareness regarding the time elapsed and the position of other aircraft.
- The RIMCAS did not provide an alert because the 'Visual' mode was selected, which does not monitor the area between the holding points and the runway edge.
- The controller did not expect an alert because the 'Cross Runway' mode was not in use.