This article describes a real-life safety concern which was discussed at a meeting of the EUROCONTROL Safety Improvement Sub-group (SISG). Details have been changed to preserve anonymity.
Sometown Airport has two towers, one for the Air Traffic Controllers controlling the taxiways and the runways and one for the Apron Controller handling the apron.
The airport has three runways, the two parallel runways 09R/27L and 09L/27R, plus the crossing runway 18/36, only used in extreme crosswind situations (Figure 1).
During recent years there have been a number of runway incursions on runway 18/36, including a few serious incidents.
Two taxiing aircraft from runway 09R avoided collision only by one pilot braking hard to avoid the other aircraft. The incident happened on runway 18/36; the first aircraft taxiing towards the apron via runway 18/36 was under control of an Apron Controller, while the second aircraft about to cross the same runway, was on an ATC Tower frequency. The part of the runway where the incident occurred was temporarily handed over from the ATC Tower to the Apron Tower and a third person, an Apron Controller.
The recommendation was clear: Change the traffic concept to secure a clear interface between the two towers.
The implementation plan was well prepared. It included a commitment from management and gained the acceptance of Sometown Airport. The ATC Tower cap was rebuilt for the introduction of a new ground position and the controllers were trained in handling the new concept. The new ground position would handle the traffic, typically taxiing from crossing runway 18/36 and east of the runway, e.g. for departure runway 09L or 27L, after landing runway 09R or 27R until they had crossed runway 18/36 (fig. 2).
Prior to implementation of the new concept, a promotional tour was conducted. This included Aircraft Operators meetings, the distribution of 4000 flyers and special visits to the four major local operators.
What happened? Well, the two groups of controllers were fighting each other, and the number of reported runway incursions increased from 15 for the first six months 2006 to 46 for the last part of the year. The pilots were complaining, the new strict sector borders often resulted in an extra stop by runway 18/36 and an extra frequency change made no pilot happy. In addition the Airport Operator, although at first supporting the change, now was not pleased at all.
But there were no serious incidents similar to those reported before the change.
What are the lessons learned? The full extent of the problem became visible. Force of habit is enormous. Perhaps this was an area where the method of handling the traffic was smart and smooth, but not necessary always perfectly safe. The change seems at least to have made it safer, but it needs acceptance from the operational people involved. This will take time.