From Pairwise to Curved Approach
How can airports increase runway efficiency while maintaining safe separation and reducing environmental impact? Heathrow’s use of Pairwise, an addition to Intelligent Approach, the arrivals-spacing tool created by NATS and Leidos just over a decade ago, offers one answer.
The tool provides a totally new way of separating arriving aircraft, with operational analysis indicating improvements in landing rates, delay performance and carbon emissions.
Traditionally, arrivals have been spaced on final approach by grouping aircraft types into a few categories that take account of an aircraft’s weight and the amount of wake it creates. Pairwise is far more granular and uses the specific characteristics of the individual aircraft type, meaning controllers can safely reduce separation between some pairs. This increases the overall flow of traffic and adds valuable tactical capacity to the operation.
The development team is already working on further enhancements for Pairwise based on real-world operational data. This includes reassessing aircraft runway occupancy times to ensure optimum performance delivery while maintaining safety and efficiency, as well as a concept known as Curved Approach to extend time-based spacing beyond the runway centreline and into the surrounding terminal airspace.
Curved Approach is intended to help controllers sequence aircraft arriving on multiple Required Navigation Performance approaches alongside those using conventional straight-in approaches. Separation indicators presented on the controller’s radar display support consistent spacing as aircraft converge towards the runway. RNP uses satellite-based navigation to allow aircraft to follow accurately defined lateral and vertical flight paths. These routes can reduce track miles, fuel use and emissions, but their geometry may make it more difficult to maintain runway throughput in some operating environments.
The concept remains in development, but it illustrates how arrival-management tools can help airports accommodate more varied approach paths while balancing capacity, operational resilience and environmental performance.