From Pairwise to Curved Approach: How intelligent spacing is transforming Air Traffic Management

In August, we released some very encouraging analysis of the first six months of Pairwise separation at Heathrow.

The average landing rate, delay performance and carbon emissions have all seen significant improvements since we became the first air traffic service in the world to introduce Pairwise as part of our Intelligent Approach arrivals spacing tool.

Pairwise is a totally new way of separating arriving aircraft. 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 our controllers can safely reduce the separation between some pairs.

This increases the overall flow of traffic and adds valuable tactical capacity to the operation.

Intelligent Approach – developed by NATS and Leidos – is the only true time-based spacing tool available today, and Pairwise is just the latest example of how it is helping airports to make the absolute most out of their available runways to maximise operational resilience and efficiency.

And it doesn’t stop there. The team are already working on further enhancements for Pairwise based on the real-world operational data we’ve now collated. This includes reassessing aircraft runway occupancy times to ensure we’re delivering optimum performance while maintaining safety and efficiency. Those will be introduced as part of a trial phase in the coming months.

Beyond Pairwise, we’re also working on some other developments on the longer-term horizon. The one I’m most excited about is called Curved Approach.

Today, Intelligent Approach only supports airports where the aircraft fly “straight-in” approaches, typically using the Instrument Landing System (ILS). This is the standard at all major UK airports and at many others around the world, but there are an increasing number that are also making use of what are called Required Navigation Performance (RNP) approaches.

RNP is a form of highly accurate, satellite based navigation that allows aircraft to fly precisely defined lateral and vertical trajectories. These highly accurate routes can help deliver significant fuel and emission savings, but can result in a loss of overall runway throughput in some circumstances.

Curved Approach will help controllers sequence arrivals in multiple RNP routes and more traditional ILS approaches.

By extending the benefits of Intelligent Approach beyond the runway centre line and into the terminal airspace around the airport, we can help controllers to efficiently sequence aircraft on multiple RNP approaches as well as those on the ILS. Curved Approach will help sequence those arrivals via separation indicators on the radar screen, allowing those airports to maintain the valuable carbon and fuel savings whilst not compromising on capacity.

Curved Approach is still at a relatively early stage of development, but we expect it to be as much of a gamechanger for airport performance as Intelligent Approach has already been at Heathrow, Toronto, Gatwick and Amsterdam.

Find out more about Intelligent Approach and how to get in touch with the team.