Mind the gap – a year of TBS operations

We’re coming up to the first anniversary of Time Based Separation (TBS) entering operational service for Heathrow arrivals and I’m pleased to say it’s been a huge success.

For those that don’t know, TBS allows us to dynamically manage the separation between arriving aircraft based on the prevailing wind conditions. During strong headwinds, aircraft fly more slowly over the ground which has traditionally resulted in extra time between arrivals and consequently delays to arriving flights. However, TBS has allowed us to maintain the landing rate in headwinds by safely reducing the distance between arrivals.

In November alone we estimate that TBS saved 25,000 minutes of delay, despite winds of up to 60 knots on final approach. On 10 November, despite a 40 knot headwind, we had no flow regulations in place at all, something that would have been unthinkable before.

On average TBS has allowed us to land 2.9 additional aircraft an hour on strong wind days and cut Air Traffic Flow Management delays caused by headwinds by up to 60%. Importantly this has all been achieved without any increase in reported wake vortex encounters or go-arounds.

All this means a better service for passengers and a smoother and more efficient operation for everyone.

So what’s next?

Together with our partners at Lockheed Martin we’ve been speaking to interested airports and ANSPs from around the world, all keen to understand if the ‘Intelligent Approach’ concept that the TBS tool enables could benefit their own operation. We’ve also been thinking about what might be next and it’s become clear that the benefits of dynamically separating aircraft extend far beyond minimising headwind delays.

At the moment we typically group aircraft into six wake vortex categories (other countries group into as few as three or four categories), a figure that essentially stems from the fact that it’s the most combinations controllers can be reasonably expected to remember. But, with a tool in place that is dynamically calculating the correct separation between individual pairs of aircraft, there is theoretically no limit to the level of granularity we can reach, potentially going down to individual aircraft models and variants. This is a Time-Based application of a concept known as “Pairwise” and has the potential to safely reduce the separation between many wake vortex pairs.

We have just completed SESAR simulations, so it’s early days, but this is potentially very exciting and could add 1-2 extra movements an hour even at the most capacity constrained airports.

There are also potential benefits for mixed-mode (arrival and departure off one runway) operations whereby you could optimise the space between arrivals based on the expected runway occupancy time of the departure, also potentially delivering 1-2 additional movements per-hour. And we might also be able to use Intelligent Approach to tailor the arrival spacing in low visibility, taking into account the preceding aircraft’s impact on the localiser and thereby recovering some of the capacity lost due to fog.

These are all things we’re working on together with Lockheed Martin, and are testament to what’s possible when you start to build on the capability that exists within the Intelligent Approach toolkit. The next 12 months is set to be very exciting. Watch this space…

Andy will be speaking about ‘Intelligent Approach’ with Lockheed Martin at the World ATM Congress in Madrid on 9 March at 16.10 in the Honeywell Tower Theatre.