One year of time-based separation at London Heathrow
Runway capacity is a common challenge in airports globally. In some airport, it’s only at peak times or in others, like Heathrow, capacity is a premium throughout the day. Generating new capacity doesn’t need to rely on building new runways. Time Based Separation (TBS) for example has been identified as one initiative that can generate more capacity by optimising aircraft approach separations to maintain landing rates in strong headwind conditions.
London Heathrow (LHR) was the world’s first ever deployment of TBS in 2015, and it won’t be the last. EUROCONTROL has mandated 18 EU airports to deploy TBS by 2024 as part of SESAR’s Joint Undertaking.
Since its inception almost a year ago, what have the positive impacts and benefits been and how does the Time Based Separation solution at LHR actually work?
Well, the ‘Intelligent Approach’ solution, engineered by NATS and Leidos, calculates the optimum safe separation between aircraft on final approach, taking into account the size of the aircraft in front, the wake turbulence it generates, and prevailing wind conditions. It means that, in certain wind conditions, aircraft can be flown closer together due to the quick dissipation of wake turbulence.
With traditional time based separation, around 40 – 45 landings per hour can take place in calm winds at Heathrow, depending on the mix of arrivals. Before Intelligent Approach the landing rate fell between 32-36 in strong headwinds, which resulted in delays, increased holding and even cancellations.
In May to July of 2015, Intelligent Approach helped increase the number of movements in the busiest two-runway airport in the world by 20 per day, regardless of the wind conditions. In fact, in strong wind conditions an extra 49 movements per day realised, and wind related arrival delays reduced by 62%.
So, the benefits are abundantly clear. Even in its infancy, Intelligent Approach has proven the need for TBS and has gone on to be awarded an honour from the Institute of Engineering and Technology, with the airport itself receiving positive coverage across consumer media like the BBC and Wall Street Journal.
The Future of Time Based Separation
It’s not going to stop there. The LHR project has exposed other applications of the technology outside of wind-related delay. For example, in mixed mode operational environments (where a single runway is used for both landing and take-off), Intelligent Approach can safely optimise inbound separation to take account of runway occupancy on departure.
Indeed, Intelligent Approach can have a positive impact in ANY capacity constrained environment. The technology gives controllers a marker to hit on screen that has been automatically calculated in the background to generate the optimised safe separation of aircraft for the conditions at the time, improving controller efficiency as a result.
So based on the Heathrow experience, it’s clear that there are many airports who can benefit from the additional capacity and efficiency that Time Based Separation can deliver in a relatively short space of time.