Time-Based Separation: making the wind work for us

On windy days, aircraft approach speed may be reduced, thus decreasing airport capacity. To resolve this problem, the EUROCONTROL Experimental Centre (EEC) developed a solution that mitigates the wind effect by separating landing aircraft on the basis of time instead of distance, thus maintaining runway throughput.

At airports, strong winds have advantages. They rapidly disperse the wake vortices (turbulence) generated by aircraft. The strong wind also supports the reduction of distance based wake separation between aircraft in such conditions. When a constant time separation is applied, equivalent to the required distance and separation taking account of the wind, the requisite levels of safety are maintained whilst the wind induced delay can be significantly reduced.

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Increasing airport capacity

On this basis, the EEC has developed the Time-Based Separation (TBS) project. As Vincent Treve, the Runway Throughput Research Manager, explains, “using a dedicated tool and a specific man-machine interface, TBS automatically provides air traffic controllers with the required minimum separations between aircraft, while at the same time incorporating wind speed and direction in its calculations.”

In spring 2015, London Heathrow airport was the first to implement this methodology. Since then, on particularly windy days, the airport can land 2.9 additional aircraft per hour and reduce associated weather delays by up to 64%. “TBS also eases the overall workload of air traffic controllers, because the shorter landing sequences result in a mechanical increase in the flow of aircraft.”

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A major challenge

The EUROCONTROL Challenge of Growth 2013 study forecasts that if European airport capacity remains unchanged, in 2035, a predicted 1.9 million flights will not be supported by the system, affecting 120 million passengers. In real terms, this will mean more delays, more time lost in the air and on the ground, more fuel pointlessly consumed and more noxious greenhouse gas emissions.

Improving airport capacity is therefore a major challenge, and TBS is one effective solution, as are other projects being run by the EEC (such as RECAT-EU*) under the SESAR** programme.

EUROCONTROL is developing runway throughput solutions with a vision of an integrated single man-machine interface based on TBS to support Air Traffic Controller’s to safely increase productivity. “Many tools are already tried and tested. We need to continue to persuade the air traffic control service providers and airlines of their benefits in order to be able to deploy them between now and 2025,” according to Vincent Treve.

* See RECAT: a new framework for more “turbulent” aircraft

** SESAR: Single European Sky ATM Research