Time Based Separation


Time Based Separation is a new means of safely separating arriving aircraft, now in operation at Heathrow. Traditionally, air traffic controllers separate flights by set distances dependent on the aircraft type and the size of the spiraling air turbulence – or wake vortex – created as they fly. However, research has shown that in strong headwind conditions, wake vortices dissipate faster and can therefore be separated by time. Time Based Separation (TBS) takes live wind data from an aircraft and dynamically calculates the optimal safe spacing between each aircraft, improving airport resilience.


Heathrow is the busiest two runway airport in the world and is scheduled to 99% of its capacity, meaning any impact on landing rate can have major implications. The biggest single cause of delay to Heathrow arrivals is strong headwinds on final approach. The implementation of TBS leads to a landing rate similar to that in light winds and hence delays and cancellations are reduced, delivering significant benefits to the airport and its customers.


TBS was introduced at Heathrow in March 2015, research continues to further optimise the separations under the project Enhanced TBS.


Research started under the SESAR project with partners Eurocontrol, Airbus, Thales and DSNA up to validation and demonstration maturity. NATS with partners Lockheed Martin then developed an operational system and took this to implementation at Heathrow, working closely with Heathrow Airport Limited.

Project Benefits:

  • Capacity

  • Cost-savings

  • Fuel-savings

Project Maturity: Fully operational

Project Tags: Controller tools, SESAR