Time-Based Separation (TBS)

The Time-Based Separation project has developed new methods for separating arriving aircraft by time instead of applying radar distance separations in strong headwind conditions. 

  • Strong headwinds bring difficulties to airports by reducing aircraft ground speed during approach, which decreases the landing rate, resulting in delays and even cancellations. The key principle of the TBS concept is to define the minimum in-trail radar distance separation to apply, as a function of headwind, to maintain a constant time separation, as observed in low headwind conditions, consequently maintaining the landing rate.
  • TBS aims at reducing the gap in landing rates in light and strong headwind conditions. It will help maintain airport capacity at the same level in all wind conditions. The concept of time separation takes advantage of wake vortex quick dispersion in strong headwinds: this fact makes it possible to reduce the distance between landing aircraft. Although the TBS concept does not reduce the time separation with reference to the ground (i.e. the ‘zero wind’ time between aircraft is maintained), the reduction of the actual distance between aircraft in the air results in the potential for encounters with wake turbulence that has had less time to decay. As the wake strength impacting on aircraft is lower when there are heavy winds, safety levels will be maintained even if the distance between the pair of aircraft is minor.