Heathrow to lift capacity with time-based separation

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London Heathrow is to switch to time-based separation for aircraft on approach next year rather than relying on distances defined by wake vortex categories.

UK air traffic service NATS says the change is designed to reduce the loss of capacity caused by reduced airspeeds in strong headwind conditions.

Under these conditions aircraft which are correctly spaced, according to vortex requirements, land less frequently owing to their slower groundspeeds.

By assigning a time-based separation, air traffic control will be able to maintain landing rates at the hub.

Transition to time-based separation follows analysis of 100,000 flights which revealed that wake vortices dissipate more rapidly in strong winds.

This allows a relaxation of the strict distance-based separation standards designed to prevent aircraft in the approach sequence – particularly smaller types – being adversely affected by the vortices from a preceding flight.

NATS claims the change, which will take place in spring 2015, will be a “world first” and enable the airport to save over 1,300h of delays each year.

“It will reduce delays and cancellations while improving the airport’s resilience against disruption,” says NATS managing director for operations Martin Rolfe, adding that simulation has demonstrated that the safety case is “robust”.

NATS adds that the procedure could provide advantages to other airports constrained by similar meteorological conditions.