MIAMI — Flight operations at London’s Heathrow airport are set to be a bit smoother thanks to changes implemented by NATS, the company responsible for managing air traffic control for the airport and much of the United Kingdom. Called “Time Based Separation” the new aircraft sequencing process is expected to reduce wind-related delays by as much as 80,000 aggregate minutes annually for Heathrow, a facility which is renown for traffic flow challenges due to its runways being nearly 100% utilized 24×7. Once delays enter the system recovery is nearly impossible save for cancelling flights. The new TBS process aims to reduce delays and avoid cancellations on days where winds are particularly strong.
Under the traditional distance-based separation rules aircraft on approach into Heathrow are spaced out a certain number of miles from each other to allow for dissipation of wake turbulence and other vortices. Flying through such can cause control issues or even crashes but spacing too far reduces the total capacity of an airport to handle flight arrivals and departures. The new system uses real-time wind speed measurements to help reduce the aircraft spacing on days where winds are particularly strong. From the NATS statement on the new service:
NATS has studied over 150,000 flights to measure the behaviour of aircraft wake vortices in strong headwinds, with the results showing that they dissipate more quickly in windy conditions. This means aircraft can be safely separated on final approach using a time based method.
Because stronger headwinds mean slower aircraft ground speeds it is possible to bring the planes closer together time-wise while not actually moving them closer together distance-wise. Aircraft remain safely separated vis-à-vis wake turbulence issues but also closer together from a flight operations perspective. Martin Rolfe, NATS Managing Director Operations, added:
Strong headwinds are the single biggest cause of arrival delay and Heathrow and the introduction of TBS will radically reduce delays and cancellations while improving the airport’s resilience against disruption.
The new spacing system only is operational on days where headwinds at Heathrow are especially strong, roughly one in six according to the NATS statement. On those days operations can drop from a typical 40/hour by as much as 20% to 32/hour. The TBS system allows controllers to maintain much closer to the 40 operations/hour number, keeping things moving at one of the world’s busiest airports. TBS first went into service on Tuesday, March 24th and was used “in anger” (actually activated for TBS-controlled approaches rather than just monitoring) on 26 March 2015. The implementation at Heathrow is the first of its type in the world.