Longitudinal Airspace Separations Reduced Over North Atlantic

 - May 9, 2011, 7:39 AM
New navigation standards allow for five-minute longitudinal separation for properly equipped aircraft flying over the Gander and Shanwick North Atlantic oceanic sectors.

Nav Canada and UK NATS have implemented a new navigation standard that reduces longitudinal separations by half for properly equipped aircraft in North Atlantic airspace managed by the Canadian and UK air navigation service providers.

As of March 30, a procedure for five-minute longitudinal separations took effect in the Gander and Shanwick oceanic control sectors, which manage aircraft in non-radar airspace. The existing standard calls for 10-minute separation of aircraft by longitudinal axis, or about 80 nautical miles.

The Reduced Longitudinal Separation Minima (RLongSM) initiative will enable controllers to place more aircraft in the heavily loaded tracks of the world’s busiest oceanic airspace. More aircraft at optimal altitudes will reduce overall fuel burn and greenhouse gas emissions (GHG), saving airlines money.

Only aircraft equipped for automatic dependent surveillance-contract (ADS-C) and controller-pilot datalink communications (CPDLC) can make use of the new procedure. ADS-C is the automatic, periodic downlink of GPS-based aircraft position reports controlled by a ground station. CPDLC is the exchange of data messages between pilots and controllers. Nav Canada estimates that 60 percent of aircraft flying the North Atlantic tracks are so equipped.

On the ground side, reduced separations are managed through a software implementation in the Gander Automated Air Traffic System (GAATS) in Canada, and Shanwick AATS in the UK. The Gander Oceanic Control Center on the coast of Newfoundland, Canada, manages traffic in the western half of the oceanic airspace; the Shanwick Oceanic Control Center in Prestwick, Scotland, manages traffic in the eastern half. Radio stations in Gander and Shannon, Ireland, respectively, handle HF voice communications with pilots. More than 1,000 flights transit the airspace daily.

According to a Nav Canada report on emission reduction initiatives, RLongSM will allow 3 percent of flights on the North Atlantic organized track system to climb to more fuel-efficient altitudes. “The total achievable customer reduction in GHG is estimated to be 3,000 metric tons in the first year of implementation,” it said. That equates to $1 million in fuel savings.

The Atlantic Interoperability Initiative to Reduce Emissions–an effort of the FAA, the European Commission and airlines–will include an evaluation of data from RLongSM flights.