Nav Canada looks for new ways to streamline transatlantic traffic flows
When it comes to oceanic air traffic control, Nav Canada does not adhere to the philosophy of leaving things alone if they work well. Rather, it believes that for every procedure or technology it uses, there must be a better solution within reach.
It is because of this attitude that the North Atlantic airspace administered by Nav Canada is not only the busiest in the world, but also among the most sophisticated in terms of its operation. The company is continually undertaking new initiatives to improve the efficiency of transatlantic air routes—often in conjunction with its counterpart NATS in the U.K.
A good example of this is a recent technology upgrade that has allowed Nav Canada to proactively offer higher altitudes to oceanic flights. It is now looking to establish a new area of controlled airspace off Canada's northeast coast that will make the transition into North American domestic sectors much more seamless, and is also working on a way to reduce the lateral separation between transatlantic tracks. Looking further ahead, the agency is planning how it will pioneer a type of space-based surveillance system that does not need ground stations.
The Gander oceanic transition area (GOTA) is scheduled to be introduced on May 29, says Chris Mouland, Nav Canada's general manager for the Gander flight information region (FIR). It will effectively shift the boundary between domestic and oceanic airspace about 180 nm eastward over the Atlantic, extending the zone where controllers can reduce separation and more actively direct aircraft. In oceanic airspace they must use the more limited procedural control rules due to the lack of surveillance coverage.
Recent improvements in coverage are the main enabler of the GOTA, says Mouland. Nav Canada has extended its network of automatic dependent surveillance-broadcast (ADS-B) ground stations along Canada's northeast coast, and in 2012 installed ADS-B stations on the southern tip of Greenland. It has also reached an agreement with the Department of National Defense to use its northern radar system.
While the borders of the Gander oceanic FIR will not officially change, a large piece of it will be under the jurisdiction of controllers for the neighboring domestic FIR. “Although its still high-seas airspace, it will be managed by domestic controllers and aircraft will derive a lot of the benefits as if they were flying in a domestic environment,” says Mouland.
Westbound flights will be able to gain the advantages of controlled airspace more than 20 min. earlier thanks to the GOTA, and eastbound flights will retain these benefits for longer. Pilots will be able to adjust their flight profiles much more readily, changing speed and altitude for maximum fuel efficiency. Because of this, airline representatives are “pretty happy” about the change, says Larry Lachance, Nav Canada's vice president for operations.
Because westbound aircraft will exit the North Atlantic track system earlier, controllers will also have more flexibility in turning flights south toward the U.S. East Coast cities. This will be particularly useful when the track system is aligned farther north than usual due to variations in the jet stream.
New entry and exit waypoints between the track system and controlled airspace will be required, and these will be set to align with another new initiative that Nav Canada has been working on, in conjunction with NATS. This one will reduce lateral separation between North Atlantic tracks, and is known as RLatSM.
Nav Canada is aiming to introduce RLatSM in November 2015, says Lachance. The required International Civil Aviation Organization documentation is being prepared, and the company is working on the first phase of implementation with its U.K. partner and the North Atlantic System Planning Group members.
RLatSM will reduce the lateral distance between tracks to half a degree, or about 30 nm, versus the current standard of 1 deg. or 60 nm. This means that within a width of 60 nm, three tracks could be established instead of two. As a result, more tracks can be closer to the routes that are optimal due to the jet stream and other weather conditions.
Lachance says RLatSM will be introduced in operational trial mode. It will be phased in incrementally on specific tracks and flight levels, with any airline that meets the equipage requirements allowed to participate.
Initiatives like these often require minor software changes to Nav Canada's oceanic operating platform, the Gander automated air traffic system (Gaats). It has sold this system to NATS, so the same technology is in use on both sides of the Atlantic.
Nav Canada's upgrades to Gaats have enabled another major project that has recently advanced from trial mode to full operational status. The Gander Oceanic Flight Level Initiative (Gofli) makes use of Gaats to proactively offer altitude changes to pilots, who can opt to accept. Traditionally, oceanic flights under procedural control have stayed at assigned altitude levels and have to request controller clearance to climb to a more desirable level.
An interim step toward Gofli was a tool known as the request monitor. Under this process, if a pilot requested an altitude change and it was denied, the Gaats system would retain the request and regularly check to see if the desired altitude subsequently became available.
When Gofli was introduced last year, the main change was that the system would automatically check for possible altitude changes without waiting for a pilot request. It was declared fully operational in November after a trial period. NATS is expected to gain a similar capability after its own system is upgraded.
The moment a westbound aircraft crosses the FIR boundary into Gander oceanic airspace, Gofli “automatically kicks in and looks all the time for vacated altitudes,” Mouland says. For example, if an aircraft has been locked into an altitude of 35,000 ft. because another aircraft is at 36,000 ft., and the higher aircraft moves, then Gofli will prompt the controller to offer the lower aircraft a climb. The controller will then double-check for conflicts, and ask the flight crew if they would like to change altitude up to a certain level.
Pilots receive a message via data link or radio that says: “Higher flight level available if requested, advise intentions.” They respond: “Request climb to [flight level].”
Lachance says about 4,500 such altitude change offers were made within a recent one-month period, of which 1,000 were accepted. The ratio of accepted climbs varies greatly day to day, as factors such as reported turbulence might prompt pilots to keep to a certain level.
Altitude changes on long oceanic flights allow aircraft to optimize their flight profiles and save fuel. However, many pilots tend not to ask for altitude changes because they have been denied so often in the past. Initiatives such as Gofli will change that perception, Lachance says. Nav Canada is conducting an “educational awareness” campaign to demonstrate to pilots that controllers now have more options to offer optimal flight profiles. Lachance hopes “this will prompt pilots to get back to the environment of asking when they need something.”
As well as the work Nav Canada is doing, the increasing rate of advanced avionics equipage is also helping improve transatlantic ATM. For example, 78% of aircraft transiting the Gander FIR were equipped to the FANS 1/A standard as of December 2013, up from 60% at the beginning of the year. Over the same period, the ratio of aircraft meeting the required navigation performance (RNP) standard RNP4 jumped to 62% from 43%, and 94% met the RNP10 standard. ADS-B equipage rose to 90% from 86%.
Some of Nav Canada's transatlantic initiatives—including the GOTA—are aided by the expansion of its ADS-B network in recent years. The stations on the east and northeast coasts, as well as those in Greenland, provide coverage over a large area of ocean. However, the company has decided to drop plans to install an ADS-B ground station on the Hibernia oil platform off the east coast of Canada.
Currently only about half the ADS-B-equipped aircraft using Canadian airspace are certified for the use of that technology. However, a recent ruling bywill significantly expand the percentage of aircraft that can make use of ADS-B surveillance. It determined that positional signals from all equipped aircraft that meet performance specifications can be used for ATC purposes.
Nav Canada is heavily involved in the next technological advance for ADS-B, which will use receivers installed on satellites instead of ground stations. This will mean that oceanic airspace beyond the range of ground stations—such as most of the northern Atlantic—could have surveillance coverage.
A joint venture called Aireon has been established by Nav Canada and Iridium to provide satellite-based ADS-B, using a network of Iridium satellites that are to be launched beginning in February 2015. Nav Canada says the program is on track, and expects to be able to use Aireon operationally from 2018.
Surveillance coverage will mean that many of the benefits of direct air traffic control can be applied over the Atlantic, potentially including radar separation standards. Nav Canada is working on a concept of operations for Aireon service, which would be phased in gradually. The plan is to start with longitudinal separation standards of 15 nm on the existing track system, compared to the current procedural separation standard of up to 80 nm.
Lachance notes that the use of ADS-B in the GOTA will help Nav Canada gain experience in how to use ADS-B to separate traffic in oceanic airspace—a step toward the ultimate goal of handling transatlantic flights as if they were domestic operations.