Signals from space guide airplanes to greener landings

Fly into the Faroe Islands’ Vágar Airport in the North Atlantic and the airplane will be guided to the ground by satellites rather than air traffic controllers in a runway-side tower.

Faroese flag carrier Atlantic Airways switched to a purely satellite-based navigation system when it renewed its fleet in 2012. The rationale was to boost safety for the approach and takeoff from Vágar, a one-runway airport surrounded by turf-covered hills often wreathed in clouds and overlooking the deep blue waters of the Sørvágsfjørð.

“You can shut the airport down, it doesn’t matter. We can fly in anyway,” said Sámal Danielsen, a pilot and director of flight operations at Atlantic, which puts on the vast majority of flights to and from the island. He said the satellite guidance system it uses is so accurate it can land an airplane to an accuracy of within a meter.

The remote islands’ approach to air traffic management doesn’t just save manpower: It also saves time and fuel, part of an international effort to harness satellite technology to make air travel more efficient. Satellites can provide highly accurate ways of tracking aircraft over distant oceans and allow trimming of flight paths to burn less fuel.

Danielsen said Atlantic saves the equivalent of €160,000 a year in fuel costs by using satellite guidance on its three aircraft.

Some of those advances are linked to the EU’s effort to set up its own satellite navigation so that it will no longer have to rely on America’s GPS, the nascent €5 billion Galileo constellation. European airports are also making those satellite systems more precise with the European Geostationary Navigation Overlay Service, or EGNOS, which can boost the satellite signal from an accuracy of around 10 to 20 meters to between 1 and 3 meters.

Airlines and airports are using EGNOS and other space-based technology to replace the so-called instrument landing system (ILS) traditionally used to guide aircraft down to the runway under low visibility using a radio signal. ILS functions only on a single, fixed approach and is vulnerable to interference.

“Increasingly we rely on satellite navigation for aircraft,” said David Bowen, who runs air traffic management at SESAR, a joint venture between industry and the European Commission aimed at overhauling Europe’s airspace system. Some 231 airports and heliports across 20 European countries now use EGNOS-assisted landings.

The effects of that satellite revolution can be seen in the operations of the Continent’s largest airports and airlines in addition to minnows like the Faroes’ three-aircraft Atlantic. Zurich, Bremen and Frankfurt airports are among those running satellite-based systems.

Danielsen said the new navigation system cost a few million euros to install but makes valuable efficiency gains. Atlantic used to lose millions a year from weather-based diversions around the Faroes that increased fuel and maintenance costs. Now the satellite links ensure that 99.8 percent of landings go as planned, he said.

“Our diversion rate is reduced by 80 percent,” Danielsen said, enough to make the investment worth it in the long run.

The satellite guidance Atlantic uses — or Required Navigation Performance Authorization Required in technical terms — shaves three minutes off flight time on the regular run from Vágar to Copenhagen. Because the system is so reliable, aircraft carry less fuel as there’s less need to plan for extra time in the air to account for botched take-off and landing attempts. Lighter aircrafts burn even less fuel.

Multiply these efficiency savings by the 42 flights to destinations across Europe the Faroese airline runs a week in peak season, and savings start to mount.

Smooth landing

Switching from ILS to space-based satellite transmission gives air traffic managers the chance to get creative with landing protocols, prioritizing things like fuel efficiency.

“It allows us to design much more tailored approach procedures which fit the requirements of a particular runway. The more accurate navigation during that approach has a safety impact, but also environmental,” Bowen said.

On the Faroe Islands, Atlantic can use satellite guidance to make landings possible at a visibility of 800 meters, rather than the 2,500 meters it used to require, Danielsen said. Three descent routes are also programmed for arrivals at Vágar to account for changes in turbulence in airspace around the airport that might make a typical approach route difficult. 

The satellite system also makes descents smooth rather than the typical staggered landings that power engines on and off — another fuel saver.

“The approaches are made so that the aircraft flies at a constant thrust, so that engines are running just above 50 percent, from initial approach all the way down to touchdown,” Danielsen said.

The savings don’t stop at fuel. Bring in ground-augmented signals beyond EGNOS, and hub airports in densely populated areas can work on another pollution problem: noise.

The systems installed at Frankfurt — one of Europe’s largest hubs — reduce noise pollution by raising the angle of approach, meaning aircraft fly higher for longer before swooping in to land.

Infrastructure typically needed for that kind of interface include up to four receivers for Galileo or GPS satellite signal, an on-site computer facility and data broadcast transmitter out on the airfield to communicate with receivers installed in aircraft cockpits. Not all airlines have upgraded their hardware to take advantage of the signal.

In northern Germany, Bremen recently upgraded to a space-based augmentation system, or SBAS, which uses EGNOS. In April, the airport said it deployed a satellite-only system that guides pilots down to heights of just 60 meters before visibility is required to land, rather than the hundred previously required. It’s similar to the system being used in the Faroe Islands.

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The space-based system is more precise than traditional landing systems and doesn’t require ground infrastructure that is expensive to operate and requires a lot of maintenance, German air navigation service provider DFS said after the successful trial run at Bremen.

Satellite savings add up in another way too: Long-haul routes across the Atlantic can benefit from a developing space tracking systems that will make it safer for aircraft to fly closer together on favored flight paths like jet streams, which can cut fuel use. With 1,500 flights crossing the Atlantic a day, proposed fuel savings of up to 4 percent per flight make a big difference.

That system would be run by yet another space-based system, the soon-to-be finished Aireon constellation of 66 low-orbit satellites. It will allow, for the first time, tracking aircraft anywhere on the planet. According to a study by Purdue University funded by the satellite sponsors, the system would be equivalent to taking 292,822 cars off the road by letting more planes fly together at the most efficient altitudes.

“There is an emerging consensus among all members of the commercial aviation community that reducing aviation’s environmental impact is an imperative, not a choice,” the study’s authors said.

This article is part of a special report on sustainable aviation.