Traditionally, controllers have relied on the blunt safety tool of simply keeping planes far apart over vast expanses of water, because there are no ground stations for picking up a plane’s location.
“You don’t think about it. You’re flying to Europe and you think you’re in full, real-time tracking,” said Don Thoma, chief executive of the McLean-based aviation firm Aireon, whose investors include air traffic authorities in the United Kingdom, Canada, Ireland, Denmark and Italy, as well as the satellite firm Iridium.
But that’s not how it worked.
Instead, according to U.K. air traffic control provider NATS, controllers would keep a plane crossing the Atlantic about 40 nautical miles behind the plane in front of it. That’s referred to as “nose to tail” separation.
But earlier this year, NATS used Aireon’s satellite data to cut that minimum flying distance way back, to as low as 14 nautical miles, according to NATS, which worked on the effort with Canadian provider Nav Canada. Instead of getting pinged with the planes’ locations every 14 minutes, as had been true, the location updates from the satellite data came at least every eight seconds, and usually much faster, according to NATS.
With a better tool to track where planes are, air traffic controllers were able to give transatlantic pilots leeway to take more direct routes and adjust their altitude along the way to save fuel and money, participants in the effort said. That gave “airlines greater opportunity to fly the most efficient routes and levels, reducing fuel burn and harmful emissions,” according to a NATS statement.
The change also reduced the risks of “level busts,” that is, when pilots fail to follow controllers’ instructions and fly at the wrong altitude, NATS said.
Indeed, comparing flights from April to June 2019 with the same period last year, such miscues were reduced by a third in one key Atlantic region and the time spent flying at the wrong altitude dropped from 48 minutes down to three minutes, according to NATS.
That reduction in what are known as large height deviations came because pilots could easily and quickly be notified of their mistakes. In the past, pilots might not notice their error for a half-hour, Thoma said. “It’s a huge improvement,” he said.
NATS said in October that it was also rolling back the minimum “wing tip to wing tip” distance between planes, from 23 to 19 nautical miles, further upending the “traditional system” while improving safety.
Aireon says the granular and global nature of its satellite data will give governments and companies new insights in areas including managing airplane traffic and searching for patterns in the skies to help discover safety problems.
The company’s data played a key role in diagnosing similarities between a Boeing 737 Max crash in Indonesia in October 2018 and one in March of this year in Ethiopia. The data showed similar problems in how the airplanes behaved before they crashed, prompting the Federal Aviation Administration to ground the Max fleet in the United States after other countries had done so. In both cases, a flawed flight control feature repeatedly forced the planes’ noses down as pilots struggled to regain control.
Weighing the safety benefits of satellite tracking with the potential risks of flying closer together is a delicate exercise, marked by a host of technical, policy and other considerations.
The FAA has been considering how it might use satellite tracking technology in the large swaths of oceanic airspace its controllers manage. It is launching a pilot program in the Caribbean in March to further evaluate the technology “and its potential benefits,” but the agency also noted that it “does not prefer one technology over another.”
The agency said “separation standards” — how far apart planes must fly over oceans or other remote areas — depend on the communications, navigation and surveillance capabilities in each particular area.
The FAA is working with the industry “to enhance safety and increase capacity in oceanic airspace through a phased approach that leverages near-term opportunities while the agency continues to gather data and study options for a long-term solution,” the agency said in a statement.
It was an FAA mandate that airlines equip their planes with a more general tracking system that allowed Aireon to build its global surveillance system.
The FAA gave airlines until 2020 to install the broader technology, known as Automatic Dependent Surveillance-Broadcast, or ADS-B. That will be used to track planes over land with numerous ground stations around the United States.
Aireon saw that FAA mandate and tapped Iridium’s satellite network to essentially listen to that ADS-B signal, which automatically transmits signals from planes twice every second. Aireon dubs its technology “space-based ADS-B.” It is working with customers in about three dozen countries, from India to Ivory Coast, the company said.