In the not-too-distant future, it will be possible to fly anywhere over the planet in an Automatic Dependent Surveillance-Broadcast environment affording benefits equally to flight crews, operators and air traffic controllers.

Not only are countries throughout the world adding ADS-B ground stations to ultimately replace radar for primary surveillance, others with limited or no radar capability are leapfrogging directly to ADS-B as a less-expensive alternative. However, there’s real potential for global coverage absent any terrestrial network. This will materialize beginning this year with early launches of the second generation of the Iridium telecommunications satellite constellation on which ADS-B transponders will piggyback. With 66 satellites in inclined orbits, the system — conceived and managed by Iridium subsidiary Aireon LLC, and scheduled to go on line in 2018 — will assure full global coverage. Everywhere, with no voids.

The benefits afforded by ADS-B are by now legion; however, the most significant in terms of driving implementation, especially in high-density airspace and remote areas, are:

Safety, of course, manifested by much more accurate ATC surveillance (read: knowing exactly where everyone is in a specific sector or block of airspace). The return rate, or latency, of most surveillance radars varies between 4 and 12 sec. as the antenna rotates and its radio signal intermittently interrogates an aircraft’s transponder, causing the “target” — that is, data block — on the controller’s computer-generated display to appear to jump from reply to reply. But ADS-B broadcasts its position, informed by the highly accurate global positioning system (GPS), once a second, providing controllers with a near-real-time location of the aircraft as it moves seamlessly across the display.

So, while radar spends seconds “hunting” for an aircraft, ADS-B instantly communicates the aircraft’s GPS position to ATC.

With the now “old” FANS 1/A oceanic system that relies on ADS-C (for “contract”), the reporting interval is 10 min., as it isn’t really a surveillance system as much as a tool to ensure aircraft are where they’re supposed to be. This is why ADS-B has oceanic controllers excited, as the technology can build a computer-generated display mimicking radar but with almost real-time positioning.

Airspace capacity. With ADS-B’s greater accuracy, separation standards can be reduced to accommodate more aircraft in a given area of airspace. When planning began early in the century for the initiatives that became the FAA’s NextGen and Europe’s SESAR, one of the major factors in considering ADS-B for capacity enhancement was predictions that commercial air traffic would double by 2030.

Efficiency. ADS-B will allow more direct and efficient terminal area procedures and could ultimately free aircraft from the inflexible fixed route structure. With ADS-B In and Out functions, flight crews can benefit from real-time weather reporting and aircraft will be able (again, ultimately) to maintain their own separation by being able to “talk” to each other via the so-called “Internet in the sky.” Procedures enabled by ADS-B include constant-rate descents, curved approaches, and 4-D navigation.

Cost effectiveness. There are two ways ADS-B saves money. First to benefit are the system operators since it is vastly less expensive than radar. The small ground stations that accept ADS-B transponder signals — roughly the size of cellphone repeaters and consisting of antenna, receiver, target processor and telecomm links to ATC facilities — can be installed almost anywhere. And, unlike radar, they feature no moving parts, thus requiring considerably less maintenance and electric power to operate them. This makes them ideal for installation in Third World countries and elsewhere, especially in congested terminal areas where they can be sited in clusters allowing Wide Area Multilateration (WAM) services, which, as we’ll detail, are increasingly popular in Europe. For the cost of one expensive radar station, many ground stations can be purchased and installed.

The second group to benefit financially from ADS-B comprises aircraft operators, and particularly passenger and freight carriers. Due to tighter, more efficient procedures, flight times can be reduced, saving fuel and maintenance costs. According to an Aireon study, if the North Atlantic region had ADS-B surveillance, operators could realize as much as $125 million a year in fuel savings. And this feathers into . . .

Reduced emissions, especially CO2. Reduced Jet-A consumption equals lower CO2 and NOX emissions.

NextGen and ADS-B

In early planning for NextGen, ADS-B was put forward as the keystone of a comprehensive, cost-effective architecture that would initially supplement radar and ultimately reduce reliance on it to backup surveillance. The system’s effectiveness and safety potential had been demonstrated between 1999 and 2006 in the FAA’s Capstone project in Alaska, which significantly reduced accidents, especially among charter contractors and regional airlines operating in hazardous weather and terrain conditions.

The principal objective of NextGen was to bring the U.S. ATC system into the 21st century within a specific budget by incorporating proven technology that would replace a system that essentially dated from the end of World War II. Ironically, the concept of Automatic Dependent Surveillance itself was born in the same decade as part of the Future Air Navigation System (FANS) for tracking aircraft in oceanic airspace or over remote areas where radar was nonexistent.

Two advances in technology made it possible: the (then predicted) phenomenal accuracy of GPS and modern navigation equipment able to calculate position and guide aircraft within tolerances of less than 10 nm (now as tight as 1 nm, i.e., RNP 1). With navigation computers always “knowing” where they were, flight management systems (FMSs) could then report position at predetermined intervals via uplinks to geostationary communication satellites. A further advancement spawned by FANS was data link comm (or “texting for aviation” — before there was texting for everyone else), as a more reliable substitute for HF radio, thus the emergence of controller-pilot data link communications (CPDLC).

Today, FANS 1/A (“1” for Boeing, “A” for Airbus ) is being used by more than 90% of traffic on organized track systems in the Atlantic and Pacific operating areas. (The first business jet to make a North Atlantic crossing using FANS 1/A ADS-C/CPDLC equipment was a BBJ on a flight between Gary, Indiana, and Geneva to coincide with the European Business Aviation Conference and Exhibition in May 2004.)

The natural evolution from FANS to a domestic surveillance system that would enhance or eventually replace radar substituted inexpensive ground stations for the communications satellite reporting function, and in its planning for NextGen, the FAA envisioned an array of these VHF-band transceivers covering the U.S. and its territories. Then the agency made an extraordinary departure from previous ATM projects by outsourcing the design, construction, deployment and even the operation of the ground-based ADS-B network to the private sector.

Accordingly, following competitive bidding, a lease-services contract with an 18-year duration valued at $1.8 billion was awarded in 2007 to ITT, which evolved into Excelis in 2011; this year, Excelis was absorbed by Harris Corp., which retired the Excelis name. Two major subcontractors were involved in both building and operating the system: Thales and Selex, which made the radios for the ground stations, and AT&T, which provides the connectivity between the stations and the ATC facilities. Under the contract, the FAA does not own the ADS-B network; it simply leases it as a turnkey operation, which Harris runs out of a small control room in Herndon, Virginia.

“It was our responsibility to deploy the network, putting up the capital to cover installation of 650 towers [i.e., the ground stations] across the U.S. and in Guam and the Virgin Islands to provide the appropriate coverage,” Ed Sayadian, president of Harris Mission Networks, told BCA. The deployment was completed in 2013, fully tested, and the U.S.’s ADS-B network became operational. “We are now providing data feeds that provide the ADS-B information to all [equipped] aircraft, and the FAA pays us a monthly fee.

“Right now,” he continued, “the entire U.S. national airspace has ADS-B coverage. Some that did not have surveillance coverage before — for example, Alaska and the Gulf of Mexico — now have it, and as a result we have a massive safety benefit. There was no coverage over the Gulf before and now we have ‘virtual radar’ separation standards there. And we can begin to ratchet 50-nm separation down to 5- to 10-nm separation. So there is a huge capacity benefit, as well.”

Harris’ “original marching orders” were to provide the same coverage as radar today, but Sayadian claimed that, in some cases, this has been exceeded, such as in the Gulf. “We are in the process of adding a couple more sites on the Mexican east coast for better coverage of the Gulf,” he said. “Now we have 13 operational sites on oil rigs in the northern part of the Gulf and these additional sites will fill in coverage on the southern and western sites.” (While Sayadian didn’t mention it, the Helicopter Association International played a major role in getting those stations installed on drilling platforms to support all-weather rotary-wing operations to and from them.)

Other add-ons may include seven second-tier airports under evaluation for ADS-B in addition to the 35 busiest ones that were part of the original NextGen plan. “As we move forward,” Sayadian said, “we’re hoping that, with the increased equipage, the cost-benefit advantage will work for the second-tier airports, as well. There is no ADS-B coverage down to the surface for the busiest general aviation airports [such as Teterboro and Van Nuys], and they are future candidates. It will be a natural evolution to replace radar at these fields. You can get better surface coverage with as many low-cost sensors spotted around the airport as necessary to eliminate blocking and clutter issues.”

Who’s Using It?

The FAA bases ADS-B usage on avionics equipage and for general and business aviation its records show 13,161 aircraft, representing between 8.2% and 13.2% of the fleet, are equipped and presumably flying in the ADS-B network. But among air carriers, an industry segment that strongly supported the investment in the ADS-B network, equipage stood at a paltry 349 aircraft, or only 5.8% to 7% of the fleet as of September 2015. This despite the January 1, 2020, equipage deadline for access to controlled airspace.

Early equipage pricing — particularly for general aviation aircraft — and some confusion in the international ADS-B standard caused many operators to wait and see.

“Now we are starting to see solutions [for general aviation] in the $3,000 range with early discount plans, which is encouraging,” Sayadian said. On the usage side, he continued, “we are monitoring the aircraft and can see who is equipped with the legacy standard and who has the new standard, and we are seeing that, at any time, 15 to 17 aircraft in the air are equipped.”

It behooves operators to get on board with ADS-B, Sayadian believes, because “now for the first time [pilots] will have enhanced situational awareness in the cockpit. In remote places where surveillance was lacking, Alaska being an early adopter, we are seeing about a 30% decrease in safety-related incidents directly attributed to ADS-B equipage. There is a big safety aspect to this thing, so if the system saves one life, it’s hard to put a dollar value on it.”

As for radar retirements, the FAA is still evaluating its options, but Sayadian believes “primary radars will continue regardless.” It is the secondary radars that could eventually be phased out. But the more important issue, Sayadian says, is coming up with some kind of backup system for GPS, given its essential role in general navigation and in ADS-B operation in particular. If GPS goes down or is otherwise corrupted, radar then becomes the primary means of determining position and separation. Multilateration (MLAT) is a possible backup solution, Sayadian postulated.

The growing frequency of malicious cyber attacks on government and business databases begs the question of the security of a surveillance system so dependent on software and computational technology. “The ground part is very secure in terms of being hacked,” Sayadian claimed. “The ADS-B signal, the air interface, is a public standard that is published, and there is no security or encryption on the RF signal. So what we’ve done is install safety precautions on the ground to validate the integrity of the signal before it is passed on to the ATC centers. We receive a signal and do a time-of-arrival comparison to ensure the signals are not being spoofed.”

The system operators also collect legacy radar data and can conduct comparison checks against ADS-B returns. “So all that helps us to ensure security,” Sayadian said. “We are also in the midst of doing an evaluation study with the FAA and developing security threat scenarios to see how the system behaves to certain types of threats — and if we see a problem we can then develop a mitigation strategy.”

No other country has built an ADS-B network as extensive as the U.S.’s, so powerful it even provides “a fair amount of coverage” beyond the Canadian border. Nav Canada, the nation’s privatized ANSP, was an early integrator with the U.S. system, Sayadian said, adding that “in our contract we have a generic service volume that allows the FAA to order up a new station anywhere, à la Mexico.” Discussions with several Caribbean and Central American countries are ongoing, “as our operators share their airspace.”

An ADS-B Pioneer

Canada was one of the first nations to commit to ADS-B as a cheaper alternative to providing surveillance in its remote and sparsely populated northern latitudes as well as its eastern provinces. Further, as air traffic manager for a major portion of North Atlantic permanent routes and the organized track system, it has cooperated with Iceland and Denmark in siting ADS-B ground stations from its maritime provinces across the southern tip of Greenland. And it was a founding partner with Aireon in space-based ADS-B, which the two entities and other players in the North Atlantic theater plan to apply to the entire expanse of oceanic airspace under their purview.

ADS-B surveillance currently covers more than 1.5 million sq. mi. (4 million sq. km) of Canadian airspace with only 15 ground stations located in Ontario, Quebec, Manitoba, Newfoundland and Labrador Provinces plus the Nunavut Territory and Greenland. Canada led the U.S. in ADS-B when it turned on its first five ADS-B ground stations in January 2009, covering 328,186 sq. mi. (850,000 sq. km) over Hudson Bay, an area previously not directly surveilled and, thus, requiring procedural separation. Over the next two years, the remaining 10 stations were sited and activated. Nav Canada has calculated fuel cost savings and emissions reduction benefits from ADS-B use in the Hudson Bay and northeast regions and its portion of oceanic airspace through 2020 as, respectively, $379 million and 1.017 million metric tons of mostly CO2.

Rudy Keller, Nav Canada’s executive vice president, service delivery, said, “Today on the North Atlantic routes, commercial usage is close to 90% [and that’s using ADS-B, not C]. We can do it accurately through the ATM system accepting all of the codes entered into the squitters. There’s a large contingent of heavy traffic, but also some general aviation.” Nav Canada has yet to calculate a percentage figure for ADS-B equipage of general aviation traffic in its domestic airspace, and thus far, Transport Canada has not set a mandate for ADS-B equipage.

Keller says Nav Canada will continue to operate radar as primary and secondary in the FIRs along the airspace corridor that “aligns” with the FAA’s ATC system in the south. But he anticipates that there eventually will be a mandate for ADS-B equipage, so in the corridor “we will continue to have radar coverage overlapping with space-based ADS-B. What we won’t have is ground-based ADS-B.”

Asked if Nav Canada will eventually replace its ADS-B ground stations with Aireon’s service, he responded, “We believe the quality of the Aireon signal will be as reliable or good as the ground-based system, but we’ll use [the latter] for redundancy, and from 2016 to 2018 we’ll use the ground-based system to test the space-based system by comparison.” So testing will actually begin before the full Aireon constellation of 66 satellites is deployed. “Within a couple months after the full system is in the right orbits, we should have North Atlantic coverage with service improvements. Meanwhile, domestic coverage will coincide.”

The addition of space-based ADS-B “really changes the whole landscape in terms of safety, productivity and flexibility,” Keller maintains. “The value of surveillance and seeing the aircraft and communicating with it is immense considering that 70% of the globe is not under surveillance at this time. The fundamental safety difference for weather, reroutes, emergencies or sometimes adjacent aircraft is the real game changer, and it cascades into better separation standards.”

Canada maintains “an extensive degree of cooperation in every FIR that abuts those of the FAA,” Keller said, and maintains multiple agreements to exchange surveillance data, “whatever the surveillance system used: radar, ground-based ADS-B or space-based.” Meanwhile, Nav Canada, described as “a non-share capital corporation,” is collaborating with several other countries on space-based coverage through the Aireon partnership. “Under our own management responsibility, we are working with several other ANSPs including in the U.K., Portugal, Singapore, ATNS in South Africa and ASECNA elsewhere in Africa, and others.”

Iridium’s Role

Back in the days when cellular telephones were in their infancy, big and clunky with spotty service coverage and mostly tied to local areas, planners at Motorola Corp. came up with the idea of a consumer-oriented satphone network allowing connectivity anywhere on the globe. But in the decade it took to raise capital, launch a huge constellation of low-earth-orbit (LEO) communication satellites and bring the Iridium system — as it had been dubbed — on line, the cellular landscape changed significantly. But then it was possible to place a call almost anywhere in the world through a network of terrestrial towers.

There was also a limitation with the Iridium phones: They generally only worked outdoors, as they had to have uninterrupted line-of-sight with the satellites. And the service was expensive. As a result, the system failed to catch on with mainstream consumers. At that point — around 1999 — Motorola was carrying a huge debt it couldn’t service and had no choice but to put Iridium into bankruptcy and planned to de-orbit the satellites.

But along came Dan Colussy to the rescue in 2000. Chairman and CEO of UNC Corp., he saw potential in the satellite network, which provided full global coverage, including places where there was no cellular service. He assembled an investor group to support a new global telecom system based on the Iridium network targeted exclusively at business and applications in areas with no mobile phone access. In 2001, a streamlined company renamed Iridium Satellite was relaunched, and Colussy signed his first customer, the U.S. federal government. Next, he focused on the small population of the world not accessible by the cell network, but representing substantial activity, such as fishing and other maritime activity, aviation operations, construction projects in remote areas, conservation, exploration, etc. International business aviation operators were quick to sign on, as Iridium offered a low-cost handset with a small antenna, voice and low-speed data transmission, and coverage everywhere they flew — the only service available at the time with those features.

By 2006, Iridium Satellite was growing by 20% and plans began for a second-generation network, as the original Motorola-built satellites had been designed for a lifespan of only five years (but are still operating as this is written). The following year the company unveiled Iridium Next, a complete replacement of the original satellite network featuring backward compatibility, increased capacity to accommodate growth and flexible satellite architecture to support new voice and data services with more than half a megabit per second speed.

The new satellites would also benefit from nearly 20 years of technological advances since their predecessors had been designed. This allowed Iridium engineers to consider other applications for the network beyond just telecomm, perhaps allowing third-party missions from users at other companies that would lease space on the satellites. Thus, the “hosted payload” concept was born.

“So we were talking to government agencies and came across the concept of hosting an ATC payload on the satellites forming the network,” Don Thoma, Aireon’s CEO, recounted. “And ADS-B is the current paradigm with mandates in the U.S. and around the world to use it; all the aircraft coming off the production line are equipped with ADS-B avionics installed. To provide ATC in remote regions, you needed a system with global coverage.” And with 66 satellites in low earth orbits of 484 sm. (780 km.), it was possible to pull this off. 

A key enabler was the capability of the satellites to interlink — satellite-to-satellite routing — allowing signals to be passed among them without relaying to the ground, resulting in a meshed communications network in the sky. “The advantage is that you can communicate from anywhere to anywhere else on the planet without having to use a ground station in the local area,” Thoma pointed out. “It’s very useful over the ocean or in very remote areas, so it’s truly global without the necessity for ground stations to achieve complete connectivity. And there is very low latency, too, so in effect, it can report in real time.”

Finally, for a space-based network to support the worldwide ADS-B mission, the system had to be compatible with contemporary ADS-B avionics with no modifications. “So the objective was global coverage, no change to the avionics and real-time surveillance,” Thoma enumerated. “This is where we started discussions with the FAA, Nav Canada, U.K. NATS and other ANSPs.”

Real-Time Surveillance

To serve the North Atlantic, Nav Canada wanted an improvement over ADS-C that could reduce longitudinal separation from 30 to 15 nm on the organized track system with near-real-time surveillance that could allow easier climbs to achieve better fuel efficiency.

“ADS-B is a more accurate surveillance system than ADS-C,” Thoma said, “as you can see an aircraft once a second, whereas ADS-C is programmed for once every 10 min. So, if you can’t see a plane in real time, you can’t do tactical ATC. Under ADS-C, you have to keep longer distance in trail to ensure there is safe separation. A clear distinguisher is that ADS-B is a surveillance system and ADS-C is a conformance-monitoring or tracking system. Along with CPDLC, there are huge savings — and Iridium was already approved to support CPDLC and FANS 1/A [with the existing satellite constellation].”

Out of these discussions came Aireon LLC, a 2012 joint venture between Iridium and Nav Canada, with the Canadian ANSP contributing $150 million for a 51% ownership. Since then, Aireon has raised an additional $120 million by signing additional partners Irish Aviation Authority (6% ownership), Italy’s ENAV (12.5%) and Denmark’s Naviair (6%). Aireon will use the additional capitalization to build the ADS-B components for the Iridium Next satellites that the company is scheduled to begin launching late this year.

Altogether, it will take eight launches over two years to put up 66 satellites plus six spares (nine more will be stored on the ground), replacing the original Iridium constellation. The primary launch vehicle is the Space X Falcon 9, but the first two launches will be aboard Russian Dnepr rockets operated by Cosmtotrak. The satellites will be distributed 12 each among six orbital planes, traveling at 16,777 mph (27,000 kph).

Because satellite coverage overlaps, there are no voids and ADS-B reception should be available anywhere in the world, even in Antarctica. The receivers will listen on the 1090 MHz ADS-B frequency. Excelis/Harris has been contracted to oversee Aireon’s ground-based facilities, controlling them from its center in Herndon. Iridium is responsible for controlling the satellites out of its center 13 mi. away in Leesburg, Virginia.

Aireon has signed long-term service agreements with its five investor/co-owners to begin using the system in 2018 when it goes on line.  “And we have signed MOUs with FAA, Nav Portugal, Iceland, ASECNA [in sub-Saharan Africa], ATNS in South Africa, India, Singapore, New Zealand, and Airservices Australia,” Thoma said.  The MOUs are in place to perform technical evaluations of the space-based system’s capability, to conduct workshops with the ANSPs’ operations people and regulators to determine how their systems can be improved by using it, and to examine how Aireon would provide benefits to the airlines and ANSPs with possible long-term service agreements.  

In early October, Aireon and Airservices Australia jointly announced that their MOU would not only explore facilitating smoother transitions with neighboring FIRs, reducing costs to operators and enhancing safety, but introducing ADS-B services to the majority of the 20 million sq. nm. (51.7 sq. km.), or eleven percent of the globe, that Airservices manages that constitutes oceanic airspace.  (As the accompanying sidebar explains, Australia was the first nation to install a network of ADS-B ground stations across its continent.  Currently, more than 60 percent of aircraft operating under IFR in Airservices Australia airspace are ADS-B-equipped.)

According to Airservices’ Greg Hood, executive general manager for ATC, the ANSP is interested in determining “the potential safety benefits and the technology and efficiency benefits [Aireon] may offer to our customers, especially for oceanic services and in cross-boundary coordination with our neighbors.”   

Thoma added that, in addition to the ANSPs with which Aireon has signed MOUs, “We are talking to all the world’s ANSPs, as well, to educate them, especially in airspace without adequate surveillance.  This is a turnkey solution that can get them going right away.  Plus, the airlines are very supportive of it. ICAO has a North Atlantic regional group to institute 15-nm. separation by February 2018 by using space-based ADS-B.”

SESAR Comes Alive

According to Christos Rekkas, who heads Eurocontrol’s surveillance modernization section, “ADS-B is the key enabler for the future surveillance system in SESAR,” or the Single European Sky, ATM Research. When the upgrade program becomes fully mature sometime in the 2020s, the “ATM Research” suffix will be dropped.

In addition to the ADS-B benefits listed earlier, Rekkas added reduced radio frequency saturation due to use of CPDLC. This and all the other benefits can be realized in low-density areas, where procedural control is in effect, as well as in medium- and high-density areas covered with radar.

“In the first case,” Rekkas said, “we expect reduction of separation minima, reduced fuel burn and CO2 emissions, and increased safety. And if we move to the radar environment, which is a significant part of Europe, the main benefit is cost effectiveness in that we are introducing a technology that is lower cost and at the same time more efficient with use of the communication spectrum. Therefore, the total benefit depends on the airspace where it is applied.”

Most of Continental Europe has medium- to high-density traffic, so the main benefit is said to be improved cost effectiveness. In areas on the Continent where surveillance is limited or nonexistent, introduction of ADS-B is expected to allow reduced separation minima and improvement of routings, among other things. Aireon’s ADS-B holds the potential to “drastically increase” the ADS-B surveillance area, including enabling surveillance over oceanic airspace managed by EU and Eurocontrol members Portugal, Ireland and the U.K.

SESAR is on schedule and will be completed by 2016 when the SESAR Joint Undertaking will begin the modernization program’s next phase, SESAR 2020, which will run to 2024 and include evolution of systems and applications not yet fully mature. “Moreover,” Rekkas said, “additional work will be performed on [concepts] that have emerged since the program was started, like UAS [unmanned aerial systems]. It will also include more applications of ADS-B, using data derived from the aircraft via data link, both ADS-B Out and In.”

Focusing on just ADS-B, Rekkas claimed progress has been made in ground station deployment, with close to 800 in place across Western Europe. The deployment initiative is being driven by either ADS-B alone or as part of multilateration, which consists of a cluster of ADS-B stations receiving transmissions from aircraft transponders. By comparing the time of arrival of the signals, it can compute the aircraft’s position and provide additional surveillance data. “The same infrastructure thereby provides two forms of surveillance,” Rekkas pointed out, “ADS-B plus multilateration. It’s popular in Europe because multilateration can be used to replace or complement radar without being dependent on ADS-B avionics equipment [because it is accessed via the aircraft’s existing transponder].”

As a consequence, the number of stations is growing fast. “Soon we will have more than 1,000 ground stations deployed,” Rekkas said. “Eurocontrol has been coordinating the deployment, but it should be noted that there is no obligation on the part of the ANSPs to participate, as it is their choice. But it is growing much faster than we expected, driven by the operational needs, the technology and generally lower cost. And it gets you two layers of surveillance for less money.”

ADS-B In providing basic traffic situational awareness to the flight crew has been operational in Europe since 2012 on a voluntary basis. This was a Eurocontrol pioneer project with a number of airlines involved, including some U.S. ones — Delta, United and USAirways — plus Swiss, Virgin Atlantic and Lufthansa. “By now, the numbers of operations are in the thousands,” Rekkas said. “Benefits have been operator-specific, and its use has been much appreciated by the pilots. It can be assumed that business aircraft have been using it, as well, but we have no statistics.” Other applications of ADS-B In are yet to be implemented, and there is no mandate for equipage of ADS-B with the higher level data intake function.

But the European Commission EU Regulation 1207/2011 for Surveillance Performance and Interoperability mandates ADS-B Out as well as Mode S Elementary and Enhanced Surveillance. This rule was amended in 2014 with new dates for ADS-B Out and Mode S Enhanced Surveillance equipage. For Mode S Elementary Surveillance, the mandate applies to all IFR/GAT (General Air Traffic) aircraft, with compliance dates of January 2015 for “forward fit” (i.e., on the assembly line for new aircraft) and December 2017 for retrofits.

For ADS-B and Enhanced Surveillance Mode S, the mandate applies to IFR/GAT aircraft weighing more than 5.7 metric tons or having maximum cruising true airspeeds higher than 250 kt., with compliance dates of June 2016 for forward fit and June 2020 for retrofit. A second amendment not yet published is expected to address issues raised by stakeholders, such as aircraft below the 5.7 tons/250 kt. threshold not currently covered.

As for current fleet equipage, Rekkas said, “Today in Europe we are detecting about 12,600 aircraft with ADS-B, and out of that number, aircraft with the legacy standard are on the order of 10,000 plus, and the ones with the new standard about 2,000. Out of that, about 6,000 plus are the ones that can perform well for ADS-B operations in non-radar environments, and about 2,000 aircraft having the new standard can perform ADS-B operations everywhere, i.e., in any type of airspace.”

Compatibility Issue

Many U.S. business aviation operators upgrading to ADS-B are concerned as to whether their equipment will be compatible with the European SESAR system. “To a very large extent, there is compatibility with the U.S.,” Rekkas promised. “There is a difference in that, in the U.S., the GPS positioning performance is more demanding. This was mainly driven by some specific operational scenarios in the U.S. that were not considered for Europe. But for someone flying from the U.S. properly equipped [in an FAA-registered aircraft], there will not be a problem. Aircraft using the legacy standard, ‘EASA Acceptable Means of Compliance,’ AMC 20-24, the minimum baseline for ADS-B operations in Canada or Australia, will not be compatible with the European system after the mandate. At this stage, U.S. and Europe have mixed traffic with reference to ADS-B equipage, but after the mandates, the aircraft addressed by the rules will be required to be equipped.”

For non-equipped aircraft visiting Europe, “we don’t know yet, but there may be some restrictions,” Rekkas continued. “If you enter an airspace where ADS-B is used operationally before the mandate — for example, the periphery of Europe — and are not equipped, you don’t get the benefits of reduced separation. In addition, restrictions exist to prevent the use of avionics installations producing misleading information via ADS-B. Similarly, after the mandate, restrictions may apply.”

As in the U.S., some surveillance radar will survive the proliferation of ADS-B and multilateration. “ADS-B can complement or replace radars at the end of their operational life, but this is an option that the ANSPs will have to consider,” Rekkas said. “If you are in low-density airspace, then you can operate with the legacy ADS-B avionics, as per AMC 20-24, which has less demanding requirements than the rule.” Thus, for one layer of surveillance, ADS-B will be required on the ground in low-density airspace.

“This is why, in the North Atlantic corridor, aircraft can use the legacy ADS-B standard certified to AMC 20-24 and be surveilled by ADS-B ground-based equipment as sole surveillance means,” Rekkas explained. “In medium- or high-density airspace, the rule-compliant avionics, certified to EASA CS-ACNS, will be required and surveillance will be provided by at least two layers of ground surveillance — for example, ADS-B with radar or multilateration. If the traffic is mixed with reference to ADS-B equipage, you will still need surveillance to be provided by at least two layers of radars or radar and multilateration. The ongoing second amendment of EU Regulation 1207/2011 will determine when all aircraft will have to be equipped with ADS-B avionics, and by then, ADS-B can be one of the two surveillance layers and replace radar.”

On top of these layers is Aireon’s space-based system. Referencing Aireon’s European stakeholders Italy, Ireland and Denmark, Rekkas also revealed that “U.K. NATS will use space-based ADS-B after 2018 in the Shanwick FIR, and IAA Ireland will monitor and gather data from the Aireon satellites to coordinate search and rescue on a global scale. If an ANSP somewhere needs data on an aircraft, they can provide it. As long as the equipment is operating on the aircraft, the aim is that it can be tracked globally. In Europe there is expressed interest in using space-based ADS-B also in other areas such as the Mediterranean Sea and in Denmark.”

Eurocontrol maintains “close cooperation” with the FAA, Nav Canada and Airservices Australia in support of “global interoperability” of ADS-B, Rekkas said. “In addition, we have done ADS-B presentations to other countries, such as during visits of their staffs in Europe or other events. But unfortunately, there’s not a lot of recent information from Russia on their ADS-B plans.”