Automatic Dependent Surveillance–Broadcast (ADS-B), one of the foundations of NextGen, is a surveillance technology that helps pilots and air traffic controllers create a safer, more efficient National Airspace System (NAS). ADS-B Out relies on aircraft avionics, a constellation of GPS satellites, and a network of ground stations across the country to transmit an aircraft's position, ground speed, and other data to air traffic controllers. Its coverage area and position accuracy are greater than that of radar, and it can also be used as a more cost effective surveillance solution in remote areas such as over the Gulf of Mexico or in certain mountainous regions.
The FAA has mandated that aircraft operating in most controlled U.S. airspace be equipped for ADS-B Out by January 1, 2020. ADS-B In, which is not mandated, offers additional situation awareness benefits to operators who equip with suitable avionics via in-cockpit display of nearby aircraft.
For airlines, having ADS-B In allows pilots to use enhanced applications such as In-Trail Procedures (ITP) and Interval Management. ITP allows pilots to safely climb or descend with reduced separation on oceanic routes. Interval Management (IM), a key element in future Trajectory Based Operations in the NAS, allows pilots to meet tight time constraints when entering the terminal area in a queue with other arrivals. Avionics standards and certified equipment are available for ITP, with the FAA supporting the operations in oceanic airspace. IM is under development and the FAA is not yet supporting such operations.
Pilots with ADS-B Out and In greatly increase their situation awareness by having real-time traffic in the cockpit. This image shows traffic arriving into Ronald Reagan Washington National Airport from the south on a typical afternoon. (Photo courtesy of ForeFlight)
General aviation operators who equip with 978-megahertz receivers can also benefit from having access to a variety of no-cost flight-information services, including near real-time composite weather radar images, winds, lightning, and terminal weather forecasts. This represents a significant safety and operational enhancement for pilots, most notably improved situation awareness.
ADS-B has been integrated into automation platforms at all 24 en route air traffic control facilities and into more than 100 terminal radar approach control (TRACON) facilities, including the 30 busiest terminal areas, and is being integrated into the remaining 50 terminal areas as their automation platforms are updated. The FAA plans to integrate ADS-B into all TRACON facilities before January 2020.
ADS-B for Airlines
As of January 1, 2018, more than 5,100 U.S.-registered airliners had been equipped with ADS-B, representing about 80 percent of the fleet, and more than 1,700 international air carrier aircraft had equipped.
ADS-B in the Gulf
As a result of a partnership between the United States and Mexico, ADS-B separation services are now available to border-area controllers, providing seamless coverage for air traffic routes across the Gulf of Mexico. Additional ADS-B ground stations in Mexico have enabled the use of more efficient aircraft separation and increased capacity over the Gulf from 75 to about 85 aircraft per hour.
The additional ground infrastructure will save operators a total of $70 million through 2035 by enabling a greater number of gulf flights over the U.S.-Mexican airspace boundary. Increased capacity reduces delays during peak periods, saving aircraft operating costs and passenger time.
For airlines that fly regular routes over the Gulf of Mexico, such as JetBlue, the ADS-B infrastructure means more efficient flights with fewer diversions due to weather, especially with offshore routes. Flights that use a special ADS-B route in the gulf due to thunderstorms or headwinds on legacy routes save an average of 7–11 minutes of flight time and burn less fuel, which saves money and cuts aircraft exhaust emissions compared to flights using traditional routes over land. In partnership with the FAA, United Airlines installed ADS-B in 110 Boeing 737s that operate throughout the NAS, including offshore routes from Houston to the Caribbean and along the U.S. East Coast. The airline is one of many that are installing ADS-B.
ADS-B Over the Oceans
A NextGen capability that can reduce separation between equipped aircraft in often crowded transoceanic airspace is operational. ITP, an ADS-B In application, enables reduced separation between aircraft. ITP allows ADS-B-equipped aircraft to safely climb or descend with separation reduced to as close as 15 nautical miles compared to the normal in-trail separation distance of 30–80 nautical miles or more, depending on equipage capability, enabling pilots of transoceanic flights to access more optimal, fuel-saving altitudes.
Hawaiian Airlines has equipped its entire A330 twin-engine widebody fleet with this capability, and also is equipping its A321neo single-aisle aircraft with ITP.
In addition to potential fuel savings, ITP also enhances pilots' situation awareness. Aircraft equipped with ITP have an ADS-B In display that gives pilots a top-down view of the surrounding airspace. With a better understanding of the complete traffic picture, flight crews can make more-informed requests of air traffic control, with a better chance of getting approval for their occasional ITP climb requests.
In a 2015 FAA report about the benefits of ADS-B and ITP, operators reported that ITP-equipped aircraft saved an average of 86 gallons of fuel per flight compared to non-equipped aircraft.
ADS-B at the Airport
ADS-B also plays an important role in airport operations through the Airport Surface Detection System–Model X (ASDE-X) and Airport Surface Surveillance Capability (ASSC) ground-surveillance systems. These systems combine radar, ADS-B and other data sources to enable controllers to track the surface movement of aircraft and airport ground vehicles, which helps reduce taxiway conflicts and runway incursions. ASDE-X is in place at 35 major airports across the United States. ASSC is operational at San Francisco and Cleveland and will be in place at a total of eight airports by January 2020. With ASDE-X and ASSC, controllers and pilots with ADS-B In and cockpit displays see aircraft and ground vehicles on the airport surface, and on approach and departure paths within 2 miles of the airport.
ADS-B for General Aviation
Aircraft equipage is vital to the success of ADS-B and NextGen. The FAA estimates that between 106,000–167,000 general aviation aircraft may need to equip with ADS-B. Approximately 60,000 aircraft have been equipped with ADS-B Out avionics and are ready for the 2020 mandate.
FAA and industry leaders represented in the Equip 2020 partnership continue to identify barriers delaying operators from equipping with ADS-B Out based on the results of working groups formed in four areas:
- Air carrier equipage
- General aviation equipage
- Education and benefits
- Installation and approvals
Typical prices for general aviation ADS-B Out equipment have dropped significantly, with several models available for less than $2,000 before incentives, not including installation costs. Declining prices have helped address cost concerns that operators may have about equipping, especially for older aircraft. Additionally, from September 2016 through September 2017, the FAA offered a $500 incentive per aircraft owner to help general aviation operators defray ADS-B equipment and installation costs, and to encourage them to equip early. This incentive applied to U.S.-registered, fixed-wing, single-engine piston aircraft on a first-come, first-served basis. About 12,500 general aviation aircraft owners reserved a rebate. The FAA resumed offering these rebates starting October 12, 2018. All 9,792 rebates were reserved as of May 13, 2019.
To support Equip 2020, the FAA launched the Equip ADS-B website to help aircraft operators get a clear explanation of what airspace requires ADS-B, a list of FAA-certified ADS-B equipment, answers to frequently asked questions, and more. Operators may use an automated online tool to validate the performance of their ADS-B installation and receive an ADS-B performance report.
The FAA is leading the development of avionics standards for Interval Management (IM), a suite of applications that use ADS-B In capabilities to precisely manage the controller-assigned spacing between aircraft pairs. IM enables more efficient flight paths through congested airspace, and maximizes airspace and airport utilization. These capabilities will require new avionics, ground automation, decision support systems, and procedures. Budget considerations will dictate when the FAA can afford to field the needed enhancements to air traffic control automation and decision support tools to assist the envisioned IM operations.