NextGen

Thursday, July 18, 2024

The Next Generation Air Transportation System, or NextGen, is an FAA initiative to transform the U.S. National Airspace System (NAS). NextGen programs are now operational-digital communications have supplemented voice communications, navigation and surveillance have transitioned from ground-based to primarily satellite-enabled, and segmented information exchange has advanced to enterprise-level information sharing through a single connection.

Controllers and pilots have enhanced awareness of traffic, which makes flying safer. Improved efficiency and capacity reduce delays, cancellations, fuel consumption, and engine exhaust emissions. NextGen has delivered $10.9 billion in benefits between calendar years 2010 and 2023 from more than 20 NextGen capabilities through more than 200 implementations across the country. The FAA expects the benefits to continue to grow from current and future capabilities and with continued equipping of aircraft by industry.

NextGen modernization also enables a shift from tactical and reactive air traffic control to strategic integrated air traffic management. An overarching FAA goal is Trajectory Based Operations (TBO), an air traffic management concept providing a common understanding of planned aircraft flight paths in three spatial dimensions plus time for all stakeholders. The completed NextGen infrastructure provides a clear path forward for TBO. Expected benefits include improved flight efficiency, increased airspace and airport throughput, and improved operational predictability and flexibility.

Foundational Formation

The FAA built a new infrastructure for the NAS to accommodate the latest technologies. The En Route Automation Modernization (ERAM) system and Standard Terminal Automation Replacement System (STARS) give controllers more productive workstations. The systems also support NextGen with modern software architectures that serve as the foundation for advanced air traffic management capabilities.

ERAM operates at 20 en route centers across the country where controllers handle high-altitude traffic. STARS serves pilots in terminal airspace around airports at more than 200 FAA and Department of Defense (DoD) terminal radar approach control facilities, and 600 FAA and DoD air traffic control towers. For flights over oceans, controllers use the Advanced Technologies and Oceanic Procedures system for their workstations.

Time-based management, which involves the use of flight-specific crossing times at defined points along the flight trajectory, is assisted through the multiple tools embedded in three automated decision support systems: Traffic Flow Management System (TFMS), Time Based Flow Management (TBFM), and Terminal Flight Data Manager (TFDM). These systems enable the transition to TBO.

TFMS is used to optimize airspace capacity and fleet performance as well as the efficiency of individual flights. TFMS helps plan and implement traffic management initiatives, which are used to balance demand with capacity in the NAS during less-than-ideal conditions. The system operates at the Air Traffic Control System Command Center as well as at en route centers and some large terminal radar approach control facilities.

TBFM uses time instead of distance to help controllers sequence air traffic, which makes better use of available capacity and enables delays needed for merging and spacing to be taken at more fuel-efficient altitudes. TBFM operates at all 20 en route centers.

TFDM modernizes control tower equipment and operations. Specifically, TFDM simplifies the sequence of departing aircraft, leading to improved situational awareness and reduced delays. Deployment has started and is scheduled to continue through 2029 to 49 airports.

Automation and decision support systems receive information from many sources. System Wide Information Management (SWIM) provides a single point of access for relevant and reliable aeronautical, flight, weather, and surveillance information in near-real time. SWIM delivers the infrastructure, standards, and services needed to optimize a secure data exchange.

As the digital data-sharing backbone of NextGen, SWIM enables operational excellence and innovation. It delivers the right information to the right people at the right time with greater efficiency, agility, and resiliency to provide a common situational awareness that facilitates collaborative decision-making.

Weather information is of critical interest because of its hazards, and weather is a leading cause of delays. The NextGen Weather Processor (NWP) will establish a common weather processing platform that replaces multiple legacy FAA weather processors and hosts new capabilities. NWP will produce improved weather radar mosaics and predictions that support the best selection of aircraft routing and precise spacing for departing and arriving aircraft, resulting in safer, more efficient, and more predictable NAS operations. Common Support Services-Weather (CSS-Wx) will establish an aviation weather publishing capacity for the NAS, enabling the standardization of weather information and universal access.

Other elements of NextGen are best described by various phases of flight.

Taxi and Takeoff

Data Communications (Data Comm) has revolutionized predeparture communications between air traffic controllers and pilots. Air traffic controllers at 65 airports across the country can issue Data Comm departure clearances to equipped aircraft at the gate and revise them multiple times while an aircraft is taxiing, reducing delays and cancellations. Controllers transmit typed digital clearances that pilots accept with a push of a button on their flight computer, minimizing radio congestion and avoiding incorrectly hearing and reading back a message. Controllers and pilots can spend more time on other tasks.

Automatic Dependent Surveillance-Broadcast (ADS-B) is the satellite-enabled system that replaced ground-based radars as the primary source of aircraft surveillance. ADS-B coverage is available wherever radar coverage exists, as well as in some areas that lack radar coverage, such as Alaska and the Gulf of Mexico. ADS-B uses GPS signals and aircraft avionics to transmit (ADS-B Out) the aircraft's location to ground receivers and properly equipped aircraft. The ground receivers deliver that information to controller screens and surrounding aircraft equipped to receive a signal (ADS-B In). Aircraft flying in a large portion of controlled U.S. airspace must be equipped for ADS-B Out.

Controllers can track aircraft while taxiing and after takeoff with ADS-B. The technology is used for surface surveillance at 35 airports with Airport Surface Detection Equipment, Model X and eight airports with Airport Surface Surveillance Capability. The integration of real-time vehicle and aircraft locations into control tower displays increases controller situational awareness of all activities in the airport movement area, enhancing safety.

Additional NextGen improvements derive from policy changes guided by research.

Wake turbulence is generated from an aircraft in flight. Wake Turbulence Recategorization enables the FAA to safely reduce the distance between various aircraft based on takeoff weight, landing speed, wingspan, and the aircraft's ability to withstand a wake encounter. Consolidated wake turbulence standards have harmonized separation reductions at 93 terminal radar approach control facilities and 330 air traffic control towers, raising efficiency at many constrained airports.

Closely Spaced Parallel Operations (CSPO) refers to the simultaneous departures and approaches of aircraft pairs to airports with parallel runways less than 4,300 feet apart. CSPO can increase airport capacity through reduced separation standards, expanded applications of dependent (when diagonal spacing is required) and independent runway operations, and enabling operations in low-visibility conditions. For instance, the FAA approved a reduced diagonal spacing requirement from 1.5 nautical miles to 1 nautical mile at eight busy airports with runways separated by less than 2,500 feet for simultaneous dependent approaches.

Climb and Cruise

At busy airports after taking off, the predictability and repeatability of Performance Based Navigation (PBN) enables Equivalent Lateral Spacing Operations (ELSO). PBN delivers new, more precise procedures and routes that primarily use satellite-enabled navigation in equipped aircraft. Aircraft fly a PBN area navigation (RNAV) standard instrument departure procedure during ELSO, which increases capacity because more aircraft can safely take off from the same runway during the same period.

At cruising altitudes, PBN routes allow pilots to fly along paths not bound to the location of ground-based navigation aids. The new routes can shorten flying distance, saving time and reducing fuel consumption and emissions.

Data Comm en route services provide digital data exchanges between controllers and pilots during the cruise phase of flight. Instead of having only voice communications available, equipped aircraft can receive and acknowledge some controller instructions - including full route clearances, speed and altitude revisions, and communications transfers - electronically with the push of a button. This capability will be available at all en route centers by 2025.

ADS-B has enabled the FAA to increase efficiency by reducing the separation standard from 5 to 3 nautical miles in some en route airspace below 23,000 feet.

With optional ADS-B In equipment, pilots can access real-time traffic, flight, and weather information that enhances safety. For instance, the ADS-B Traffic Advisory System is a low-cost alerting capability for general aviation intended to reduce the risk of aircraft collisions.

In-Trail Procedures (ITP) is an ADS-B application that reduces the separation between aircraft during oceanic flights. Aircraft equipped with ITP software can fly more often at more fuel-efficient or less-turbulent flight levels. Another potential application of ADS-B is Interval Management, which would enable pilots to increase throughput by better managing spacing between aircraft at cruising altitudes.

Arrival and Approach

Arrival is the first segment of flight down to the runway. RNAV standard arrivals with an optimized profile descent allow an aircraft to descend from cruising altitude with engines at near idle speed. Aircraft can fly longer at more fuel-efficient altitudes and not level off multiple times, which requires pilots to adjust the engine thrust setting. The procedure reduces fuel consumption, engine exhaust emissions, and noise exposure.

For the final leg of flight, Required Navigation Performance (RNP) approach procedures provide a tighter lateral navigation accuracy than RNAV. RNP requires onboard performance monitoring and alerting, and enhances safety when flying near obstacles and terrain.

Established on RNP (EoR) is a separation standard using a PBN instrument approach procedure that reduces flight distance during simultaneous operations at airports with parallel runways, saving time and reducing fuel consumption, emissions, and noise exposure. The FAA approved EoR as a national standard in 2016 for simultaneous independent operations, and it is available at Denver International Airport, George Bush Intercontinental Airport in Houston, and Los Angeles International Airport.

More than 150,000 aircraft in the NAS are equipped to fly a different type of RNP approach procedure using GPS with the Wide Area Augmentation System (WAAS). WAAS-enabled approaches to general aviation airports provide access that would otherwise be unavailable and offer vertical guidance for more stable approaches to the runway.

The FAA is working with industry partners to evaluate the value of ADS-B applications that help pilots and controllers manage spacing between aircraft. Two ADS-B applications have the potential to help pilots during the approach.

CDTI-Assisted Visual Separation (CAVS) takes advantage of the Cockpit Display of Traffic Information (CDTI). After acquiring the traffic to follow by looking out the window, flight crews can rely on CAVS information for continuous visual observation during approaches to the same runway under visual meteorological conditions. CAVS is expected to reduce go-arounds caused by traffic flying too close on the final approach.

CDTI-Assisted Separation on Approach is similar to CAVS except that pilots can acquire the traffic to follow on the CDTI without looking through the window. Pilots also can continue flying at lower ceiling thresholds and with reduced spacing along the approach path during certain weather conditions to enable higher throughput.

Expanded Low Visibility Operations reduced minimum ceilings and runway visual range through a combination of ground equipment and navigation procedures. Another way to improve capacity is with the Enhanced Flight Vision System and Synthetic Vision Guidance System, which are authorized by the FAA to be used when natural vision is restricted. These systems can provide access to airports that would be denied because of low visibility.

Two automated tools available apart from the decision support systems are the Converging Runway Display Aid and Automated Terminal Proximity Alert. Controllers manage the sequence of arrival flows on converging or intersecting runways with the display aid, which operates at nine busy airports and enhances an airport's throughput under certain conditions. The proximity alert tool, which is available at 14 terminal radar approach control facilities, informs controllers of gaps so they can tell pilots to adjust their speed or direct them on a shorter path to the runway.

Non-Traditional Operations

Part of NextGen is accommodating the growth of non-traditional forms of aviation operating at different altitudes. The FAA is developing traffic management concepts and evaluating technologies to safely incorporate unmanned aircraft systems (UAS), spacecraft, and other emerging aircraft into the NAS without disrupting existing traffic.

DroneZone, Low Altitude Authorization and Notification Capability, Airborne Collision Avoidance System, and RemoteIdentification are technologies supporting the growth of UAS traffic and UAS integration into the NAS in different operating environments. The FAA has published concepts of operation for UAS traffic management and urban air mobility (UAM), a subset of advanced air mobility, that take on the challenge of expanding UAS and UAM operations in the NAS.

The increased application of NextGen technologies also enables the FAA to integrate space operations safely and efficiently into the NAS, clearing the way for routine access to low Earth orbit and beyond for government and commercial users. The Space Data Integrator and Hazard Risk Assessment and Management software will increase overall air traffic management efficiency and safety for space operations, reducing airspace closure times and providing better situational awareness to affected controllers.

Beyond NextGen

With NextGen firmly in place, the FAA is beginning to pivot to a new iteration of airspace modernization. The FAA's vision is for a future airspace system that will be interconnected on communication networks, flexible to accommodate diverse operations, and include all stakeholders. Collaboration will be foremost within traffic management services that integrate the increased number and variety of aircraft and new missions into the NAS.