Air Traffic Management Technology Demonstration 1 (ATD1)

Crowded Skies

At any given moment, up to 5,000 aircraft crowd U.S. skies. In 2010, the National Airspace System (NAS) managed the progress of nearly 10 million flights. Such high air traffic demand, operating with procedures that were largely in place from the earliest days of commercial aviation, does not always result in the most efficient or coordinated operations. As a result, the air transportation system often experienced significant delays and lost productivity, and produced greater amounts of noise pollution, carbon dioxide, and other greenhouse gas emissions than if operations were more efficient. As air traffic demand is projected to double by 2030, our old air traffic control system will be further strained and the environment adversely affected.

Improving the efficiency of the terminal area, which is the volume of airspace surrounding airports to a radius of about 50 miles, is an especially complex task due to operating characteristics that are quite distinct from the en route environment. Terminal area controllers manage both ascending and descending aircraft, more frequent turns, a wider range of separation standards, as well as terrain and increased traffic density within shorter time horizons.

NextGen: The Airspace System of the Future

NASA collaborated with the Federal Aviation Administration (FAA) and other industry partners to develop several advanced automation tools that provided air traffic controllers, pilots, and other airspace users with more accurate real-time information about the nation’s traffic flow, weather, and routing. The greater precision of this information was a key enabler of the Next Generation Air Transportation System (referred to as NextGen). NextGen is a comprehensive transformation of the NAS, which will be safer, more reliable and more efficient, and will reduce the impact of aviation on the environment. The transition to NextGen was vital to improving system performance, meeting continued growth in air traffic, and increasing the Nation’s mobility to support economic progress. The ATM Technology Demonstration-1 (ATD-1) showcased an integrated set of NextGen technologies that provided an efficient arrival solution for managing aircraft beginning from just prior to top-of-descent and continuing down to the runway.

These technologies were:

Automatic Dependent Surveillance – Broadcast (ADS-B)
Area Navigation (RNAV) Arrival Routes
Optimized Profile Descent (OPD) Procedures
Terminal Metering
Flight Deck Interval Management (FIM)
Controller Managed Spacing (CMS) tools

These ATM technologies were tested separately and each has demonstrated throughput, delay, and/or fuel-efficiency benefits. Together, the technologies demonstrated the feasibility of high throughput of efficient arrival operations during peak traffic conditions in the terminal area. Simply put, the integration of these terminal arrival tools allowed arrival aircraft to safely fly closer together on more fuel-efficient routes to increase capacity, reduce delay, and minimize fuel burn, noise, and greenhouse gas emissions.

Using the ATD-1 technologies, both pilots and controllers have more accurate and timely information and advisories, thus reducing the need for extensive coordination and negotiation between them to achieve more efficient operations. Terminal Metering (based on precision scheduling enhancements to the Traffic Management Advisor [TMA]) determines an arrival schedule based on airport conditions, airport capacity, required spacing, and weather conditions and utilizes new, more direct RNAV routes that extend from en route airspace and continue through terminal airspace to the runway. The schedule, determined well in advance of when it is executed, is communicated to both controllers and flight crews. Flight crews will know their intended flight path, which aircraft they ought to be following, and the desired spacing interval at certain points along their designated RNAV route to reach the destination airport safely and on schedule. Controllers will no longer have to make tactical, last second decisions concerning merges and arrival slots, and will not likely need to provide as many interventions as they did in busy traffic conditions.

To achieve the precise schedule set by TMA, some flight decks are now equipped with sophisticated onboard avionics. Flight Deck Interval Management (FIM) tools provide guidance to pilots on whether to speed up or slow down to precisely merge and space their aircraft relative to others. The FIM tools calculate speed advisories using information provided by ADS-B technology aboard the aircraft that is more accurate than traditional radar. Flight crews are able to make finer adjustments to their speed and react more quickly to achieve ideal spacing. The tighter control enabled by FIM reduce excess spacing buffers and result in higher terminal throughput.

NextGen leveraged the ADS-B infrastructure that was implemented by the FAA. ADS-B uses a Global Positioning Satellite (GPS) System receiver aboard the aircraft to determine that aircraft’s exact position. The ADS-B system combines the position data with the aircraft’s identifier, course, speed, and altitude, then continuously broadcasts the information to other ADS-B equipped aircraft flying in the area. The information is also broadcast to a network of ADS-B ground stations, which in turn feed controller displays and other air traffic control technologies. ADS-B information provides greater situational awareness to flight crews and allows spacing responsibility to be shifted from the ground to the air, alleviating controller workload.

For aircraft not equipped with FIM and ADS-B technologies in the mid-term, new Controller Managed Spacing (CMS) decision support tools provide controllers with the information needed to properly space aircraft to meet terminal metering schedules created by TMA. CMS display enhancements indicate to the controller where an aircraft is scheduled to be along its RNAV route, and calculate the speed advisories needed to maintain this schedule.

Optimized Profile Descent (OPD) Procedures allow aircraft to fly a continuous, gliding descent at low engine power. Contrary to the typical “dive and drive” procedures in which aircraft fly powered constant-altitude segments in a step-down fashion, OPDs are considered “green descents” because they reduce fuel consumption, environmental emissions, and noise pollution. Decision support tools synchronize the descents of all arrival aircraft and advise controllers of the RNAV route and speed profile needed so that each can maintain an efficient descent and remain properly separated from preceding and following aircraft. OPD enhancements make green descents possible during more traffic conditions, even heavy congestion, all while satisfying terminal metering schedules and achieving precise in-trail spacing to maximize terminal throughput.

The more orderly, precise, and direct traffic flow enabled by the ATD-1 technologies make the National Airspace System more predictable overall. This will allow airspace users to better respond to unexpected delays caused by convective weather and other airspace constraints. Instead of tactically absorbing delay close to the airport, where it is traditionally handled using path stretching and holding patterns, subtle variations in speed can now be applied from cruise altitude to landing to distribute small amounts of delay over a longer portion of the flight. Strategically absorbing delay in this way relieves congestion that would normally build up near the airport, further increasing the efficiency of terminal area traffic flows.

Additional Steps to Achieve NextGen

ADS-B now serves as the surveillance source for the NAS. To further the widespread implementation of ADS-B, the Aviation Rulemaking Committee recommended that demonstrations, such as ATD-1, should be used to help both the government and industry evaluate potential benefits and costs of such implementation, as well as to understand the necessary equipment standards, aircraft certification guidance, and operational approvals. NASA teamed with the FAA and other industry partners to demonstrate the capabilities of integrated terminal area scheduling with an operational field trial in 2014-2015. The goals of the field demonstration were to validate the benefits of the terminal area integrated arrival solution, system interoperability, and requirements for technology transfer.

The first phase of demonstration activities involved development of prototype systems, integration of all of the technologies, and initial human-in-the-loop simulations in NASA laboratories. The next phase involved development of the demonstration systems, follow-on simulations using FAA facilities and personnel, flight testing of avionics, and shadow testing of the integrated system. The last phase finalized the demonstration plans and culminated in a field trial in a controlled, yet realistic operational environment at a major U.S. airport.

ATD-1 was truly collaborative endeavor between government and industry. It involved the support, cooperation, and financial commitment of NASA and the FAA, as well as key industry and commercial aviation partners. NASA foundational research and technologies in terminal area scheduling, controller decision support tools, and flight deck automation actively leveraged the FAA’s NextGen infrastructure. The participation of airspace users, avionics and aircraft manufacturers, and system integrators helped enable these integrated terminal area ATM technologies to be evaluated in an operational environment. The demonstration was the next major step in NASA’s NextGen research and development process, and it brought us one step closer to realizing the air transportation system of the future.

Benefits of ATD-1’s Integrated Terminal Area Scheduling Technologies:

System Benefits