Flight Management System

A flight management system (FMS) is a flight computer system that uses a large database to allow routes to be preprogrammed and fed into the system by means of a data loader. The system is constantly updated with respect to position accuracy by reference to conventional navigation aids, inertial reference system technology, or the satellite global positioning system. The sophisticated program and its associated database ensures that the most appropriate navigation aids or inputs are automatically selected during the information update cycle. A typical FMS provides information for continuous automatic navigation, guidance, and aircraft performance management, and includes a control display unit (CDU). [Figure 1-15]

FMS Control Display Unit. This depicts an aircraft
established on the Atlantic City, NJ, RNAV (GPS) Rwy 13
instrument approach procedure at the Atlantic City
International Airport, KACY. The aircraft is positioned at the
intermediate fix UNAYY inbound on the 128 degree magnetic
course, 5.5 nautical miles from PVIGY, the final approach fix.

Avionics and Instrumentation

The proliferation of advanced avionics and instrumentation has substantially increased the capabilities of aircraft in the IFR environment.

National Airspace System Plans

FAA planners’ efforts to devise a broad strategy to address capacity issues resulted in the Operational Evolution Plan (OEP)—the FAA’s commitment to meet the air transportation needs of the U.S. for the next ten years.

To wage a coordinated strategy, OEP executives met with representatives from the entire aviation community— including airlines, airports, aircraft manufacturers, service providers, pilots, controllers, and passengers. They agreed on four core problem areas:

•  Arrival and departure rates.
• En route congestion.
• Airport weather conditions.
• En route severe weather.

The goal of the OEP is to expand capacity, decrease delays, and improve efficiency while main taining safety and security. With reliance on the strategic support of the aviation community, the OEP is limited in scope, and only contains programs to be accomplished over a ten-year period. Programs may move faster, but the OEP sets the minimum schedule. Considered a living document that matures over time, the OEP is continually updated as decisions are made, risks are identified and mitigated, or new solutions to operational problems are discovered through research.

An important contributor to FAA plans is the Performance-Based Operations Aviation Rulemaking Committee (PARC). The objectives and scope of PARC are to provide a forum for the U.S. aviation community to discuss and resolve issues, provide direction for U.S. flight operations criteria, and produce U.S. consensus positions for global harmonization.

The general goal of the committee is to develop a means to implement improvements in operations that address safety, capacity, and efficiency objectives, as tasked, that are consistent with international implementation. This committee provides a forum for the FAA, other government entities, and affected members of the aviation community to discuss issues and to develop resolutions and processes to facilitate the evolution of safe and efficient operations.

Current efforts associated with NAS modernization come with the realization that all phases must be integrated. The evolution to an updated NAS must be well orchestrated and balanced with the resources available. Current plans for NAS modernization focus on three key categories:

• Upgrading the infrastructure.

• Providing new safety features.

• Introducing new efficiency-oriented capabilities into the existing system.

It is crucial that our NAS equipment is protected, as lost radar, navigation signals, or communications capabilities can slow the flow of aircraft to a busy city, automation system accurate aircraft position informawhich in turn, could cause delays throughout the entire tion. This more accurate information will be used to region, and possibly, the whole country. improve the efficiency of the system—the third cate gory of modernization goals.

The second category for modernization activities focuses on upgrades concerning safety. Although we cannot control the weather, it has a big impact on the NAS. Fog in San Francisco, snow in Denver, thunderstorms in Kansas, wind in Chicago; all of these reduce the safety and capacity of the NAS. Nevertheless, great strides are being made in our ability to predict the weather. Controllers are receiving better information about winds and storms, and pilots are receiving better information both before they take off and in flight—all of which makes flying safer. [Figure 1-4]

Another cornerstone of the FAA’s future is improved navigational information available in the cockpit. The Wide Area Augmentation System (WAAS) initially became operational for aviation use on July 10, 2003. It improves conventional GPS signal accuracy by an order of magnitude, from about 20 meters to 2 meters or less.

Moreover, the local area augmentation system (LAAS) is being developed to provide even better accuracy than GPS with WAAS. LAAS will provide localized service for final approaches in poor weather conditions at major airports. This additional navigational accuracy will be available in the cockpit and will be used for other system enhancements. More information about WAAS and LAAS is contained in Chapters 5 and 6.

The Automatic Dependent Surveillance (ADS) system, currently being developed by the FAA and several airlines, enables the aircraft to automatically transmit its location to various receivers. This broadcast mode, commonly referred to as ADS-B, is a signal that can be received by other properly equipped aircraft and ground based transceivers, which in turn feed the Other key efficiency improvements are found in the deployment of new tools designed to assist the controller. For example, most commercial aircraft already have equipment to send their GPS positions automatically to receiver stations over the ocean. This key enhancement is necessary for all aircraft operating in oceanic airspace and allows more efficient use of airspace. Another move is toward improving text and graphical message exchange, which is the ultimate goal of the Controller Pilot Data Link Communications (CPDLC) Program.

In the en route domain, the Display System Replacement (DSR), along with the Host/Oceanic Computer System Replacement (HOCSR) and Eunomia projects, are the platforms and infrastructure for the future. These provide new displays to the controllers, upgrade the computers to accept future tools, and provide modern surveillance and flight data processing capabilities. For CPDLC to work effectively, it must be integrated with the en route controller’s workstation.

Brief History of the National Airspace System (NAS)

About two decades after the introduction of powered flight, aviation industry leaders believed that the airplane would not reach its full commercial potential without federal action to improve and maintain safety standards. In response to their concerns, the U.S. Congress passed the Air Commerce Act of May 20, 1926, marking the onset of the government’s hand in regulating civil aviation. The act charged the Secretary of Commerce with fostering air commerce, issuing and enforcing air traffic rules, licensing pilots, certifying aircraft, establishing airways, and operating and maintaining aids to air navigation. As commercial flying increased, the Bureau of Air Commerce— a division of the Department of Commerce—encouraged a group of airlines to establish the first three centers for providing ATC along the airways. In 1936, the bureau took over the centers and began to expand the ATC system. [Figure 1-2] The pioneer air traffic controllers used maps, blackboards, and mental calculations to ensure the safe separation of aircraft traveling along designated routes between cities.

On the eve of America’s entry into World War II, the Civil Aeronautics Administration (CAA)—charged with the responsibility for ATC, airman and aircraft certification, safety enforcement, and airway development— expanded its role to cover takeoff and landing operations at airports. Later, the addition of radar helped controllers to keep abreast of the postwar boom in commercial air transportation.

Following World War II, air travel increased, but with the industry's growth came new problems. In 1956 a midair collision over the Grand Canyon killed 128 people. The skies were getting too crowded for the existing systems of aircraft separation, and with the introduction of jet airliners in 1958 Congress responded by passing the Federal Aviation Act of 1958, which transferred CAA functions to the FAA (then the Federal Aviation Agency). The act entrusted safety rulemaking to the FAA, which also held the sole responsibility for developing and maintaining a common civil-military system of air navigation and air traffic control. In 1967, the new Department of Transportation (DOT) combined major federal transportation responsibilities, including the FAA (now the Federal Aviation Administration) and a new National Transportation Safety Board (NTSB).

By the mid-1970s, the FAA had achieved a semi-automated ATC system based on a marriage of radar and computer technology. By automating certain routine tasks, the system allowed controllers to concentrate more efficiently on the task of providing aircraft separation. Data appearing directly on the controllers’ scopes provided the identity, altitude, and groundspeed of aircraft carrying radar beacons. Despite its effectiveness, this system required continuous enhancement to keep pace with the increased air traffic of the late 1970s, due in part to the competitive environment created by airline deregulation.

To meet the challenge of traffic growth, the FAA unveiled the NAS Plan in January 1982. The new plan called for more advanced systems for en route and terminal ATC, modernized flight service stations, and improvements in ground-to-air surveillance and communication. Continued ATC modernization under the NAS Plan included such steps as the implementation of Host Computer Systems (completed in 1988) that were able to accommodate new programs needed for the future.[Figure 1-3]

In February 1991, the FAA replaced the NAS Plan with the more comprehensive Capital Investment Plan (CIP), which outlined a program for further enhancement of the ATC system, including higher levels of automation as well as new radar, communications, and weather forecasting systems. One of the CIP’s programs currently underway is the installation and upgrading of airport surface radars to reduce runway incursions and prevent accidents on airport runways and taxiways. The FAA is also placing a high priority on speeding the application of the GPS satellite technology to civil aeronautics. Another notable ongoing program is encouraging progress toward the implementation of Free Flight, a concept aimed at increasing the efficiency of high-altitude operations.

Airport Surveillance Radar

The direction and coordination of IFR traffic within specific terminal areas is delegated to airport surveillance radar (ASR) facilities. Approach and departure control manage traffic at airports with ASR. This radar system is designed to provide relatively short-range coverage in the airport vicinity and to serve as an expeditious means of handling terminal area traffic. The ASR also can be used as an instrument approach aid. Terminal radar approach control facilities (TRACONs) provide radar and nonradar services at major airports. The primary responsibility of each TRACON is to ensure safe separation of aircraft transitioning from departure to cruise flight or from cruise to a landing approach.

Most ASR facilities throughout the country use a form of automated radar terminal system (ARTS). This system has several different configurations that depend on the computer equipment and software programs used. Usually the busiest terminals in the country have the most sophisticated computers and programs. The type of system installed is designated by a suffix of numbers and letters. For example, an ARTS-IIIA installation can detect, track, and predict primary, as well as secondary, radar returns. [Figure 1-13]

ARTS-III Radar Display

On a controller’s radar screen, ARTS equipment automatically provides a continuous display of an aircraft’s position, altitude, groundspeed, and other pertinent information. This information is updated continuously as the aircraft progresses through the terminal area. To gain maximum benefit from the system, each aircraft in the area must be equipped with a Mode C altitude encoding transponder, although this is not an operational requirement. Direct altitude readouts eliminate the need for time consuming verbal communication between controllers and pilots to verify altitude. This helps to increase the number of aircraft that may be handled by one controller at a given time.

The FAA has begun replacing the ARTS systems with newer equipment in some areas. The new system is called STARS, for Standard Terminal Automation Replacement System. STARS is discussed in more detail later in this chapter.

Standard Terminal Automation Replacement System

The FAA has begun modernizing the computer equipment in the busiest terminal airspace areas. The newer equipment is called STARS, for Standard Terminal Automation Replacement System. The system's improvements will enhance safety while reducing delays by increasing system reliability and lowering life- cycle operating and maintenance costs. STARS also will accommodate the projected growth in air traffic and provide a platform for new functions to support FAA initiatives such as Free Flight. STARS offers many advantages, including an open architecture and expansion capability that allow new software and capacity to be added as needed to stay ahead of the growth in air traffic. Under the first phase of terminal modernization, STARS is being deployed to 47 air traffic control facilities. As of July 2005, 37 FAA and 22 Department of Defense sites were fully operational with STARS. The first phase is expected to be complete in fiscal year 2007. By then, STARS will be operational at 18 of the FAA's 35 most critical, high-volume airports, which together handle approximately 50 percent of air traffic. STARS consists of new digital, color displays and computer software and processors that can track 435 aircraft at one time, integrating six levels of weather information and 16 radar feeds.

For the terminal area and many of the towers, STARS is the key to the future, providing a solid foundation for new capabilities. STARS was designed to provide the software and hardware platform necessary to support future air traffic control enhancements.

ATC Facilities

FAA figures show that the NAS includes more than 18,300 airports, 21 ARTCCs, 197 TRACON facilities, over 460 air traffic control towers (ATCTs), 58 flight service stations and automated flight service stations (FSSs/AFSSs), and approximately 4,500 air navigation facilities. Several thousand pieces of maintainable equipment including radar, communications switches, ground-based navigation aids, computer displays, and radios are used in NAS operations, and NAS components represent billions of dollars in investments by the government. Additionally, the aviation industry has invested significantly in ground facilities and avionics systems designed to use the NAS. Approximately 47,000 FAA employees provide air traffic control, flight service, security, field maintenance, certification, system acquisition, and other essential services.

Differing levels of ATC facilities vary in their structure and purpose. Traffic management at the national level is led by the Command Center, which essentially “owns” all airspace. Regional Centers, in turn, sign Letters of Agreement (LOAs) with various approach control facilities, delegating those facilities chunks of airspace in which that approach control facility has jurisdiction. The approach control facilities, in turn, sign LOAs with various towers that are within that airspace, further delegating airspace and responsibility. This ambiguity has created difficulties in communication between the local facilities and the Command Center. However, a decentralized structure enables local flexibility and a tailoring of services to meet the needs of users at the local level. Improved communications between the Command Center and local facilities could support enhanced safety and efficiency while maintaining both centralized and decentralized aspects to the ATC system.

Flow Control

ATC provides IFR aircraft separation services for NAS users. Since the capabilities of IFR operators vary from airlines operating hundreds of complex jet aircraft to private pilots in single engine, piston-powered airplanes, the ATC system must accommodate the least sophisticated user. The lowest common denominator is the individual controller speaking to a single pilot on a VHF voice radio channel. While this commonality is desirable, it has led to a mindset where other opportunities to interact with NAS users have gone undeveloped. The greatest numbers of operations at the 20 busiest air carrier airports are commercial operators (airlines and commuters) operating IFR with some form of ground-based operational control. Since not all IFR operations have ground-based operational control, very little effort has been expended in developing ATC and Airline Operations Control Center (AOC) collaboration techniques, even though ground-based computer-to-computer links can provide great data transfer capacity. Until the relatively recent concept of Air Traffic Control-Traffic Flow Management (ATC-TFM), the primary purpose of ATC was aircraft separation, and the direct pilot-controller interaction was adequate to the task. Effective and efficient traffic flow management now requires a new level of control that includes the interaction of and information transfer among ATC, TFM, AOCs, and the cockpit. [Figure 1-17]

Flow Control Restriction

As the first step in modernizing the traffic flow management infrastructure, the FAA began reengineering traffic flow management software using commercial off-the-shelf products. In FY 1996, the FAA and NASA collaborated on new traffic flow management research and development efforts for the development of collaborative decision making tools that will enable FAA traffic flow managers to work cooperatively with airline personnel in responding to congested conditions. Additionally, the FAA provided a flight scheduling software system to nine airlines.

Surveillance Systems

Surveillance systems are set up to enable the ATC system to know the location of an aircraft and where it is heading. Position information from the surveillance system supports many different ATC functions. Aircraft positions are displayed for controllers as they watch over the traffic to ensure that aircraft do not violate separation criteria. In the current NAS, surveillance is achieved through the use of long-range and terminal radars. Scanning the skies, these radars return azimuth and slant range for each aircraft that, when combined with the altitude of the aircraft broadcast to the ground via a transceiver, is transformed mathematically into a position. The system maintains a list of these positions for each aircraft over time, and this time history is used to establish short-term intent and short-term conflict detection. Radars are expensive to maintain, and position information interpolated from radars is not as good as what the aircraft can obtain with SATNAV. ADS-B technology may provide the way to reduce the costs of surveillance for air traffic management purposes and to get the better position information to the ground.

New aircraft systems dependent on ADS-B could be used to enhance the capacity and throughput of the nation’s airports. Electronic flight following is one example: An aircraft equipped with ADS-B could be instructed to follow another aircraft in the landing pattern, and the pilot could use the on-board displays or computer applications to do exactly that. This means that visual rules for landing at airports might be used in periods where today the airport must shift to instrument rules due to diminishing visibility. Visual capacities at airports are usually higher than instrument ones, and if the airport can operate longer under visual rules (and separation distances), then the capacity of the airport is maintained at a higher level longer.