WO2002099769A1 - Air traffic management system and method - Google Patents

Air traffic management system and method Download PDF

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Publication number
WO2002099769A1
WO2002099769A1 PCT/US2002/016905 US0216905W WO02099769A1 WO 2002099769 A1 WO2002099769 A1 WO 2002099769A1 US 0216905 W US0216905 W US 0216905W WO 02099769 A1 WO02099769 A1 WO 02099769A1
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WIPO (PCT)
Prior art keywords
aircraft
airspace
flight
delay
traffic
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PCT/US2002/016905
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French (fr)
Inventor
Carl Dean
Robert W. Schwab
John A. Brown
Aslaug Haraldsdottir
David L. Allen
Richard L. Wurdack
Paul A. VAN TULDER
David W. Massy-Greene
Edward J. Porisch
David A. Nakamura
Anthony W. Warren
Jeffrey L. Aimar
Monica S. Alcabin
Kathleen Pirotte
Mary Nakasone
Gary H. Wood
Michael L. Ulrey
Arek Shakarian
Ramprasad S. Krishnamachari
Steven H. Glickman
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The Boeing Company
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Publication of WO2002099769A1 publication Critical patent/WO2002099769A1/en

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    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G5/00—Traffic control systems for aircraft, e.g. air-traffic control [ATC]
    • G08G5/0043—Traffic management of multiple aircrafts from the ground

Definitions

  • the present invention relates to an air traffic management system and to a method for controlling aircraft in an airspace to assure appropriate and safe spacing (i.e., "separation assurance").
  • GCNSS Global Communication, Navigation and Surveillance System
  • Boeing is developing an Air Traffic Management (ATM) system that will dramatically increase capacity, improve safety, and remain affordable for those who use the system.
  • the system should reduce the number of delays as well as the duration of any delays that are required. Such delays are frequently the result of weather at airports or on congested routes within the controlled airspace.
  • Creating an air traffic system that is viable well into the future will require a fundamental change to how the system operates.
  • the solution will employ sophisticated software and satellite-based communication, navigation and/or surveillance (CNS) technology.
  • controllers gain access to information commonly stored in the flight management computers (FMCs) of transport airplanes to learn the ture position of each airplane under control and its intended trajectory.
  • the controllers integrate this information into the other information, like ground radar and weather, upon which they rely for making control decisions, using air traffic control computers (ATCs).
  • ATCs air traffic control computers
  • the Figure shows a schematic representation of a preferred two-way communication network between airplanes and air traffic controllers to achieve the desired air traffic control improvements of the present invention.
  • Phase 2 Traj ectory-B ased Flight Planning 51 6.3
  • Phase 3 Trajectory-Based Separation Management 53
  • Airspace System Requirements describes the main requirements for a functional ATM system.
  • the key issues are safety, capacity, delay management, access, affordability, and collaborative planning. These elements are valued differently by the stakeholders of the existing system, and these differences must be reconciled to move ahead with NAS reform.
  • the Operational Concept discusses the ATM system of today, providing a context for a discussion of the concept for tomorrow.
  • the future concept which is the basis of the present invention includes the interrelated elements of flow management, traffic management, flight management, airspace management, and airport surface management.
  • Section 4 describes some of the features of Boeing's baseline concept, and a key subsection compares and contrasts the Boeing concept with the system of today, and with the NAS Operational Evolution Plan (developed by MITRE for the FAA).
  • GCS Global Communication, Navigation and Surveillance System
  • C Control
  • N Navigation
  • S Surveillance
  • GNSS Global Communication, Navigation and Surveillance System
  • Such a system will extend the functionality of GPS-based navigation to incorporate enhanced Position, Velocity and Time services, as well as adding important new communication and surveillance functions for a completely integrated ATM operating environment.
  • Economic Benefits (Section 6) makes a preliminary attempt to assess the benefits of Boeing's new operational concept to the stakeholders. This section defines 8
  • the section explains the manner in which the forecasted benefits are derived, using established industry sources.
  • the type of weather delays inflicted upon the NAS are described in some detail, with percentage of delay ascribed to each type.
  • the projected benefits are summarized for each proposed operational enhancement, and specified in Net Present Value terms.
  • Performance Requirements expands the requirements identified in Section 3 into technical performance requirements for separation assurance and flow management. This section provides the lion's share of the technical performance criteria that must be met by any future ATM concept. Performance criteria for communication, navigation and surveillance are discussed in the en route and terminal area environments.
  • Stakeholder Impact (Section 8) identifies the primary users and owners of the NAS, and describes the ways in which each stakeholder is affected by the proposed operational enhancements. Avionics for commercial airlines are described in some detail. Information is provided for other stakeholders such as general aviation, military, business aviation, airports, and air traffic service providers.
  • Transition Planning Considerations (Section 9) identifies various challenges to implementing a new operational concept for the NAS.
  • a large, complex, highly integrated heritage system such as today's NAS is not easily converted to something new.
  • the vital transition issues must be approached in tandem rather than individually.
  • This section describes issues of equipment transition, operational transition, institutional transition, and personnel transition (training and cost factors).
  • Various types of training are considered critical for the successful transition to a new operational concept.
  • the Boeing system will provide trajectory-based separation of airplanes 10 in an airspace, relying on sharing of information commonly programmed today into flight management computers (FMCs) 12 on commercial transport aircraft. Little additional (new) data is required.
  • the Boeing system simply provides access to this existing information to the planning computers 14 of the air traffic controllers 16. Basically, the trajectory information defines the path on which the airplane intends to fly.
  • the system provides a robust communication network, especially providing near real-time, accurate weather data 18 to the aircraft and the controllers. Capacity in the airspace is increased by simplifying the airspace and relying on the trajectories together with accurate monitoring of the true position of the aircraft using GPS (the Global Positioning System). Controllers know where the planes actually are and where they intend to go.
  • GPS Global Positioning System
  • Communication likely will relay transmission through a constellation of satellites 20, thereby ensuring that information can be provided around the world or anywhere in the airspace without significant ground stations or ground infrastructure 22.
  • the satellite implementation is, perhaps, more important, then, for under- or developing countries which lack such ground-based infrastructure, but it should also benefit the US going forward.
  • the system is readily accessible to commercial and general aviation.
  • the controllers also have data from radar 24.
  • the NAS is one of the largest systems in the world. It is made up of enroute centers, terminal control centers, airports, ground navigation aids, space-based components, thousands of airplanes, and the people to operate them. The system operates safely, but recent performance indicates that it may be reaching saturation. This fact represents a challenge for changing the system. Two earlier changes provided a paradigm change for the system. The capacity constraints of the system indicate it is time for another paradigm change. Over 65% of the transport category airplanes operating in scheduled service in the NAS currently have the ability to provide controllers with high accuracy, high 10
  • GNSS Global Navigation Satellite System
  • D Airspace A volume of space around an air traffic control operation. Every aircraft flies through various airspaces on any given flight. It flies from the control of one air traffic control operation to the control of an adjoining one.
  • D Arc. Air Traffic Control. A service operated by appropriate authority to promote the safe, orderly and expeditious flow of air traffic. 11
  • D ATM Air Traffic Management -All facilities and services used to plan, manage and control air traffic
  • D CNS Communication, Navigation and Surveillance. Refers to the services used to support air traffic management. These include all CNS services that operate from aircraft to aircraft, aircraft to ground, and ground to ground.
  • D CNS/ATM The combined system of Air Traffic Management and the Communication, Navigation and Surveillance support services.
  • D NAS National Airspace System. The common network of United States-controlled airspace, air navigation facilities, equipment and services, airports or landing areas.
  • D TRACON Terminal Radar Approach Control. A terminal air traffic control facility that uses radar and non-radar capabilities to provide approach control services to aircraft arriving, departing, or transiting airspace controlled by the facility.
  • the current ATC system is fundamentally unchanged from the time that radar was introduced. Although use of computers, active transponders, and modern color displays have improved the presentation of data for the air traffic controllers, the controllers' job is essentially the same.
  • the controllers have to manage aircraft in their sectors based on their individual skills and experience. While there has been a great deal of research into decision aids for en route controllers, installation of these tools has been limited. To deal with congestion, airspace has been resectorized into smaller sectors, and more controllers have been added. There is a limit to how small a sector can be effectively managed, as well as the increased workload and complexity entailed by passing aircraft between sectors more often. Increasing controller positions is not a viable long-term option in the current system. There are problems and limitations in the terminal area that need to be addressed as well: 13
  • a limiting factor for advanced surveillance is the extent of aircraft equipage. Support of advanced communications (e.g. data link applications and transmission media) and automatic position reporting is strictly voluntary today. Until a significant percentage of the aircraft are equipped, the full advantages to be gained from those upgrades will not be achieved.
  • the systemic problems today that may be limiting capacity include: D Limitations in controller ability to handle more than about 30 aircraft due to voice congestion on a single Very High Frequency (VHF) channel
  • the current ATC system can be characterized as one prone to delays due to safety-related issues (e.g. aircraft proximity to one another in various phases of flight; surface movement; operations in weather-impacted areas). Projections for future growth will place more of these demands on the system. 2.2 Historical Perspective
  • VFR Visual Flight Rules
  • the Air Commerce Act of 1926 provided oversight of testing and licensing of pilots and crews, issuing certificates of airworthiness and registration numbers for the aircraft, and producing maps and charts. It also provided for building '"lighted" airways with lights placed on the ground at regular intervals to support night flying. Controllers Introduced
  • Controllers were added at airports as traffic increased to regulate takeoffs and landings, normally relying on colored flags to communicate with the pilots. Light guns were soon added to allow the controllers to more accurately point to specific aircraft, using different combinations of colors and steady or flashing lights to convey instructions to the pilots. This practice had limited usefulness since the pilots did not have the ability to acknowledge any of the instructions. Two-Way Communication Established
  • Radio use was instituted in the early 1930s. Radio equipage was a concern due to weight, size, and power requirements, especially for operators of smaller aircraft. Even if equipped, pilots were under no obligation to establish radio communication with controllers. The development of aircraft navigation instrumentation supported flights in weather conditions that would have precluded flights a few years earlier. With more 15
  • Air Traffic Control Units were established in 1935 to assist in separation of aircraft operating on federal airways. Operated by four airlines, these centers used flight plan information and pilot position reports to manually track aircraft and to advise pilots when potential conflicts were detected. Aircraft operated primarily under existing VFR. There was no legal obligation to use the ATCUs, and there were few aircraft requiring their advice (that were not associated with the sponsor airlines) that would operate in Instrument Flight Rules (IFR) conditions. By 1937, the lack of a legal requirement to file flight plans, the issue of the controller's legal authority, and perceived (if not real) favoritism of the controllers to the airlines that employed them led to transfer of the ATCUs to the Department of Commerce, which re-established the centers as Air Traffic Control Stations (ATCSs). In 1938, the Department of Commerce became the licensing authority for all civilian controllers, both in the centers and the airport towers. Engine Technology Leads to Bigger Aircraft
  • Secondary radars were introduced not only to aid long-range detection (which is difficult with primary radars), but also to provide target identification on the scope.
  • the evolution of secondary radars and the ability to support data tags on the radar scope eliminated the need for primary radars in the en route phase. (Primary radars are still needed in the terminal area to support critical approach and landing operations.)
  • radar displays with on-screen alphanumeric character labels allowed aircraft ID to be displayed with the target. Further improvements in transponders allowed the aircraft to return altitude and identification data that could be displayed for the controllers as well.
  • the correlation of radar ID with flight plan data in the form of data tags was probably the most significant aspect of first generation automation systems, e.g. ARTS and HOST. This proved to be a significant step forward in the use of computers to support ATC functions.
  • MIT Miles-in-trail
  • the NAS already has one of the lowest hull loss rates of any system in the world. This current rate, however, cannot be considered the target value for the future NAS; as traffic volume increases, the rate must be lowered to avoid an increase in total number of hull losses.
  • the 1997 National Civil Aviation Review Commission report stated that based on current traffic projections a major hull loss would occur somewhere in the world every 7-10 days by 2010. The new architecture must address the prime contributors to the accident rate. Controlled Flight Into Terrain (CFIT) remains a prime contributor. While significant action has been taken by aircraft manufacturers by installing an Enhanced Ground Proximity Warning System (EGPWS), more significant changes to the airspace and to procedure design can be done to further reduce this prime contributor to hull losses.
  • EGPWS Enhanced Ground Proximity Warning System
  • ADS-B Automatic Dependent Surveillance-Broadcast
  • multilateration as the surveillance medium
  • Aircraft-to-aircraft collisions are increasing. Airborne collisions are mainly associated with general aviation (GA) aircraft, while all classes of aircraft have been involved in ground collisions, predominantly following unauthorized or erroneously authorized runway incursion. All collisions are the result of a lack of awareness of the other aircraft. Methods of increasing awareness must start with increased training and reinforcement during pilot certification testing. It is unlikely that training will be the complete answer.
  • GA general aviation
  • TCAS Traffic Alert and Collision Avoidance System
  • a passive approach would be to assist the pilot in navigating the aircraft around increasingly complex airports. Measures might include improved airport signs and indication methods, sequenced centerline lighting, improvements in Surface Management Guidance and Control Systems (SMGCS) and cockpit aids with varying complexities. The latter might include electronic moving maps and runway activity monitoring. More active methods could include provision of unauthorized runway entry alerting to the controller for transmission to the pilot either by voice or data link. Such alerts might also be provided by flight deck systems. Developing cost effective versions of ADS-B and/or multilateration will directly contribute to improving safety for general aviation, a major contributor to runway incursions. 20
  • SMGCS Surface Management Guidance and Control Systems
  • the highest level of airport surface awareness will be achieved by the use of a moving map that displays cleared taxi routes uplinked to the aircraft from the tower.
  • the system could automatically generate the most efficient route for the aircraft involved, or that would optimize traffic flows and avoid aircraft-to-aircraft and aircraft-to- vehicle conflicts in congested conditions.
  • Low-level alerts could be provided for transgressions that do not result in hazards.
  • Runway activity could be depicted, as could taxiways that are unable to support the operations of the particular aircraft model (e.g. load-bearing or wingspan issues).
  • cost-effective solutions can be used by the general aviation community.
  • the most significant safety improvements for the airspace are:
  • the capacity goal is to accommodate traffic growth depicted in the CMO while reducing the delay in the system. While delay is a difficult metric to measure, the CNS/ATM Focused Team (Metric' s Subgroup) recognizes the elasticity between capacity and delay. In a free market, the operators decide how to use capacity (e.g. add service or reduce delay). We plan based upon a forecast of an initial capacity increase of 37% by 2009, and a net end state capacity increase of 100% by 2019. 21
  • the existing ATM system is forced to manage airspace based on current observed demand since there is considerable uncertainty in aircraft departure and arrival times.
  • the emphasis today is on managing the observed flow using traditional control strategies such as Miles-in-Trail, Holding Stacks, Terminal Area Vectoring, and Intermediate Altitude Level-offs.
  • These control strategies manage airspace to achieve overall flow objectives by reducing complexity in order to limit and stabilize controller workload.
  • efficiency of operations and throughput objectives are sometimes sacrificed in order to keep overall workload within manageable dimensions.
  • More predictable aircraft flow is highly desirable since control can be better distributed to achieve long-term and medium-term flow objectives while preserving short-term separation assurance capability.
  • the NASA Center-TRACON Automation System (CTAS) decision support tools are based on accurate trajectory synthesis and flow predictions for medium- and short-term arrival management. Field tests of CTAS show both the promise and the difficulty of achieving reliable trajectory and flow predictions. To achieve more capacity may require more changes in aircraft flight management, and better integration of airborne and ground automation systems.
  • Delay has traditionally been used as the most direct measure of the ATM system and is generally described as the difference between an aircraft's scheduled arrival time and the actual arrival. However, all delay is not equal. Delay can be divided into predictable and unpredictable delay, and this distinction is important because airlines treat them differently and manage the effect in different ways. Delay is related to other metrics - predictability, flexibility, efficiency, and access - and these can be used to mitigate delay, depending on when the delay occurs. 22
  • Predictable delay is most useful during the airline schedule planning process (60-90 days prior to the actual flight).
  • Predictable delay is built into airline schedules by increasing block times to maintain schedule integrity. This addition to block time not only affects the number of aircraft required to fly the schedule, but also the staff and facilities necessary to operate the flights, to maintain the aircraft, and to serve the customers.
  • Airlines also plan aircraft schedules and network interdependencies to include unpredictable delays, so as to assure network integrity.
  • Flexibility is more significant as a flight's departure time approaches. Resource flexibility is used in crew scheduling, airplane routing, aircraft assignment, and gate control processes up to 30 days in advance. Maximum flexibility in route planning can be used up to 90 minutes before the scheduled departure as airline dispatch processes concentrate on meeting the airline's schedule commitments. After departure, flexibility is used by airlines to make tactical "trade-off decisions to mitigate the schedule impact of unpredictable delays. Unplanned delays, such as traffic flow control, changing weather conditions, and mechanical problems drive up the costs associated with maintaining schedule integrity needed for passenger connections, crew pairings, and required aircraft maintenance. Predictability and flexibility are not independent. Predictability is used by the airlines to plan revenue, while flexibility is used to reduce the losses against the planned revenue when unplanned delays occur.
  • Efficiency and access also affect. Efficiency is a measure of achieved costs compared with optimum costs based on flight time and fuel burn, and affects direct operating costs of a single flight. Because airlines fly millions of flights per year, small increments in direct operating cost savings on every flight can add up to significant savings. Access addresses the means by which NAS users can use ATM system resources. For example, increasing the capacity of airports in low visibility operations or the ability to use Special Use Airspace (SUA) when not being used by the military represents an increase in access. Access can affect efficiency. 3.4 Access Generally speaking, access describes the ability to use the resources of the
  • NAS. Resources include airspace (of various kinds) and services.
  • Measures of accessibility include topological distance, route distance, travel time, and travel cost. Cost can be something as simple as landing charges or as complex as amortization of the cost of equipage to enter exclusionary airspace.
  • our definition of access also includes an acknowledgment of the existence of barriers or impediments to accessing services such as IFR clearances. When impediments become high they become barriers to access. Access is a high-value measure of system performance, especially those users in the general aviation (GA) and military communities. It has also become an issue when major metropolitan areas served by commercial airlines have significant capacity restrictions placed on them while corporate aircraft operate into adjacent feeder airports with little or no restrictions.
  • Noise in the lower terminal area is a significant limitation to capacity now and is an inhibitor to increasing capacity at congested hub airports.
  • a similar problem is that of air pollution due to inefficient fuel burn while queued up on the surface, at low altitudes during approach, and during take-off.
  • RNP could be used to substantially mitigate the terminal area noise problems.
  • curved approaches over less noise-sensitive areas and Continuous Descent Approaches using Vertical Navigation (VNAV) and energy management have the potential to decrease substantially arrival noise per aircraft, enabling increased throughput without increasing average noise levels.
  • VNAV Vertical Navigation
  • the sensing concept includes the deployment of near-term systems such as ⁇ TWS (Integrated Terminal Weather System), and the development of long-term forecasting systems based on regional grid sizes.
  • ⁇ TWS Integrated Terminal Weather System
  • NWS RUC system Rapid Update Cycle weather forecasting based on NEXRAD radars and one-hour forecast updates.
  • the operations area includes the use of advanced navigation and surveillance technologies to achieve marginal VFR and Category I or better IMC operations as all-weather replacements for existing VFR operations.
  • the use of advanced navigation and communications technologies may be appropriate for weather based rerouting and flow enhancement when normal routings are disrupted due to severe weather.
  • the NAS is a single system and must be operated using a common international frame of reference. It should address the common goals of safety along with a balancing of controller workload and capacity. The individual preferences of the system users must also be considered.
  • a cooperative framework should extend from the advance schedule planning process through the completion of each flight. Whenever possible, the NAS should enable the ability of the stakeholders to collaborate fully on the reaction to spontaneous events, such as en route and terminal weather, equipment outages, changes in SUA status, and other planned/unplanned events.
  • the FAA constantly makes adjustments to its practices and procedures based on input from the users and inclusion of new equipment into the NAS. This overview represents the practices and procedures in place during the Spring Summer 2000 period.
  • Site-specific or limited tool system deployments such as CTAS, Surface Movement Advisor (SMA), User Request Evaluation Tool (URET), etc. are not included in this discussion of today's system. 4.1.1 The Daily Schedule
  • ACSCC Air Traffic Control System Command Center
  • Each flight definition includes the aircraft/flight ID, aircraft type, proposed departure time, and historical route of flight.
  • the actual flight plan is provided approximately two hours before scheduled departure time.
  • the start of the operational planning day begins at 5:00 AM ET with a weather telecon among several major airlines' meteorologists and the ATCSCC. This telecon, repeated every two hours, produces a collaborative convective forecast product to be used for operational planning. Based on the last operational plan issued at 4:00 AM and the most recent convective forecast, the ATCSCC issues an update to the operational plan at 6:00 AM ET for the next six hours. The ATCSCC then gathers current operational data from FAA sources (equipment status, staffing, SUA, etc.) and the users via telephone and data links.
  • FAA sources equipment status, staffing, SUA, etc.
  • the flight plan clearance is transmitted to the flight deck either by voice or data link. If a flight will not be affected by any capacity-limiting initiatives when it is ready to depart, the flight crew merely follows the local airport procedure to leave the gate.
  • a taxi clearance to the departure runway is delivered to the aircraft via two-way radio by tower ATC. All instructions to cross runways and sequence with other surface traffic are accomplished by ATC using visual sighting or position reports. When the flight reaches the departure end of the runway it is cleared for takeoff based on current traffic conditions and appropriate traffic management initiatives.
  • Departures are traditionally routed by a TRACON via radar vectors to a departure corridor that corresponds with their intended route of flight.
  • An electronic transfer of track control is made from the TRACON to the appropriate en route center followed by voice communications transfer.
  • the flight proceeds to climb to its ATC- assigned cruising altitude.
  • the routing may either be a great circle or a point-to-point route based on ground navigation aids.
  • TMIs Traffic Management Initiatives
  • ATC uses Traffic Management Initiatives (TMI) to prevent system overload.
  • TMIs are imposed on an as-needed basis and can include one or more of the following: speed control, altitude changes and miles in trail, sequencing, airborne holding, fix balancing, ground delay programs, and ground stop programs.
  • speed control altitude changes and miles in trail
  • sequencing airborne holding
  • fix balancing ground delay programs
  • ground stop programs ground stop programs.
  • an aircraft with a ground delay will be given an Expect Departure Clearance Time based on the arrival rate at the affected airport.
  • a time-based metering program in the HOST computer provides times for each aircraft to cross a given point to meet the identified arrival capacity of the airport. Defining the in-trail distance between aircraft may also be used to accomplish the same result.
  • ATC provides a taxi routing, all clearances to cross runways, and sequencing with other surface traffic via VHF/UHF voice radio.
  • GNSS Global Navigation Satellite System
  • AOC airline operational control center
  • FANS-1 was specifically designed for use in oceanic and remote airspace, and includes Automatic Dependent Surveillance-Addressed (ADS-A).
  • ADS-A allows ATC globally to receive the current position of the airplane via data link along with the aircraft's intent (future flight path) as defined in its flight management computer (FMC) flight plan including ETA at intended waypoint(s).
  • FMC flight management computer
  • ADS-A reduces voice channel congestion, reduces workload and reliably provides data that can be fed directly into an ATC flight data processor. It eliminates several opportunities for human error.
  • ATN Telecommunications Network
  • ATN includes a more capable ADS-A function as a baseline.
  • ADS-B Automatic Dependent Surveillance - Broadcast
  • ADS-B is similar to ADS-A, but the data are broadcast for all equipped, line-of-sight users to use rather than sent by network to a specific user.
  • ADS-B is currently operated on a trial basis in US and European domestic airspace. Only about 120 aircraft worldwide have ADS-B. About 70% of these operate only in Alaska and are general aviation (GA) aircraft. The transport category aircraft that are equipped have only ride-along certification to use ADS-B, i.e. the system transmits solely for test and validation purposes.
  • Airspace One of the NAS's most significant resources is airspace; managing the resource allocation of that airspace is a significant consideration for achieving the safety, capacity, affordability and access goals of the year 2016 system.
  • the airspace classification system defines six classes of airspace based on altitude, type of flight (Visual Flight Rules /Instrument Flight Rules), and equipage.
  • Class A formerly the Positive Control Area, begins at 18,000 feet Mean Sea Level (MSL) and ends at Flight Level (FL) 600 (approximately 60,000 feet MSL). Only Instrument Flight Rules (TFR) flights are permitted and separation is provided by
  • Class B formerly the "Terminal Control Area,” extends from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of IFR operations or passenger traffic.
  • the configuration of each Class B airspace is tailored for each airport, and consists of layers of increasing volume as altitude increases. Published instrument procedures apply once an aircraft enters the airspace.
  • An ATC clearance is required for any aircraft to operate in the airspace; all cleared aircraft receive separation services within the airspace.
  • the cloud clearance requirement for Visual Flight Rules (VFR) operations in this airspace is "clear of clouds" regardless of altitude.
  • Class A equipment is required; the pilot-in-command is not required to be instrument rated.
  • Class C extends from the surface to 4,000 feet above the actual airport elevation surrounding those airports that have an operational control tower, are serviced by a radar approach control, and have a certain number of JFR operations or passenger traffic.
  • the configuration of each Class C airspace area is individually tailored, but usually consists of a 5 NM radius core surface area around the airport, a 10 NM radius shelf area that extends from 1,200 - 4,000 feet above the airport elevation, and, generally, an outer area with a normal radius of 20 NM. In the vertical, this airspace extends from the lower limits of radar/radio coverage up to the ceiling of the approach control's delegated airspace, excluding the Class C airspace and other airspace as appropriate.
  • VFR aircraft are separated from IFR aircraft by either visual separation, 500 feet vertical except when operating behind a heavy jet, or targets are projected to pass.
  • Aircraft must have a two-way radio and operable radar beacon transponder with automatic altitude reporting equipment.
  • Class D extends from the surface to 2,500 feet above the airport elevation surrounding those airports that have an operational control tower.
  • the Class D airspace configuration at each airport is individually tailored. When instrument procedures are published, the airspace will normally be designed to contain the 32
  • Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent Class A, B, C, or D airspace.
  • Class G airspace is uncontrolled airspace outside Class A, B, C, D, or E airspace. 4.2.2 tomorrow's Concept of Airspace Management Mandate for Fundamental Airspace Management Change
  • the sector itself needs to be re-designed to take advantage of a global information infrastructure and enhanced knowledge of aircraft intent obtained from appropriately equipped aircraft. Sectors need to become larger, not shrink, with growing traffic densities so that the workload associated with coordination can be limited. Vertical boundaries may vary within the same piece of airspace to 33
  • GA aircraft e.g., pleasure flying, agricultural operations, flight training, corporate flying, and other activities
  • flight information services such as weather information, special use airspace status, and NOTAMS, prior to departure and during flight.
  • DOD Dept. of Defense
  • the airspace is shaped like a cone based on the flight characteristics of participating aircraft and the airport's configuration. Airspace not included in these cones could provide access to non-participating aircraft that are capable of flying a precise route or tube. In advisory airspace, higher levels of equipage will be needed consistent with the required performance levels imposed by the traffic densities and safety levels.
  • This airspace will be consolidated into larger control structures to simplify coordination and improve services. These structures will be dynamically reconfigurable, to allow better response to weather events and other transients. A much safer basis of operation should be available at low cost to equipped users by providing enhanced weather data, global navigation services and surveillance of nearby aircraft.
  • Issues to validate include: (1) Fixed versus flex versus free routings in en route, transition and approach and landing airspace; (2) Potential for separation assurance concepts which are not based on fixed geographical regions, but are based on aircraft-pair (or some other method); (3) Identification of minimum equipage requirements to operate in the various airspace classes; (4) Applicability of the Required System Performance concept for airspace services delivery; (5) Interfaces to non-US positive control airspace; and (6) Interfaces to non-US procedural control airspace
  • Coordinated traffic flow planning is one of the cornerstones around which the new operational concept is built. Departure, en route and arrival flow management functions are combined in a real-time centralized plan to optimally spread delay for the daily predicted capacity/demand imbalance in the NAS. The plan is coordinated in 35
  • CFMA Central Flow Management Agency
  • SOC System Operational Control
  • Collaborative Decision Making uses fast-time coordinated flow planning tools and real-time communications equipment available at all locations. Organizations with capabilities comparable to airline SOCs could provide similar services to smaller commercial operators, GA and/or the military.
  • the output of the planning tools allows the service provider and system users to understand the current and forecast system limitations, and optimally allocate airspace resources and user preferred trajectories before capacity shortfalls and demand imbalances begin to cause delay. Simply put, more precise predictive tools allow the maximum capacity to be available.
  • the coordinated flow planning provides potential solutions including dynamically re-configuring airspace and suggesting amending flight profiles to best balance users' demands for services and create the most capacity.
  • the CFMA has the ability to dynamically balance demand and capacity in the system to prevent traffic overloads and to better react to disruptions. Stakeholders will communicate quickly with the agency, and CFMA has tools to support real-time replanning of all scheduled departures and flights.
  • the heart of the new CFMA is the replanning system.
  • This system receives all of the filed flight plans, active flight plans, current surveillance information, local and system-wide weather as well as forecast weather.
  • This system provides a common view of the NAS with real-time display of the traffic situation and near-term (2 - 3 hours) simulated traffic flow predictions. Real-time status and performance data is provided by decision support tools to departure, arrival and en route flow management functions and the agents at field units.
  • This system is to enable rapid processing of re-routing requests by the users.
  • the system is able to evaluate all of the re-routing requests, balance sector demand with available capacity and send these re-routes back to the users.
  • the system will initially allow a small percentage of the requested re-routes to fly through weather that the software believes will probably not occur. This approach is 36
  • the CFMA replanning tool allows the users to prioritize ground holds if the weather does not allow for approval of all re-routes.
  • a rule base (similar to the collaborative decision systems already in use) assures equitable treatment for all users and airports.
  • This replanning tool coupled with simulated traffic flow prediction and high performance data connections among all parties, will enable dynamic reactions to transient flow changes, reducing delays and cancellations while maintaining safety by preventing sector overloads.
  • Departure, en route, and arrival flow management functions located at field traffic management units are continuously running local sector flow monitor functions. Coordinated by the CFMA replanning tool, the flow monitoring functions assure that the traffic load remains balanced with available capacity and that the rerouting services better respond to transient events and the interface with other national or oceanic airspace environments.
  • the submitted flight plan changes may be accepted as submitted or modified by the replanning tool. The reasons for departure delays might be sector loading (which should be minimal) or a route adjustment greater than a fixed percentage of the filed replan.
  • the system will initially be limited to pre- departure flight plan changes and use existing data link on commercial aircraft. Reroutes during the initial implementation phase would be submitted only by user SOCs, but in later phases they could be submitted from the flight deck and would be coordinated back with the SOCs.
  • the CFMA-accepted re-routes would be 37
  • the Boeing operational concept supports the use of 3-D trajectories (3-D tubes) in all airspace regimes, and the use of 4-D trajectory concepts when appropriate.
  • 3-D trajectories 3-D tubes
  • the use of RVSM and RNP-1 RNAV routings will add needed vertical flight levels and make more airspace available to relieve congestion.
  • the use of 3-D tubes can enable more effective use of airspace for procedural separation with crossing and descending traffic.
  • the descent stage of flight it may be possible to support both 3-D tubes and 4-D arrival times at critical arrival fixes. This would be achieved by integrating 3-D RNP RNAV routing and vertical profiles, and enhanced FMS energy management of thrust and drag to achieve desired airspeed profiles.
  • the aircraft would manage high integrity airspeed and vertical flight profiles, and the ground automation would implement enhanced wind field surveillance to compute aircraft ground speeds on descent, and arrival times at critical fixes for terminal area merging and flow management.
  • the 3-D or 4-D clearance (contract) negotiated between each flight and the service provider plus the improved surveillance and intent information are responsible for the planned reductions in separation, increased system capacity and enhanced safety.
  • Individual controllers are able to handle increased traffic loads through the use of conflict detection and resolution software. Conflicts are identified well into the future along with potential mitigating strategies allowing the controller to make the decision and cause the minimum impact on individual flight profiles. Dynamic organization of airspace based on ongoing capacity modeling software also contributes to controller productivity and system capacity.
  • a significant improvement of the new system is enhanced accuracy and update rate of aircraft surveillance systems achieved through data fusion of classic radar, ADS-B, and other sensors such as multilateration.
  • Surveillance will improve from radar displays or position reports to fused radar/position report data (with intent). Positions will be transmitted by the aircraft to the ground at a much higher return rate that will allow for higher displayed/system-utilized position accuracy, reduced separation, and increased safety.
  • position information update rate using radar surveillance is determined by the rate of revolution of the radar; 12 RPM for terminal radar and 5 RPM for en route.
  • the Sector Controller/Planner will have a future conflict detection capability with suggested resolutions to reduce separation loss with a minimal affect on each flight's profile.
  • the level of equipment sophistication air and ground
  • separation maintenance may be transferred to the flight deck, but separation assurance will remain with the service provider.
  • a pilot accepting a 3-D trajectory clearance is expected to fly the intended trajectory with high assurance of staying within the horizontal and vertical containment bounds (tube boundaries) defined by RNP RNAV standards, e.g. RTCA document DO236A (See Figure 4.3-1).
  • the probability of being outside the intended containment bounds will be acceptably small, and if necessary to fly outside these bounds, the ground side will be alerted with an appropriate "unable horizontal/vertical RNP" message.
  • the service provider agrees to provide priority separation services 39
  • This "contract” between aircrew and ground control provides a basis for using airspace more efficiently until it is required by either side to modify the clearance, or the aircraft flies outside the domain of applicability.
  • an emissions-friendly precision descent profile including the landing runway based on current/forecast weather and traffic conditions at the flight's estimated time of touchdown. This profile includes top of descent, speeds, routing, and touchdown time. User preferences are also considered in the calculations. Pertinent information on each flight's expected touchdown time, landing runway, taxi route, and expected time at the gate will be electronically passed to the terminal.
  • This information will be used to determine the best taxi route, alert ground crews of arriving aircraft, post the most accurate arrival time on terminal screens, and determine and minimize the domino effects of delays on subsequent flights for the aircraft and crew members. Separation at touchdown is based on runway occupancy time for the conditions (dry, wet, standing water, snow, wind, etc.) calculated for each runway. Also considered are location of high speed turnoffs and aircraft type. Highly accurate wake vortex detection and prediction equipment plus curved approaches and varied final approach slope angles facilitate reductions in wake vortex separation. VFR landing rates are achieved in most weather conditions.
  • a routing to the terminal gate is data linked to the aircraft. Position information on each active flight and schedules of those approaching pushback time have been considered when developing this routing. Clearance to cross all runways will be provided by the controlling agency. With the use of synthetic vision the use of runway lights is almost negated.
  • the surface monitor also includes a conflict detection system to assist in preventing runway incursions.
  • negotiated flight plans will be loaded into the FMC either via wired or wireless Gatelink or through company data link using VHF radio or satellite communications. After pilot validation, the crew will downlink the flight 40
  • ATC will uplink the clearance for direct loading into the FMC.
  • airline SOCs could negotiate routes directly with ATC, to be uplinked to the aircraft and to the SOC simultaneously following the crew's request for delivery of clearance. If the plan is revised while the aircraft is still on the ground, resulting in fuel burn increases acceptable to the aircraft model, the crew can accept the new clearance. If the fuel burn increase unacceptable, the crew must refuse the new clearance.
  • the flight plan may include a Required Time of Arrival (RTA) at a point late in the flight plan (metering fix or runway threshold).
  • RTA Required Time of Arrival
  • ETA at crossing and critical fixes will be updated online to facilitate conflict management en route.
  • Acceptance of multiple RTAs and accurate achievement of such RTAs will require some level of functional change in all FMCs.
  • Many current FMCs do not accommodate RTA functions in the descent and none provide adequately for the rapid and frequent updating in wind and temperature data necessary to guarantee accurate RTA, particularly in the descent.
  • Wind and temperature data will be obtained from ground- based measurement systems and from other aircraft. All data will be data linked to the aircraft, possibly by broadcast.
  • the FMC must be able to assess the viability of inter-RTA times if more than one RTA is defined for the route.
  • the crew receives suitable cues to unacceptability of one or more RTAs.
  • conflict management will be facilitated through the use of new route, altitude and airspeed clearances uplinked to the aircraft.
  • Tactical changes will occur through negotiation between ATC and crew, while strategic changes will require three-way negotiation among ATC, crew and the airline's SOC so the schedule impact is contained. Such strategic changes may also result from scheduling requirements as well as aircraft-to-aircraft conflict management, and associated changes will originate in the airline's SOC.
  • ATC will uplink a clearance for flight completion.
  • This clearance includes descent instructions and vertical path window constraints, assigned standard arrival procedure, transition, and approacehes including runway, ideal runway turnoff, any change to the metering fix or touchdown RTA, and gate assignment.
  • the aircraft will be able to maintain precisely the cleared trajectory and waypoint arrival timing, providing high levels of predictability of intent for use in conflict prediction and resolution in the terminal area, and to use available runway capacity most efficiently.
  • the operational concept greatly reduces controller workload by removing stepped descents and vectoring and greatly simplifying sequencing.
  • the FMC can provide flight path intent that can be used to refine FAST's calculations.
  • the FMC can also accept 4-D flight path updates directly from active FAST functions with pilot concurrence.
  • the US contains slightly less than half of the world's air passenger traffic, jet aircraft, and airports. There are about 17,000 airports in the US, of which 3,500 are public airports with at least one lighted and paved runway. Only 500 airports have 42
  • the Air Traffic Control Tower (ATCT) or Ground Control delivers a taxi clearance to the departure runway to the pilot via two-way VHF radio.
  • the pilot is instructed by ATC to cross runways and to sequence with other surface traffic.
  • the ATCT uses radar displays, visual sighting, or position reports from the pilot to route the aircraft on the surface.
  • the first improvement is the accuracy of current and anticipated aircraft position information and the flow of that information to personnel involved in all aspects of airport operations.
  • the second will result from the ability to conduct simultaneous independent approaches in IMC to parallel runways spaced significantly less than 3,400 ft.
  • the third is reducing arrival spacing due to wake vortex requirements. New technologies, research, and changes to current ATC rules and separation assurance functions will enable these improvements.
  • Airport surface surveillance will change from radar displays, visual sightings, or position reports to fused radar/position report data (with intent, target tags, and conflict detection). Position information will be transmitted by the aircraft to the surveillance sensor at a much higher return rate, thereby allowing greater position accuracy, reduced separation, and increased safety. This position information will be transmitted to concerned entities, including local ATCT, ramp control, and airport operational personnel. This will enable the smooth flow of traffic on the airport surface and the smooth processing of aircraft at the gate. ATCT personnel will have tools to optimize runway assignment, sequencing and spacing of arrivals, departures, and taxiing aircraft. Planning and replanning tools will be available to all personnel to optimize use of runways, taxiways, gates, or maintenance and service facilities. Airside Management
  • an aircraft's trajectory will be updated with a noise- and emissions-friendly precision descent profile that includes the landing runway, based on the airport's current forecast weather, operating configuration, aircraft / operator preferences, and traffic conditions at the flight's estimated time of touchdown.
  • a taxiway routing to the terminal gate is data linked to the aircraft.
  • the expected time at the gate will be dynamically updated in the terminal building on the Flight Information Display System (FIDS).
  • FIDS Flight Information Display System
  • the aircraft's assigned baggage claim will also be displayed at the gate and on FIDS displays.
  • the number of passengers will be transmitted electronically from the aircraft and used by the resource 44
  • a closed-loop structure assures separation in today's JFR positive control airspace. Navigation and guidance is performed by the cockpit crew and avionics. Surveillance is performed by secondary radar and radar data processing (RDP) and display system. Communication is performed by the sector controller and crew using VHF voice radio and position prediction. Conflict detection and resolution planning are performed by the sector and data controllers. Thus, the separation assurance loop closure is performed by a human-to-human voice radio connection, based on a 2- dimensional relative position display.
  • the current minimum allowed separation is 5 NM in en route airspace and 3 NM in TRACON airspace, which was based on the performance of analog RDP systems and operator confidence in intervention through voice radio in case of impending violations.
  • RNP Required Navigation Performance
  • RCP Required Communication Performance
  • RSP Required Surveillance Performance
  • Table 5.1-1 lists the various factors that have been analytically or empirically quantified.
  • the terminal area is sufficient to allow a successful avoidance maneuver if detection occurs at 3 NM relative spacing, given the surveillance accuracy, reaction time and avoidance maneuver time, nominal aircraft speeds and closing angles of less than 130 degrees.
  • the surveillance accuracy of 0.25-0.1 NM is a small contributor to the overall spacing minimum of 3 or 5 NM.
  • the human and aircraft reaction times dominate the loop closure performance, and a model that includes all the relevant factors must be used to establish safe spacing targets. 5.1.1 Air Traffic Manager
  • the traffic management function is divided into four time horizons: 1) Imminent, 2) Short-Term, 3) Medium-Term and 4) Long-Term, corresponding to top level ATM functions of planning or flow management, detection/prediction and intervention.
  • Each of these temporal levels is necessary for continuous traffic management.
  • the imminent level may be supported by some airborne conflict avoidance system such as TCAS TJ while the mid- and short-term may use ground- based decision support tools such as conflict probe.
  • the controller becomes a manager of the system and intervenes when needed. Extensive conformance monitoring tools and conflict detection/resolution tools are available. 5.1.2 Surveillance
  • PSD Primary Surveillance Radar
  • SSR Secondary Surveillance Radar
  • Range capability is a function of system average power.
  • the direction of the "target” is determined by where the rotating antenna receives the reflection.
  • Older analog radars are sensitive to weather and have a relatively slow update rate. Their usable range is limited by required accuracy; the greater the accuracy requirement, the shorter the usable range. Angular accuracy also reduces with range.
  • Secondary Surveillance Radar (SSR) SSR
  • Secondary, or "cooperative radars” are transponder-based, using interrogation/reply capability to get ATC-assigned code and altitude. This data is used for conflation of radar returns with specific flights on radar displays.
  • the range and directional accuracy of the more modern secondary radars is very good. They are designed to support ranges of at least 60 NM around each airport and up to approximately 200 NM for en route surveillance. Typical scan rate is about one report per 5-second interval. Azimuth accuracies depend on the equipment. Integrity of the identified aircraft (the probability of misidentification on the controller's display) is also an issue.
  • Precision Runway Monitor radars and associated displays are installed to support special approach applications. These primary radars are updated once-per- second, and are accurate to the order of three meters. In IFR conditions they enable a reduced separation standard for approach and departure beyond what would be allowed by the standard terminal area secondary surveillance radar. This is important 47
  • Controllers have a combination of information from radars and other sources (usually flight-related information) to maintain required en route separation.
  • Primary radars designed for en route use provide line-of-sight (approximately 250 miles for targets at 40,000 feet) coverage and scan at a rate of one report per 12-second interval.
  • Technical performance capabilities, in terms of detection probability and accuracy, are similar to those of the terminal radars, but are less accurate than terminal surveillance due to the larger distances (for position reports at ranges greater than 150 miles).
  • en route tracking and data report quality are lower for en route surveillance. For example, velocity estimates can be poor and aircraft tracking is typically poor in turn maneuvers as a result of lag errors that can be 30 - 60 seconds. For these reasons horizontal separation standards are larger for en route than for terminal airspace.
  • En route airspace uses a networked system of Air Route Surveillance Radars (ARSR) which provides continuous monitoring of aircraft flying in domestic airspace above ⁇ 9000 ft. (FAA goal is above 6000 ft.).
  • ARSR Air Route Surveillance Radars
  • Each radar is networked to one or more ARTCCs to provide continuous monitoring of aircraft across NAS-managed airspace. There are “holes” of coverage in mountainous areas. Procedural separation is provided where there is no radar coverage.
  • Primary radars are positioned to achieve at least dual radar coverage throughout NAS- managed airspace. This provides very high reliability for long-range radars.
  • Co-located with the en route primary radars are SSRs that enable code identifier, altitude, and tracking.
  • This combination of en route primary and secondary radars supports a minimum en route separation standard of 5 NM. This standard is determined not only by radar technical performance, but also considers factors such as communication quality and availability, pilot and controller reaction and intervention 48
  • en route separation is normally 7 to 8 miles.
  • Surveillance is also provided in the terminal area and the descent/climb regions by a mix of primary and secondary radars. They provide uniform coverage with sufficient continuity and reliability to support all-weather, day/night operations while handling growing traffic and maintaining safety margins.
  • ASR Airport Surveillance Radar
  • TRACON Radio-Reliable and Low-power radar
  • Small airports may only have access to an SSR, or may have no surveillance capability other than that provided by voice reporting and tower controllers.
  • radar service may be provided by either a TRACON or an ARTCC to a point where radar is lost, where they receive procedural control.
  • dual primary/secondary radar sensors provide redundancy.
  • the radar processing and display paths employ direct and indirect channels. In the rare case of a failure of a single sensor terminal primary radar, the long range radar can be routed for temporary replacement. Due to slower scan rate, several separation parameters must be expanded. If the TRACON with the failed radar is an ARTS facility, the host ARTCC can send position and alphanumeric data derived from the ARTCC host computer to the TRACON displays.
  • This combination of terminal area primary and secondary radars supports a minimum separation standard of 3 NM when within TBD miles of the radar, and allows for simultaneous independent approaches to parallel runways with no less than 4300 ft. separation. For en route, this standard also considers factors other than 49
  • Two that are unique for terminal area operations are runway occupancy time and wake turbulence.
  • TCAS radar-based separation assurance
  • ACAS collision avoidance systems Today, radar-based separation assurance is augmented by the airplane-based TCAS or ACAS collision avoidance systems.
  • TCAS is a "safety net", i.e., a secondary system that provides the flight crew with situation awareness of proximate traffic, and commands an emergency maneuver when controllers have failed to provide separation assurance.
  • the TCAS function uses a single transponder for air-air interrogation / response of traffic.
  • ground-based capabilities include short-term conflict alert that serves as an augmentation to controllers.
  • ADS-A enhances surveillance by making available to a range of airplane- specific data that is unavailable in the primary/secondary radar environment.
  • "Addressable” means a suitably-equipped ATM entity establishes a contract(s) with the aircraft to receive information. There are many data sets, but the basic set provides current position/altitude/time, next waypoint altitude and ETA, and the following down-path waypoint. Other information can include airplane proximate meteorological data and other kinds of intent information.
  • ADS-A systems have been certified to an essential level and are, therefore, approved for position tracking in oceanic areas without voice/radar backup. They will likely be used differently in the domestic environment where, for example, information regarding upcoming waypoints may be need by trajectory/flow management functions. In this case, ADS-A information would not be used to give radar-like information but would augment radar and ADS-B with mid-term intent data.
  • ADS-B is a further surveillance enhancement where each vehicle broadcasts its own position, altitude, velocity and intent data to other equipped vehicles and ground ATM sites. This information will be used for enhanced situational awareness and aircraft tracking. Performance requirements and certification levels will relate to the operational tasks enabled by the system. For example, Cockpit Display of Traffic Information (CDTI) uses ADS-B information to generate a controller-like cockpit 51
  • Traffic Information System - Broadcast is another approach to exchange information to support enhanced surveillance. It involves a ground system collecting surveillance data from all available sources (radar, SSR, ADS-A, ADS-B, etc.) and fusing it into a "big picture" of the traffic and intent situation in an area. The compiled data will be transmitted to users, similar to ADS-B. As with ADS-B, performance requirements and certification levels will be related to the operational tasks that the system will provide.
  • Enhanced departure/approach and transition area surveillance will be required to meet the need for widespread deployment of regional traffic flow management systems.
  • Enhanced surveillance performance in the climb/descent transition area surrounding terminal airspace will also be required so that en route controllers can more accurately structure and merge the arriving and departing aircraft consistent with terminal area flow operations.
  • Enhanced surveillance will also be one factor that permits reduced IFR separation during approaches and departures.
  • RSP Separation Standard
  • Timeliness This will specify latency on a system and element level.
  • Voice communication via standard VHF analog radios is the current standard for pilot/controller communication.
  • One frequency is allocated per ATC entity.
  • frequency congestion is a major problem due to the number of aircraft being controlled and the requirement for multiple discrete voice 53
  • a common data link known by its protocol specification "ACARS ARINC 623" is widely used for airline company information and other non-critical flight data transfer.
  • ACARS uses a specific subset of the frequencies allocated to VHF communications. Although ATC pre-departure clearances are delivered via the ACARS network, there are no other ATS instructions or clearances that are delivered over this medium due to its inadequate integrity.
  • VHF frequencies are separated by 25 KHz.
  • a short term fix to the frequency congestion problem is a new VHF radio standard that separates communications frequencies by 8.33 KHz, tripling the number of channels available. While this can be applied to voice communication, ACARS still requires 25 KHz channel spacing.
  • 8.33 KHz radios are considered an interim solution, US airlines are equipping with them to comply with European requirements and the anticipation that a requirement may emerge in the US.
  • ATN Access to IP
  • Digital communication will grow and provide increased functionality among the service providers and system users. Message sets with different levels of urgency will require specific levels of service; however, it is not certain that data link will ever be able to satisfy time-critical message requirements. It will be critical to minimize errors in data transmission in order to rely on the digital communications for overall separation reductions and for collaborative decision making.
  • NEXCOM Network Generation Communications
  • VOR VHF Omnidirectional Range
  • DME VOR/Distance Measuring Equipment
  • Deviations from a desired course to that navaid are monitored and corrected by the flight crew or autopilot.
  • the VOR system is angular, which means errors increase with distance to the navaid.
  • VOR-based airways must have a VOR at 55
  • RNAV systems can define and fly any route over the earth, and are widely available in commercial jet transports, regional jets, and business aircraft.
  • RNAV systems provide great flexibility, as they contain large databases of geographic fixes, navigation aids, and procedures. These elements are connected together to form flight plans made up of waypoints. These "trajectories" can be located to optimize traffic flow and to increase operational efficiency.
  • RNAV systems use data radiated from existing ground-based VOR/DME navigation aids to determine an estimated aircraft position that, for en route navigation, has greater accuracy than was achievable using the angular VOR system alone. They do not have to fly over, toward, or close to the stations.
  • RNAV systems can achieve 0.3 - 0.5 NM (95%) accuracy by using data from standard ground-based navaids. With this positioning accuracy, RNAV systems provided the technology with the potential to significantly improve efficiency of the NAS.
  • the recent addition of satellite-based positioning improved the achievable accuracy to better than 0.1 NM (95%) everywhere in the NAS. Even with the improved accuracy, however, RNAV systems have not been used widely, due to the lack of dedicated procedures and the inability of the NAS to use this new technology while still serving the least capable users.
  • RNAV systems provided a significant airborne capability, they were mainly confined to mimicking the VOR-based airways and procedures system. They provided work-saving benefits, but the certification standards rarely required performance beyond that required of the legacy airways-based system. It was assumed they would operate in such a system with existing mitigation techniques to detect navigation errors and blunders. As a result, these systems were not designed to 56
  • RNP Required Navigation Performance
  • RNP performance is based on providing an assurance of containing aircraft navigation-related errors to two different probability levels, and ensuring continuity of this assurance.
  • the containment concept is key, as it provides the necessary assurance to airspace planners that the aircraft will remain within given boundaries with the prescribed probability level. This assurance can be used as one element in collision risk assessments and will allow current safety levels to be maintained at higher traffic density and/or reduced lateral separation.
  • the basic RNP accuracy requirement states that the actual aircraft position must be within the RNP value (expressed in nautical miles) for 95% of the flight time. For example, an aircraft operating on an RNP 4 airway must remain within 4 NM of the computed navigation position at least 95% of the flight time. There is no assumption or requirement on the specific technology used to achieve this; however, the aircraft avionics integrator must be cognizant of the levels of RNP for which operations are desired as this will affect which navigation sensors are included. RNP values with standard ground-based VOR/DME navaids, the LORAN system, or 57
  • inertial navigation systems are larger than those achievable with satellite-based navigation systems.
  • the RNP containment continuity requirement is that the probability of loss of a specific RNP capability (e.g. RNP 2) be less than 10-4 per flight hour.
  • the containment continuity can be considered in assessing the types of supporting infrastructure as well as airborne equipage. "Legacy" RNAV Systems and RNP operations
  • RNAV systems that have not been certified for RNP-based operations
  • the most significant difference with RNP is the lack of containment integrity and containment continuity. It may be possible to accommodate these systems in an RNP environment by the applying traditional separation and obstacle assessment criteria as a way to mitigate the lack of formal RNP performance assurance.
  • the VOR-based airway structure is the starting baseline for moving to a new NAS, since it will continue to provide the structure for most of today's operations.
  • Some RNAV operations have been implemented through the National Route Program and special authorizations. Route Structure Replication as RNAV. 2001-2005 58
  • the conventional route structure replacement can start with the replicating conventional routes using named latitude/longitude fixes and flight paths compatible with RNAV. This would be the initial ATS RNAV route baseline. Its benefit will be in familiarity with the RNAV concept, equipment, and use in an operational environment. The retention of many existing fix names is also an important factor in minimizing the impact of this transition. Training will emphasize that waypoints are not tied to the ground navigation aids. Route Structure with RNAV Optimizations, 2003-2010
  • RNAV SIDs. STARS, Transitions and Approaches. 2001-2010 RNP RNAV-based terminal area procedures are likely to provide benefits driven by fuel reductions through reduced track length and more consistent performance and traffic flow. Procedures with various RNP values will accommodate different airplane capabilities and provide alternate minima.
  • RNAV RNAV Flexible/Random Routing
  • RNAV system capabilities allow tactical operations, including diverting from a preplanned route with parallel offsets or direct-to. This improves efficiency by avoiding weather, SUA or traffic. However, these improvements and flexibility will 59
  • Precise navigation based on space-based signals with possible augmentation from the ground, will allow for converging/curved approaches with lower decision heights, optimum noise routings, and precision approach through automatic landing.
  • the current flow management system functional structure and the planning cycle involved in reaction to severe weather events relies heavily on human operator performance and telephone coordination, with minimal automation and information infrastructure support.
  • the figure reflects the large number of agents involved in collaborative decision making, where planning teleconferences may include over a hundred individuals.
  • Some troublesome issues with current flow management techniques include: Weather forecast uncertainty; No automation tool to generate coordinated re-routes around airspace restrictions; and Coordination of planning strategies by voice over phone lines between SCC, ATC and SOC.
  • the preferred ATM system will:
  • D Account for flight replans within a given compute time including forecast delay, routine circuitry and sector/airport utilization
  • the Boeing system is based on a timely, low-risk ATM transition plan.
  • the plan considers the transition for operations, architecture, and the implementation phases from the current system to one supporting a new basis for operating the NAS. 60
  • This new system will provide quality air traffic services to all system users for the next fifteen years, assuming we start today.
  • the system will move NAS operations from today's flight planning and radar-based air traffic system to a trajectory-based system in which current and future position of the aircraft is available to system service providers.
  • the NAS architecture will change from an increasing number of disjointed tools and procedures to a set of integrated solutions.
  • the Boeing transition plan is based on a three-phased deployment of a set of technology elements which develop increasing functionality, provide increasingly integrated solutions and allow significant capacity and safety gains, especially during the later program phases.
  • the basis for transformation is the integrated introduction of three enabling elements: (1) the flight trajectory as the basis of air traffic management, (2) a new information infrastructure to allow significant increase in the quantity, timeliness and reliability of information available among all personnel, including, in phase 3 of the program, an integrated CNS satellite services capability, and (3) airspace and procedures changes necessary to transform the operation of the system.
  • This architectural and operational transformation will move the NAS from a fragmented collection of technologies and procedures to a seamless, trajectory-based ATM system in which flow planning, flight planning and air traffic separation management are integrated and share a common information set.
  • Boeing will develop a trajectory-based flow planning system to replace the existing set of national, regional and airport level planning tools and procedures.
  • this trajectory-based approach will be applied to the sector flight planning.
  • trajectory-based separation functions will be developed and deployed.
  • Prefered ATM will include CTAS, conflict free advisories to controllers as currently provided by URET, data link, CPDLC, CDM, and designated high altitude airspace.
  • Significant numbers of new runways will be needed to meet the traffic growth expected during the next 10 to 20 years.
  • Boeing ATM and CNS initiatives complement efforts to increase runway capacity in two significant ways. First, ATM and CNS technologies will improve the capacity of airports and runways operating 61
  • ATM and CNS technologies can relieve constraints on airspace as runway capacity grows.
  • Phase 1 Traj ectory-B ased Flow Planning
  • Phase 1 will introduce the dramatic changes to the national and regional flow management operation in the NAS.
  • Our intent is to immediately introduce a new national level flow planning and management system to support greatly improved system schedule integrity maintenance during periods of disruption.
  • This will include a set of trajectory-based planning and replanning tools, hosted at the system command center (SCC) that will support: D A flight trajectory-based projection of system loading
  • the engine of this system planning, coordination and information exchange system is the National System Flow model.
  • the model would be operated by the FAA Air Traffic Control System Command Center.
  • This central planning function will provide the national level delay allocation, and coordinate flow responses initiated at the regional and airport levels.
  • the system replanning in response to NAS operating constraints will initially be limited to pre-departure plan changes and will use existing data link capability, which already resides in transport aircraft.
  • the participating flight planning and airline SOCs will use their existing systems to develop and accept revised flight plans.
  • the SCC requires the capability to transmit revised trajectory-based flight plans to existing regional control centers.
  • a new information distribution system will provide coordinated delay responses for national, regional and airport level flow planning. It will also be necessary to provide information exchange between the ATCSCC and the airline SOCs.
  • Further incremental communication enhancements include the addition of dynamic data inputs and the ability to expand the capability of the SCC.
  • the use of trajectories in regional flow applications will be integrated with the SCC planning system.
  • Other improved functions include allocation of delay across control domains; central accounting for delay already imposed on a flight; and exchange of data between central, regional, and airport planning.
  • Airport-level arrival and departure metering tools should be integrated into a seamless set of flow planning tools.
  • the data link to aircraft would initially use the existing ACARS network and aircraft data link equipment capable of pilot-controller communication. This will accommodate the transition to a more efficient architecture.
  • the FAA air-to-ground data link capability would evolve to an integrated system allowing flight plan exchange and FMS loading. Initially, replans will be constrained to pre-departure. Information links between airport flight status tools (e.g., ASDE-X) and the National System Flow Model would be added.
  • Aircraft-to-ATC communication during this phase will use data link for pre-departure pilot-to-tower coordination among aircraft. Control of traffic by would continue to be based on voice, but planning revision would be transferced to the emerging data link capability.
  • the interfacility communications connectivity (including airline SOC) will be developed during this phase.
  • the NAS flow response currently is a coarse set of national technologies and tools (based on filed flight plans) and largely decoupled regional (miles in trail) and airport level flow planning. This will move to an integrated set of tools and methods, based on the National System Flow Model, coordinated with SOCs and among the various ATC flow agents. It is expected that flow planning will be needed at all levels in the system end state, but local and regional flow actions will be better coordinated with national flow planning.
  • Phase 2 Trajectory-Based Flight Planning
  • trajectory-based flight planning and dynamic replanning will be implemented in the en route regions, and later in the terminal areas.
  • This phase will transform the flight planning function from the current "flight strips" to a full trajectory-based capability.
  • Our plan calls for a trajectory-based capability in the flight plan processing system so that en route and terminal controllers have integrated trajectory-based planning tools on hand.
  • These tools can support a variety of applications, including conflict probes, dynamic replanning tools and airport metering tools such as CTAS.
  • This capability will facilitate sector planning, inter-sector coordination and sector-traffic management unit coordination, and airport traffic planning.
  • system can support change, based on aircraft equipage updating schedules, airspace and flight planning procedures development, and training times.
  • Aircraft will have a data link (ACARS VDL/2 will probably be adequate), an FMS and a GPS navigation system (for a high-integrity time fix). Air-to-ground data link exchange of dynamic flight replanning data is assumed. Early applications could be for FMS-to-sector planning tools, such as a second-generation conflict probe. Equipped aircraft also would provide current state information and trajectory to the National System Flow Model to improve the fidelity of its solutions.
  • Dynamic replanning communications will be transmitted by data link.
  • a key transition issue is the performance adequacy of the initial data link to support terminal area trajectory exchanges. Requirements for these applications may affect the timing of the transition to a new satellite-based data link.
  • Interfacility communications will provide connectivity of flow planning and flight planning elements.
  • Navigation during this phase will be based on GPS, both for navigation and time estimation; there will be a residual ground-based backup system for contingencies.
  • Airspace changes will be less significant in the en route airspace. Sector and terminal control region boundaries will begin to be modified consistent with phase 2 implementation. Significant trajectory-based terminal planning and replanning 65
  • Phase 2 Phase 2 implementation strategy requires that airlines operating at affected locations implement the changes, and limits air traffic training requirements to personnel associated with affected facilities. This approach minimizes the equipage rate (managed by locality), puts air traffic training on a manageable schedule, and allows the phased introduction of new procedures. Operator benefits associated with the implementation are substantial and help the airline equipage business case.
  • Phase 3 Trajectory-Based Separation Management The third phase will introduce precise trajectories into the air traffic separation management process. This step will provide the largest capacity benefits but will require the most exacting performance requirements. High levels of CNS accuracy, integrity, and availability will be needed. A significant upgrade of current CNS capabilities will be required, both in the ground infrastructure and on the airplane.
  • This phase introduces high-integrity trajectory-based flight plans ("contracts"), which are mutually agreed upon by aircraft operators and service providers that stipulate the precise procedure to be flown.
  • Various integrity-enhancing capabilities will provide conformance monitoring, both within ground automation and on the airplanes.
  • This phase will require significant development of en route, arrival, departure, and missed-approach planning/replanning tools to provide accurate, de- conflicted flight profiles to the aircraft and to monitor aircraft conformance to planned descent profiles. It will probably be necessary to modify the existing controller displays to present the trajectory information.
  • the controllers' procedures, tasks and training regimes will change.
  • the planning tools will be coupled with new capability, such as LA AS -based procedures and other airspace operating changes.
  • GCS Global Communication, Navigation and Surveillance System
  • GCNSS Global Communication, Navigation and Surveillance System
  • GPS Global Positioning System
  • GCNSS would encompass and extend the functionality provided by GPS by providing enhanced position velocity and time services adequate to support safety-of-life issues.
  • the GCNSS would provide additional services and capabilities by adding communication and surveillance functions.
  • the GCNSS concept represents a complete paradigm shift from the legacy navigation systems and existing communication and surveillance technologies.
  • the fusion and integration of CNS provides opportunities for new synergistic services. Properly implemented, the integration provides inherent redundancy that enhances total system integrity and reliability. Finally, the integration provides opportunities to lower the overall cost of providing CNS services relative to the cost of fielding and maintaining the host of CNS systems which GCNSS may replace.
  • the benefits of an ATM enhancement include increased capacity or decreased disruption.
  • An increase in capacity means the ability to fly more flights with the same amount of disruption (delay and cancellations) as in the current system.
  • Decreased disruption means the ability to fly the same number of flights with fewer cancellations and delays.
  • the proposed set of operational enhancements have been evaluated in three separate benefit models that calculate the net present value of the benefits of the proposed operational enhancement over the next twenty years. Benefits are measured as the difference between how the proposed concept would perform relative to how the current system would perform, assuming forecasted growth in operations. All 68
  • benefits are measured in terms of decreased disruption (delays and cancellations) for the forecasted set of operations against a do-nothing approach.
  • Each model includes a set of timing assumptions regarding when the implementation will start and how long it will take.
  • the first benefits model evaluates a Traffic Flow Management operational concept that will improve the air traffic system's ability to respond to convective weather events.
  • the second benefits model evaluates the airport benefits from the Trajectory Management operational enhancement.
  • the third benefits model evaluates the en route benefits from the Trajectory Management operational enhancement. 7.1 Forecast Methodology
  • the forecast starts with traffic projections from the Boeing Current Market Outlook.
  • the CMO forecasts a 2.9% increase in operations over the next 20 years. (This is very close to FAA forecasts, which project a 2.9% annual growth in traffic through 2011, when the forecast ends.) Over 20 years, this results in 77% more flights.
  • the future schedules are based upon the year 2000 CMO process. This process uses an analysis of the 1999 OAG and creates forecasts for the future years 2004, 2009, 2014, and 2019. We use CMO forecasts of departures and available seat miles
  • ASMs ASMs by equipment type and major airline.
  • ten specific major US airlines were considered with three artificially aggregated carriers for cargo, foreign, and other US.
  • the forecasts were scaled up to represent the future time periods of 2005, 2010, 2015, and 2020. After scaling, the forecast showed a 77% increase in total departures from year 2000 to year 2020 with an average flight distance increase from about 688 miles to 696 miles, and with an increase from 173 seats per mile 69
  • lift i.e., number of seats
  • the set of non-stop airport pairs for an airline is called its route map.
  • An analysis of existing schedules is first used to identify the route map for each major airline and, for each airport pair in the route map, the lift currently allocated to that pair.
  • the future required lift for an airport pair is then calculated by factoring its current lift into the future by the ratio of the total CMO forecast ASMs divided by the total current ASMs for that airline. For this analysis it was assumed that there are no new non-stop airport pairs and that each existing pair, within an airline, grows at the same rate.
  • the existing schedules are also analyzed to uncover the bank structure employed at each major airline hub. It is assumed that this bank structure will remain the same in future time periods although the maximum bank sizes will be permitted to grow.
  • the departures (or arrivals) assigned to the hubs are then allocated to the airline banks in order to maximize schedule quality (using the Boeing Decision).
  • the last step in the process is to finalize the departure and arrival times for all flights (by any airline) while observing an airport specific limitation on the number of operations (takeoffs or landings) which may occur in any five minute time window.
  • Second priority for flights not involving hub-spoke operations, is given to departure and arrival times from the existing schedules. All other flights are scheduled to maximize schedule quality (again, using the Decision Window Model) while observing the airport specific operations limits.
  • the top airports were assumed to grow by 50% in their ability to process takeoffs and landings by the year 2020. A small subset of these was assumed to grow by 100%. Maximum bank sizes were assumed to grow in a corresponding manner.
  • An important limitation of the schedules generated thus far is that they are not efficiently tail routable, that is, tail routings would result in a large number of inefficiently utilized airplanes. 7.1.3 Delay and Cancellation Growth
  • delay growth curves are for a do-nothing scenario — the system evolves as it has historically and there are no new runways/airports beyond what is currently planned in the FAA's 2000 Aviation Capacity Enhancement Plan.
  • Delay growth is measured in terms of the increase in arrival delay minutes per flight, including block time creep, over time.
  • Method 1 Historical Extrapolation The first curve was developed from extrapolation of historical data from 1976 to
  • TAOS Terminal Area Operations Strategy
  • VMC Visual Meteorological Conditions
  • MVMC Marginal Visual Meteorological Conditions
  • IMC Instrument Meteorological Condition
  • airports had 51% of all the NAS operations in 2000 and are run much closer to capacity than the remaining airports in the NAS. If delay minutes per flight are assumed to grow at a slower rate of 3% rate per year at the remaining airports, the resulting NAS delay growth rate is 7.5% per year. The assumption in this approach is that all delay will grow at the same rate as airport delay.
  • a new runway will truly reduce delays if it will enable the airport to have an additional independent arrival stream during poor weather. Rough estimates are that these runways will reduce delay by 2-5% throughout the NAS, under current operating assumptions. Another objection to this level of delay growth is that airlines will never allow delay to grow at these levels and will take actions like create new hubs, avoid congested airports, etc to alleviate congestion. This is a valid objection, therefore we have made
  • the starting point was arrival delay minutes, according to COD As, during the convective weather season, April 1 - October 31. In year 2000, the average arrival delay during that period was 15.7 minutes per flight. To estimate this delay, estimates were made of the percent delay caused by weather (60%) and the percentage of weather-caused delay caused by convective weather during the convective weather season (40%), meaning 24% of the delay during that season was caused by convective weather. This period encompasses a little less than 2/3 of all operations during the year, resulting in 15% of annual delay caused by convective weather. Industry sources were used to estimate the delay percentages.
  • TAOS analysis was used to estimate terminal delay for the top 25 airports and then extrapolated to a NAS-wide delay.
  • the TAOS analysis developed curves that predict the delay minutes per flight for VMC, MVMC and EVIC conditions based on the number of daily operations.
  • TAOS developed delay curves as follows: 74
  • SEA runway constrained airport
  • EWR airspace constrained airport
  • ORD airspace constrained airport
  • DIA unconstrained airport.
  • IFRl/2 is equivalent to CAT ITU and IFR3 is equivalent to CAT JJIa.
  • VMC the curve for VMC was developed from the VFR delay numbers.
  • IMC the curve for IMC was developed from the IFR or IFRl/2 delay numbers.
  • the curve for MVMC was interpolated from the VMC and IMC curves.
  • IFR4 Equivalent to CAT UIc
  • C/AFT CNS/ATM Focused Team
  • the delay curves for the representative airports (SEA, EWR, ORD, and DIA) for 2000 - 2020 were developed using a power curve fit function.
  • the FAA's Terminal Area Forecasts, FY 2000 - 2015 provided a count of the number of operations at each airport in year 2000. With the count of operations and the delay curves by airport, the curves developed above were used to estimate the delay minutes per flight for VMC, MVMC and J C operations at each airport.
  • TAM Total Airspace and Airport Modeler
  • the New York model included Newark, La Guardia, Kennedy, and Teterboro Airports and the airspace interactions between those airports. Besides the airspace, only the runways and runway exits for each airport were included in the model; a detailed surface model for each airport was not included. Models were developed for the best good weather configuration and the worst bad weather configuration. Trajectory Management — En Route
  • VMC 0/10/20% Trajectory management will increase sequencing and spacing accuracy, by reducing uncertainty in trajectory prediction.
  • the benefit models cover the years 2001-2021 and use a discount rate of
  • a 10 percentile is a value so low it is believed there is only a 10% chance the actual outcome will be below that value.
  • a 90th percentile is a value so high it is believed there is only a 10% chance the actual outcome will be above that value.
  • a 50th percentile is a value such that it is believed the actual outcome is equally likely to be above or below that value.
  • Delay has two components.
  • the primary metric airlines are measured against is arrival delay—the difference between the actual arrival time and the scheduled arrival time.
  • arrival delay the difference between the actual arrival time and the scheduled arrival time.
  • Block time creep results from airlines extending their block time to meet industry targets for on-time arrivals.
  • the benefits for each concept are summarized in the table below.
  • the second and third columns are the total reduction in delay and cancellation for the NAS in 2020, when the system is fully implemented.
  • the fourth column is the Net Present Value
  • Capacity/Delay Elasticity Assuming flights grow at the forecasted 2.9% per year, there will be 77% more flights in 2020. Based on that flight growth, we forecast two delay curves. If delay grows 3% annually, delay would increase to 1.8 times today's level. A 30% reduction in delay means delay will increase to 1.3 times year 2000' s level. Ii delay grows 8% annually, delay would increase to 4.7 times today's level. A 30% reduction in delay would mean that delay will increase to be 3.1 times the year 2000 level.
  • Airplanes with Digital Integrated Avionics use the latest generation of avionics.
  • Avionics functions such as flight management reside on a card within a fully integrated system such as AIMS on the 777.
  • AIMS AIMS on the 777.
  • CNS/ATM upgrades to digital integrated avionics systems.
  • the cost and schedules requirements for CNS/ATM upgrades that use digital integrated avionics systems may be significantly different from those airplanes that employ digital federated avionics architectures.
  • Airplanes with Digital - Federated Architecture use avionics systems where each function resides more or less on its own individual hardware platform. For example, flight management computer, display functions and air data functionality are each contained in separate Line Replaceable Units. Each of the avionics systems share data over digital busses (e.g. ARINC 429). There are few technical barriers to CNS/ATM upgrades for airplanes that employ digital federated avionics systems.
  • Airplanes with Hybrid Avionics are typically analog airplanes that have received avionics upgrades to support some digital avionics, e.g. FMCs and display systems.
  • CNS/ATM upgrades may be more difficult and costly to accomplish compared to all digital systems since airplane data required to support a new
  • CNS/ATM function might not be readily accessible to a new or updated avionics system.
  • the airlines will also be required to update their SOC work stations in order to provide the functionality needed to support improved exchange of flight plan information with their aircraft fleet, air traffic control and the Air Traffic Control System Command Center.
  • Airspace Accessibility Access to airspace and air traffic services will be important considerations for GA in the future system.
  • users In the existing system, users have the flexibility to choose the extent to which they require air traffic services.
  • RTCA Report DO-266 user groups from around the country provided input regarding their priorities for airspace redesign.
  • Airspace designs currently allow flexible access around, through, over, and under busy airports.
  • General aviation stakeholders do not want airspace redesign to adversely affect the accessibility and operational flexibility provided by the existing VFR and IFR flight environments.
  • the requirements for access directly relate to aircraft equipage and pilot certification/training requirements.
  • General aviation stakeholders will be concerned about the impact of new equipment requirements, new regulations, and new operational and airspace restrictions. Stakeholders would desire a "real-time" ability to access special use airspace.
  • Airlift aircraft must be equipped to operate within the system. Procedures to allow tactical aircraft to accomplish their mission must be addressed. 83
  • Determining the sequence of the transition elements is a critical component of program management. Should the new equipment and procedures be integrated separately or together? Should the entire system transition at once or facility by facility? This decision is significant since a 'waterfall' approach would require the new equipment to communicate with the current system until the total transition is complete. Many other critical risk factors must be understood. Proper risk management planning will require substantial efforts to enable the program to be successful.
  • ATC simulators use the host computer resources. During busy periods there is a concern that the simulators may overload the host computing capacity. Future simulators need a separate full-time computer resource with access to the operational database.
  • New high fidelity simulators will be mandatory, due to the magnitude of developing new procedures/equipment and operational simulation. Simulators will be needed throughout the concept development process (e.g., airspace/procedures/equipment layout prototyping/design, work processes, safety analysis, human factors identification). After initial concept development, simulators will be needed to train controllers for tower, terminal, en route, and ATCSCC. Simulators may also be needed for flight operations personnel and cockpit crew.
  • ATC simulation is extremely limited and labor intensive when compared to the sophistication of aircraft simulators. (It might be prudent to develop a teaming relationship with an established manufacturer of simulation equipment to begin initial talks on this potential market.)
  • the transition training recommended in the Boeing approach requires much more than financial backing to be successful. It requires that participants at all levels must understand how they fit into the overall picture and how their individual actions affect the performance of the total system.
  • the first step in the transition plan will be to list and prioritize the airports that present the greatest constraints to overall capacity growth in the NAS. For each airport, the current master plan will be reviewed. The master plan will help to determine any improvements that are identified and in the pipeline. The master plan will identify any improvement alternatives and the reveal the preferred alternative. The preferred alternative will have been approved by the community, airlines, and other airport operators. 88
  • the next step will be to perform a constraints analysis to identify the constraints to capacity growth at each airport.
  • the constraints analysis will include interviews with people at airport authorities, ATCTs, TRACONs, airlines (including ramp personnel), and the airport consultant. This will help uncover the factors that constrain capacity through the entire airport system.
  • the next step will be to determine what can be done to mitigate each of the constraints and to determine the cost. Some of the constraints could be mitigated by construction, others by the purchase of equipment or the addition of new technology, and others by a change in ATC procedures.
  • the set of alternatives would be analyzed by the Preliminary Design toolset to determine the best combination of alternatives.
  • the identified airport improvements would need to be approved by an airport (technical) advisory committee with representatives from airport staff, airlines, other operators at the airport, the neighboring community, and the airport consultant.
  • the FAA is currently planning the NAS architecture through 2015. Near-term involves sustaining the current system's operational capability. Selected enhancements are included where costs and program risks can be contained, such as in 89
  • Free Flight Phase 1 Deploying advanced CNS/ATM technology will be necessary to avoid traffic gridlock.
  • Preliminary design consists of defining system requirements and objectives, analyzing functions and operations, and defining the system architecture. The remaining steps are system design and development, integration in the laboratory, validation testing, and system operation and maintenance.
  • the discipline of the systems engineering process has been vital to the successful completion of airplane development programs, where a team of thousands of engineers develops and certifies a complex, real-time, human-in-the-loop, safety critical system.
  • the development of a major ATC system upgrade is even more complex, because it shares the safety criticality and human-in-the-loop real-time nature of airplane development, and further requires that the existing system remain operational while supporting transition to the new system.
  • Preliminary design is intended to clarify the product goals and objectives, develop mission evaluation methods and tools, define a wide range of configurations and technology options, result in trade studies, and baseline a configuration for negotiation with customers.
  • the Preliminary Design (PD) process is driven by overall system performance objectives, and supported by a baseline of the current system, a comprehensive analysis toolset and an inventory of technology options and human performance considerations.
  • the PD process provides a set of system enhancement alternatives and associated performance data that allows trades to be made prior to decisions on major system concept and architecture options.
  • a forecast of future traffic levels is the primary input to establishing system objectives.
  • Various organizations publish annual traffic forecasts for their stakeholder group, and the FAA also publishes a 20-year forecast of traffic for all major airports. It is the FAA's responsibility to accommodate the predicted demand within the constraints of safety, affordability, and environmental issues.
  • Task 1 in the Boeing proposal considers the predicted 20-year traffic levels and the driver for change. The engineering and operational solution is driven by these growth targets, along with the other key system performance objectives.
  • Task 2 develops a plan for a detailed study of a particular airspace region in the current NAS, which is selected based on an examination of the primary system performance concerns identified early in Task 3 (which will actually begin prior to Task 2).
  • Task 2 develops assumptions about airport infrastructure plans, airline business strategies and fleet mix predictions. Alternative future scenarios can be defined in this task, to span the range of possible futures.
  • the system baseline incorporates the current operational concept and existing system architecture, and describes a set of operational scenarios sufficient to define normal, rare-normal and non-normal behavior.
  • the baseline provides the current system performance data needed to select airspace regions in need of substantial operational improvements, and also serves as the basis for the evaluation of airspace alternatives that concludes the PD analysis. Task 3 will involve the establishment of such a baseline for the current NAS . 92
  • the baseline of the current system provides a basis for evaluating the most important current and future system 'performance states'.
  • the challenge is to reduce the performance characterization to a manageable set of conditions (which include weather, rare-normal, and abnormal events) in a set of baseline operational scenarios.
  • Subsystem performance benchmarking is also required to determine the performance of the CNS and ATM elements of the current system.
  • the performance of the existing navigation, communications, radar, and air traffic and flow management systems is an important indicator of current system operating capability, and is reflected in the separation standards and working methods of the system operators. 10.3.4 Perform Mission Analysis
  • the Mission Analysis involves forecasting the future demand on the air transportation system.
  • the generation of traffic demand involves the prediction of future flight activity levels for commercial airplanes, general aviation and military aircraft.
  • the forecast begins with a city-pair analysis of US domestic and international flight segments.
  • a nominal flight schedule (similar to the Official Airline Guide) can be developed based on assumed economic growth, average airplane size, assumed airport infrastructure, and airline hubbing and schedule frequency assumptions.
  • Converting the flight schedule into a traffic demand model is based on a modeling of the system-wide flight planning activity, which translates the origin-destination schedule into flight profiles. These profiles are based on assumptions of the future concept of operations for postulated future use of airspace and airways. The flight profiles are based also on assumptions of how users will fly between city-pair destinations, e.g., how the airline fleet will be used, including assumptions of the criteria for single airplane flight planning. Section 7.1 describes an initial Mission Analysis based on the assumption that current strategies of airlines and other users will remain the same over the next 20 years. The methodology will be extended further to include additional airports and changes in airline hubbing strategies. 93
  • the traffic demand model is the basis for a traffic loading model which estimates average and peak operations counts for the affected center, sector, and terminal areas. This model can be established, based not only on the nominal flight schedule, but on assumptions of various contingency responses to system perturbations.
  • the set of operational scenarios to be evaluated for the system loading model are established as part of the system baseline. 10.3.5 Develop Operational Concept
  • the ATM operational concept describes the way in which the aviation system resources are allocated to respond to the traffic demand and meet system performance objectives.
  • An operational concept describes the functions performed in the system to deliver the required services, along with an assigning these functions to system agents and/or equipment. Services are delivered at a certain level of performance that can be quantified using the overall system performance metrics.
  • the current NAS uses a wide array of technologies, many of which originated in World War ⁇ , with stepwise improvements since then to fine-tune performance.
  • Today's tactical radar control concept, with its associated voice radio communications and reactive flow management response, will likely be unable to cope with the predicted growth in traffic while continuing to maintain or improve safety.
  • the desired performance will require a major change in the system operation and supporting technology, so that the human operators can achieve a substantially higher level of performance.
  • a higher level of system throughput could be achieved through more coordinated dynamic traffic planning functions, combined with a precision trajectory- based separation assurance to allow a reduction in effective traffic spacing.
  • the system baseline provides the foundation for examining particular problem areas and performance issues for the selected airspace region. This, along with the performance objectives and framework, will guide the development of new concepts. Airspace and Airways
  • the operational concept will consider the nature of routes and flight levels in the chosen airspace region and timeframe. This includes fixed flight level vs. cruise- climb profiles for en route operation, and the associated vertical separation standard. 94
  • the separation assurance function assesses the potential improvements in capacity, safety and affordability. With an eye to potential increases in capacity and affordability, we will examine the future "sector," or the unit of work associated with separation assurance in the system. This will include the roles and responsibilities to airborne and ground elements in the separation assurance function. This development may lead to requirements for improved technical performance of the supporting CNS/ATM technologies, and to the identifying human cognitive processes and critical human performance factors that must be addressed. 95
  • the performance analysis is based on a representation of the system functional architecture, using finite state-machine methodology for an event-driven, scenario- based dynamic analysis.
  • the system resources (such as CNS and human operators) are represented in a parameterized form to permit a sufficient range of alternatives to be explored. The parameters will be obtained from detailed simulation models and/or experiments.
  • Human factors tools such as Man-Machine Integration Design and Analysis System (MIDAS) and Performance and Usability Modeling in ATM 96
  • An overall toolset that connects technical and human performance to the system performance metrics through models of regional and national air traffic flow is at the heart of both the Level HI and II dynamic traffic simulation models.
  • the overall toolset should consist of a number of separate models, integrated either at runtime or through input/output data sharing, depending on the level of coupling deemed necessary.
  • a number of key metrics will be identified by the PD process so as to perform cost, benefits and safety evaluation of the new operational concepts.
  • a number of modeling tools are already available, but they are neither integrated in a comprehensive evaluation toolset nor are they yet suitable to address the challenges posed by the long-term system performance objectives.
  • Safety modeling and analysis connects the failure modes and associated probabilities of components (hardware, software and human agents) with the probabilities of the top-level (presumably undesirable) events, such as loss of separation. This is accomplished in two steps.
  • the bottom-level "Reliability Model” block represents the process of turning the failure mode behavior of the hardware, software and humans 97
  • the second step is to transform the probabilities of these operational states into probabilities of the top-level events by doing Monte Carlo simulations of the traffic, depending on the operational states.
  • a Boeing tool called “Reliability Performance Module” (RPM) contributes to this process, and produces probabilities for all sequences of fault or error events. Examples of "error or fault sequence” include: “Arrival controller transposes flight numbers USAir 5829 and USAir 5289", “BA125 loses transponder", and "Secondary radar produces spurious data”.
  • the reliability tool automatically cycles through all such sequences of fault and error events (of incremental length up to a specified maximum). It also calculates probabilities for all of these sequences based on the assumed failure rates or probabilities for the fundamental failure modes.
  • the probability of being in one of the three operational states is computed by simply summing the probabilities of all sequences assigned to that state. This part of the process involves discrete-event style simulation. So far, no explicit continuous type simulations have been used (although such simulations might be used to produce certain parameters for discrete-event simulation).
  • FHA Functional Hazard Analysis
  • Component and Agent-level FMECAs determines the possible faults, errors and failures of the fundamental components of the system, including hardware, software, and human agents.
  • FMECA Failure Modes, Effects and Criticality Analysis.
  • This process should also identify the probabilities or failure rates associated with the failure modes of these elements. These probabilities or failure rates eventually feed into the calculations done by the analysis tool which produce the top- level event probabilities.
  • the top-down part of the analysis would impose, or allocate, requirements on the subsystems, which would then ultimately flow down to the subsystem components or agents.
  • this component-level information will be provided or derived independently, and then used to produce the top-level event probabilities by using the process shown in the diagram. These top- level probabilities are then compared to the system-level requirements in order to determine certifiability.
  • Integrity is but one of several metrics which are used to judge a system's reliability and safety. The others are accuracy, latency, continuity and availability. Here are some brief definitions:
  • D Accuracy a measure of the ability of a system or subsystem to deliver its output with a specified variability. Examples: 1) A certain radar reports target positions with one standard deviation of 0.1 NM (at a specified range). 2) A given mode of GPS reports aircraft position with one standard deviation of 100 meters. Given the assumption of a distribution for the measurements (normal, for example), accuracy involves both a distance and a probability.
  • D Latency a measure of the timeliness of required data, for example, sensor measurements, controller clearances, pilot responses or requests. Large latencies introduce extra "slop" in the system, and can compromise safety margins.
  • D Continuity the (conditional) probability that a system continues to operate properly, given that it operates properly now. This is especially important in stressful situations where an interruption would greatly overload controllers or pilots.
  • D Availability The a priori probability that a system will be available at a given time in the future. It is desirable to have confidence in system availability once operations begin.
  • D Integrity If a component, subsystem or system is unlikely to deceive the user, it is said to have integrity.
  • the usual measure of integrity is the probability of an undetected error.
  • a high integrity system has a very low probability of undetected error (or errors).
  • Undetected errors can be the most malicious kind, because an unaware user may proceed blithely into a dangerous situation. For example, if aircraft IDs are transposed without realizing it, a command intended for one aircraft may be given to the other, causing it to blunder into the path of yet another aircraft. Or, a radar may produce faulty position data which looks just good enough not to be noticed, and a separation violation is missed.
  • One familiar application of the integrity idea is in RNP. See section 5.1.4.3 for a description of RNP integrity. 102
  • the methodology and tools must be flexible and hierarchical in nature, for two reasons.
  • the first reason has to do with the nature of the design process itself. We typically analyze high-level low-fidelity models in the early part of the design process, more detailed higher-fidelity models towards the end of the design process, and various stages in between.
  • the tools must have the ability to represent high-level functionality, as well as the ability to expand these functional representations hierarchically into lower-level detailed sub-models.
  • the tactical control of aircraft represents the short time period which characterizes the terminal area.
  • the time scale of the control loops get longer, the geographical area grows from TRACON to regional to national, and the numbers of aircraft, controllers, and other agents increase.
  • the safety tool suite must support detailed models for the far right (terminal area) portion which include individual aircraft, controllers, pilots and other agents.
  • the TRACONs and their interactions would become the fundamental modeling elements, as would the regions and their interactions at the national level.
  • the parameters for the safety analysis of a model at a given level would be provided by the safety analysis of the model at the next level down. 10.3.7 Select Technology Sets
  • Task 7 will evaluate alternative technologies to select promising candidates.
  • the functional requirements for an arrival management concept could include weather forecasting and aircraft trajectory intent information.
  • the weather requirements could be met by a ground- based system, or by aircraft-based weather observations for frequent updating of regional weather forecasts.
  • intent requirements could be satisfied by using data link, on-board FMS capability and trajectory negotiations.
  • the functional performance requirements will be allocated to the technology subsystems.
  • the technology sets must be sampled across all CNS/ATM categories and not simply within individual technology groups such as communication.
  • use of precision RNAV routings could be a means of increasing capacity in the terminal area.
  • a safety analysis may identify the need for enhanced surveillance and alerting to assist the air traffic manager in monitoring path conformance. This could be provided by airborne-based monitoring and path conformance in the navigation function, by transmission of aircraft position and intent, or by conventional radar monitoring and path conformance alerting.
  • the system solution might require two or more such monitoring systems to achieve the required level of operational availability and integrity. 10.3.8 Assess Architecture Impact Task 8 will examine, for the case study, the effect of the planned NAS architecture on the alternative operational concepts.
  • Baseline and Planned Architecture Interface This task will investigate the system interfaces affected by the new technology sets, based on the case study parameters and the planned evolution of the baseline architecture. For each technology set, the target systems and/or interfaces will be identified. This identification will be for both ground system architecture and for airborne systems, where appropriate. We will use tools or data bases such as the FAA's NAS CATS-I, if available.
  • Timing and Risk Assessment This task will analyze the timing of block changes in the baseline architecture for the target end systems, interfacing systems, and enabling systems for the technology sets selected. This assessment will identify technology, timing and programmatic risks for the alternatives being considered. Fleet equipage rates will likewise be considered. 104
  • Life Cycle Cost Impact This task will assess the life cycle cost impact on the baseline ground and airborne architectures. For a case study, this will be based on a parametric cost estimation. More comprehensive tools will be considered, if available. This will provide delta-costs for the baseline NAS time period, for both recurring and non- recurring items.
  • Airspace and Procedure Design Criteria New preliminary airspace design criteria will need to be developed to support the new operational concepts. Examples are route separation minima and air traffic procedural criteria for obstacle clearance or traffic handling. We will assess the needed criteria to ensure the optimum use of the specified technology sets. The case study will make assumptions about new criteria availability. The evaluation will enable the system architect to estimate the impact of operational changes by extending the requirements analysis and technology tradeoffs beyond the initial point design, and to gather specific data on operational changes that users can expect to see in the future case study airspace. Preliminary Airspace Design: System performance will be evaluated on new airspace designs, predicated on the performance expected from the improved operational 105
  • Evaluate 2010 NAS V4.0, V5.0 Cases The current baseline case will be augmented by FAA planned architecture changes.
  • Evaluate 2010 PD Concepts A and B The new concept options proposed by the PD case study will be evaluated and compared with the baseline and planned cases.
  • Safety Analysis Comparing the alternative operational concept options applied to the case study airspace, and the "Do-Nothing" case, the safety analysis will develop possible scenarios for each operational concept that capture particular non-normal sequences of events. These will include possible human (pilot, controller) and system mitigating actions, and a preliminary estimate of the particular operational safety outcomes for the alternative concepts. Top-level safety characteristics of the different concepts will be estimated for the case study airspace operations. Assess System Alternatives: The alternatives will be rated for airspace performance characteristics and the cost and risk parameters from Task 8. An investment analysis will refine the rating to support the full application of the PD process. This rating will allow decisions on future architecture plans to be driven by comprehensive design data.

Abstract

The proposed architecture for an air traffic management system concentrates on information exchange to provide trajectory-based flow and flight planning, and separation assurance. The various Control, Navigation, and Surveillance elements are combined into a concept of a satellite-based Global Communication, Navigation and Surveillance System (GCNSS). Such a system would extend the functionality of GPS-based navigation to incorporate enhanced Position, Velocity and Time services, as well as adding important new communication and surveillance functions for a completely integrated ATM operating environment. The GCNSS would have three major segments: space, ground and users. Such a system represents a paradigm shift in the current conception of airborne navigation, communication and surveillance (CNS).

Description

AIR TRAFFIC MANAGEMENT SYSTEM AND METHOD
TECHNICAL FIELD The present invention relates to an air traffic management system and to a method for controlling aircraft in an airspace to assure appropriate and safe spacing (i.e., "separation assurance").
BACKGROUND OF THE INVENTION Discussion is integrated into to the DETAILED DESCRIPTION.
SUMMARY OF THE INVENTION
The proposed architecture for air traffic management of the present invention concentrates on trajectory-based flow and flight planning, and separation assurance. The various Control, Navigation, and Surveillance elements are combined into a concept of a Global Communication, Navigation and Surveillance System (GCNSS). Such a system would extend the functionality of GPS-based navigation to incorporate enhanced Position, Velocity and Time services, as well as adding important new communication and surveillance functions for a completely integrated ATM operating environment. GCNSS would have three major segments: space, ground and users. Such a system represents a paradigm shift, in the current conception of airborne navigation, communication and surveillance. While ground-based systems would remain in the US National Airspace System (NAS) for some time or in the corresponding air traffic management systems of other countries or authorities, dependence on the ground-based systems would lessen over time to the point where they could be selectively phased out.
Boeing is developing an Air Traffic Management (ATM) system that will dramatically increase capacity, improve safety, and remain affordable for those who use the system. The system should reduce the number of delays as well as the duration of any delays that are required. Such delays are frequently the result of weather at airports or on congested routes within the controlled airspace. Creating an air traffic system that is viable well into the future will require a fundamental change to how the system operates. The solution will employ sophisticated software and satellite-based communication, navigation and/or surveillance (CNS) technology.
In a preferred embodiment, controllers gain access to information commonly stored in the flight management computers (FMCs) of transport airplanes to learn the ture position of each airplane under control and its intended trajectory. The controllers integrate this information into the other information, like ground radar and weather, upon which they rely for making control decisions, using air traffic control computers (ATCs).
BRIEF DESCRIPTION OF THE DRAWING
The Figure shows a schematic representation of a preferred two-way communication network between airplanes and air traffic controllers to achieve the desired air traffic control improvements of the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
This description is taken from Boeing's document entitled "National Airspace System Modernization, A Capacity Driven Plan, Edited Version 1-A, May 9, 2001. This document was first released to the public on June 3, 2001. Listed page numbers in the following Table of Contents refer to the page in the Boeing document and may not correspond to the page numbers of this specification. The Table does, however, provide the major sunsectiopns of this DETAILED DESCRIPTION.
Table of Contents
1 Introduction 6 1.1 Scope 6 1.2 Purpose and Audience 7
1.3 Key Words and Definitions 7
2 The Problem And Its Roots 8
2.1 Lack of System Capacity 8
2.2 Historical Perspective 9 3 Airspace System Requirements 12
3.1 Safety 12 3.2 Capacity 15
3.2.1 Capacity Goals 15
3.2.2 Traffic Growth Estimation 16
3.2.3 Operational and Flow Planning Limitations on Capacity 16
3.3 Delay Management 16
3.4 Access 17
3.5 Environmental (Noise and Emissions) 18
3.6 Effect of Severe Weather and Low Visibility on Capacity 18
3.7 Affordability 18
3.8 Collaborative Planning 19
4 Operational Concept 20
4.1 Today's System 20
4.1.1 The Daily Schedule 20
4.1.2 Positive Controlled Airspace 21
4.1.3 Procedural Control Airspace 21
4.2 Airspace Management 23
4.2.1 Existing Airspace Classes 23
4.2.2 Tomorrow's Concept of Airspace Management 24
4.2 Flow Management 27
4.3 Traffic Management 28
4.4 Flight Management 30
4.5 Airports 31
4.6 Concept Differences 33
5 Performance Requirements 36
5.1 Separation Assurance - System Level 36
5.1.1 Air Traffic Manager 37
5.1.2 Surveillance 39
5.1.2.1 Today's System 39
5.1.2.2 En Route 40
5.1.2.3 Emerging Techniques for Enhanced Surveillance 42
5.1.2.4 Future Surveillance System Requirements 42 5.1.3 Communication 43
5.1.3.1 Current System 43
5.1.3.2 Emerging Techniques for Enhanced Communications 44
5.1.3.3 Future Communication Requirements and Plans 44 5.1.4 Navigation 44
5.1.4.1 Today's Airways-Based Navigation System 44
5.1.4.2 Area Navigation 45
5.1.4.3 Required Navigation Performance 45
5.1.4.4 Transition from Airways-based Operations to RNAV and RNP 46 5.1.4.5 Landing System 47
5.2 Flow Management - System Level 47
6 Architecture Elements 49
6.1 Phase 1: Trajectory-Based Flow Planning 50
6.2 Phase 2 : Traj ectory-B ased Flight Planning 51 6.3 Phase 3: Trajectory-Based Separation Management 53
7 Economic Benefits 55
7.1 Forecast Methodology 55
7.1.1 Flight Growth 55
7.1.2 Schedule Forecast 55 7.1.3 Delay and Cancellation Growth 56
7.2 Calculation Methodology 59
7.2.1 Net Delay Reduction and Cancellation Reduction 59
7.2.2 Net Delay % by Cause 61
7.2.3 Net Delay Reduction Estimates 62 Delay Cause 62
7.2.4 Net Present Value Calculations 63
7.3 Summary of Benefits 64
8 Stakeholder Impact 66
8.1 Airlines 66 8.1.1 Airline System Operational Center (SOC) Impact 67
8.2 General Aviation 67 8.2.1 Leveraging New Technologies 68
8.3 Military 68
8.4 Airports 68
8.5 Air Traffic 68 9 Transition Planning Considerations 69
9.1 Equipment Transition 69
9.2 Operational Transition for Airspace 69
9.3 Institutional Transition 70
9.4 Personnel Transition 70 9.5 Cost of Transition Training 70
9.6 Airports - A Special Challenge in Transition Planning 71 10 A Methodology for Preliminary Design of Airspace System Definition 73
10.1 The FAA's NAS Architecture and Operational Concept 73
10.2 Industry System Development Approach 74 10.3 Preliminary Design Process for Airspace System Definition 75
10.3.1 Establish NAS Objectives 76
10.3.2 Develop Study Plan 77
10.3.3 Baseline Current System Performance 77
10.3.4 Perform Mission Analysis 77 10.3.5 Develop Operational Concept 78
10.3.6 Analyze Required Performance 79 10.3.6.1 Safety Methodology and Tools 81
10.3.7 Select Technology Sets 86
10.3.8 Assess Architecture Impact 86 10.3.9 Evaluate Airspace and Alternatives 87
Executive Summary
The Boeing Air Traffic Management system will revamp the US National Airspace System (NAS) to achieve specific gains in capacity, safety and efficiency. The Introduction (Section 1) that follows briefly introduces the current NAS, describes Boeing's ATM business unit, and supplies a few key terms. The Problem 7
and Its Roots (Section 2) provides a brief history of air traffic control in the US, and summarizes how the US got to the situation in which it finds itself today. Airspace System Requirements (Section 3) describes the main requirements for a functional ATM system. The key issues are safety, capacity, delay management, access, affordability, and collaborative planning. These elements are valued differently by the stakeholders of the existing system, and these differences must be reconciled to move ahead with NAS reform.
The Operational Concept (Section 4) discusses the ATM system of today, providing a context for a discussion of the concept for tomorrow. The future concept which is the basis of the present invention includes the interrelated elements of flow management, traffic management, flight management, airspace management, and airport surface management. Section 4 describes some of the features of Boeing's baseline concept, and a key subsection compares and contrasts the Boeing concept with the system of today, and with the NAS Operational Evolution Plan (developed by MITRE for the FAA).
Architecture Elements (Section 5) describes the framework architecture of the new Boeing ATM system to rebuild the current ATM system in the NAS. The section defines the concept of trajectory-based ATM for the separate operating environments, and explains Boeing's vision of how this concept can be successfully implemented. While new runways are considered to be an important factor in any future NAS, the approval and construction of new runways at major choke points is problematical. The proposed Boeing architecture concentrates on trajectory-based flow and flight planning, and separation assurance.
The various Control (C), Navigation (N), and Surveillance (S) elements are combined into a concept of a Global Communication, Navigation and Surveillance System (GCNSS). Such a system will extend the functionality of GPS-based navigation to incorporate enhanced Position, Velocity and Time services, as well as adding important new communication and surveillance functions for a completely integrated ATM operating environment. Economic Benefits (Section 6) makes a preliminary attempt to assess the benefits of Boeing's new operational concept to the stakeholders. This section defines 8
the nature of the benefits (increased capacity, decreased disruption, and quantifying the value of time saving and cost avoidance). The section explains the manner in which the forecasted benefits are derived, using established industry sources. The type of weather delays inflicted upon the NAS are described in some detail, with percentage of delay ascribed to each type. The projected benefits are summarized for each proposed operational enhancement, and specified in Net Present Value terms.
Performance Requirements (Section 7) expands the requirements identified in Section 3 into technical performance requirements for separation assurance and flow management. This section provides the lion's share of the technical performance criteria that must be met by any future ATM concept. Performance criteria for communication, navigation and surveillance are discussed in the en route and terminal area environments.
Stakeholder Impact (Section 8) identifies the primary users and owners of the NAS, and describes the ways in which each stakeholder is affected by the proposed operational enhancements. Avionics for commercial airlines are described in some detail. Information is provided for other stakeholders such as general aviation, military, business aviation, airports, and air traffic service providers.
Transition Planning Considerations (Section 9) identifies various challenges to implementing a new operational concept for the NAS. A large, complex, highly integrated heritage system such as today's NAS is not easily converted to something new. The vital transition issues must be approached in tandem rather than individually. This section describes issues of equipment transition, operational transition, institutional transition, and personnel transition (training and cost factors). Various types of training are considered critical for the successful transition to a new operational concept.
Methodology for Preliminary Design of Airspace Systems Definition (Section 10) describes the Boeing concept of a preliminary design process to support the definition of an airspace system. This process will be used to select the toolset required to implement the new operational concept in various airspace segments of the NAS. A complete design process such as this has never been performed on the NAS before. This process is critical to successfully analyze which technologies and procedures should be applied to the operational environments in the NAS.
1 Introduction The Boeing system will provide trajectory-based separation of airplanes 10 in an airspace, relying on sharing of information commonly programmed today into flight management computers (FMCs) 12 on commercial transport aircraft. Little additional (new) data is required. The Boeing system simply provides access to this existing information to the planning computers 14 of the air traffic controllers 16. Basically, the trajectory information defines the path on which the airplane intends to fly. The system provides a robust communication network, especially providing near real-time, accurate weather data 18 to the aircraft and the controllers. Capacity in the airspace is increased by simplifying the airspace and relying on the trajectories together with accurate monitoring of the true position of the aircraft using GPS (the Global Positioning System). Controllers know where the planes actually are and where they intend to go. Communication likely will relay transmission through a constellation of satellites 20, thereby ensuring that information can be provided around the world or anywhere in the airspace without significant ground stations or ground infrastructure 22. The satellite implementation is, perhaps, more important, then, for under- or developing countries which lack such ground-based infrastructure, but it should also benefit the US going forward. The system is readily accessible to commercial and general aviation. The controllers also have data from radar 24.
The NAS is one of the largest systems in the world. It is made up of enroute centers, terminal control centers, airports, ground navigation aids, space-based components, thousands of airplanes, and the people to operate them. The system operates safely, but recent performance indicates that it may be reaching saturation. This fact represents a challenge for changing the system. Two earlier changes provided a paradigm change for the system. The capacity constraints of the system indicate it is time for another paradigm change. Over 65% of the transport category airplanes operating in scheduled service in the NAS currently have the ability to provide controllers with high accuracy, high 10
integrity position and intent information from their flight management computers. In the present invention, this information will be used by the controllers to more effectively plan their work and to allow them to execute needed tactical changes.
The advent of the Global Navigation Satellite System (GNSS) has demonstrated that space-based assets can be used to provide NAS services. These space-based services have the potential of providing the needed performance at more affordable cost, not only for the NAS, but also for worldwide operations.
The success of any change and new implementation in the air traffic management system requires: (1) establishing the ground rules for the baseline system today;
(2) understanding, defining, rating and prioritizing potential solutions and alternatives; and
(3) minimizing the risks and achieving the goals, objectives, and schedules that are described for the present invention. 1.1 Scope
This section describes the current NAS ATM concepts and the changes proposed by the Boeing ATM Project. In describing the Boeing solution, it describes the requirements needed to effect this change; the architecture; the potential economic benefits; the methodologies used to analyze the problems; Boeing's proposed solutions; the related impacts on airports and stakeholders; and, finally, considerations for the transition from the current system to the new ATM system.
1.2 Purpose and Audience [deleted as irrelevant to the present invention]
1.3 Key Words and Definitions In this specification, the following key words are defined to help those unfamiliar with this domain.
D Airspace - A volume of space around an air traffic control operation. Every aircraft flies through various airspaces on any given flight. It flies from the control of one air traffic control operation to the control of an adjoining one. D Arc.- Air Traffic Control. A service operated by appropriate authority to promote the safe, orderly and expeditious flow of air traffic. 11
D ATM: Air Traffic Management -All facilities and services used to plan, manage and control air traffic
D CNS: Communication, Navigation and Surveillance. Refers to the services used to support air traffic management. These include all CNS services that operate from aircraft to aircraft, aircraft to ground, and ground to ground.
D CNS/ATM: The combined system of Air Traffic Management and the Communication, Navigation and Surveillance support services. D NAS: National Airspace System. The common network of United States-controlled airspace, air navigation facilities, equipment and services, airports or landing areas. D TRACON: Terminal Radar Approach Control. A terminal air traffic control facility that uses radar and non-radar capabilities to provide approach control services to aircraft arriving, departing, or transiting airspace controlled by the facility.
2 The Problem And Its Roots The air travelers of the world are currently being subjected to increasing flight delays. The underlying cause of the delays is the need to provide safe air travel in the face of steadily increasing growth in air traffic. Delays are caused by the requirement to keep aircraft separated by distances based on aircraft and ground-based equipment capabilities to ensure safety margins for the separation of in-flight aircraft. Many delays are centered today at a few key airports, but the impacts of those delays are propagated back into the entire air route structure to avoid airspace saturation above and around the congested airports. The future doesn't look any better without major changes and investments to increase capacity. Satisfying capacity will currently be met with increasing the number of small to mid-sized aircraft, with a percentage decline in large capacity aircraft over the next 20 years. The world fleet is projected to grow to 31,755 airplanes by 2019, according to Boeing's Current Market Outlook. Projected growth of demand for air transport, both passenger and cargo, will cause increased delays unless significant changes are made in the basic structure of ATM. Changes to ATM have traditionally occurred as reactions to accidents, particularly those taking a great toll in human lives. Very little has been done to accommodate growth or technological advances that might affect air traffic. In fact, 12
safety initiatives can lead to reduced system capacity. This reactive philosophy has resulted in delays in the system that will make it impossible for airlines to sustain growth because they cannot operate economically. While many areas are seeing a growth in air traffic delays today, current trends in the demand for air transportation will lead to unacceptable delays for most air traffic worldwide within seven years. The effects of this worldwide growth will be most evident in areas of the United States (primarily the Northeast corridor) and Northern Europe.
The prime role of ATC has been to prevent collisions and to maintain traffic flow, both in the air and on the airport surface. While this satisfied most safety concerns up to the 1970s, the growth in air traffic and the increased use of higher performance jet aircraft has created greater demand for the sparse airways available for civil flight operations.
One has only to look at the daily news to find examples of commercial air transport problems that can be tied to the increased traffic handled by current ATM systems: Near mid-air collisions; Runway incursions by aircraft and ground vehicles; Growth in flight delays; and Increased customer dissatisfaction. 2.1 Lack of System Capacity
The current ATC system is fundamentally unchanged from the time that radar was introduced. Although use of computers, active transponders, and modern color displays have improved the presentation of data for the air traffic controllers, the controllers' job is essentially the same. The controllers have to manage aircraft in their sectors based on their individual skills and experience. While there has been a great deal of research into decision aids for en route controllers, installation of these tools has been limited. To deal with congestion, airspace has been resectorized into smaller sectors, and more controllers have been added. There is a limit to how small a sector can be effectively managed, as well as the increased workload and complexity entailed by passing aircraft between sectors more often. Increasing controller positions is not a viable long-term option in the current system. There are problems and limitations in the terminal area that need to be addressed as well: 13
D Lack of airspace to perform arrival and departure management, e.g. airspace limitations due to noise, terrain, and interactions and dependencies between nearby airports and nearby runways (San Francisco is an example) D Lack of capacity due to inadequate runways, taxiways and gates (LaGuardia / Newark are examples)
D Dramatic reduction in capacity as weather conditions (San Francisco, St. Louis, and Seattle are examples)
A limiting factor for advanced surveillance is the extent of aircraft equipage. Support of advanced communications (e.g. data link applications and transmission media) and automatic position reporting is strictly voluntary today. Until a significant percentage of the aircraft are equipped, the full advantages to be gained from those upgrades will not be achieved. The systemic problems today that may be limiting capacity include: D Limitations in controller ability to handle more than about 30 aircraft due to voice congestion on a single Very High Frequency (VHF) channel
D Limitations in flow rate on descent and climb due to inadequate surveillance performance and due to trajectory uncertainty and lack of reliable intent data
The current ATC system can be characterized as one prone to delays due to safety-related issues (e.g. aircraft proximity to one another in various phases of flight; surface movement; operations in weather-impacted areas). Projections for future growth will place more of these demands on the system. 2.2 Historical Perspective
The demand for commercial air transport saw little growth in the early years, even with the availability of cheap war-surplus aircraft. Small, slow, unreliable aircraft did little to attract passengers. Accidents involving single passenger, war- surplus aircraft drew relatively little attention. When engine and structural technologies advanced to the point that aircraft were able to carry larger numbers of passengers for long distances, passenger capacity increased to the point that accidents drew much more attention. Early Aviation 14
The lack of navigation aids and limited aircraft navigation instrumentation limited early flights to daylight hours utilizing Visual Flight Rules (VFR). By the mid- 1920s, the transcontinental route between Chicago and Cheyenne was indicated by gas lights positioned along the route to allow routine night flying, when the weather cooperated.
The first attempt to develop air traffic control rules occurred in 1922. The basic form of control was initially a simple one-way traffic flow system. For example, "inbound traffic stay North of a road or river and outbound traffic stay to the South." By 1925, the desire to instill public confidence in flying within the US led to the passage of the Air Commerce Act to promote, rather than regulate, civilian aviation. Early regulation was limited to licensing of pilots and mechanics and to regulate the use of airways. "See and avoid" was the only guidance for pilots. When visibility was low, aircraft didn't fly.
The Air Commerce Act of 1926 provided oversight of testing and licensing of pilots and crews, issuing certificates of airworthiness and registration numbers for the aircraft, and producing maps and charts. It also provided for building '"lighted" airways with lights placed on the ground at regular intervals to support night flying. Controllers Introduced
"Controllers" were added at airports as traffic increased to regulate takeoffs and landings, normally relying on colored flags to communicate with the pilots. Light guns were soon added to allow the controllers to more accurately point to specific aircraft, using different combinations of colors and steady or flashing lights to convey instructions to the pilots. This practice had limited usefulness since the pilots did not have the ability to acknowledge any of the instructions. Two-Way Communication Established
Radio use was instituted in the early 1930s. Radio equipage was a concern due to weight, size, and power requirements, especially for operators of smaller aircraft. Even if equipped, pilots were under no obligation to establish radio communication with controllers. The development of aircraft navigation instrumentation supported flights in weather conditions that would have precluded flights a few years earlier. With more 15
aircraft flying in "instrument conditions," the "see and avoid" protocol of VFR was unworkable. That fact, coupled with the entry of higher flying, faster aircraft created potential controller confusion in separating these differing types of aircraft.
Air Traffic Control Units (ATCUs) were established in 1935 to assist in separation of aircraft operating on federal airways. Operated by four airlines, these centers used flight plan information and pilot position reports to manually track aircraft and to advise pilots when potential conflicts were detected. Aircraft operated primarily under existing VFR. There was no legal obligation to use the ATCUs, and there were few aircraft requiring their advice (that were not associated with the sponsor airlines) that would operate in Instrument Flight Rules (IFR) conditions. By 1937, the lack of a legal requirement to file flight plans, the issue of the controller's legal authority, and perceived (if not real) favoritism of the controllers to the airlines that employed them led to transfer of the ATCUs to the Department of Commerce, which re-established the centers as Air Traffic Control Stations (ATCSs). In 1938, the Department of Commerce became the licensing authority for all civilian controllers, both in the centers and the airport towers. Engine Technology Leads to Bigger Aircraft
Until aircraft had capacity for multiple passengers (greater than six), longer range (beyond a couple of hundred miles), and better speed (significantly faster than trains), the growth of passenger air travel was limited. Advances in engine technology led to bigger and faster aircraft with increased payloads and fuel capacity. Increased Need for Long Range Control
Once bigger and faster aircraft like the DC-3 started into service, the growth in air travel increased dramatically. This led to a greater number of aircraft flying in JFR conditions and in the vicinity of most terminal areas. It then became essential to monitor and control this increasing number of higher performance aircraft at greater distances.
Positive control was inhibited by the necessity to monitor aircraft by creating and updating paper strips for each aircraft. These were laid out on a flat surface and moved by hand to represent the relative locations of each aircraft. Due to position 16
uncertainties, aircraft were spaced at large distances from one another to provide adequate safety margins.
Radar Allowed Controllers to Monitor Airspace
Even after radar was introduced, its surveillance capability was limited to a practical range of about 200 miles. Aircraft outside that range required the dependence on voice position reporting over radio for flight tracking. Large expenditures for a broad network of en route surveillance radars helped fill the gaps that allowed the 1956 collision of two aircraft whose pilots attempted to give passengers a better view of the Grand Canyon by leaving radar-controlled airspace. Radar gave the controllers the ability to monitor the positions of aircraft in real time. One shortcoming was the inability to see smaller aircraft or aircraft at bad viewing angles. The addition to the aircraft of transponders (which amplified and enhanced the radar returns) resulted in more reliable detection and display of traffic, regardless of aircraft size. Still, the accuracy of radar systems degraded as the distance from the radar site increased, requiring increased separation distances. Secondary radars were introduced not only to aid long-range detection (which is difficult with primary radars), but also to provide target identification on the scope. The evolution of secondary radars and the ability to support data tags on the radar scope eliminated the need for primary radars in the en route phase. (Primary radars are still needed in the terminal area to support critical approach and landing operations.)
Although radar gave the controllers a better understanding of the situation in the airspace they controlled, there was little coordination between adjacent terminal areas. This contributed to a collision over Brooklyn in 1960, where one aircraft was controlled by LaGuardia and the other by Idlewild Airport (now JFK). Although the radar displays indicated that the aircraft were coming together, each controller was able to talk to only one of the aircraft and was unable to coordinate appropriate avoidance procedures. Consolidation of several airports' airspace into a common facility called a Terminal Radar Approach Control (TRACON) helped to alleviate this problem. 17
The use of radar displays with on-screen alphanumeric character labels allowed aircraft ID to be displayed with the target. Further improvements in transponders allowed the aircraft to return altitude and identification data that could be displayed for the controllers as well. The correlation of radar ID with flight plan data in the form of data tags was probably the most significant aspect of first generation automation systems, e.g. ARTS and HOST. This proved to be a significant step forward in the use of computers to support ATC functions.
Problems arose with unequipped VFR aircraft sharing the same airspace as the more equipped aircraft. Again it took a mid-air collision to create a requirement for controlled areas around major terminals, this time between a Boeing 727 and a Cessna in 1967. After this, all aircraft entering such airspace were required to have a certain minimum level of equipage. While trying to resolve the objections of the small aircraft owners in 1969, another similar collision occurred, forcing the establishment of this rule. Today, all aircraft operating in congested terminal areas (Class B and C airspace), and in other designated airspace, are required to have transponders. Procedural Changes Introduced to Reduce Congestion
The growth of jet aircraft in the civil aviation fleet required changes in how controllers handled congestion. When dealing with a predominantly piston-powered fleet, the controllers could stack aircraft over a congested airport and gradually spiral them into the airport. With higher-flying, faster aircraft to manage, flow control was instituted in the early 1980s to hold departures on the ground until a landing slot was available at the destination airport. The philosophy was that it was safer to be on the ground than to be holding in the air awaiting a landing slot. The primary reason that holding stacks were discontinued with the introduction of flow control was the lack of experienced ground controllers.
In Europe today, limited holding stacks are primary control mechanisms for feeding aircraft onto final approach. The holding speed is typically about 250 knots, the same as the typical entry speed into the terminal area. At this speed and at altitudes between 12,000ft and 18,000ft, airplane holding is relatively efficient. Miles-in-trail (MIT) restrictions are also used as a flow control mechanism for airborne aircraft. MIT is used to avoid saturation of terminal facilities and to smooth 18
out the flow of arrival traffic into congested hub areas. Still, excessive flight delays and increased traffic volumes have led to delayed departures, long taxi times and potentially lower flight spread. This has resulted in institutionalized delay or block time creep, resulting in more wasted flight time for the airlines.
3 Airspace System Requirements
NAS modernization needs to accommodate multiple requirements. The source and relative importance of each defining requirement needs to be understood to achieve stakeholder consensus on NAS modernization. This section provides an overview and priority structure for the requirements which will drive the changes in the NAS modernization plan. 3.1 Safety
The NAS already has one of the lowest hull loss rates of any system in the world. This current rate, however, cannot be considered the target value for the future NAS; as traffic volume increases, the rate must be lowered to avoid an increase in total number of hull losses. The 1997 National Civil Aviation Review Commission report stated that based on current traffic projections a major hull loss would occur somewhere in the world every 7-10 days by 2010. The new architecture must address the prime contributors to the accident rate. Controlled Flight Into Terrain (CFIT) remains a prime contributor. While significant action has been taken by aircraft manufacturers by installing an Enhanced Ground Proximity Warning System (EGPWS), more significant changes to the airspace and to procedure design can be done to further reduce this prime contributor to hull losses.
Potential methods of further reducing CFIT accidents are as follows: D Elimination of step-down approach procedures; this process has already begun with the use of constant approach angle overlay approaches replacing VOR- (Very High Frequency Omnidirectional Range) and NDB-based (Non-Directional Beacon) approach procedures. This initiative should be extended eventually to eliminate approach procedures lacking vertical approach path guidance D Installation of vertical situation displays in aircraft; this would enhance pilot awareness of vertical separation from the surface beyond that provided by EGPWS. 19
D Improved Minimum Sector Altitude Warning equipment using Automatic Dependent Surveillance-Broadcast (ADS-B) and/or multilateration as the surveillance medium would provide a safety function more independent of aircraft equipage and crew awareness. Loss of control is the second largest cause of fatal accidents, however, most of the solutions to resolve this cause are regulatory.
Aircraft-to-aircraft collisions are increasing. Airborne collisions are mainly associated with general aviation (GA) aircraft, while all classes of aircraft have been involved in ground collisions, predominantly following unauthorized or erroneously authorized runway incursion. All collisions are the result of a lack of awareness of the other aircraft. Methods of increasing awareness must start with increased training and reinforcement during pilot certification testing. It is unlikely that training will be the complete answer.
The Traffic Alert and Collision Avoidance System (TCAS) has been effective at preventing mid-air collisions between suitably equipped aircraft, and equipage with similar functionality should be encouraged for all. ADS-B may prove to be a suitable medium for surveillance sensing in the provision of collision alerting, especially for general aviation aircraft.
The most urgent need is to eliminate runway incursions, and here again pilot awareness must be improved. A passive approach would be to assist the pilot in navigating the aircraft around increasingly complex airports. Measures might include improved airport signs and indication methods, sequenced centerline lighting, improvements in Surface Management Guidance and Control Systems (SMGCS) and cockpit aids with varying complexities. The latter might include electronic moving maps and runway activity monitoring. More active methods could include provision of unauthorized runway entry alerting to the controller for transmission to the pilot either by voice or data link. Such alerts might also be provided by flight deck systems. Developing cost effective versions of ADS-B and/or multilateration will directly contribute to improving safety for general aviation, a major contributor to runway incursions. 20
The highest level of airport surface awareness will be achieved by the use of a moving map that displays cleared taxi routes uplinked to the aircraft from the tower. The system could automatically generate the most efficient route for the aircraft involved, or that would optimize traffic flows and avoid aircraft-to-aircraft and aircraft-to- vehicle conflicts in congested conditions. Low-level alerts could be provided for transgressions that do not result in hazards. Runway activity could be depicted, as could taxiways that are unable to support the operations of the particular aircraft model (e.g. load-bearing or wingspan issues). Again, cost-effective solutions can be used by the general aviation community. The most significant safety improvements for the airspace are:
D Reduction in CFTT accidents through the provision of continuous precision descent approaches to replace step down approaches
D Reduction in runway incursion and other active runway problems through the phased introduction of tower monitoring and alert systems and airplane based guidance systems
D Improvement and integration of the situational traffic display for flight crew and controller
D Approval of a low cost, sole source navigation system for GA which will support the use of continuous descent approaches 3.2 Capacity
Since deregulation, the growth of air transport category operations in the NAS has been driven primarily by economics. Current projections from the Boeing Current Market Outlook (CMO) indicate a 2.9% annual growth in traffic from 2000 to 2020. This equals a 77% increase in overall traffic. 3.2.1 Capacity Goals
The capacity goal is to accommodate traffic growth depicted in the CMO while reducing the delay in the system. While delay is a difficult metric to measure, the CNS/ATM Focused Team (Metric' s Subgroup) recognizes the elasticity between capacity and delay. In a free market, the operators decide how to use capacity (e.g. add service or reduce delay). We plan based upon a forecast of an initial capacity increase of 37% by 2009, and a net end state capacity increase of 100% by 2019. 21
The major constraints to capacity are (1) Runway occupancy time, (2) Wake vortex separations, (3) Final approach separation standards, (4) Controller workload, (5) Noise, (6) En route congestion, and Departure runway congestion
3.1.2 Traffic Growth Estimation [deleted as irrelevant to this invention]
3.1.3 Operational and Flow Planning Limitations on Capacity
The existing ATM system is forced to manage airspace based on current observed demand since there is considerable uncertainty in aircraft departure and arrival times. The emphasis today is on managing the observed flow using traditional control strategies such as Miles-in-Trail, Holding Stacks, Terminal Area Vectoring, and Intermediate Altitude Level-offs. These control strategies manage airspace to achieve overall flow objectives by reducing complexity in order to limit and stabilize controller workload. However, efficiency of operations and throughput objectives are sometimes sacrificed in order to keep overall workload within manageable dimensions. More predictable aircraft flow is highly desirable since control can be better distributed to achieve long-term and medium-term flow objectives while preserving short-term separation assurance capability. The NASA Center-TRACON Automation System (CTAS) decision support tools are based on accurate trajectory synthesis and flow predictions for medium- and short-term arrival management. Field tests of CTAS show both the promise and the difficulty of achieving reliable trajectory and flow predictions. To achieve more capacity may require more changes in aircraft flight management, and better integration of airborne and ground automation systems. 3.3 Delay Management
Delay has traditionally been used as the most direct measure of the ATM system and is generally described as the difference between an aircraft's scheduled arrival time and the actual arrival. However, all delay is not equal. Delay can be divided into predictable and unpredictable delay, and this distinction is important because airlines treat them differently and manage the effect in different ways. Delay is related to other metrics - predictability, flexibility, efficiency, and access - and these can be used to mitigate delay, depending on when the delay occurs. 22
Predictable delay is most useful during the airline schedule planning process (60-90 days prior to the actual flight). Predictable delay is built into airline schedules by increasing block times to maintain schedule integrity. This addition to block time not only affects the number of aircraft required to fly the schedule, but also the staff and facilities necessary to operate the flights, to maintain the aircraft, and to serve the customers. Airlines also plan aircraft schedules and network interdependencies to include unpredictable delays, so as to assure network integrity.
Flexibility is more significant as a flight's departure time approaches. Resource flexibility is used in crew scheduling, airplane routing, aircraft assignment, and gate control processes up to 30 days in advance. Maximum flexibility in route planning can be used up to 90 minutes before the scheduled departure as airline dispatch processes concentrate on meeting the airline's schedule commitments. After departure, flexibility is used by airlines to make tactical "trade-off decisions to mitigate the schedule impact of unpredictable delays. Unplanned delays, such as traffic flow control, changing weather conditions, and mechanical problems drive up the costs associated with maintaining schedule integrity needed for passenger connections, crew pairings, and required aircraft maintenance. Predictability and flexibility are not independent. Predictability is used by the airlines to plan revenue, while flexibility is used to reduce the losses against the planned revenue when unplanned delays occur.
Efficiency and access also affect. Efficiency is a measure of achieved costs compared with optimum costs based on flight time and fuel burn, and affects direct operating costs of a single flight. Because airlines fly millions of flights per year, small increments in direct operating cost savings on every flight can add up to significant savings. Access addresses the means by which NAS users can use ATM system resources. For example, increasing the capacity of airports in low visibility operations or the ability to use Special Use Airspace (SUA) when not being used by the military represents an increase in access. Access can affect efficiency. 3.4 Access Generally speaking, access describes the ability to use the resources of the
NAS. Resources include airspace (of various kinds) and services. The quality of 23
access is frequently described by the ease in reaching one place from another. Measures of accessibility include topological distance, route distance, travel time, and travel cost. Cost can be something as simple as landing charges or as complex as amortization of the cost of equipage to enter exclusionary airspace. However, our definition of access also includes an acknowledgment of the existence of barriers or impediments to accessing services such as IFR clearances. When impediments become high they become barriers to access. Access is a high-value measure of system performance, especially those users in the general aviation (GA) and military communities. It has also become an issue when major metropolitan areas served by commercial airlines have significant capacity restrictions placed on them while corporate aircraft operate into adjacent feeder airports with little or no restrictions. Some metrics for evaluating access could include:
Dimensions and size of the airspace; Operating hours; Availability of traffic advisory services and other services (e.g. Flight Information Services); Environmental concerns; Aircraft equipment/functionality requirements and capabilities; and Flight crew qualifications (e.g. for Category in approaches)
Enhancing access to airspace, airports, and services, both in the air and on the ground, should include consideration of variation in en route and terminal weather, and airborne equipment availability.
3.5 Environmental (Noise and Emissions)
Noise in the lower terminal area is a significant limitation to capacity now and is an inhibitor to increasing capacity at congested hub airports. A similar problem is that of air pollution due to inefficient fuel burn while queued up on the surface, at low altitudes during approach, and during take-off. Required Navigation Procedures
(RNP) could be used to substantially mitigate the terminal area noise problems. For example, curved approaches over less noise-sensitive areas and Continuous Descent Approaches using Vertical Navigation (VNAV) and energy management have the potential to decrease substantially arrival noise per aircraft, enabling increased throughput without increasing average noise levels.
3.6 Effect of Severe Weather and Low Visibility on Capacity 24
In many areas there is sufficient capacity to meet traffic demand when visibility is VFR, but problems develop rapidly as visibility degrades or when severe weather occurs. Airports such as San Francisco and Boston are forced to reduce arrival capacity by a factor of two when visibility drops to marginal VFR conditions. The effect of severe weather is even more dramatic, since flights may be cancelled or diverted on a national basis due to regional weather conditions such as thunderstorms. Future mitigation will minimize the effect of weather on NAS operations.
Two possible methodologies to minimize weather-induced delays are: D Development and deployment of regional weather surveillance and forecasting systems for enhanced flow management
D Development of all-weather, low-visibility technologies and flow procedures to minimize the effect of weather on NAS operations.
The sensing concept includes the deployment of near-term systems such as ΓTWS (Integrated Terminal Weather System), and the development of long-term forecasting systems based on regional grid sizes. One likely technology for future enhancement is the NWS RUC system (Rapid Update Cycle weather forecasting based on NEXRAD radars and one-hour forecast updates). The operations area includes the use of advanced navigation and surveillance technologies to achieve marginal VFR and Category I or better IMC operations as all-weather replacements for existing VFR operations. Finally, the use of advanced navigation and communications technologies may be appropriate for weather based rerouting and flow enhancement when normal routings are disrupted due to severe weather. 3.7 Affordability
The business test of affordability will determine the solution set of infrastructure and people to meet the need for NAS modernization. All must see that the solution for the future system is "affordable." Even for the FAA, affordability is a complex issue. Life cycle costs and expenditure rates are all part of what must be considered. The FAA must consider the interaction of new infrastructure with the timely de-commissioning of the old and the affect on O&M costs. The increased trend in operating costs is tied to traffic growth, lack of technology-enabled controller productivity increases, and increased controller pay 25
scales. There is a need for strong management controls, greater risk sharing with contractors, and a cost accounting system.
3.8 Collaborative Planning
The NAS is a single system and must be operated using a common international frame of reference. It should address the common goals of safety along with a balancing of controller workload and capacity. The individual preferences of the system users must also be considered. A cooperative framework should extend from the advance schedule planning process through the completion of each flight. Whenever possible, the NAS should enable the ability of the stakeholders to collaborate fully on the reaction to spontaneous events, such as en route and terminal weather, equipment outages, changes in SUA status, and other planned/unplanned events.
4 Operational Concept This section on operational concept presents the core part of Boeing's vision to improve the NAS. The section begins with a discussion of the daily process of NAS- level traffic planning, describing the procedures used to dynamically adjust to changing conditions. The discussion then points out the current state of radar coverage, procedural control, and airplane equipage. The section continues with descriptions of the concepts for five key management domains: Airspace
Management, Flow Management, Traffic Management, and Flight Management, and Airports. The current state of each domain is described, followed by a presentation of the future operational concept, as envisioned by Boeing Air Traffic Management. Section 4.7 concludes by comparing today's system with Boeing's vision, and also with FAA/MΓTRE'S NAS Operational Evolution Plan, the current paradigm for NAS modernization. 26
4.1 Today's System
The FAA constantly makes adjustments to its practices and procedures based on input from the users and inclusion of new equipment into the NAS. This overview represents the practices and procedures in place during the Spring Summer 2000 period. Site-specific or limited tool system deployments such as CTAS, Surface Movement Advisor (SMA), User Request Evaluation Tool (URET), etc. are not included in this discussion of today's system. 4.1.1 The Daily Schedule
After 12:00 AM ET the major airlines provide the FAA's Air Traffic Control System Command Center (ATCSCC) with their intended flight schedules for the coming day. Each flight definition includes the aircraft/flight ID, aircraft type, proposed departure time, and historical route of flight. The actual flight plan is provided approximately two hours before scheduled departure time.
The start of the operational planning day begins at 5:00 AM ET with a weather telecon among several major airlines' meteorologists and the ATCSCC. This telecon, repeated every two hours, produces a collaborative convective forecast product to be used for operational planning. Based on the last operational plan issued at 4:00 AM and the most recent convective forecast, the ATCSCC issues an update to the operational plan at 6:00 AM ET for the next six hours. The ATCSCC then gathers current operational data from FAA sources (equipment status, staffing, SUA, etc.) and the users via telephone and data links.
Special operations such as Expendable/Reusable Launch Vehicles and Unmanned Aerial Vehicles do not account for a significant amount of today's NAS operations. These operations are carried out in SUA, which can account for large amounts of airspace being unavailable to non-participating users. At 7:00 AM ET the ATCSCC initiates a telecon with the Air Route Traffic Control Centers (ARTCC), TRACONs and users to discuss the proposed operational plan and reach consensus. If consensus cannot be reached then the ATCSCC makes the decision and issues the plan. Historically, the majority of system restrictions are based either on reduced airport or airspace capacity due to weather. This could mean convective weather, or 27
low ceilings/reduced visibility at an airport that requires instrument approaches rather than visual separation.
Approximately two hours before proposed departure time the major airlines transmit their flight plans to the FAA's HOST computer. Most companies request the most cost-effective route based on the forecast conditions, current/planned traffic management initiatives, and historically approved routings for their flight.
When a flight is nearing its departure time the flight plan clearance is transmitted to the flight deck either by voice or data link. If a flight will not be affected by any capacity-limiting initiatives when it is ready to depart, the flight crew merely follows the local airport procedure to leave the gate. A taxi clearance to the departure runway is delivered to the aircraft via two-way radio by tower ATC. All instructions to cross runways and sequence with other surface traffic are accomplished by ATC using visual sighting or position reports. When the flight reaches the departure end of the runway it is cleared for takeoff based on current traffic conditions and appropriate traffic management initiatives.
Departures are traditionally routed by a TRACON via radar vectors to a departure corridor that corresponds with their intended route of flight. An electronic transfer of track control is made from the TRACON to the appropriate en route center followed by voice communications transfer. The flight proceeds to climb to its ATC- assigned cruising altitude. The routing may either be a great circle or a point-to-point route based on ground navigation aids. 4.1.2 Positive Controlled Airspace
Surveillance is traditionally provided by radar with controller interventions to maintain separation assurance. The traditional separations used in each phase of positive controlled flight are:
D Departure Visual/wake turbulence
D Transition Area 3 nautical miles (NM) lateral/longitudinal and 1,000 feet vertical D En-route 5 NM lateral/longitudinally and 1 ,000 below Flight Level 290 and 2,000 feet vertically above Flight Level 290 D Transition 3 NM lateral/longitudinal and 1,000 feet vertically 28
□ Final Approach Visual separation or 3-6 NM (includes wake turbulence) reducing to 2 V% inside the outer marker Each transition between portions of flight is driven by the accuracy and reliability of the communication, navigation and surveillance sources used by the users and providers.
When demand exceeds capacity at an airport, ATC uses Traffic Management Initiatives (TMI) to prevent system overload. TMIs are imposed on an as-needed basis and can include one or more of the following: speed control, altitude changes and miles in trail, sequencing, airborne holding, fix balancing, ground delay programs, and ground stop programs. For example, an aircraft with a ground delay will be given an Expect Departure Clearance Time based on the arrival rate at the affected airport. For aircraft already en route a time-based metering program in the HOST computer provides times for each aircraft to cross a given point to meet the identified arrival capacity of the airport. Defining the in-trail distance between aircraft may also be used to accomplish the same result.
Once an aircraft lands, ATC provides a taxi routing, all clearances to cross runways, and sequencing with other surface traffic via VHF/UHF voice radio.
The majority of flights within the United States Flight Information Region (FIR) are under radar surveillance. A conflict alert software tool deriving aircraft position information from radar provides the controller with alerts of potential traffic conflicts approximately two minutes prior to loss of separation. With only the basic flight plan and requests from flight crews to express intent, future flight path with high fidelity updated Estimated Times of Arrival (ETA) at identified waypoints are not readily accessible to the controller. This lack of precise intent information precludes strategic planning and forces the planning controller to limit introduction of aircraft into the sector in order to better control the workload and enable continuation of approved separation. 4.1.3 Procedural Control Airspace
In those few areas where procedural control is still required (mountainous / remote terrain, oceanic areas), automation tools to assist the controller in identifying potential conflicts are generally not available. Oakland Center has limited use of a 29
'look ahead" function for its oceanic airspace to assist the controllers in identifying potential conflicts.
The traditional separations used in procedural phases of flight are: D Departure Visual/wake turbulence, time, speed, distance D Transition Area Time, speed, distance and 1,000 feet vertical
D En route 10 minutes or 20 miles DME (domestic) and standard vertical D En route oceanic Standard ICAO separation is 100 miles or
20 minutes and standard vertical D Transition Time, speed, distance and 1,000 feet vertical
D Final Approach Visual/wake turbulence, time
Nearly 65% of transport category airplanes registered in the United States have advanced flight management systems. The navigation solutions can be updated by the Global Navigation Satellite System (GNSS) that provides an accurate position and consistent time source. While 6000 of these airplanes are fitted with data link communication capability (either Very High Frequency (VHF) or satellite), functionality is limited to communication with the operator's airline operational control center (AOC). As of January, 2001, about 850 aircraft worldwide are equipped with Future Air Navigation System (FANS)-l or -A (Boeing or Airbus respectively) which provides controller-to-pilot data link communication as well as ADS, but these functions are currently used only in oceanic and remote NAS airspace at three centers. FANS-1 was specifically designed for use in oceanic and remote airspace, and includes Automatic Dependent Surveillance-Addressed (ADS-A). ADS-A allows ATC globally to receive the current position of the airplane via data link along with the aircraft's intent (future flight path) as defined in its flight management computer (FMC) flight plan including ETA at intended waypoint(s). In areas where it is in use, ADS-A reduces voice channel congestion, reduces workload and reliably provides data that can be fed directly into an ATC flight data processor. It eliminates several opportunities for human error. These functions, along with the use of GPS as a primary source of navigational data, are beginning to permit reduction in traffic separation in certain oceanic and remote areas. ADS-A also facilitates the 30
development of high performance decision aiding tools for the controller (such as flight plan conformance monitoring and conflict probe). All FANS-1/A-equipped aircraft can provide ADS-A downlinks. Intent information is generally limited to the next two waypoints, but the system specification allows for reporting ten waypoints. The next generation data link function specification, the Aeronautical
Telecommunications Network (ATN), includes a more capable ADS-A function as a baseline.
Automatic Dependent Surveillance - Broadcast (ADS-B) is similar to ADS-A, but the data are broadcast for all equipped, line-of-sight users to use rather than sent by network to a specific user. ADS-B is currently operated on a trial basis in US and European domestic airspace. Only about 120 aircraft worldwide have ADS-B. About 70% of these operate only in Alaska and are general aviation (GA) aircraft. The transport category aircraft that are equipped have only ride-along certification to use ADS-B, i.e. the system transmits solely for test and validation purposes. 4.2 Airspace Management
One of the NAS's most significant resources is airspace; managing the resource allocation of that airspace is a significant consideration for achieving the safety, capacity, affordability and access goals of the year 2016 system. Today airspace is divided into controlled and uncontrolled portions. 4.2.1 Existing Airspace Classes
The airspace classification system defines six classes of airspace based on altitude, type of flight (Visual Flight Rules /Instrument Flight Rules), and equipage. Class A, formerly the Positive Control Area, begins at 18,000 feet Mean Sea Level (MSL) and ends at Flight Level (FL) 600 (approximately 60,000 feet MSL). Only Instrument Flight Rules (TFR) flights are permitted and separation is provided by
ATC. Operation in Class A airspace requires (1) aircraft and pilots equipped/qualified for and operating on an IFR flight plan, (2) an operable coded radar beacon transponder having either Mode 3/A 4096 code capability, replying to Mode 3/A interrogations, or a Mode S capability, replying to Mode 3/A interrogations in accordance with the applicable provisions specified in TSO C-112, and (3) automatic pressure altitude reporting equipment having a Mode C capability that automatically 31
replies to Mode C interrogations by transmitting pressure-altitude information in 100- foot increments, to ATC on an assigned frequency.
Class B, formerly the "Terminal Control Area," extends from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of IFR operations or passenger traffic. The configuration of each Class B airspace is tailored for each airport, and consists of layers of increasing volume as altitude increases. Published instrument procedures apply once an aircraft enters the airspace. An ATC clearance is required for any aircraft to operate in the airspace; all cleared aircraft receive separation services within the airspace. The cloud clearance requirement for Visual Flight Rules (VFR) operations in this airspace is "clear of clouds" regardless of altitude. Class A equipment is required; the pilot-in-command is not required to be instrument rated.
Class C extends from the surface to 4,000 feet above the actual airport elevation surrounding those airports that have an operational control tower, are serviced by a radar approach control, and have a certain number of JFR operations or passenger traffic. The configuration of each Class C airspace area is individually tailored, but usually consists of a 5 NM radius core surface area around the airport, a 10 NM radius shelf area that extends from 1,200 - 4,000 feet above the airport elevation, and, generally, an outer area with a normal radius of 20 NM. In the vertical, this airspace extends from the lower limits of radar/radio coverage up to the ceiling of the approach control's delegated airspace, excluding the Class C airspace and other airspace as appropriate. Separation service is provided, which occurs in the outer area after two-way radio communication and radar contact are established. VFR aircraft are separated from IFR aircraft by either visual separation, 500 feet vertical except when operating behind a heavy jet, or targets are projected to pass. Aircraft must have a two-way radio and operable radar beacon transponder with automatic altitude reporting equipment.
Class D extends from the surface to 2,500 feet above the airport elevation surrounding those airports that have an operational control tower. The Class D airspace configuration at each airport is individually tailored. When instrument procedures are published, the airspace will normally be designed to contain the 32
procedures. No separation services are provided to VFR aircraft. Two-way radio communications is required. This airspace was formerly known as Airport Traffic Area and Control Zone.
If the airspace is not, and it is controlled airspace, Class E airspace applies. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent Class A, B, C, or D airspace.
Class G airspace is uncontrolled airspace outside Class A, B, C, D, or E airspace. 4.2.2 Tomorrow's Concept of Airspace Management Mandate for Fundamental Airspace Management Change
Global CNS services make many of the old airspace entities unnecessary, even counter-productive, in a "clean sheet" airspace design. New airspace design and management should be based on user needs, not technology artifacts. Air routes need not be constrained to airspace corridors based on ground navaids. Of course, better flight intent tools are needed for the controller to make the separation services viable in an environment where air route structure is removed, and where dynamic change occurs. The introduction of reduced vertical separation minima (RVSM) in US domestic airspace will allow for increased capacity and provide more cost efficient altitudes to the users. Current terminal areas, whose size was set in an era of primary radar surveillance, today cause significant coordination problems in dense airspace surrounding multi-runway and multi-airport complexes. Some minimal level of fixed transitions may be necessary to permit orderly management of arrival and departure traffic flows around major congestion points. Clearly, early automation programs like CTAS are hindered by the old center-TRACON boundaries that required multi-center and multiple Traffic Management Advisor (TMA) operations.
The sector itself needs to be re-designed to take advantage of a global information infrastructure and enhanced knowledge of aircraft intent obtained from appropriately equipped aircraft. Sectors need to become larger, not shrink, with growing traffic densities so that the workload associated with coordination can be limited. Vertical boundaries may vary within the same piece of airspace to 33
accommodate the operational needs of the users, e.g., departure and arrival profiles. A few high altitude sectors to span the whole of the NAS are part of the future operational concept.
Global availability of navigation and precision landing guidance procedures will provide operations at remote fields with the same quality as has been reserved for busy runways serving large airports. (This capability could require upgrading airport equipment to support precision approaches.) Aircraft-to-aircraft surveillance in uncontrolled airspace with improved weather knowledge will permit safe operations in restricted corridors for uncontrolled aircraft and will allow continued access to high density airfields.
The airspace design needs to account for the operational requirements of GA aircraft. GA aircraft (e.g., pleasure flying, agricultural operations, flight training, corporate flying, and other activities) are a significant percentage of daily operations. These aircraft require access to flight information services, such as weather information, special use airspace status, and NOTAMS, prior to departure and during flight.
The operation of Dept. of Defense (DOD) aircraft in the future system is also a high priority. Strategic operations are affected most by equipment requirements of the majority of the military transports and tankers. DOD upgrade resources are being consumed in RVSM, Airborne Collision Avoidance System (ACAS) and FANS-1 systems. Further initiatives will require additional upgrades. Tactical aircraft require unique procedures and airspace to accomplish their missions and, therefore, represent a different kind of challenge. Equipment requirements may prove difficult because of restricted cockpit space.
The Boeing Airspace Management Baseline Concept
Boeing proposes three broad classes of users: (1) aircraft filing a flight plan (and providing trajectory intent) for separation services, (2) those choosing to receive some services, and (3) those choosing to fly without FAA cognizance. Separation-assured airspace requires the highest level of equipment to participate. This airspace is designed from the surface up to the transition of 34
arrivals/departures in en route airspace. The airspace is shaped like a cone based on the flight characteristics of participating aircraft and the airport's configuration. Airspace not included in these cones could provide access to non-participating aircraft that are capable of flying a precise route or tube. In advisory airspace, higher levels of equipage will be needed consistent with the required performance levels imposed by the traffic densities and safety levels. This airspace will be consolidated into larger control structures to simplify coordination and improve services. These structures will be dynamically reconfigurable, to allow better response to weather events and other transients. A much safer basis of operation should be available at low cost to equipped users by providing enhanced weather data, global navigation services and surveillance of nearby aircraft.
There will remain low-density airspace regions where see-and-avoid remains the basis of flight. No special airplane CNS equipage will be required to fly in this "uncontrolled" airspace. Separation responsibility will remain with the participating pilots. Concept Issues and Trade-Offs
Issues to validate include: (1) Fixed versus flex versus free routings in en route, transition and approach and landing airspace; (2) Potential for separation assurance concepts which are not based on fixed geographical regions, but are based on aircraft-pair (or some other method); (3) Identification of minimum equipage requirements to operate in the various airspace classes; (4) Applicability of the Required System Performance concept for airspace services delivery; (5) Interfaces to non-US positive control airspace; and (6) Interfaces to non-US procedural control airspace
4.2 Flow Management
Coordinated traffic flow planning is one of the cornerstones around which the new operational concept is built. Departure, en route and arrival flow management functions are combined in a real-time centralized plan to optimally spread delay for the daily predicted capacity/demand imbalance in the NAS. The plan is coordinated in 35
real time by the Central Flow Management Agency (CFMA) with the regional traffic management agencies and the System Operational Control (SOC) facilities.
Collaborative Decision Making (CDM) uses fast-time coordinated flow planning tools and real-time communications equipment available at all locations. Organizations with capabilities comparable to airline SOCs could provide similar services to smaller commercial operators, GA and/or the military. The output of the planning tools (including weather information) allows the service provider and system users to understand the current and forecast system limitations, and optimally allocate airspace resources and user preferred trajectories before capacity shortfalls and demand imbalances begin to cause delay. Simply put, more precise predictive tools allow the maximum capacity to be available.
During periods when demand is forecast to exceed capacity, the coordinated flow planning provides potential solutions including dynamically re-configuring airspace and suggesting amending flight profiles to best balance users' demands for services and create the most capacity.
The CFMA has the ability to dynamically balance demand and capacity in the system to prevent traffic overloads and to better react to disruptions. Stakeholders will communicate quickly with the agency, and CFMA has tools to support real-time replanning of all scheduled departures and flights. The heart of the new CFMA is the replanning system. This system receives all of the filed flight plans, active flight plans, current surveillance information, local and system-wide weather as well as forecast weather. This system provides a common view of the NAS with real-time display of the traffic situation and near-term (2 - 3 hours) simulated traffic flow predictions. Real-time status and performance data is provided by decision support tools to departure, arrival and en route flow management functions and the agents at field units.
The purpose of this system is to enable rapid processing of re-routing requests by the users. The system is able to evaluate all of the re-routing requests, balance sector demand with available capacity and send these re-routes back to the users. The system will initially allow a small percentage of the requested re-routes to fly through weather that the software believes will probably not occur. This approach is 36
acceptable because the majority of aircraft have very accurate weather radar and the flow management tools will allow the agent managing en route traffic to handle deviations when necessary. This percentage will rise as the ability to spread delay to different regions and flow management functions is demonstrated and performance is established.
The CFMA replanning tool allows the users to prioritize ground holds if the weather does not allow for approval of all re-routes. A rule base (similar to the collaborative decision systems already in use) assures equitable treatment for all users and airports. This replanning tool, coupled with simulated traffic flow prediction and high performance data connections among all parties, will enable dynamic reactions to transient flow changes, reducing delays and cancellations while maintaining safety by preventing sector overloads.
The coordination of arriving and departing flights will require special decision support tools such as the NASA En-route Descent Advisor (EDA), the Terminal Management Advisory (TMA), the Direct-To Advisor, and the Expedite Departure
Tool (EDT) of the NASA CTAS system. These limited deployment tools need further development to take advantage of evolving technologies such as RNP area navigation (RNAV) routings and direct data link of aircraft arrival and departure intent.
Departure, en route, and arrival flow management functions located at field traffic management units are continuously running local sector flow monitor functions. Coordinated by the CFMA replanning tool, the flow monitoring functions assure that the traffic load remains balanced with available capacity and that the rerouting services better respond to transient events and the interface with other national or oceanic airspace environments. The submitted flight plan changes may be accepted as submitted or modified by the replanning tool. The reasons for departure delays might be sector loading (which should be minimal) or a route adjustment greater than a fixed percentage of the filed replan. The system will initially be limited to pre- departure flight plan changes and use existing data link on commercial aircraft. Reroutes during the initial implementation phase would be submitted only by user SOCs, but in later phases they could be submitted from the flight deck and would be coordinated back with the SOCs. The CFMA-accepted re-routes would be 37
automatically coordinated with the affected regional traffic management units and updated with the active flight plans. Initially only the major users that wish to equip will interface with the replanning tool in order to provide the capability to rapidly transmit the requested re-routes, and other users will be replanned manually by agents. 4.3 Traffic Management
The Boeing operational concept supports the use of 3-D trajectories (3-D tubes) in all airspace regimes, and the use of 4-D trajectory concepts when appropriate. In en route airspace, the use of RVSM and RNP-1 RNAV routings will add needed vertical flight levels and make more airspace available to relieve congestion. On departure and from climb-out to cruise, the use of 3-D tubes can enable more effective use of airspace for procedural separation with crossing and descending traffic. Finally, in the descent stage of flight, it may be possible to support both 3-D tubes and 4-D arrival times at critical arrival fixes. This would be achieved by integrating 3-D RNP RNAV routing and vertical profiles, and enhanced FMS energy management of thrust and drag to achieve desired airspeed profiles. In this concept, the aircraft would manage high integrity airspeed and vertical flight profiles, and the ground automation would implement enhanced wind field surveillance to compute aircraft ground speeds on descent, and arrival times at critical fixes for terminal area merging and flow management. The 3-D or 4-D clearance (contract) negotiated between each flight and the service provider plus the improved surveillance and intent information are responsible for the planned reductions in separation, increased system capacity and enhanced safety. Individual controllers are able to handle increased traffic loads through the use of conflict detection and resolution software. Conflicts are identified well into the future along with potential mitigating strategies allowing the controller to make the decision and cause the minimum impact on individual flight profiles. Dynamic organization of airspace based on ongoing capacity modeling software also contributes to controller productivity and system capacity.
Readily-available automation tools providing necessary information (e.g., emergency airfields, major roads/towns, local weather conditions, topography, etc.) will allow controllers to handle more traffic and manage larger areas of airspace that 38
may be dynamically re-designed to meet system demands. This information must be easily accessible to the controller, especially during emergencies.
Individual controller productivity is increased through precise aircraft navigation capabilities, enlarged airspace responsibilities, and numerous software tools that handle routine tasks. These software improvements will also require sophisticated backup systems to provide the controller with almost identical support during the infrequent primary system failures.
A significant improvement of the new system is enhanced accuracy and update rate of aircraft surveillance systems achieved through data fusion of classic radar, ADS-B, and other sensors such as multilateration. Surveillance will improve from radar displays or position reports to fused radar/position report data (with intent). Positions will be transmitted by the aircraft to the ground at a much higher return rate that will allow for higher displayed/system-utilized position accuracy, reduced separation, and increased safety. Currently, position information update rate using radar surveillance is determined by the rate of revolution of the radar; 12 RPM for terminal radar and 5 RPM for en route.
The Sector Controller/Planner will have a future conflict detection capability with suggested resolutions to reduce separation loss with a minimal affect on each flight's profile. The level of equipment sophistication (air and ground) will determine the actual separation standards applied to each flight. Based on agreement between the service provider and each flight with appropriate operational approval, separation maintenance may be transferred to the flight deck, but separation assurance will remain with the service provider. There will be conformance monitoring tools to assure that each airplane is actually flying according to the transmitted trajectory. A pilot accepting a 3-D trajectory clearance is expected to fly the intended trajectory with high assurance of staying within the horizontal and vertical containment bounds (tube boundaries) defined by RNP RNAV standards, e.g. RTCA document DO236A (See Figure 4.3-1). The probability of being outside the intended containment bounds will be acceptably small, and if necessary to fly outside these bounds, the ground side will be alerted with an appropriate "unable horizontal/vertical RNP" message. The service provider agrees to provide priority separation services 39
from other aircraft, and avoid disturbing the trajectory of such aircraft unless urgently needed for safety of flight. This "contract" between aircrew and ground control provides a basis for using airspace more efficiently until it is required by either side to modify the clearance, or the aircraft flies outside the domain of applicability. As each flight approaches its destination its "contract" is updated with an emissions-friendly precision descent profile including the landing runway based on current/forecast weather and traffic conditions at the flight's estimated time of touchdown. This profile includes top of descent, speeds, routing, and touchdown time. User preferences are also considered in the calculations. Pertinent information on each flight's expected touchdown time, landing runway, taxi route, and expected time at the gate will be electronically passed to the terminal. This information will be used to determine the best taxi route, alert ground crews of arriving aircraft, post the most accurate arrival time on terminal screens, and determine and minimize the domino effects of delays on subsequent flights for the aircraft and crew members. Separation at touchdown is based on runway occupancy time for the conditions (dry, wet, standing water, snow, wind, etc.) calculated for each runway. Also considered are location of high speed turnoffs and aircraft type. Highly accurate wake vortex detection and prediction equipment plus curved approaches and varied final approach slope angles facilitate reductions in wake vortex separation. VFR landing rates are achieved in most weather conditions.
As the flight clears the runway, a routing to the terminal gate is data linked to the aircraft. Position information on each active flight and schedules of those approaching pushback time have been considered when developing this routing. Clearance to cross all runways will be provided by the controlling agency. With the use of synthetic vision the use of runway lights is almost negated. The surface monitor also includes a conflict detection system to assist in preventing runway incursions. 4.4 Flight Management
Prior to pushback, negotiated flight plans will be loaded into the FMC either via wired or wireless Gatelink or through company data link using VHF radio or satellite communications. After pilot validation, the crew will downlink the flight 40
plan to ATC as a clearance request. ATC will uplink the clearance for direct loading into the FMC. Alternatively, airline SOCs could negotiate routes directly with ATC, to be uplinked to the aircraft and to the SOC simultaneously following the crew's request for delivery of clearance. If the plan is revised while the aircraft is still on the ground, resulting in fuel burn increases acceptable to the aircraft model, the crew can accept the new clearance. If the fuel burn increase unacceptable, the crew must refuse the new clearance.
The flight plan may include a Required Time of Arrival (RTA) at a point late in the flight plan (metering fix or runway threshold). ETA at crossing and critical fixes will be updated online to facilitate conflict management en route. Acceptance of multiple RTAs and accurate achievement of such RTAs will require some level of functional change in all FMCs. Many current FMCs do not accommodate RTA functions in the descent and none provide adequately for the rapid and frequent updating in wind and temperature data necessary to guarantee accurate RTA, particularly in the descent. Wind and temperature data will be obtained from ground- based measurement systems and from other aircraft. All data will be data linked to the aircraft, possibly by broadcast. The FMC must be able to assess the viability of inter-RTA times if more than one RTA is defined for the route. The crew receives suitable cues to unacceptability of one or more RTAs. Once the aircraft departs, conflict management will be facilitated through the use of new route, altitude and airspeed clearances uplinked to the aircraft. Tactical changes will occur through negotiation between ATC and crew, while strategic changes will require three-way negotiation among ATC, crew and the airline's SOC so the schedule impact is contained. Such strategic changes may also result from scheduling requirements as well as aircraft-to-aircraft conflict management, and associated changes will originate in the airline's SOC.
Route/speed/altitude constraints resulting in the aircraft's being unable to meet downstream RTAs will necessitate re-negotiation. In general, the ATC system and airline SOC will know the effects of strategic clearance changes on RTAs, and new RTAs should be included in the trajectory change clearance. However, the FMC must confirm the viability of the RTA based on updated wind data consistent with ground 41
automation. If the FMC predicts that the aircraft cannot meet one or more RTA, a renegotiation will result. A re-negotiation will also result if changes in wind and/or temperature render one or more RTA unachievable. The FMC will provide a cue to the pilot if an RTA loses viability. For users who do not benefit from close cooperation with an SOC, changes to flight plan, "contracts" may be transmitted to an aircraft in the form of sets of constraints (waypoints over which the aircraft must fly, altitude limitations and RTA), to avoid traffic conflicts and ensure separation from active SUA and weather events. Such flight planning will ideally require trajectory optimization functions of the FMC that in turn will require a much broader wind and temperature data set. This will be significantly beneficial only on long sectors and for terminal area arrival management. For aircraft lacking the functionality, optimization will be limited to the use of great circle routes between constraint points and FMC-derived speeds and altitudes.
As the aircraft approaches the optimum top-of-descent point, ATC will uplink a clearance for flight completion. This clearance includes descent instructions and vertical path window constraints, assigned standard arrival procedure, transition, and approacehes including runway, ideal runway turnoff, any change to the metering fix or touchdown RTA, and gate assignment. The aircraft will be able to maintain precisely the cleared trajectory and waypoint arrival timing, providing high levels of predictability of intent for use in conflict prediction and resolution in the terminal area, and to use available runway capacity most efficiently. The operational concept greatly reduces controller workload by removing stepped descents and vectoring and greatly simplifying sequencing. At airports using the Final Approach Spacing Tool (FAST), the FMC can provide flight path intent that can be used to refine FAST's calculations. The FMC can also accept 4-D flight path updates directly from active FAST functions with pilot concurrence. 4.5 Airports Today's Airports
The US contains slightly less than half of the world's air passenger traffic, jet aircraft, and airports. There are about 17,000 airports in the US, of which 3,500 are public airports with at least one lighted and paved runway. Only 500 airports have 42
airline service. Fifty airports board over two-thirds of all passengers. The Boeing CMO predicts that traffic will double over the next 20 years.
For airports to handle the projected increase in traffic, they need more runways during all weather conditions. During VFR, the limiting factor is the runway occupancy time, so the more runways the better. Of the 15 new runways to be constructed between 2001 and 2007, only one third will help to ease delay in IMC, when delays are most excessive. The most-delayed airports do not have room to construct additional runways with a runway centerline separation of 4,300 ft (or 3,400 ft with Precision Runway Monitor (PRM)) from an existing runway, to enable an additional independent approach stream during IMC.
We need more efficiency and safety on the airport surface. In today's system the pilot is in voice contact with the tower until touchdown. Once the aircraft has touched down and exited the runway, the pilot is handed off to Ground Control to receive taxiing instructions. At some airports the pilot may contact ramp control at this point, since some airlines manage the ground movement of their aircraft at their hubs. The pilot proceeds directly to the appropriate gate, which is transmitted by the airline's SOC. Passengers deplane; ground service equipment services the aircraft; pilots perform necessary checks; and, the aircraft undergoes its turnaround to prepare for next departure. Delays may occur due to equipment maintenance, servicing the aircraft, or the delayed arrival of the next flight crew.
Once the aircraft is serviced, the crew boarded, and the passengers enplaned, flight plan clearance is transmitted to the flight deck. If the flight is not affected by capacity limiting initiatives transmitted by ATC, the flight leaves the gate at the appropriate time. The Air Traffic Control Tower (ATCT) or Ground Control delivers a taxi clearance to the departure runway to the pilot via two-way VHF radio. The pilot is instructed by ATC to cross runways and to sequence with other surface traffic. The ATCT uses radar displays, visual sighting, or position reports from the pilot to route the aircraft on the surface. When the aircraft reaches the departure end of the runway, it is cleared for takeoff based on current traffic conditions. 43
Tomorrow's Concept
The first improvement is the accuracy of current and anticipated aircraft position information and the flow of that information to personnel involved in all aspects of airport operations. The second will result from the ability to conduct simultaneous independent approaches in IMC to parallel runways spaced significantly less than 3,400 ft. The third is reducing arrival spacing due to wake vortex requirements. New technologies, research, and changes to current ATC rules and separation assurance functions will enable these improvements.
Airport surface surveillance will change from radar displays, visual sightings, or position reports to fused radar/position report data (with intent, target tags, and conflict detection). Position information will be transmitted by the aircraft to the surveillance sensor at a much higher return rate, thereby allowing greater position accuracy, reduced separation, and increased safety. This position information will be transmitted to concerned entities, including local ATCT, ramp control, and airport operational personnel. This will enable the smooth flow of traffic on the airport surface and the smooth processing of aircraft at the gate. ATCT personnel will have tools to optimize runway assignment, sequencing and spacing of arrivals, departures, and taxiing aircraft. Planning and replanning tools will be available to all personnel to optimize use of runways, taxiways, gates, or maintenance and service facilities. Airside Management
Upon approach, an aircraft's trajectory will be updated with a noise- and emissions-friendly precision descent profile that includes the landing runway, based on the airport's current forecast weather, operating configuration, aircraft / operator preferences, and traffic conditions at the flight's estimated time of touchdown. As the flight clears the runway, a taxiway routing to the terminal gate is data linked to the aircraft. Landside Management
The expected time at the gate will be dynamically updated in the terminal building on the Flight Information Display System (FIDS). The aircraft's assigned baggage claim will also be displayed at the gate and on FIDS displays. The number of passengers will be transmitted electronically from the aircraft and used by the resource 44
planning tool to determine the optimum number of arrival gate and baggage personnel, and customs officers and immigration officials for arriving international flights. This information could be transmitted to rental car agencies, concessions personnel, and parking personnel. 4.6 Concept Differences
See the referenced Boeing report. 5 Performance Requirements 5.1 Separation Assurance - System Level
A closed-loop structure assures separation in today's JFR positive control airspace. Navigation and guidance is performed by the cockpit crew and avionics. Surveillance is performed by secondary radar and radar data processing (RDP) and display system. Communication is performed by the sector controller and crew using VHF voice radio and position prediction. Conflict detection and resolution planning are performed by the sector and data controllers. Thus, the separation assurance loop closure is performed by a human-to-human voice radio connection, based on a 2- dimensional relative position display.
The current minimum allowed separation, as measured by the RDP system, is 5 NM in en route airspace and 3 NM in TRACON airspace, which was based on the performance of analog RDP systems and operator confidence in intervention through voice radio in case of impending violations. There is no known analytical justification for these separation standards. Thus, it has not been established how the various performance factors such as Required Navigation Performance (RNP), Required Communication Performance (RCP) and Required Surveillance Performance (RSP) and others would combine to establish a safe separation minimum for a given operational concept and technology architecture. The methodology and toolset in our proposal will address this question, and Boeing has performed an analysis of some of the performance factors in the current operation. Table 5.1-1 lists the various factors that have been analytically or empirically quantified.
Table 5.1-1 Air Traffic Performance Factors En Route Factor Performance
Navigation Accuracy 1 NM 45
Surveillance SSR 0.25 NM, 12 sec update
Surveillance SSR Monopulse 0.1 NM, 12 sec update
ATC-Comm-Crew- Aircraft reaction time 45 second
Avoidance maneuver 15 second Short term conflict alert time 3 minute
Terminal Area Factor
Navigation Accuracy 0.3 NM (best DME-DME)
Surveillance 0.25, 5 sec update
ATC-Comm-Crew- Aircraft reaction time 45 second Avoidance maneuver 15 second
Short term conflict alert time 3 minute
The terminal area, the 3 NM separation standard, is sufficient to allow a successful avoidance maneuver if detection occurs at 3 NM relative spacing, given the surveillance accuracy, reaction time and avoidance maneuver time, nominal aircraft speeds and closing angles of less than 130 degrees. The surveillance accuracy of 0.25-0.1 NM is a small contributor to the overall spacing minimum of 3 or 5 NM. The human and aircraft reaction times dominate the loop closure performance, and a model that includes all the relevant factors must be used to establish safe spacing targets. 5.1.1 Air Traffic Manager
The traffic management function is divided into four time horizons: 1) Imminent, 2) Short-Term, 3) Medium-Term and 4) Long-Term, corresponding to top level ATM functions of planning or flow management, detection/prediction and intervention. Each of these temporal levels is necessary for continuous traffic management. The imminent level may be supported by some airborne conflict avoidance system such as TCAS TJ while the mid- and short-term may use ground- based decision support tools such as conflict probe. The controller becomes a manager of the system and intervenes when needed. Extensive conformance monitoring tools and conflict detection/resolution tools are available. 5.1.2 Surveillance
5.1.2.1 Today's System 46
The goal of en route surveillance is "positive control" to provide tactical separation assurance and strategic flow planning. Surveillance is radar-based, providing controllers with aircraft state and providing input to separation automation and load/flow management functions. The two main types of radar used are in the NAS today are Primary Surveillance Radar (PSR) and Secondary Surveillance Radar (SSR). Precision Radars are used in a few locations to support special approach and landing operations. Primary Surveillance Radar (PSR)
These radars radiate energy and monitor for reflected returns. The time interval between transmission and return is used to compute a range. Range capability is a function of system average power. The direction of the "target" is determined by where the rotating antenna receives the reflection. Older analog radars are sensitive to weather and have a relatively slow update rate. Their usable range is limited by required accuracy; the greater the accuracy requirement, the shorter the usable range. Angular accuracy also reduces with range. Secondary Surveillance Radar (SSR)
Secondary, or "cooperative radars" are transponder-based, using interrogation/reply capability to get ATC-assigned code and altitude. This data is used for conflation of radar returns with specific flights on radar displays. The range and directional accuracy of the more modern secondary radars is very good. They are designed to support ranges of at least 60 NM around each airport and up to approximately 200 NM for en route surveillance. Typical scan rate is about one report per 5-second interval. Azimuth accuracies depend on the equipment. Integrity of the identified aircraft (the probability of misidentification on the controller's display) is also an issue.
Precision Runway Monitor (PRM) Radars
Precision Runway Monitor radars and associated displays are installed to support special approach applications. These primary radars are updated once-per- second, and are accurate to the order of three meters. In IFR conditions they enable a reduced separation standard for approach and departure beyond what would be allowed by the standard terminal area secondary surveillance radar. This is important 47
for high density airports where it is essential to maintain maximum throughput as the weather deteriorates. 5.1.2.2 En Route
Controllers have a combination of information from radars and other sources (usually flight-related information) to maintain required en route separation. Primary radars designed for en route use provide line-of-sight (approximately 250 miles for targets at 40,000 feet) coverage and scan at a rate of one report per 12-second interval. Technical performance capabilities, in terms of detection probability and accuracy, are similar to those of the terminal radars, but are less accurate than terminal surveillance due to the larger distances (for position reports at ranges greater than 150 miles). As a consequence, en route tracking and data report quality are lower for en route surveillance. For example, velocity estimates can be poor and aircraft tracking is typically poor in turn maneuvers as a result of lag errors that can be 30 - 60 seconds. For these reasons horizontal separation standards are larger for en route than for terminal airspace.
En route airspace uses a networked system of Air Route Surveillance Radars (ARSR) which provides continuous monitoring of aircraft flying in domestic airspace above ~ 9000 ft. (FAA goal is above 6000 ft.). Each radar is networked to one or more ARTCCs to provide continuous monitoring of aircraft across NAS-managed airspace. There are "holes" of coverage in mountainous areas. Procedural separation is provided where there is no radar coverage.
Considerable redundancy is built into the en route surveillance system. Primary radars are positioned to achieve at least dual radar coverage throughout NAS- managed airspace. This provides very high reliability for long-range radars. Co-located with the en route primary radars are SSRs that enable code identifier, altitude, and tracking.
This combination of en route primary and secondary radars supports a minimum en route separation standard of 5 NM. This standard is determined not only by radar technical performance, but also considers factors such as communication quality and availability, pilot and controller reaction and intervention 48
time, volume of controller's airspace, traffic density etc. In practice, en route separation is normally 7 to 8 miles.
One knowledgeable author offered a performance assessment of the current surveillance system. "It is assumed that the combined surveillance system performance provides a probability of accurate information display to the controller to allow the separation assurance function to be performed which exceeds 99.99999%.
This is not validated and does need to be benchmarked."
Terminal/ Approach and Transition Areas
Surveillance is also provided in the terminal area and the descent/climb regions by a mix of primary and secondary radars. They provide uniform coverage with sufficient continuity and reliability to support all-weather, day/night operations while handling growing traffic and maintaining safety margins.
At most medium and large capacity, surveillance data is provided by a primary radar (typically called Airport Surveillance Radar, or ASR), a co-located secondary radar, and a TRACON. Small airports may only have access to an SSR, or may have no surveillance capability other than that provided by voice reporting and tower controllers. In this latter case, in IFR conditions, radar service may be provided by either a TRACON or an ARTCC to a point where radar is lost, where they receive procedural control. At some large airports, dual primary/secondary radar sensors provide redundancy. Similarly, the radar processing and display paths employ direct and indirect channels. In the rare case of a failure of a single sensor terminal primary radar, the long range radar can be routed for temporary replacement. Due to slower scan rate, several separation parameters must be expanded. If the TRACON with the failed radar is an ARTS facility, the host ARTCC can send position and alphanumeric data derived from the ARTCC host computer to the TRACON displays.
This combination of terminal area primary and secondary radars supports a minimum separation standard of 3 NM when within TBD miles of the radar, and allows for simultaneous independent approaches to parallel runways with no less than 4300 ft. separation. For en route, this standard also considers factors other than 49
technical performance capability of the radars. Two that are unique for terminal area operations are runway occupancy time and wake turbulence.
With a PRM, the FAA believes that simultaneous independent approaches can be carried out safely to parallel runways with 2500 feet of separation. It is envisioned that an offset of 2.5 degrees to one of the centerlines will be required and flown only to Category I minimums. Although display update rates greater than once-per-second are feasible (using radar or other technologies) further reductions in the parallel approach separation standard are probably not a function of tracking accuracy but are considered to be limited by human and aircraft performance, and wake vortex. Use of PRM in IFR conditions is expected to provide improved runway throughput rates and may allow reductions in longitudinal spacing between aircraft on instrument approaches. Surveillance Augmentation
Today, radar-based separation assurance is augmented by the airplane-based TCAS or ACAS collision avoidance systems. TCAS is a "safety net", i.e., a secondary system that provides the flight crew with situation awareness of proximate traffic, and commands an emergency maneuver when controllers have failed to provide separation assurance. The TCAS function uses a single transponder for air-air interrogation / response of traffic. In a similar fashion, ground-based capabilities include short-term conflict alert that serves as an augmentation to controllers. Limitations of Today's Surveillance Systems
Much of the wide distributed surveillance equipment in the NAS today is aging and is widely distributed. This makes it difficult and costly to maintain and update. Although radar data is shared, there are many radars/sensors that are incompatible with others, making it difficult or impossible to network their data.
Many of the existing surveillance systems have limited automation capabilities and, therefore, support mainly a tactical environment.
Even new SSRs are limited as to the number of airplanes they can successfully interrogate and process. And the "true identification" of a particular aircraft can sometimes be in error. 50
There are invisible "cones of silence" above the primary terminal/approach radars. In some transition areas, surveillance is crude due to coverage only by en route radars with lower data rates. Some satellite airports without a co-located radar have inadequate low altitude coverage. En route radars cannot "see" low altitude areas within mountainous areas.
5.1.2.3 Emerging Techniques for Enhanced Surveillance
ADS-A enhances surveillance by making available to a range of airplane- specific data that is unavailable in the primary/secondary radar environment. "Addressable" means a suitably-equipped ATM entity establishes a contract(s) with the aircraft to receive information. There are many data sets, but the basic set provides current position/altitude/time, next waypoint altitude and ETA, and the following down-path waypoint. Other information can include airplane proximate meteorological data and other kinds of intent information.
ADS-A systems have been certified to an essential level and are, therefore, approved for position tracking in oceanic areas without voice/radar backup. They will likely be used differently in the domestic environment where, for example, information regarding upcoming waypoints may be need by trajectory/flow management functions. In this case, ADS-A information would not be used to give radar-like information but would augment radar and ADS-B with mid-term intent data.
For oceanic separation of 100 NM lateral/10 minutes longitudinal, position reports generated from any source are required every 80 minutes. If separation minimum drops to 30 NM, ADS-A will be required to provide reports every 20 or 30 minutes depending on accuracy of aircraft position data. (See "RNP" in section 5.1.4, Navigation).
ADS-B is a further surveillance enhancement where each vehicle broadcasts its own position, altitude, velocity and intent data to other equipped vehicles and ground ATM sites. This information will be used for enhanced situational awareness and aircraft tracking. Performance requirements and certification levels will relate to the operational tasks enabled by the system. For example, Cockpit Display of Traffic Information (CDTI) uses ADS-B information to generate a controller-like cockpit 51
display of all nearby aircraft equipped with ADS-B. This enhances situational awareness, and will enable more efficient in-trail spacing and climb performance. However, since these features are not critical to continued safe flight, the CDTI function will not require performance requirements as stringent as those expected for ATM tracking of aircraft position and intent.
Traffic Information System - Broadcast (TIS-B) is another approach to exchange information to support enhanced surveillance. It involves a ground system collecting surveillance data from all available sources (radar, SSR, ADS-A, ADS-B, etc.) and fusing it into a "big picture" of the traffic and intent situation in an area. The compiled data will be transmitted to users, similar to ADS-B. As with ADS-B, performance requirements and certification levels will be related to the operational tasks that the system will provide.
5.1.2.4 Future Surveillance System Requirements
Enhanced departure/approach and transition area surveillance will be required to meet the need for widespread deployment of regional traffic flow management systems. Enhanced surveillance performance in the climb/descent transition area surrounding terminal airspace will also be required so that en route controllers can more accurately structure and merge the arriving and departing aircraft consistent with terminal area flow operations. Enhanced surveillance will also be one factor that permits reduced IFR separation during approaches and departures. Required Surveillance Performance
The emerging concept of RSP will identify top-level system performance requirements for the surveillance portion of the overall ATM system. Those system- level requirements will then be allocated to the system element level. This will be a complex undertaking and must consider all potential system users. RSP is expected to address at least accuracy, availability, continuity and integrity for the detection, identification and tracking functions. Separation Standard
The most fundamental surveillance requirements should support a separation standard of X NM in the en route area, Y NM in the transition area, and Z NM in the approach/departure area. To achieve this, values will have to be specified for the RSP 52
elements listed below. Ranges of values will be appropriate (approximate?), as the performance requirements will vary depending on the operational need and, perhaps, the user.
1. Accuracy - system level. This will specify the overall accuracy the system needs to achieve desired NAS surveillance requirements. This will then be allocated to individual elements.
2. Timeliness. This will specify latency on a system and element level.
3. Integrity. This must consider the entire system including the airplane (or ground vehicles), ground network (if applicable) and ground ATM equipment. 4. Continuity of Function (COF). The level of built-in reliability is dependent on the operational need and consequences of the surveillance function becoming unavailable. Continuity of function requirements must be allocated amongst the system elements, and they may vary within the system depending on density, usual weather patterns, etc. Since some aircraft will want to able to operate in all areas, they will need a uniform, minimum COF requirement (consistent with their class). Any location-dependent variations of COF requirements will most likely be manifested by differences in ground and networking equipment requirements. Surveillance System Transition Considerations
From an air-to-ground point of view, the transition from a radar-based surveillance system to the new system could be quite simple. ADS-B provides more accurate, timely data than radar, and radar-like procedures could be used initially. As confidence is gained and automation becomes available, intent data could be used increasingly to predict conflicts and offer avoidance measures. If air-to-air is to be used also, or instead of ground-based separation assurance, then the transition is likely to be more difficult and require planning, experimentation and negotiation. 5.1.3 Communication 5.1.3.1 Current System
Voice communication via standard VHF analog radios is the current standard for pilot/controller communication. One frequency is allocated per ATC entity. At busy airports and TRACONs, frequency congestion is a major problem due to the number of aircraft being controlled and the requirement for multiple discrete voice 53
communications with each aircraft. This occasionally results in lost or garbled messages, or the requirement to repeat and confirm instructions.
A common data link, known by its protocol specification "ACARS ARINC 623", is widely used for airline company information and other non-critical flight data transfer. ACARS uses a specific subset of the frequencies allocated to VHF communications. Although ATC pre-departure clearances are delivered via the ACARS network, there are no other ATS instructions or clearances that are delivered over this medium due to its inadequate integrity.
Since the number of VHF communication frequencies is fixed, few are allocated to ACARS. These few frequencies must be re-used across the NAS. Where inadequate numbers of ACARS frequencies serve busy hubs, congestion and occasional loss of ACARS messages make it difficult to receive the necessary data/clearances. 5.1.3.2 Emerging Techniques for Enhanced Communications Today, VHF frequencies are separated by 25 KHz. A short term fix to the frequency congestion problem is a new VHF radio standard that separates communications frequencies by 8.33 KHz, tripling the number of channels available. While this can be applied to voice communication, ACARS still requires 25 KHz channel spacing. Even though 8.33 KHz radios are considered an interim solution, US airlines are equipping with them to comply with European requirements and the anticipation that a requirement may emerge in the US.
Digital data link is seen as a critical solution to the growing demand for communication services. In the NAS, Controller to Pilot Data Link Communication (CPDLC) implementation is scheduled to commence June 2002 in a limited area. This initial application, compliant with ICAO Aeronautical Telecommunication
Network (ATN) standards, will involve a very limited "message set" (a fixed set of standard messages used in the ATS today) as a replacement for some voice communications. Data will be collected on effectiveness, efficiency, human factors, and integrity of the new digital communication. Implementation will be expanded nationwide in June 2003 with an expanded message set. In approximately 2010, oceanic coverage may be introduced. 54
5.1.3.3 Future Communication Requirements and Plans
Digital communication will grow and provide increased functionality among the service providers and system users. Message sets with different levels of urgency will require specific levels of service; however, it is not certain that data link will ever be able to satisfy time-critical message requirements. It will be critical to minimize errors in data transmission in order to rely on the digital communications for overall separation reductions and for collaborative decision making.
Generation Communications (NEXCOM) is being proposed as a way to carry voice and data digitally using ATN. There is an ongoing comparison between NEXCOM and a combination of the 8.33 KHz standard for voice, and current digital protocols for other data. One existing protocol used in FANS-compliant avionics and ground systems may be adapted to an Internet Protocol (IP) that will satisfy requirements currently applied to ATN, but may allow lower upgrade costs in existing aircraft. 5.1.4 Navigation
5.1.4.1 Today' s Airways-B ased Navigation System
Navigation in the NAS today is almost exclusively along airways that have been defined by ground-based VHF Omnidirectional Range (VOR) or VOR/Distance Measuring Equipment (DME) navigation aids. Layout of the airways was driven by where it was convenient or possible to locate navigation aids. The resulting airway system forced aircraft to fly paths that were not the most direct route from origin to destination. In addition, the fixed number of airways and common over-fly points (VORs) occasionally created congestion and limited the volume of traffic that could be accommodated. This system hasn't changed much in 50 years and must still accommodate the least-capable aircraft, which is one equipped only with a VOR/DME receiver. It is manually tuned sequentially to the next VOR in the flight plan. Deviations from a desired course to that navaid are monitored and corrected by the flight crew or autopilot. The VOR system is angular, which means errors increase with distance to the navaid. To contain the error magnitude, VOR-based airways must have a VOR at 55
least every XX miles. This positioning limits airborne navigation errors to 4.0 NM (TBV). A combination of requirements on avionics systems, the navaids themselves and the assumption of essentially full secondary surveillance radar coverage provide integrity of navigation along the VOR-based system. The accuracy and integrity of this system determine the placement of adjacent airways. 5.1.4.2 Area Navigation
Modern RNAV systems can define and fly any route over the earth, and are widely available in commercial jet transports, regional jets, and business aircraft. RNAV systems provide great flexibility, as they contain large databases of geographic fixes, navigation aids, and procedures. These elements are connected together to form flight plans made up of waypoints. These "trajectories" can be located to optimize traffic flow and to increase operational efficiency.
The RNAV systems use data radiated from existing ground-based VOR/DME navigation aids to determine an estimated aircraft position that, for en route navigation, has greater accuracy than was achievable using the angular VOR system alone. They do not have to fly over, toward, or close to the stations. In the terminal environments, RNAV systems can achieve 0.3 - 0.5 NM (95%) accuracy by using data from standard ground-based navaids. With this positioning accuracy, RNAV systems provided the technology with the potential to significantly improve efficiency of the NAS. The recent addition of satellite-based positioning improved the achievable accuracy to better than 0.1 NM (95%) everywhere in the NAS. Even with the improved accuracy, however, RNAV systems have not been used widely, due to the lack of dedicated procedures and the inability of the NAS to use this new technology while still serving the least capable users. 5.1.4.3 Required Navigation Performance
While RNAV systems provided a significant airborne capability, they were mainly confined to mimicking the VOR-based airways and procedures system. They provided work-saving benefits, but the certification standards rarely required performance beyond that required of the legacy airways-based system. It was assumed they would operate in such a system with existing mitigation techniques to detect navigation errors and blunders. As a result, these systems were not designed to 56
provide unprecedented flexibility based in part on guaranteed airborne minimum performance and functionality.
Required Navigation Performance (RNP) was developed to fill this gap. This concept builds upon the original RNAV concept. It requires that a minimum set of RNAV features, including displays and alerts, be available on all aircraft operating in RNP airspace. The RNP concept also quantifies the navigation performance required to operate in a particular environment. The required performance can readily be associated with airspace requirements, and is stated in terms of accuracy, integrity and continuity, along with the minimum set of airplane capabilities. Airspace planners will use this a priori knowledge as they design new RNP operations. Benefits will accrue from these new operations in the areas of reduced separation, obstacle clearance assurance, and more efficient and flexible arrival/approach/departure procedures. Airspace managers can depend on RNP/RNAV-capable aircraft to execute their flight plans with a high degree of conformance and repeatability. RNP Performance Parameters
RNP performance is based on providing an assurance of containing aircraft navigation-related errors to two different probability levels, and ensuring continuity of this assurance. The containment concept is key, as it provides the necessary assurance to airspace planners that the aircraft will remain within given boundaries with the prescribed probability level. This assurance can be used as one element in collision risk assessments and will allow current safety levels to be maintained at higher traffic density and/or reduced lateral separation. RNP Accuracy - 95% Containment Assurance
The basic RNP accuracy requirement states that the actual aircraft position must be within the RNP value (expressed in nautical miles) for 95% of the flight time. For example, an aircraft operating on an RNP 4 airway must remain within 4 NM of the computed navigation position at least 95% of the flight time. There is no assumption or requirement on the specific technology used to achieve this; however, the aircraft avionics integrator must be cognizant of the levels of RNP for which operations are desired as this will affect which navigation sensors are included. RNP values with standard ground-based VOR/DME navaids, the LORAN system, or 57
inertial navigation systems are larger than those achievable with satellite-based navigation systems.
RNP Integrity - 99.999% Containment Assurance
Also known as "containment integrity ", the requirement is that the actual aircraft position is not outside an area bounded by 2 x the RNP value without an alert to a probability of 10-5 per flight hour. This containment integrity probability and bound can be easily applied in evaluating airspace dimensions and operational risk. RNP Continuity
The RNP containment continuity requirement is that the probability of loss of a specific RNP capability (e.g. RNP 2) be less than 10-4 per flight hour. The containment continuity can be considered in assessing the types of supporting infrastructure as well as airborne equipage. "Legacy" RNAV Systems and RNP operations
For RNAV systems that have not been certified for RNP-based operations, the most significant difference with RNP is the lack of containment integrity and containment continuity. It may be possible to accommodate these systems in an RNP environment by the applying traditional separation and obstacle assessment criteria as a way to mitigate the lack of formal RNP performance assurance.
Additional operational efficiencies will be realized when the lateral RNP concept is combined with vertical navigation and time of arrival control capabilities. 5.1.4.4 Transition from Airways-based Operations to RNAV and RNP
The transition can be accomplished through a reasonable number of steps involving aeronautical information services, procedure designers, state authorities/regulators, and aircraft operators. Route Structure Based upon Fixed Ground Navaids
The VOR-based airway structure is the starting baseline for moving to a new NAS, since it will continue to provide the structure for most of today's operations. Some RNAV operations have been implemented through the National Route Program and special authorizations. Route Structure Replication as RNAV. 2001-2005 58
The conventional route structure replacement can start with the replicating conventional routes using named latitude/longitude fixes and flight paths compatible with RNAV. This would be the initial ATS RNAV route baseline. Its benefit will be in familiarity with the RNAV concept, equipment, and use in an operational environment. The retention of many existing fix names is also an important factor in minimizing the impact of this transition. Training will emphasize that waypoints are not tied to the ground navigation aids. Route Structure with RNAV Optimizations, 2003-2010
After users are familiar with the initial ATS RNAV route baseline, simple adjustments can be made to selected parts of the route to start fixing choke points.
Changes in routes would include new named latitude/longitude fixes to create separate or parallel routes around choke points. With an initial single RNP value as a basis for the changes, conventional separation standards are probably acceptable if communication and surveillance environments remain as they are today. This could have minimal impact on ATS if an RNP capability level for operations is specified which, in turn, leads to a RNP-capability qualification requirement for the aircraft population. In transition, a need to discriminate capability would affect airborne systems, ATS procedures and ATS tools. RNAV SIDs. STARS, Transitions and Approaches. 2001-2010 RNP RNAV-based terminal area procedures are likely to provide benefits driven by fuel reductions through reduced track length and more consistent performance and traffic flow. Procedures with various RNP values will accommodate different airplane capabilities and provide alternate minima. Environmental benefits could include noise and emissions reductions. Voice radio frequency congestion will be relieved by increased use of pre-cleared RNAV departure, climb, descent and arrival procedures, which will also ease the controller's sequencing tasks. RNP RNAV Flexible/Random Routing, 2008-2015
The RNAV system capabilities allow tactical operations, including diverting from a preplanned route with parallel offsets or direct-to. This improves efficiency by avoiding weather, SUA or traffic. However, these improvements and flexibility will 59
trade off with potential downstream effects with sector control, terminal area arrival transitions, procedure transitions and approaches.
5.1.4.5 Landing System
Precise navigation, based on space-based signals with possible augmentation from the ground, will allow for converging/curved approaches with lower decision heights, optimum noise routings, and precision approach through automatic landing.
5.2 Flow Management - System Level
The current flow management system functional structure and the planning cycle involved in reaction to severe weather events relies heavily on human operator performance and telephone coordination, with minimal automation and information infrastructure support. The figure reflects the large number of agents involved in collaborative decision making, where planning teleconferences may include over a hundred individuals.
Some troublesome issues with current flow management techniques include: Weather forecast uncertainty; No automation tool to generate coordinated re-routes around airspace restrictions; and Coordination of planning strategies by voice over phone lines between SCC, ATC and SOC. The preferred ATM system will:
D Characterize and reduce (if possible) weather prediction uncertainty in terms of probability of correct prediction for a given time horizon
D Automate tool performance parameters
D Account for flight replans within a given compute time, including forecast delay, routine circuitry and sector/airport utilization
D Coordinate performance in terms of number of agents dynamically involved, flight plan update rate, communication bandwidth, availability and integrity
D Assess general flight and flow planning system reliability.
6 Architecture Elements
The Boeing system is based on a timely, low-risk ATM transition plan. The plan considers the transition for operations, architecture, and the implementation phases from the current system to one supporting a new basis for operating the NAS. 60
This new system will provide quality air traffic services to all system users for the next fifteen years, assuming we start today. The system will move NAS operations from today's flight planning and radar-based air traffic system to a trajectory-based system in which current and future position of the aircraft is available to system service providers. The NAS architecture will change from an increasing number of disjointed tools and procedures to a set of integrated solutions.
The Boeing transition plan is based on a three-phased deployment of a set of technology elements which develop increasing functionality, provide increasingly integrated solutions and allow significant capacity and safety gains, especially during the later program phases. The basis for transformation is the integrated introduction of three enabling elements: (1) the flight trajectory as the basis of air traffic management, (2) a new information infrastructure to allow significant increase in the quantity, timeliness and reliability of information available among all personnel, including, in phase 3 of the program, an integrated CNS satellite services capability, and (3) airspace and procedures changes necessary to transform the operation of the system. This architectural and operational transformation will move the NAS from a fragmented collection of technologies and procedures to a seamless, trajectory-based ATM system in which flow planning, flight planning and air traffic separation management are integrated and share a common information set. In phase 1 of implementation, Boeing will develop a trajectory-based flow planning system to replace the existing set of national, regional and airport level planning tools and procedures. In phase 2, this trajectory-based approach will be applied to the sector flight planning. In phase 3, trajectory-based separation functions will be developed and deployed. Prefered ATM will include CTAS, conflict free advisories to controllers as currently provided by URET, data link, CPDLC, CDM, and designated high altitude airspace. Significant numbers of new runways will be needed to meet the traffic growth expected during the next 10 to 20 years. Boeing ATM and CNS initiatives complement efforts to increase runway capacity in two significant ways. First, ATM and CNS technologies will improve the capacity of airports and runways operating 61
under instrument flight rules. Second, ATM and CNS technologies can relieve constraints on airspace as runway capacity grows.
6.1 Phase 1 : Traj ectory-B ased Flow Planning
Phase 1 will introduce the dramatic changes to the national and regional flow management operation in the NAS. Our intent is to immediately introduce a new national level flow planning and management system to support greatly improved system schedule integrity maintenance during periods of disruption. This will include a set of trajectory-based planning and replanning tools, hosted at the system command center (SCC) that will support: D A flight trajectory-based projection of system loading
D A common view of system status and predictions for service provider and system operators
D Assessment of alternatives against user and service provider criteria
D Coordination of replanning efforts to ensure that system agents work to common objectives
D Communication of replanning information to affected stakeholders
D System metrics for operational assessment and analysis
The engine of this system planning, coordination and information exchange system is the National System Flow model. The model would be operated by the FAA Air Traffic Control System Command Center. This central planning function will provide the national level delay allocation, and coordinate flow responses initiated at the regional and airport levels.
The system replanning in response to NAS operating constraints will initially be limited to pre-departure plan changes and will use existing data link capability, which already resides in transport aircraft. The participating flight planning and airline SOCs will use their existing systems to develop and accept revised flight plans. The SCC requires the capability to transmit revised trajectory-based flight plans to existing regional control centers. A new information distribution system will provide coordinated delay responses for national, regional and airport level flow planning. It will also be necessary to provide information exchange between the ATCSCC and the airline SOCs. Much of the 62
telephone exchange in today's system will be replaced by high bandwidth data exchange. This will initially support pre-flight replanning, but later transition to inflight replanning capability.
The inability to coordinate changes in response to disruptive events is a major shortcoming of the current system. Development of a sophisticated information exchange function in the first phase will provide the communications building blocks for later stages of NAS modernization.
Further incremental communication enhancements include the addition of dynamic data inputs and the ability to expand the capability of the SCC. The use of trajectories in regional flow applications will be integrated with the SCC planning system. Other improved functions include allocation of delay across control domains; central accounting for delay already imposed on a flight; and exchange of data between central, regional, and airport planning. Airport-level arrival and departure metering tools should be integrated into a seamless set of flow planning tools. The data link to aircraft would initially use the existing ACARS network and aircraft data link equipment capable of pilot-controller communication. This will accommodate the transition to a more efficient architecture. The FAA air-to-ground data link capability would evolve to an integrated system allowing flight plan exchange and FMS loading. Initially, replans will be constrained to pre-departure. Information links between airport flight status tools (e.g., ASDE-X) and the National System Flow Model would be added.
Aircraft-to-ATC communication during this phase will use data link for pre-departure pilot-to-tower coordination among aircraft. Control of traffic by would continue to be based on voice, but planning revision would be transferced to the emerging data link capability. The interfacility communications connectivity (including airline SOC) will be developed during this phase.
Navigation will use existing ground navaids, but aircraft with primary GPS authority will be increasingly enabled for use. Scheduled retirement of ground navaids could begin, as the Wide Area Augmentation System (WAAS) is granted capability to provide sole-source data. 63
Surveillance would continue to use en route and terminal control radar. The phased introduction of airport digital flight status will begin, tied to the central flow planning facility.
We expect there will be little change to airspace management during this phase. The major change will be to the flow planning system. The NAS flow response currently is a coarse set of national technologies and tools (based on filed flight plans) and largely decoupled regional (miles in trail) and airport level flow planning. This will move to an integrated set of tools and methods, based on the National System Flow Model, coordinated with SOCs and among the various ATC flow agents. It is expected that flow planning will be needed at all levels in the system end state, but local and regional flow actions will be better coordinated with national flow planning. 6.2 , Phase 2: Trajectory-Based Flight Planning
During this phase, trajectory-based flight planning and dynamic replanning will be implemented in the en route regions, and later in the terminal areas. This phase will transform the flight planning function from the current "flight strips" to a full trajectory-based capability.
In today's flight data processing system, large changes to the flight path during the en route portion of flight make precise, automated tracking of an airplane impossible. Time estimates are crude, especially where climb or descent occurs.
Our plan calls for a trajectory-based capability in the flight plan processing system so that en route and terminal controllers have integrated trajectory-based planning tools on hand. These tools can support a variety of applications, including conflict probes, dynamic replanning tools and airport metering tools such as CTAS. This capability will facilitate sector planning, inter-sector coordination and sector-traffic management unit coordination, and airport traffic planning.
Many new applications based on the precision management of trajectories will be developed. Initially, the deployment will be to a single facility but follow-on deployments to other facilities will rapidly follow. Transition to the overall architecture will be paced by the rates at which en route and terminal automation 64
system can support change, based on aircraft equipage updating schedules, airspace and flight planning procedures development, and training times.
Trajectory and other flight information will require airplane-ground information exchange and developing new interfacility air traffic data exchanges (including regional traffic flow management exchange with sector level flight planning and replanning activities). Developing robust planning and replanning tools for terminal area operations will be a major challenge. Today's busy terminal operations are almost exclusively tactical during high volume operations. More robust terminal area planning and replanning functions could provide substantial gains. Aircraft will have a data link (ACARS VDL/2 will probably be adequate), an FMS and a GPS navigation system (for a high-integrity time fix). Air-to-ground data link exchange of dynamic flight replanning data is assumed. Early applications could be for FMS-to-sector planning tools, such as a second-generation conflict probe. Equipped aircraft also would provide current state information and trajectory to the National System Flow Model to improve the fidelity of its solutions.
Voice communications for tactical intervention will continue, but we expect that the frequency of voice communications will drop dramatically with the availability of en route trajectory management. Dynamic replanning communications will be transmitted by data link. A key transition issue is the performance adequacy of the initial data link to support terminal area trajectory exchanges. Requirements for these applications may affect the timing of the transition to a new satellite-based data link. Interfacility communications will provide connectivity of flow planning and flight planning elements.
Navigation during this phase will be based on GPS, both for navigation and time estimation; there will be a residual ground-based backup system for contingencies.
Surveillance on the airport surface and in the terminal area would use a fusion of data: aircraft position and intent, radar, and surface secondary-source position.
Airspace changes will be less significant in the en route airspace. Sector and terminal control region boundaries will begin to be modified consistent with phase 2 implementation. Significant trajectory-based terminal planning and replanning 65
activities will probably be limited to prototyping and to better coordinated use of tools like CTAS with FMS data exchanges.
Our Phase 2 implementation strategy requires that airlines operating at affected locations implement the changes, and limits air traffic training requirements to personnel associated with affected facilities. This approach minimizes the equipage rate (managed by locality), puts air traffic training on a manageable schedule, and allows the phased introduction of new procedures. Operator benefits associated with the implementation are substantial and help the airline equipage business case. 6.3 Phase 3: Trajectory-Based Separation Management The third phase will introduce precise trajectories into the air traffic separation management process. This step will provide the largest capacity benefits but will require the most exacting performance requirements. High levels of CNS accuracy, integrity, and availability will be needed. A significant upgrade of current CNS capabilities will be required, both in the ground infrastructure and on the airplane. This phase introduces high-integrity trajectory-based flight plans ("contracts"), which are mutually agreed upon by aircraft operators and service providers that stipulate the precise procedure to be flown. Various integrity-enhancing capabilities will provide conformance monitoring, both within ground automation and on the airplanes. This phase will require significant development of en route, arrival, departure, and missed-approach planning/replanning tools to provide accurate, de- conflicted flight profiles to the aircraft and to monitor aircraft conformance to planned descent profiles. It will probably be necessary to modify the existing controller displays to present the trajectory information. The controllers' procedures, tasks and training regimes will change. The planning tools will be coupled with new capability, such as LA AS -based procedures and other airspace operating changes.
This will require significant investment in the information architecture. One of the governing principles of our ATM architecture will be to facilitate the insertion of technology at block point change times. The following capabilities will be phased into the architecture, consistent with technology readiness and operational need: Communication 66
High performance, digital air-to-ground and ground-to-ground communications will be required during Phase 3. Implementing a satellite-based communication system would cause minimal system disruption. Because safety-of- flight services share the same communications, the decision to move to a new communications band will be made by all stakeholders, based on economics and performance. Navigation
The evolution toward reliance on satellite navigation has been slowed somewhat by the lack of augmentation systems to provide increased integrity. New satellite systems could improve the WAAS solution and provide reliability sufficient to allow aircraft to navigate using a single set of navigation satellites. This approach would allow the removal of most ground navaids, as determined by a rigorous safety analysis. Surveillance Surveillance is currently accomplished primarily using radar and Mode-S/C transponders. Advances in satellite surveillance will provide this function with greater accuracy and equivalent or enhanced integrity and availability. The introduction of this equipment could affect the need for redundant radar installations, and transponder-TCAS interoperability will need to be addressed. The Global Communication, Navigation and Surveillance System (GCNSS)
Our CNS concept for Phase 3 is of a Global Communication, Navigation and Surveillance System (GCNSS). The GCNSS would be a significant extension of the current Global Positioning System (GPS) that is owned and operated by the US government. GCNSS would encompass and extend the functionality provided by GPS by providing enhanced position velocity and time services adequate to support safety-of-life issues. The GCNSS would provide additional services and capabilities by adding communication and surveillance functions. The synergies between the navigation, communication and surveillance services, coupled with the focus on high integrity services to support safety-of-life applications, will result in a system of tremendous utility. 67
The GCNSS concept represents a complete paradigm shift from the legacy navigation systems and existing communication and surveillance technologies. The fusion and integration of CNS provides opportunities for new synergistic services. Properly implemented, the integration provides inherent redundancy that enhances total system integrity and reliability. Finally, the integration provides opportunities to lower the overall cost of providing CNS services relative to the cost of fielding and maintaining the host of CNS systems which GCNSS may replace.
Extensive changes will be needed to airspace structures, airspace management, and procedure definition to achieve the safety and capacity objectives of this phase. Fundamental changes to the controller' s job is envisioned - a transformation from air traffic controller to air traffic manager. Even the separation assurance function is envisioned as one of management, not control. In this program phase, many significant changes to today's operating rules and procedures will need to be redefined and retrained. Completion of Phase 3 will integrate a new information infrastructure across flow management, flight planning, and separation assurance domains. This phased approach enables numerous applications that will exploit the core trajectory-based concept developed in Phase 1. Development and execution of training will be significant, but the time frame of this implementation enables the progressive training of ATC personnel to allow a smooth introduction.
7 Economic Benefits
The benefits of an ATM enhancement include increased capacity or decreased disruption. An increase in capacity means the ability to fly more flights with the same amount of disruption (delay and cancellations) as in the current system. Decreased disruption means the ability to fly the same number of flights with fewer cancellations and delays. The proposed set of operational enhancements have been evaluated in three separate benefit models that calculate the net present value of the benefits of the proposed operational enhancement over the next twenty years. Benefits are measured as the difference between how the proposed concept would perform relative to how the current system would perform, assuming forecasted growth in operations. All 68
benefits are measured in terms of decreased disruption (delays and cancellations) for the forecasted set of operations against a do-nothing approach. Each model includes a set of timing assumptions regarding when the implementation will start and how long it will take. The first benefits model evaluates a Traffic Flow Management operational concept that will improve the air traffic system's ability to respond to convective weather events. The second benefits model evaluates the airport benefits from the Trajectory Management operational enhancement. The third benefits model evaluates the en route benefits from the Trajectory Management operational enhancement. 7.1 Forecast Methodology
7.1.1 Flight Growth
The forecast starts with traffic projections from the Boeing Current Market Outlook. The CMO forecasts a 2.9% increase in operations over the next 20 years. (This is very close to FAA forecasts, which project a 2.9% annual growth in traffic through 2011, when the forecast ends.) Over 20 years, this results in 77% more flights.
7.1.2 Schedule Forecast
From the CMO, a year 2020 Official Airline Guide (OAG) was developed that aligns to the forecasted growth in operations. In this section we describe the traffic forecast for scheduled airline flights in or out of the contiguous United States. The approach relies on 1) projections from the CMO, 2) an analysis of existing schedules as represented by the year 2000 OAG, and 3) algorithms for realizing the future schedules in an "optimal" way.
The future schedules are based upon the year 2000 CMO process. This process uses an analysis of the 1999 OAG and creates forecasts for the future years 2004, 2009, 2014, and 2019. We use CMO forecasts of departures and available seat miles
(ASMs) by equipment type and major airline. For this analysis, ten specific major US airlines were considered with three artificially aggregated carriers for cargo, foreign, and other US. The forecasts were scaled up to represent the future time periods of 2005, 2010, 2015, and 2020. After scaling, the forecast showed a 77% increase in total departures from year 2000 to year 2020 with an average flight distance increase from about 688 miles to 696 miles, and with an increase from 173 seats per mile 69
flown to about 179 seats per mile flown. Thus, this baseline CMO forecast projects the vast majority of future demand to be met by increased frequencies.
While the CMO forecast provides the total number of departures by equipment type and major airline, it does not indicate the assignment of these departures to particular non-stop airport pairs. In order to facilitate this assignment we must calculate the
"lift" (i.e., number of seats) to be allocated to each such airport pair for the future time period. The set of non-stop airport pairs for an airline is called its route map. An analysis of existing schedules is first used to identify the route map for each major airline and, for each airport pair in the route map, the lift currently allocated to that pair. The future required lift for an airport pair is then calculated by factoring its current lift into the future by the ratio of the total CMO forecast ASMs divided by the total current ASMs for that airline. For this analysis it was assumed that there are no new non-stop airport pairs and that each existing pair, within an airline, grows at the same rate. The existing schedules are also analyzed to uncover the bank structure employed at each major airline hub. It is assumed that this bank structure will remain the same in future time periods although the maximum bank sizes will be permitted to grow.
Once the future lift requirements (by airport pair and airline) are calculated, then an allocation process is undertaken to assign the forecast CMO airline/equipment departures to the individual airport pairs. The objective is to match as closely as possible both the required future lift on each airport pair, and the forecast ASM's to be flown by each type of equipment for the given airline. This must be accomplished while respecting the design range limitations of the equipment.
The departures (or arrivals) assigned to the hubs are then allocated to the airline banks in order to maximize schedule quality (using the Boeing Decision
Window Model as applied to the local markets) while respecting the maximum bank sizes and flow conservation. The last step in the process is to finalize the departure and arrival times for all flights (by any airline) while observing an airport specific limitation on the number of operations (takeoffs or landings) which may occur in any five minute time window. 70
To keep things fair across airlines a (randomized) list of all flights is constructed and processed sequentially. First priority is given to the banked flights. Second priority, for flights not involving hub-spoke operations, is given to departure and arrival times from the existing schedules. All other flights are scheduled to maximize schedule quality (again, using the Decision Window Model) while observing the airport specific operations limits. In the baseline analysis, the top airports were assumed to grow by 50% in their ability to process takeoffs and landings by the year 2020. A small subset of these was assumed to grow by 100%. Maximum bank sizes were assumed to grow in a corresponding manner. An important limitation of the schedules generated thus far is that they are not efficiently tail routable, that is, tail routings would result in a large number of inefficiently utilized airplanes. 7.1.3 Delay and Cancellation Growth
Two methods were used to develop a range for delay growth over the next 20 years. The delay growth curves are for a do-nothing scenario — the system evolves as it has historically and there are no new runways/airports beyond what is currently planned in the FAA's 2000 Aviation Capacity Enhancement Plan. Delay growth is measured in terms of the increase in arrival delay minutes per flight, including block time creep, over time.
Method 1 — Historical Extrapolation The first curve was developed from extrapolation of historical data from 1976 to
2000. During that period, flights grew at an annual 2.1% rate and delay minutes per flight (including block time creep) grew at an annual rate of 2.7%.
To develop the delay curve during that period, Boeing used several sources as no single source covered the entire period. For 1976 - 1986, delay data was developed using data from three major US air carriers: American, Eastern and United Airlines. This data compared actual flight times versus ideal flights times for airplanes operating in an environment devoid of conflicting flights. The remainder of the data was based on arrival delay, which is measured by the difference between flight times of all the major carriers against their published flight times. Data for years 1987-1994 were extracted from a FAA report, Total Cost of Air Carrier Delay. The data for year 2000 was extracted from CODAS and OPSNET. The 71
difference between this data and the data from 1976 - 1986 is that the published flight times include a time called "block time creep" which is used to meet industry goals of 65% on-time arrivals. The causes of delay, which are hidden in the block time creep increment are many, including increased circuity mandated by the ATC system and weather, both of which are beyond the control of the airline.
An attempt has been made to compensate for the block time creep. American Airlines estimates block time creep at 30 seconds per year for the years 1987 - 2000, an extra 6.5 minutes per flight. According to a Mitre-CAASD study (NAS -Wide Trends in Historic Block Times), block time creep was 4.1 minutes from 1984 to year 1998, or 18.4 seconds per year. This does compensate for the rate of block time creep increase but not for the existing creep in 1986, for an additional minute has been added. To estimate the future annual delay growth, we factored the historical delay growth by the ratio of future traffic to historical traffic:
Annual Delay Growth = 2.7% * (2.9%/2.1%) = 3.7% One would expect delay to grow at a faster rate in the next 20 years because the system is being operated much closer to capacity levels. With this in mind, the lower bound for delay growth was set at 4% per year. Using delay growth curves extrapolated along this line for the do-nothing scenario would assume that NAS improvements are being made at about the same rate and effectiveness as they have been for the last 25 years. A 4% annual growth in delay will result in delay minutes per flight, including block time creep, growing by 120% over the next 20 years.
Method 2— SIMMOD Analyses A second delay curve was developed using Boeing's internal study titled Terminal Area Operations Strategy (TAOS). TAOS developed delay curves, by airport, by visibility condition (Visual Meteorological Conditions (VMC), Marginal Visual Meteorological Conditions (MVMC), and Instrument Meteorological Condition (IMC)) for the daily number of operations at the top 25 airports. To project delay at each airport in 2020, historical weather data was used in conjunction with the forecasted operations in year 2020. Delay in year 2000 was also calculated using these curves. Using this approach, delay growth was estimated at 12.3% annually for the top 25 airports, assuming a 2.4% annual growth in traffic at these airports. These 72
airports had 51% of all the NAS operations in 2000 and are run much closer to capacity than the remaining airports in the NAS. If delay minutes per flight are assumed to grow at a slower rate of 3% rate per year at the remaining airports, the resulting NAS delay growth rate is 7.5% per year. The assumption in this approach is that all delay will grow at the same rate as airport delay.
In Russell Chew's paper "Free Flight, Preserving Airline Opportunity," similar results were forecast using SIMMOD to project delay growth at the top 50 airports. According to that study, the growth in delay minutes per flight would be 8.5% for terminal delay and 6.4% for airspace delay. This assumes a 2.4% annual growth in flights and is just simulating VFR delay. Delay in other conditions would be even higher. Most delay is taken at the terminal as opposed to airspace. With that in mind, both of these analyses confirm about an 8% annual growth in delay. An 8% annual growth in delay will result in delay minutes per flight, including block time creep, growing 4.7 times over the next 20 years. The SIMMOD analyses do not take into account new runways. A new runway will truly reduce delays if it will enable the airport to have an additional independent arrival stream during poor weather. Rough estimates are that these runways will reduce delay by 2-5% throughout the NAS, under current operating assumptions. Another objection to this level of delay growth is that airlines will never allow delay to grow at these levels and will take actions like create new hubs, avoid congested airports, etc to alleviate congestion. This is a valid objection, therefore we have made
8% delay growth our 90th percentile estimate.
7.2 Calculation Methodology
7.2.1 Net Delay Reduction and Cancellation Reduction For each concept, estimates were made regarding the delay and cancellation reduction for the concept when fully implemented. The sections below describe the methodology and results for the three proposed concepts.
Data limitations prevented an estimate for cancellation reduction for the two trajectory management concepts — all reductions were modeled as delay reduction. For the en route concept, it makes sense to model any improvement as delay reduction since the concept is only addressing a small portion (3%) of all delay. 73
For the airport concept, flights are cancelled especially in MVMC and IMC conditions due to terminal capacity. In this case delay reduction is a proxy for cancellation reduction. Future evolutions of this analysis will address cancellations for the airport concept.
Flow Management - Convective Weather
To estimate delay caused by convective weather, the starting point was arrival delay minutes, according to COD As, during the convective weather season, April 1 - October 31. In year 2000, the average arrival delay during that period was 15.7 minutes per flight. To estimate this delay, estimates were made of the percent delay caused by weather (60%) and the percentage of weather-caused delay caused by convective weather during the convective weather season (40%), meaning 24% of the delay during that season was caused by convective weather. This period encompasses a little less than 2/3 of all operations during the year, resulting in 15% of annual delay caused by convective weather. Industry sources were used to estimate the delay percentages.
For cancellations, year 2000 Department of Transportation data reported 3.1% of the flights were cancelled across the NAS, during the convective weather season. An assumption was made that the percent of cancellations caused by convective weather is the same as the percent of delay caused by convective weather, which is 24% during the convective weather season.
Initial Boeing estimates are that the proposed flow management concept will reduce convective-weather caused delay by 15% and convective-weather caused cancellations by 30%.
Trajectory Management— Airport
For the airport component of the trajectory management concept, TAOS analysis was used to estimate terminal delay for the top 25 airports and then extrapolated to a NAS-wide delay. The TAOS analysis developed curves that predict the delay minutes per flight for VMC, MVMC and EVIC conditions based on the number of daily operations. TAOS developed delay curves as follows: 74
1. Identify top 25 airports (# operations)
2. Categorize airports into three types: runway constrained (those airports whose instrument weather operations are constrained by the configuration of the runways), airspace constrained (those airports whose instrument weather operations are constrained by close proximity of other airports), unconstrained (those airports that don't fit into the other two categories).
3. Further subdivide into good weather, medium weather, and poor weather based on percentage of time airport is above and below 1000 ft ceiling and 3 miles visibility
4. Identified SEA as runway constrained airport, EWR as airspace constrained airport, ORD as airspace constrained airport, and DIA as unconstrained airport. These airports were used to model all 25 airports.
5. Obtained SIMMOD prediction of delay for current and anticipated future capacities for representative airports for VFR and IFR from FAA Capacity Design Team Studies for SEA and EWR. The same data was obtained for ORD and DIA from Landrum & Brown, Inc.
6. In the SEA Capacity Desi n Team Study, IFRl/2 is equivalent to CAT ITU and IFR3 is equivalent to CAT JJIa. For all of the representative airports, the curve for VMC was developed from the VFR delay numbers. The curve for IMC was developed from the IFR or IFRl/2 delay numbers. The curve for MVMC was interpolated from the VMC and IMC curves.
7. In the SEA Capacity Design Team Study, IFR4 (equivalent to CAT UIc) delay was assumed to be 4 minutes (based on CNS/ATM Focused Team (C/AFT) input). Demand is so little that delay is not an issue.
8. The delay curves for the representative airports (SEA, EWR, ORD, and DIA) for 2000 - 2020 were developed using a power curve fit function.
9. Assumed the curve shapes of all airports of the same type have the same shape, scaled by their VMC capacity and daily number of operations from year 2000 OAG. A family of curves for VMC, MVMC, and EVIC were developed for each of the top 25 airports. 75
10. Using OAG data for top 25 airports and CMO data, developed a current NAS fleet mix and landing capability of the fleet, and a NAS percentage annual change in fleet mix based on the change in landing capabilities.
11. Obtained airport weather data for top 25 airports from Boeing Atmospheric Physics Group.
12. Developed weather breakdowns using acquired Boeing Atmospheric Physics Group data (ceiling and visibility breakdown for each airport from National Climatic Data Center) and Landrum & Brown chart (estimated VMC/MVMC/IJ^1,2/JFR3/IFR4 from Landrum & Brown VFR/CATI/CATH/CATm numbers for top 25 airports.
The FAA's Terminal Area Forecasts, FY 2000 - 2015 provided a count of the number of operations at each airport in year 2000. With the count of operations and the delay curves by airport, the curves developed above were used to estimate the delay minutes per flight for VMC, MVMC and J C operations at each airport.
To estimate the reduction in delay from the proposed operational concept, Total Airspace and Airport Modeler (TAAM) was used to build models for the airspace regions surrounding New York and Chicago area airports. The baseline model for each regional area was developed using Enhanced Traffic Management System (ETMS) data for September 27, 2000, which was a good weather, high traffic day for the airports modeled.
The New York model included Newark, La Guardia, Kennedy, and Teterboro Airports and the airspace interactions between those airports. Besides the airspace, only the runways and runway exits for each airport were included in the model; a detailed surface model for each airport was not included. Models were developed for the best good weather configuration and the worst bad weather configuration. Trajectory Management — En Route
For the en route portion of the trajectory management operational enhancement, we use Free Flight, Preserving Airline Opportunity to forecast delay as a function of increased operations into the future. Internal engineering judgment, and simulation where possible, were used to forecast the performance of the proposed operational 76
enhancements. Estimates were that 3% of all delay was caused by en route volume and the proposed operational enhancement would reduce en route delay by 70%.
7.2.2 Net Delay % by Cause
One interesting result of this analysis is the forecast percentage of delay minutes by cause. According to our calculations, 50% of the identifiable delay is caused by weather (Convective Weather Delay + MVMC Delay + IMC Delay). In addition, some of the delay in the other category could potentially be caused by weather delay (windstorms, removing snow after storms, and non-convective weather not local to an airport). The division of the pie matches well with the industry conventional wisdom that claims weather causes 60-75% of all delay.
The other notable conclusion from this chart is the largest contributor to delay is airport delay (VMC delay +MVMC Delay +IMC Delay) which causes 57% of all delay.
7.2.3 Net Delay Reduction Estimates The net delay reduction estimates for each of the delay causes and their rationale are summarized in the table below:
Delay Cause Delay Reduction %
VMC 0/10/20% Trajectory management will increase sequencing and spacing accuracy, by reducing uncertainty in trajectory prediction.
MVMC 80/90/100%
Application of RNP/RNAV and air traffic management automation tools (Center
TRACON Automation System, Converging Runway Display Aid, and Precision Runway Monitory) will allow high throughput operations in marginal visibility.
IMC 30/45/65%
Reduction in wake vortex separations (solution TBD). Short curved approaches based on GPS Landing Systems which eliminates certain airspace interactions which result in runway dependencies. Precision missed approach capability will eliminate closely spaced parallel runway dependencies.
Enroute 50/70/90% 77
Reduction in spacing buffers and controller workload due to ATM automation tools. Convective Weather 5/15/30%
Better use of available capacity through better weather prediction capabilities and traffic flow planning. Real-time communications, collaboration with the system users and fast time planning and replanning tools will enable rapid decision making for traffic flow planning.
7.2.4 Net Present Value Calculations
To calculate the net present value of the three concepts, three separate benefit models were built. The benefit models cover the years 2001-2021 and use a discount rate of
10%. All costs are modeled in year 2001 dollars. The analyses include sensitivity to uncertainty. For every uncertainty in a model, we've collected 10/50/90 percentiles.
A 10 percentile is a value so low it is believed there is only a 10% chance the actual outcome will be below that value. A 90th percentile is a value so high it is believed there is only a 10% chance the actual outcome will be above that value. A 50th percentile is a value such that it is believed the actual outcome is equally likely to be above or below that value.
Dollarizing Delays and Cancellations
To 'dollarize' the benefits of the proposed operational concepts, we took the projected reduction in total delay minutes and total cancellations and put a dollar value on them.
To dollarize delay, we used Air Transport Association (ATA) and internal Boeing numbers to compute the cost of a minute of delay. According to the ATA
(http://www.air-transport.org/public/gridlock/ag2a.htm) for commercial air carriers, a gate delay costs $25 per minute, a taxi delay $30 per minute and an airborne delay $47 per minute. These figures are strictly direct operating cost and do not include any allowance for ownership costs and disruption costs. Disruption costs are negligible for delays less than 15 minutes.
Boeing experts estimate that delays longer than 15 minutes cost the airlines
$72 per minute for a 737-sized aircraft, which is the average size aircraft in the US commercial air carrier fleet. This figure includes allowances for factors such as customer service personnel rearranging flights, recatering due to spoilage from long 78
delay, and extra food and drinks. Delays have been broken down into delays minutes less than 15 minutes and delays greater than 15 minutes and applied these costs were applied accordingly.
Delay has two components. The primary metric airlines are measured against is arrival delay— the difference between the actual arrival time and the scheduled arrival time. There is a hidden amount of delay in the schedule called block time creep. Block time is the time in the schedule for flying from an origin to a destination. Block time creep results from airlines extending their block time to meet industry targets for on-time arrivals. As congestion increases, airlines will continue to add block time, in order to minimize missed connections and flight delays. We have not directly assessed the block time pad in the schedule today, however, the delay growth curves used to dollarize delay savings don't distinguish between delay against schedule and block time creep.
There are no industry sources for the cost of a cancellation. Boeing estimates put the cost at $20,000 for the average commercial aircraft in the NAS fleet, which has around 158 seats. If you estimate the average ticket price at $300 per seat with a 70% load factor, the average revenue per flight would be about $30,000. Implementation Timing The benefits from each of the concepts are phased in according to an implementation made over time. The start year for each implementation is set at 2005 with a 7-year duration for getting full NAS conversion. Benefits are assumed to accrue on a straight line basis, starting at 0% of the benefits achieved in the implementation year and 100% of the benefits achieved at end of implementation. Delay and Cancellation Growth Without a significant change to the ATC system, delays and cancellations will grow over time. The benefit models grow delay and cancellations over time. Delay minutes per flight are expected to grow at a base case of 5% rate per year over the next 20 years. Cancellations are expected to grow at 3% rate per year. Both of these figures are unacceptable given the clamor over airline problems today. The alternative is to ration capacity, resulting in higher ticket prices and unmet travel needs. This would result in a hidden cost to the industry of lost revenue and a hidden cost to the 79
economy of unmet travel needs. Instead of trying to quantify these hidden costs, it is assumed that traffic needs are met resulting in increased delay relative to a scenario where traffic is rationed.
7.3 Summary of Benefits
The benefits for each concept are summarized in the table below. The second and third columns are the total reduction in delay and cancellation for the NAS in 2020, when the system is fully implemented. The fourth column is the Net Present Value
(NPV) of the benefits, using a 10% discount rate and modeling all cash flows in year
2001 dollars.
Operational Enhancement Net Delay Reduction Net Cancellation Reduction
Flow Management — Convective
Weather 2.1% 4.2% $3.3B Trajectory Management — Airports 26.2% NA $23.9B
Trajectory Management— Enroute 2.1% NA $1.1B
Total 30.3% 4.2% $28.3B
Capacity/Delay Elasticity Assuming flights grow at the forecasted 2.9% per year, there will be 77% more flights in 2020. Based on that flight growth, we forecast two delay curves. If delay grows 3% annually, delay would increase to 1.8 times today's level. A 30% reduction in delay means delay will increase to 1.3 times year 2000' s level. Ii delay grows 8% annually, delay would increase to 4.7 times today's level. A 30% reduction in delay would mean that delay will increase to be 3.1 times the year 2000 level.
In either case, this analysis shows that significant additional enhancements will have to be made to the air traffic system to meet demand and simply keep delays at year 2000 levels, much less remove delay from the current system. A 30% delay reduction will allow us to meet year 2012 traffic levels, with year 2000 delay levels, assuming a 3% increase in delay per year. If delay grows at an 8% rate, additional traffic at today's levels would only be accommodated through 2004. 80
8 Stakeholder Impact
8.1 Airlines
Airplanes with Digital Integrated Avionics use the latest generation of avionics. Avionics functions such as flight management reside on a card within a fully integrated system such as AIMS on the 777. There are few technical barriers to implementing CNS/ATM upgrades to digital integrated avionics systems. The cost and schedules requirements for CNS/ATM upgrades that use digital integrated avionics systems may be significantly different from those airplanes that employ digital federated avionics architectures.
Airplanes with Digital - Federated Architecture use avionics systems where each function resides more or less on its own individual hardware platform. For example, flight management computer, display functions and air data functionality are each contained in separate Line Replaceable Units. Each of the avionics systems share data over digital busses (e.g. ARINC 429). There are few technical barriers to CNS/ATM upgrades for airplanes that employ digital federated avionics systems.
Airplanes with Hybrid Avionics are typically analog airplanes that have received avionics upgrades to support some digital avionics, e.g. FMCs and display systems. CNS/ATM upgrades may be more difficult and costly to accomplish compared to all digital systems since airplane data required to support a new
CNS/ATM function might not be readily accessible to a new or updated avionics system.
Airplanes with Classic Analog Avionics use mostly analog avionics present the greatest technical and cost issues associated with CNS/ATM upgrades. 8.1.1 Airline System Operational Center (SOC) Impact
The airlines will also be required to update their SOC work stations in order to provide the functionality needed to support improved exchange of flight plan information with their aircraft fleet, air traffic control and the Air Traffic Control System Command Center.
8.2 General Aviation 81
System and Airspace Accessibility Access to airspace and air traffic services will be important considerations for GA in the future system. In the existing system, users have the flexibility to choose the extent to which they require air traffic services. In RTCA Report DO-266, user groups from around the country provided input regarding their priorities for airspace redesign. Airspace designs currently allow flexible access around, through, over, and under busy airports. General aviation stakeholders do not want airspace redesign to adversely affect the accessibility and operational flexibility provided by the existing VFR and IFR flight environments. The requirements for access directly relate to aircraft equipage and pilot certification/training requirements. General aviation stakeholders will be concerned about the impact of new equipment requirements, new regulations, and new operational and airspace restrictions. Stakeholders would desire a "real-time" ability to access special use airspace. User inputs will be required for airspace redesign. Many existing Class B airspaces, such as Los Angeles International (LAX), have VFR fly-through routes which are available to aircraft equipped with transponders and VOR or equivalent navigation capability. Southern California TRACON airspaces have also added VFR waypoints to GPS databases, to provide additional capability to users to identify visual checkpoints. Providing access through and around the busier airports will be important, as will the ability to leverage modern navigation capabilities to provide this access. However, redesign must not impose undue restrictions on aircraft not equipped to operate under RNAV. 8.2.1 Leveraging New Technologies The future airspace design must take advantage of improved capabilities provided by modern CNS equipment. However, GA stakeholders are very sensitive to the costs for any equipment change, and especially mandated equipment changes. Airspace and procedures redesign should provide incentives to invest in affordable advanced avionics that permit direct or user-preferred routings and improved precision approach capability. 82
The most recent FAA General Aviation and Activity Survey for which complete avionics data were available (1995) indicated that a rising percentage of aircraft were equipped with GPS (either VFR or IFR units). In the RTCA DO-266 report, users suggested that a "benefits driven" airspace design would encourage equipage. In particular, DO-266 noted that "airspace must be designed to maximize the impact of available technology, but must also accommodate mixed equipage. There must be specific "benefits driven" recommendations on the optimal equipment needed to operate within specific airspace.
Space and weight limitations have led to combining communication and navigation capability into a single unit. System performance analysis is needed to define the minimum performance required and assess whether current minimum equipage is capable of delivering the necessary performance for a certain level of airspace access. As an example, several existing Class B airspaces have existing JFR and VFR transition routes (which are clear of major airport arrival and departure flows) and which provide improved access for transiting flights and reduce controller workload. These routes may be RNAV or VOR-based. These transition routes must be available in the future system, as well.
Business Aviation Business Aviation is a subset of GA, but often has different operating characteristics than the recreational GA fleet. The business jet market is one of the fastest growing segments in aviation today. We will need to do some research in this area to develop the same ranking system as for the transport category airplanes.
The requirements for business jets would be similar to those of transport category aircraft if they were to operate in the same airspace. An improved definition of the airplane equipage requirements and implementation schedules is required before an impact assessment can be completed. 8.3 Military
Airlift aircraft must be equipped to operate within the system. Procedures to allow tactical aircraft to accomplish their mission must be addressed. 83
8.4 Airports
The benefits to airports from this new operational concept are increased capacity and reduced delay. Increased capacity means more passengers and more operations, translating to increased airport revenues.
9 Transition Planning Considerations
Perhaps the single greatest impediment to any NAS modernization is the ability to successfully manage the complex set of change factors. We need to address considerations as diverse as airplane equipage, ground architecture changes, satellite equipment changes, airspace design and operational procedure changes, and most difficult of all, the management of change for institutions and people (both service provider and system user communities). Each of these change issues is challenging and the issues are interrelated. The section identifies key issues associated with the various aspects of system change if a significant modernization program is to be successful. Significant resources are needed to address these most critical program risks. Individuals at all levels in the ATM structure will need to accept the idea of change to achieve optimal implementation results.
Determining the sequence of the transition elements is a critical component of program management. Should the new equipment and procedures be integrated separately or together? Should the entire system transition at once or facility by facility? This decision is significant since a 'waterfall' approach would require the new equipment to communicate with the current system until the total transition is complete. Many other critical risk factors must be understood. Proper risk management planning will require substantial efforts to enable the program to be successful.
Successful completion of the transition will require a comprehensive change management plan. This plan must begin early to ensure maximum acceptance of the change. Involvement by experts in the field of change management should begin early and should continue to project completion. 84
9.1 Equipment Transition
Much attention has been devoted to defining the complex investment models for airplane and ground equipage. It is difficult to find a voluntary basis for all participants to go forth in a coordinated fashion, and often it does not succeed. System capability is variable by airplane and by airspace region. Transition of the capability of an existing airplane fleet can take three to five years. Military and GA equipage refresh cycles could be longer. Air traffic systems also require substantial lead-time from concept to full operational capability. New systems such as the Microwave Landing System, which require development of international standards, can have development lives of twenty years or more. These systems' technologies are often obsolete before they become fielded.
ATC simulators use the host computer resources. During busy periods there is a concern that the simulators may overload the host computing capacity. Future simulators need a separate full-time computer resource with access to the operational database.
9.2 Operational Transition for Airspace
Ii equipment replacement is difficult, airspace operational change is more so. Current airspace operations have evolved into a patchwork of airspace and ATC procedures. The basis of these rules and procedures is difficult to reconstruct and system change is almost always evolutionary and incremental in impact. Significant (revolutionary) change requires a long period of operational trials and data collection, salesmanship and intestinal fortitude. System safety remains a paramount concern for each controller. The safety assessment basis of new procedures and airspace rules often has subtle safety consequences that are difficult to predict. Additionally, the rules designed to ensure safety, e.g., Terminal Instrument Procedures (TERPS), need to be updated to reflect the advances in system technology. Consequently, dramatic change is difficult.
Additionally, there is little standardization between individual ATC centers. The system operation diverges from region to region and facility to facility, based on historic practices, local preferences, skills development and managerial expectations. Consequentially, it is not uncommon for a fully trained controller in one facility to fail 85
to qualify in another. Also, any discussion of needed airspace boundary modifications produces significant pushback from the controllers whose salary structure is based on traffic volume.
9.3 Institutional Transition Institutions have their cultures. The FAA and the various users of the NAS are cases in point. Change within the FAA requires long and arduous coordination across many organizations with divergent objectives and motivations. Integration teams try to bridge these differences, but often just add more layers of coordination and complexity. Other stakeholders involved in system planning and operation include the airlines and Air Transport Association, airline pilots and general aviation flyers, controllers and their unions, Aircraft Owners and Pilots Association (AOPA), United States Department of Defense, United States Department of Transportation, National Business Aircraft Association, Regional Airline Association, Cargo Airline Association, local airport authorities and many more. Operational, business and engineering personnel must interact and communicate. Change management means that stakeholders feel they have all contributed to the change and benefited, else significant change to the ATM system may fail.
To begin the change process, system users, the FAA and other institutional stakeholders must agree that business as usual will not work. An agreed-upon new operational concept and approach to achieving this concept must have commitments from these frequently conflicting groups. Ongoing dialogue must prevail throughout the process to maintain the focus.
9.4 Personnel Transition
People will need to accept change for new implementations to be successful. New roles and responsibilities will be required for all stakeholders. Operational people are often heavily invested in the current system's rules and procedures. A key issue for modernization is the managing personnel change that must accompany significant system operational change. This begins with the hiring policies/practices to identify those people best suited to operate the new system. Much of today's controller training is on the job. It may take years to produce a fully trained controller. New training regimes must be defined, validated and implemented, to support the needed 86
system change. Issues of training and currency for pilots and controllers are difficult and expensive.
On the airplane side, questions include how our new system concepts will affect the cockpit operation. Besides new cockpit equipage, questions remain regarding the impact on flight operations and how much training will be needed for flight crews to make the transition. The airlines may need active encouragement to provide the necessary training for their flight crews. The system will not operate at its optimum levels without adequate flight crew training. 9.5 Cost of Transition Training The dramatic role changes envisioned in our operational concept for both the FAA and system users will require extensive training in two distinct areas: operational systems training and organizational culture training. Quantifying the benefits of this training will be extremely difficult, yet this training is crucial to the success of the transition. A significant challenge will be to obtain and keep the necessary budget for this training throughout the transition period.
Operational systems training is much easier to sell because the requirement is generally well understood. The various providers and users of the system will need to understand how the new tools reduce workload, increase productivity and improve safety in order to achieve maximum effectiveness of the system. This training will include procedures/airspace development, equipment prototyping/design, work processes and operational concept familiarity. Cultural training, which must precede all other training, will be required for the entire existing FAA and system user community. This training should provide insight to all participants into how each person fits into the system and how their individual actions can affect the performance of the total system. Changes in attitude required to alter the culture of an organization require a minimum of five years to accomplish. This training must begin early to assure maximum individual acceptance of the need for change. Once the operational concept has been agreed upon, the knowledge, skills and abilities (KSAs) of those who will be working within this new system must be identified. A revised selection process incorporating the newly identified KSAs and an associated 87
training program must be developed. An inventory must be taken of the KSAs in the existing workforce in order to tailor their transition training.
New high fidelity simulators will be mandatory, due to the magnitude of developing new procedures/equipment and operational simulation. Simulators will be needed throughout the concept development process (e.g., airspace/procedures/equipment layout prototyping/design, work processes, safety analysis, human factors identification). After initial concept development, simulators will be needed to train controllers for tower, terminal, en route, and ATCSCC. Simulators may also be needed for flight operations personnel and cockpit crew. Currently, ATC simulation is extremely limited and labor intensive when compared to the sophistication of aircraft simulators. (It might be prudent to develop a teaming relationship with an established manufacturer of simulation equipment to begin initial talks on this potential market.) The transition training recommended in the Boeing approach requires much more than financial backing to be successful. It requires that participants at all levels must understand how they fit into the overall picture and how their individual actions affect the performance of the total system.
9.6 Airports - A Special Challenge in Transition Planning
Changes at airports often affect people and institutions far beyond the stakeholder groups normally associated with aviation. There are many constraints to airport capacity growth, unique to each airport. Some constraints are physical, such as lack of available land for the construction of new runways, and others are not as tangible, such as environmental constraints that restrict changes to airspace procedures. The first step in the transition plan will be to list and prioritize the airports that present the greatest constraints to overall capacity growth in the NAS. For each airport, the current master plan will be reviewed. The master plan will help to determine any improvements that are identified and in the pipeline. The master plan will identify any improvement alternatives and the reveal the preferred alternative. The preferred alternative will have been approved by the community, airlines, and other airport operators. 88
The next step will be to perform a constraints analysis to identify the constraints to capacity growth at each airport. The constraints analysis will include interviews with people at airport authorities, ATCTs, TRACONs, airlines (including ramp personnel), and the airport consultant. This will help uncover the factors that constrain capacity through the entire airport system. Once the factors have been identified and prioritized, the next step will be to determine what can be done to mitigate each of the constraints and to determine the cost. Some of the constraints could be mitigated by construction, others by the purchase of equipment or the addition of new technology, and others by a change in ATC procedures. The set of alternatives would be analyzed by the Preliminary Design toolset to determine the best combination of alternatives. A cost/benefit analysis of each proposed alternative would be performed that considers the points of view of the airport, airlines, and service provider. When considering alternatives to relieve constraints at each airport, airport resources will have to be sized appropriately. It doesn't make sense to have excess capacity on the runways if there are not enough aircraft gates at the terminal building or adequate parking facilities for passengers using the airport.
The identified airport improvements would need to be approved by an airport (technical) advisory committee with representatives from airport staff, airlines, other operators at the airport, the neighboring community, and the airport consultant.
10 A Methodology for Preliminary Design of Airspace System Definition
This section presents a methodology for the Preliminary Design of Airspace Systems Definition, which will enable us to perform the necessary analysis to apply the most appropriate solutions to each operational environment. The section begins with a discussion of the FAA NAS Architecture, which is more of a "bottom-up" collection of disparate technologies than a cohesive plan based on a "top-down" analysis of operational needs. We seek to remedy this with our methodology. 10.1 The FAA's NAS Architecture and Operational Concept
The FAA is currently planning the NAS architecture through 2015. Near-term involves sustaining the current system's operational capability. Selected enhancements are included where costs and program risks can be contained, such as in 89
Free Flight Phase 1. Deploying advanced CNS/ATM technology will be necessary to avoid traffic gridlock.
The standard investment analysis process used today examines a single technology solution against only one performance objective. It ignores the operational relationships among the multiple system performance requirements. Additionally, the focus on bottom-up technology often fails to consider fully the potential of multiple technology 'enablers' to make significant changes in a number of performance indices. This narrow approach is institutionalized through a segregation of Communications, Navigation, Surveillance (CNS) and Air Traffic Management (ATM) programs, and generally ineffective systems engineering approaches in the ATM arena. While this structure served the industry well into the 1980s, the complexity of the long-term modernization problem now requires a much more comprehensive engineering approach. 10.2 Industry System Development Approach The systems engineering process for a large, complex system such as NAS modernization divides the life cycle of a major system development into several distinct phases. "Preliminary design" consists of defining system requirements and objectives, analyzing functions and operations, and defining the system architecture. The remaining steps are system design and development, integration in the laboratory, validation testing, and system operation and maintenance. The discipline of the systems engineering process has been vital to the successful completion of airplane development programs, where a team of thousands of engineers develops and certifies a complex, real-time, human-in-the-loop, safety critical system. The development of a major ATC system upgrade is even more complex, because it shares the safety criticality and human-in-the-loop real-time nature of airplane development, and further requires that the existing system remain operational while supporting transition to the new system.
Preliminary design is intended to clarify the product goals and objectives, develop mission evaluation methods and tools, define a wide range of configurations and technology options, result in trade studies, and baseline a configuration for negotiation with customers. 90
In the early days of the existing airspace system, technologies were directly inserted into the architecture without conducting a full preliminary design process. At the time, the airspace system was less complex and traffic demands were low, so both the advantages and the method of inserting technologies were more 'obvious', and an abbreviated design process was appropriate. In today's complex airspace system a full preliminary design process is a necessity. Preliminary design for the NAS has never been performed, and, therefore, tools and methods must be developed to support the process, including applied research operations analysis, systems analysis, and selection, development, and integration of significant analysis and simulation tools into an analysis environment.
10.3 Preliminary Design Process for Airspace System Definition
The Preliminary Design (PD) process is driven by overall system performance objectives, and supported by a baseline of the current system, a comprehensive analysis toolset and an inventory of technology options and human performance considerations. The PD process provides a set of system enhancement alternatives and associated performance data that allows trades to be made prior to decisions on major system concept and architecture options.
Existing ATM analysis tools and data sets do not adequately support the long-term system definition problem, and thus there is a need to improve the toolset using case studies to validate the PD process, derive tools and data requirements, and verify toolset functionality during implementation.
10.3.1 Establish NAS Objectives
Economic growth is the primary influence on NAS system performance objectives. The resulting demand for mobility can be satisfied by various modes of transportation, and policy makers can influence the types of travel within a region. In aviation, there are also a variety of aircraft and CNS/ATM services needed, and each is represented as a stakeholder group expressing their needs for access, capacity, safety and affordability. The various airspace users often have conflicting views of future needs, so a forum is needed to derive a consensus set of system objectives. Methodology and decision aid 91
tools can assist in selecting a reasonable set of airspace system objectives. The key to reaching consensus is to use reliable data that quantifies the potential improvements expected from proposed system enhancements, so that rational tradeoffs can be made by each stakeholder group. The book Value Focused Thinking (by Ralph Keeney) describes a methodology for establishing objectives. This methodology provides a language and framework for trading off objectives, has been used successfully in many public policy decisions.
A forecast of future traffic levels is the primary input to establishing system objectives. Various organizations publish annual traffic forecasts for their stakeholder group, and the FAA also publishes a 20-year forecast of traffic for all major airports. It is the FAA's responsibility to accommodate the predicted demand within the constraints of safety, affordability, and environmental issues. Task 1 in the Boeing proposal considers the predicted 20-year traffic levels and the driver for change. The engineering and operational solution is driven by these growth targets, along with the other key system performance objectives.
10.3.2 Develop Study Plan
Task 2 develops a plan for a detailed study of a particular airspace region in the current NAS, which is selected based on an examination of the primary system performance concerns identified early in Task 3 (which will actually begin prior to Task 2). Task 2 develops assumptions about airport infrastructure plans, airline business strategies and fleet mix predictions. Alternative future scenarios can be defined in this task, to span the range of possible futures.
10.3.3 Baseline Current System Performance
The system baseline incorporates the current operational concept and existing system architecture, and describes a set of operational scenarios sufficient to define normal, rare-normal and non-normal behavior. The baseline provides the current system performance data needed to select airspace regions in need of substantial operational improvements, and also serves as the basis for the evaluation of airspace alternatives that concludes the PD analysis. Task 3 will involve the establishment of such a baseline for the current NAS . 92
While the underlying functions of the airspace system may be simple, the performance and behavior of the system agents (flow managers, air traffic controllers, pilots and dispatchers) is complex and difficult to characterize. The baseline of the current system provides a basis for evaluating the most important current and future system 'performance states'. The challenge is to reduce the performance characterization to a manageable set of conditions (which include weather, rare-normal, and abnormal events) in a set of baseline operational scenarios. Subsystem performance benchmarking is also required to determine the performance of the CNS and ATM elements of the current system. The performance of the existing navigation, communications, radar, and air traffic and flow management systems is an important indicator of current system operating capability, and is reflected in the separation standards and working methods of the system operators. 10.3.4 Perform Mission Analysis
The Mission Analysis (Task 4) involves forecasting the future demand on the air transportation system. The generation of traffic demand involves the prediction of future flight activity levels for commercial airplanes, general aviation and military aircraft. For the commercial airplane segment, the forecast begins with a city-pair analysis of US domestic and international flight segments. A nominal flight schedule (similar to the Official Airline Guide) can be developed based on assumed economic growth, average airplane size, assumed airport infrastructure, and airline hubbing and schedule frequency assumptions.
Converting the flight schedule into a traffic demand model is based on a modeling of the system-wide flight planning activity, which translates the origin-destination schedule into flight profiles. These profiles are based on assumptions of the future concept of operations for postulated future use of airspace and airways. The flight profiles are based also on assumptions of how users will fly between city-pair destinations, e.g., how the airline fleet will be used, including assumptions of the criteria for single airplane flight planning. Section 7.1 describes an initial Mission Analysis based on the assumption that current strategies of airlines and other users will remain the same over the next 20 years. The methodology will be extended further to include additional airports and changes in airline hubbing strategies. 93
The traffic demand model is the basis for a traffic loading model which estimates average and peak operations counts for the affected center, sector, and terminal areas. This model can be established, based not only on the nominal flight schedule, but on assumptions of various contingency responses to system perturbations. The set of operational scenarios to be evaluated for the system loading model are established as part of the system baseline. 10.3.5 Develop Operational Concept
The ATM operational concept describes the way in which the aviation system resources are allocated to respond to the traffic demand and meet system performance objectives. An operational concept describes the functions performed in the system to deliver the required services, along with an assigning these functions to system agents and/or equipment. Services are delivered at a certain level of performance that can be quantified using the overall system performance metrics.
The current NAS uses a wide array of technologies, many of which originated in World War π, with stepwise improvements since then to fine-tune performance. Today's tactical radar control concept, with its associated voice radio communications and reactive flow management response, will likely be unable to cope with the predicted growth in traffic while continuing to maintain or improve safety. The desired performance will require a major change in the system operation and supporting technology, so that the human operators can achieve a substantially higher level of performance.
A higher level of system throughput could be achieved through more coordinated dynamic traffic planning functions, combined with a precision trajectory- based separation assurance to allow a reduction in effective traffic spacing. The system baseline provides the foundation for examining particular problem areas and performance issues for the selected airspace region. This, along with the performance objectives and framework, will guide the development of new concepts. Airspace and Airways
The operational concept will consider the nature of routes and flight levels in the chosen airspace region and timeframe. This includes fixed flight level vs. cruise- climb profiles for en route operation, and the associated vertical separation standard. 94
Laterally, routes in cruise, climb and descent could be either fixed or flexible. If flexibility is accommodated, the extent in space and time, as well as the responsibility for dynamic route definition, will be included. The issue of airspace classification (static or dynamic), and the airborne and ground system requirements to operate in particular classes of airspace will be addressed, including the issue of mixed equipage. Flow Management
For each chosen region, a range of options for coordinated traffic flow planning must be investigated. The cornerstones for potential improvement in our concept are NAS information infrastructure, automation tools for arrival, departure and en route flow management, and collaborative decision making. However, there are a number of unanswered questions regarding how to combine these in a coordinated operation in complex airspace regions. We will explore the optimum allocation of delay for a predicted capacity/demand imbalance, ranging from national, regional, facility to multi-sector level. A key trade in this regard must be made between the uncertainty inherent in predicting conditions hours ahead and the need to protect elements of the system from overload. The PD toolset will be used to assess a range of delay response options for flow management, incorporating weather prediction and other sources of uncertainty. This will be the first step in validating an improved operational concept for national and regional flow management, based on significant improvements in flow planning automation tools and data communications. Traffic Management
The separation assurance function (including the guidance and navigation element) assesses the potential improvements in capacity, safety and affordability. With an eye to potential increases in capacity and affordability, we will examine the future "sector," or the unit of work associated with separation assurance in the system. This will include the roles and responsibilities to airborne and ground elements in the separation assurance function. This development may lead to requirements for improved technical performance of the supporting CNS/ATM technologies, and to the identifying human cognitive processes and critical human performance factors that must be addressed. 95
The significant changes may lead to requirements for methods and tools to allow an exploration of a broad range of concept variables. The following issues emerge for special emphasis: (1) Methods and tools to aid in exploring a range of logically consistent, hierarchical traffic flow planning and control systems to ensure a sound system design; (2) Human performance modeling methodology and knowledge of human performance factors, normal, rare- and non-normal, relevant to the functions to be performed in the system [The current emphasis on technology prototyping and human-in-the-loop simulation is too costly to apply to the new operational concepts for the purpose of preliminary design trade studies.]; The use of increased automation aids to meet performance requirements has significant implications for human performance, in light of the safety requirements in aviation. [Automation bias and over-reliance, lack of adequate feedback on operating modes, workload, vigilance, and inverting primary/secondary tasks are among the factors that need to be studied in the context of increased automation.] 10.3.6 Analyze Required Performance
We will evaluate the influence of the operational concept alternatives on the dominant system performance elements using a modeling framework that combines system functional architecture with technical performance models, to assess performance aspects such as capacity, reliability, safety and cost. While traffic load drives the model, analysis is needed for a broad range of operational concepts. All concepts must deliver the necessary services and functions, and the ATM Reference Model will enumerate the primary functions expected to be present in air traffic management regardless of the details of a given operational concept.
The performance analysis is based on a representation of the system functional architecture, using finite state-machine methodology for an event-driven, scenario- based dynamic analysis. The system resources (such as CNS and human operators) are represented in a parameterized form to permit a sufficient range of alternatives to be explored. The parameters will be obtained from detailed simulation models and/or experiments. Human factors tools such as Man-Machine Integration Design and Analysis System (MIDAS) and Performance and Usability Modeling in ATM 96
(PUMA), show potential for characterizing elements of the overall system functional models.
An overall toolset that connects technical and human performance to the system performance metrics through models of regional and national air traffic flow is at the heart of both the Level HI and II dynamic traffic simulation models. The overall toolset should consist of a number of separate models, integrated either at runtime or through input/output data sharing, depending on the level of coupling deemed necessary. A number of key metrics will be identified by the PD process so as to perform cost, benefits and safety evaluation of the new operational concepts. A number of modeling tools are already available, but they are neither integrated in a comprehensive evaluation toolset nor are they yet suitable to address the challenges posed by the long-term system performance objectives. Some of the particular modeling challenges to be addressed include:
D Influence of technical and human performance factors such as communication, navigation, surveillance, automation, ATC, and cockpit crew, on effective traffic spacing in the system.
D Representation of traffic flow performance at the national level, including the influence of the overall system architecture and regional/local conditions.
D Modeling and data collection efforts for ATM-related safety evaluation are still relatively immature. Section 10.3.6.1 describes the required safety analysis methodology.
One of the most challenging issues in this context is validation of the human performance models, for which existing data may not be readily available. This leads to a potential need for focused human-in-the loop experiments to generate validated performance parameters.
10.3.6.1 Safety Methodology and Tools Safety modeling and analysis connects the failure modes and associated probabilities of components (hardware, software and human agents) with the probabilities of the top-level (presumably undesirable) events, such as loss of separation. This is accomplished in two steps. The bottom-level "Reliability Model" block represents the process of turning the failure mode behavior of the hardware, software and humans 97
into a probabilistic characterization of the "operational states" of the system being considered, for example a TRACON. The second step is to transform the probabilities of these operational states into probabilities of the top-level events by doing Monte Carlo simulations of the traffic, depending on the operational states. A Boeing tool called "Reliability Performance Module" (RPM) contributes to this process, and produces probabilities for all sequences of fault or error events. Examples of "error or fault sequence" include: "Arrival controller transposes flight numbers USAir 5829 and USAir 5289", "BA125 loses transponder", and "Secondary radar produces spurious data". The reliability tool automatically cycles through all such sequences of fault and error events (of incremental length up to a specified maximum). It also calculates probabilities for all of these sequences based on the assumed failure rates or probabilities for the fundamental failure modes.
These failure sequences are then partitioned into so-called "operational states", which for convenience and simplicity, we have labeled Normal Position Errors, Moderate Position Errors and Severe Position Errors. (In reality, this list of operational states would be longer and more detailed.) For example, if nothing has failed (or failed minimally), we may consider the system to be in a state where the deviation of any aircraft from its intended trajectory is within the "normal" limits. If, on the other hand, the system has lost all surveillance capability, or all communication capability, these trajectory deviation errors would presumably grow into the "severe" category.
The probability of being in one of the three operational states is computed by simply summing the probabilities of all sequences assigned to that state. This part of the process involves discrete-event style simulation. So far, no explicit continuous type simulations have been used (although such simulations might be used to produce certain parameters for discrete-event simulation).
Having calculated the operational state probabilities takes us to the middle of the diagram. The next step is to connect these operational state probabilities to the probabilities of the top-level undesirable (unsafe) events, e.g., loss of separation or NMAC. This connection is made by performing a number of Monte Carlo simulations of the aircraft trajectories. A continuous type simulation model is now used. This 98
allows us to estimate the probability of the top-level unsafe event, conditional on each of the operational states. Each state determines a different set of parameters for the simulation. For each state, therefore, we obtain a conditional probability for the top- level event(s). Then we simply use the law of total probability find the absolute to combine the results of the bottom-level reliability analysis together with the conditional probabilities, to produce the final unconditional probability of the top- level event.
This portion will be one of the difficult challenges of the safety analysis, because the aircraft trajectories will depend upon the errors and faults that are assumed for the simulation. But the interactions of these trajectories depend on both the timing and sequencing of the errors and faults. The statistics produced by the Monte Carlo simulations will be affected by these orderings. Put another way, there is a coupling between the two phases of the analysis, i.e., the discrete-event and continuous simulation portions. This is cutting-edge analysis. One approach is to take advantage of work by the Netherlands National Aerospace Research Laboratory (NLR), which employs a piecewise deterministic Markov process embedded in a colored Petri net. This is part of the TOPAZ suite of tools. Another possibility is to develop a tool based on similar ideas, but using our own discrete-event simulation tool and reliability execution engine (RPM). For some situations, we may avoid difficulties by using a non-coupled approach, but based on worst-case assumptions for the "static" operational state probabilities, so as to be conservative in the overall system failure probability estimation.
The"Reliability Model" uses a simultaneous top-down and bottom-up process, composed of many different kinds of activities. "Functional Failure Analysis" (FFA) (often called a Functional Hazard Analysis, or FHA), represents the activity in which ATC experts consult with system modelers to identify the top-level functions of the system and what happens if one or more of these functions cannot be performed. They also drill down to the next levels to identify which faults, errors or failures could lead to loss of function. This discussion should also identify ways to avoid or reduce the likelihood of these failures, and how the effects of failure can be mitigated. 99
"Component and Agent-level FMECAs" determines the possible faults, errors and failures of the fundamental components of the system, including hardware, software, and human agents. (FMECA stands for Failure Modes, Effects and Criticality Analysis.) This process should also identify the probabilities or failure rates associated with the failure modes of these elements. These probabilities or failure rates eventually feed into the calculations done by the analysis tool which produce the top- level event probabilities. Early in the design process, or when doing "what-if ' comparisons of alternative operational concepts, one would probably not have (or need) detailed FMECAs. Rather, the top-down part of the analysis would impose, or allocate, requirements on the subsystems, which would then ultimately flow down to the subsystem components or agents.
However, in the later "certification" phase of the process, this component-level information will be provided or derived independently, and then used to produce the top-level event probabilities by using the process shown in the diagram. These top- level probabilities are then compared to the system-level requirements in order to determine certifiability.
In the case of equipment, it is customary to start with a detailed vendor- supplied FMECA, and distill this information into a smaller set of failure modes and effects that are relevant to the performance of the subsystem in which this component resides.
Similarly, the error-producing behavior of human agents must be understood, as well as ways to quantify it in terms of failure rates and probabilities. We need to analyze the human factors aspects of the operating environment and procedures. Currently, there is no standard "FMECA" process for humans. This activity will involve close cooperation with human factors experts to determine the proper level of detail to model the human agents, together with the error modes and some quantitative characterization of the error probabilities. This will be another significant challenge. It will be difficult enough to distill human behavior to fit the level and point of view of the airspace architecture analysis. Beyond this, certain situations or levels of fidelity may demand a context-dependent characterization of the human agent's error- producing behavior. 100
Finally, we also need similar characterization of software. One problem is that software does not really "fail" in the way that hardware does. A software fault or error is usually the result of a specification or design error. So these are really "latent" faults, which in combination with a certain situation produces an undesirable effect. It is very difficult to model this realistically.
Once the top-level FMEA has been done, and the component-level FMECAs obtained, the model building and analysis process begins, as represented by the three middle boxes in Figure 10.3-6. This is implemented in the RPM tool. This tool produces the probabilities for all sequences of individual fault or error events. The advantages of this model-based approach (over fault trees, for example) are: (1) The lengthy search process for failure sequences is done automatically by the computer, and relieves the human of this tedious, error-prone task; (2) When the system architecture changes, it is easier to change a block-diagram model that closely resembles the system than to update a fault tree, which is another level of abstraction away from the system; (3) It is easier to capture subsystem interactions via explicit modeling of their connections; and (4) It is possible to capture sequence-dependent behavior.
It still necessary to assemble domain experts to perform a rigorous, and probably lengthy, functional failure analysis; to obtain, derive or posit the failure mode behaviors and statistics of the hardware, software and human agents; to understand and model the functional behavior of the system, with careful attention to the interfaces between subsystems; and to integrate all of the above into an appropriate executable or calculational model, depending on the style of analysis.
What are the implications for a candidate airspace architecture based on such an analysis, or at least, a preliminary analysis in which reliability allocations are made to the various subsystems? For the top-level requirements to be met, the various subsystems (and eventually the component hardware, software and agents) will have to meet certain performance requirements and/or be assembled and organized in certain ways. By the latter, we mean the introduction of self- or in-line monitoring, redundancy management, mitigation, and tight control of undetected errors. These are 101
standard tools in the fight to maintain system integrity, i.e., the degree to which the system does not deceive the user(s).
Integrity is but one of several metrics which are used to judge a system's reliability and safety. The others are accuracy, latency, continuity and availability. Here are some brief definitions:
D Accuracy: a measure of the ability of a system or subsystem to deliver its output with a specified variability. Examples: 1) A certain radar reports target positions with one standard deviation of 0.1 NM (at a specified range). 2) A given mode of GPS reports aircraft position with one standard deviation of 100 meters. Given the assumption of a distribution for the measurements (normal, for example), accuracy involves both a distance and a probability.
D Latency: a measure of the timeliness of required data, for example, sensor measurements, controller clearances, pilot responses or requests. Large latencies introduce extra "slop" in the system, and can compromise safety margins. D Continuity: the (conditional) probability that a system continues to operate properly, given that it operates properly now. This is especially important in stressful situations where an interruption would greatly overload controllers or pilots. D Availability: The a priori probability that a system will be available at a given time in the future. It is desirable to have confidence in system availability once operations begin.
D Integrity: If a component, subsystem or system is unlikely to deceive the user, it is said to have integrity. The usual measure of integrity is the probability of an undetected error. A high integrity system has a very low probability of undetected error (or errors). Undetected errors can be the most malicious kind, because an unaware user may proceed blithely into a dangerous situation. For example, if aircraft IDs are transposed without realizing it, a command intended for one aircraft may be given to the other, causing it to blunder into the path of yet another aircraft. Or, a radar may produce faulty position data which looks just good enough not to be noticed, and a separation violation is missed. One familiar application of the integrity idea is in RNP. See section 5.1.4.3 for a description of RNP integrity. 102
Requirements for a Safety Modeling Tool Set
The methodology and tools must be flexible and hierarchical in nature, for two reasons. The first reason has to do with the nature of the design process itself. We typically analyze high-level low-fidelity models in the early part of the design process, more detailed higher-fidelity models towards the end of the design process, and various stages in between. Thus, the tools must have the ability to represent high-level functionality, as well as the ability to expand these functional representations hierarchically into lower-level detailed sub-models.
The second reason deals with the different time scales and levels of aggregation evident in the overall ATC system. The tactical control of aircraft represents the short time period which characterizes the terminal area. The time scale of the control loops get longer, the geographical area grows from TRACON to regional to national, and the numbers of aircraft, controllers, and other agents increase. The safety tool suite must support detailed models for the far right (terminal area) portion which include individual aircraft, controllers, pilots and other agents. At the regional level the TRACONs and their interactions would become the fundamental modeling elements, as would the regions and their interactions at the national level. The parameters for the safety analysis of a model at a given level (except the lowest level) would be provided by the safety analysis of the model at the next level down. 10.3.7 Select Technology Sets
Once the functional requirements are established, Task 7 will evaluate alternative technologies to select promising candidates. For example, the functional requirements for an arrival management concept could include weather forecasting and aircraft trajectory intent information. The weather requirements could be met by a ground- based system, or by aircraft-based weather observations for frequent updating of regional weather forecasts. Similarly, intent requirements could be satisfied by using data link, on-board FMS capability and trajectory negotiations.
Technology sets will be selected based on factors such as technology and cost risk, and compatibility with existing and proposed NAS infrastructure. In the example above, data link could potentially be used to satisfy both the weather forecasting accuracy and the trajectory intent requirements for arrival management. Thus an 103
enabling technology for one function could have benefits in other areas, both for enhanced capacity and for reduced hazard risk.
The functional performance requirements will be allocated to the technology subsystems. The technology sets must be sampled across all CNS/ATM categories and not simply within individual technology groups such as communication. For example, use of precision RNAV routings could be a means of increasing capacity in the terminal area. However, a safety analysis may identify the need for enhanced surveillance and alerting to assist the air traffic manager in monitoring path conformance. This could be provided by airborne-based monitoring and path conformance in the navigation function, by transmission of aircraft position and intent, or by conventional radar monitoring and path conformance alerting. The system solution might require two or more such monitoring systems to achieve the required level of operational availability and integrity. 10.3.8 Assess Architecture Impact Task 8 will examine, for the case study, the effect of the planned NAS architecture on the alternative operational concepts. This task will focus on the transition and timing issues associated with the technology sets and their interfaces with the existing NAS architecture plan. We will also study the alternatives in terms of cost, schedule, and technical risk. Baseline and Planned Architecture Interface: This task will investigate the system interfaces affected by the new technology sets, based on the case study parameters and the planned evolution of the baseline architecture. For each technology set, the target systems and/or interfaces will be identified. This identification will be for both ground system architecture and for airborne systems, where appropriate. We will use tools or data bases such as the FAA's NAS CATS-I, if available.
Timing and Risk Assessment: This task will analyze the timing of block changes in the baseline architecture for the target end systems, interfacing systems, and enabling systems for the technology sets selected. This assessment will identify technology, timing and programmatic risks for the alternatives being considered. Fleet equipage rates will likewise be considered. 104
Life Cycle Cost Impact: This task will assess the life cycle cost impact on the baseline ground and airborne architectures. For a case study, this will be based on a parametric cost estimation. More comprehensive tools will be considered, if available. This will provide delta-costs for the baseline NAS time period, for both recurring and non- recurring items.
Requirements for Long-Term Impact Assessment: Subsequent studies may require more detailed analysis of the transition issues, including sustaining and incremental updates. The case study is focused on broadly evaluating potential means of enhancing growth while preserving safety and cost affordability for users. This task will establish requirements to support future studies to optimize the overall implementation of the NAS architecture to achieve the long-term performance objectives.
10.3.9 Evaluate Airspace and Alternatives
Operations in the case study airspace will be evaluated to assess whether the proposed architecture meets most or all of the initial system requirements for capacity, safety and affordability. This broad evaluation will include characteristics of the classes of users defined in Task 1, the airspace characteristics defined in Tasks 3 and 5, and technology sets defined in Task 7. The effectiveness of operational changes may be evaluated against several baseline plans by evaluating the effects of the new concepts and CNS/ATM technologies on the system performance.
Airspace and Procedure Design Criteria: New preliminary airspace design criteria will need to be developed to support the new operational concepts. Examples are route separation minima and air traffic procedural criteria for obstacle clearance or traffic handling. We will assess the needed criteria to ensure the optimum use of the specified technology sets. The case study will make assumptions about new criteria availability. The evaluation will enable the system architect to estimate the impact of operational changes by extending the requirements analysis and technology tradeoffs beyond the initial point design, and to gather specific data on operational changes that users can expect to see in the future case study airspace. Preliminary Airspace Design: System performance will be evaluated on new airspace designs, predicated on the performance expected from the improved operational 105
concept and architecture. Reduced separation standards will allow the addition of routes with closer spacing; higher air traffic management productivity will allow changes in sectorization, including the potential for dynamic sector definition. The new CNS/ATM infrastructure will save costs by reducing facilities. Evaluate 2010 "Do-Nothing" Case: TAAM or an equivalent tool will evaluate the current system baseline defined in Task 2 under the traffic growth assumptions from the Mission Analysis.
Evaluate 2010 NAS V4.0, V5.0 Cases: The current baseline case will be augmented by FAA planned architecture changes. Evaluate 2010 PD Concepts A and B: The new concept options proposed by the PD case study will be evaluated and compared with the baseline and planned cases.
Safety Analysis: Comparing the alternative operational concept options applied to the case study airspace, and the "Do-Nothing" case, the safety analysis will develop possible scenarios for each operational concept that capture particular non-normal sequences of events. These will include possible human (pilot, controller) and system mitigating actions, and a preliminary estimate of the particular operational safety outcomes for the alternative concepts. Top-level safety characteristics of the different concepts will be estimated for the case study airspace operations. Assess System Alternatives: The alternatives will be rated for airspace performance characteristics and the cost and risk parameters from Task 8. An investment analysis will refine the rating to support the full application of the PD process. This rating will allow decisions on future architecture plans to be driven by comprehensive design data. While we have described preferred embodiments, those skilled in the art will readily recognize alterations, variations, and modifications which might be made without departing from the inventive concept. Therefore, interpret the claims liberally with the support of the full range of equivalents known to those of ordinary skill based upon this description. The examples are given to illustrate the invention and not intended to limit it. Accordingly, limit the claims only as necessary in view of the pertinent prior art.

Claims

106CLAIM OR CLAIMS
1. An air traffic management system or method for controlling air traffic substantially as shown and described.
2. An air traffic management method for controlling the separation of airplanes in an airspace, comprising the steps of:
(a) establishing a trajectory for each aircraft;
(b) storing the trajectory in a shared database accessible by controllers; and (c) accessing the trajectory by a controller to promote air management planning while reducing or eliminating controller adjustment of the trajectory or separation.
3. An air traffic management system, comprising: (a) a trajectory database having trajectory data for each of a plurality of aircraft operating in an airspace, the data stored on an accessible electronic media; and (b) a control station electrically connected to the database to allow access to the trajectory data for air traffic management decision making to allow adequate spacing between aircraft in the airspace.
4. The air traffic management system of claim 3 wherein information flows between the database and the control station through at least one satellite.
5. The air traffic management system of claim 3 wherein the information flows between the database and the control station through a satellite-based communication, navigation and/or surveillance (CNS) network.
6. The air traffic management system of claim 4 wherein the information includes trajectory-based information commonly programmed into flight management 107
computers on commercial transport aircraft and accurate monitoring of the true position of the aircraft using GPS (the Global Positioning System).
7. The air traffic management system of claim 4 wherein the information includes cleared taxi routes for landing aircraft to avoid ground congestion at an airport.
8. The air traffic management system of claim 4 wherein the information includes flight plans, current surveillance information, local and system-wide weather as well as forecast weather, and near-term simulated traffic flow predictions.
9. The air traffic management system of claim 4 wherein the information includes the current position of the airplane along with the aircraft's intent (future flight path), including estimated time of arrival ETA at predetermined waypoints along the path.
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