The study of Air Transportation Systems includes a wealth of specially used words in air traffic control, aeronautics, avionics, and related fields. Definitions for these words come from many sources. Sources in this glossary are noted by the use of "[x]" at the end of the definition and referenced at the end of the page.
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A
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Accreditation
The official certification that a model or simulation is acceptable for use for a specific purpose. [a]
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Advanced Concept Evaluation System (ACES)
A modeling and simulation environment for the air transportation system that is being developed at the NASA Ames Research Center. This capability captures the key feedback response mechanism of the NAS. The agent-based modeling approach that is being used represents the individual behaviors of the airspace participants (e.g., aircraft crew, controllers and airlines) and captures the critical ripple effect of the user's actions on other system participants. This modeling approach isolates the individual models so they can be enhanced, improved, and modified to represent new concepts with low development impact on the overall simulation system. [b]
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Advanced Navigation
Used generically to refer to aircraft with the most sophisticated navigation avionics/capabilities. [c]
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Agent
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Something that produces or is capable of producing an effect.
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An active or efficient cause.
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A chemically, physically, or biologically active principle.
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A means or instrument by which a guiding intelligence achieves a result.
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Software modules that manipulate models in some fashion and/or perform functions to simulate human or known black-box behavior. These would include but are not limited to:
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Automated pseudo-pilot functions, i.e., fly a given route, intercept and fly an approach to a runway, takeoff routines, etc.
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Automated functions on the controller display, such as hand-off functions, update rate of target presentations, etc.
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Conflict or traffic alerting algorithms
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Air Traffic Control behavior models - to replicate controller actions to maintain aircraft separation
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Flight Management System like module/s that control aircraft, to maintain accurate climb, cruise and descent profiles (TOC, TOD, etc.)
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Time-based weather profile updates (4D versus 3D wind models)
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Airlines Operations Control (AOC) - replicate AOC functions. Update and/or forward routing information, weather information, traffic information, clearance requests, etc.
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Air Traffic Control System Command Center (ATCSCC) - replicate the SCC to adjust arrival flow to specific airports, issues reroutes standards due to weather or Radio Navigation Aid failures, etc., issue ground delay procedures when needed, etc.
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Subroutines decompose problems functionally but have no persistent data of their own. With subroutines, data are passed as parameters. A higher order program must explicitly call upon a subroutine for it to perform its function.
Objects replaced subroutines. Objects have persistent data. A higher order program must still call upon an object for it to perform its function.
Agents have both persistent data and their own thread of control. With agent-based software, no central program provides coordination and control. The agents represent the rules or behavior of the entities of a system. They produce a global behavior that is not explicitly programmed.
In conventional top-down software systems, the software developer must consider all possible situations. Touching any one module could endanger the functionality of the entire system. With conventional software each module is called by some module that then calls upon other modules. If one module fails, the entire system stops. This paradigm can lead to software that is "brittle" and coding that is not reusable.
In contrast, agents can be independently added, removed and modified. Agents make no absolute assumptions about the actions of other agents. Each agent knows when it needs to execute and executes autonomously. In general, these software systems may be more robust in that if a single agent stops, the rest of the system may proceed. They may also be more scalable in that adding an agent does not directly affect existing agents within the software.
[b,d]
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Air Carrier
An aircraft certified by the FAA for the purpose of carrying persons or goods for hire on an established airway. The term also applies to an organization operating an aircraft. [e]
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Airborne Delay
The difference between the time of lift-off from the origin airport and touchdown at the arrival airport, minus the computer-generated optimum profile flight time for a particular flight based on atmospheric conditions, aircraft loading, aircraft type, and other flight related parameters.
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Airport Surveillance Radar
FAA short-range radar for terminal air traffic control. [e]
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Air Traffic Control (ATC)
A service that promotes the safe, orderly, and expeditious flow of air traffic, including airport, approach, and en route air traffic control. [e]
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Air Traffic Management System
Refers to issues, items, and initiatives within the purview of the Air Traffic Management system to control. For example, quality of service (timeliness, response to demand) would be considered part of the system. Does not include items such as block time and demand that are part of the aviation community's interest and to which the system responds. [c]
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Analytical Architecture
A sophisticated modeling approach that includes a conceptual framework, an analytical framework, and a solution framework. These three frameworks are integrated and permit capability based planning to be conducted. [b]
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Airline Operations Center (AOC)/Business Model
The AOC dispatch and scheduling functions are simulated as part of the business model. These AOC models or human inputs will be from the perspective of operating an airline. Weather, aircraft, and crew scheduling problems are all part of the AOC/Business Model. [b]
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Airspace
Class A - Airspace from 18,000 feet Mean Sea Level (MSL) up to and including 60,000 feet MSL over CONUS and Alaska. Unless otherwise authorized all aircraft must operate under Instrument Flight Rules (IFR).
Class B - Airspace from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of IFR operations or passenger enplanements. The configuration of each Class B airspace area is individually tailored and consists of a surface area and two or more layers (some Class B airspace areas resemble upside-down wedding cakes). An Air Traffic Control (ATC) clearance is required to operate in the area and all aircraft that are so cleared receive separation services within the airspace. Mode C transponders are required on board all aircraft. Visual Flight Rules (VFR) operations are subject to Federal Acquisition Regulation (FAR) Part 91.215 and FAR Part 91.131 requirements. Unless otherwise authorized by ATC, aircraft must be equipped with an operable two-way radio. Class B airspace areas include at least the following locations: Andrews Air Force Base MD, Atlanta Hartsfield, Boston Logan, Chicago O'Hare International Airport, Los Angeles International Airport, Miami International Airport, Newark International Airport, New York Kennedy Airport, New York La Guardia Airport, San Francisco International Airport, Washington National Airport, and Dallas/Fort Worth International Airport.
Class C - Airspace from the surface to 4,000 feet MSL above the airport elevation surrounding those airports that have an operational tower, are serviced by a radar approach control, and that have a certain number of IFR operations or passenger enplanements. Usually an operating two-way radio and a Mode C transponder are required.
Class D - Airspace from the surface to 2,000 feet MSL above the airport elevation surrounding those airports having an operational control tower. Usually an operating two-way radio is required.
Class E - Airspace that is not Class A, B, C, or D and is controlled airspace is Class E airspace. For example, Federal Airways are Class E airspace and extend upward from 1,200 feet MSL to, but not conducting in class G airspace.
Class G - Airspace that is not Class A, B, C, D, or E. Rules governing VFR flight assist the pilot in meeting the responsibility to see and avoid other aircraft. Minimum flight visibility and distance from clouds required for VFR flight are discussed in FAR Part 91.155. FAR Part 91.177 includes a requirement for VFR aircraft to remain at least 1,000 feet (2,000 feet in designated mountainous terrain) above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown.
[f]
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Architecture
To implement a given operational concept or concept of use, an architecture system describes people, procedures, hardware, software, and interfaces. To further continue the above example, an architecture might be that specific types of long range radars are connected via microwave links and land lines to large mainframe computers that format and present radar data on 20x20 inch displays, where the use of this displayed data is governed by fixed procedures. [b]
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Arrival Delay
Refers to the amount of time that an aircraft is delayed beyond the scheduled time of arrival for that aircraft at an airport. Although arrival delay can be reported by many types of air traffic facilities, usually only en route centers will report these statistics. [b]
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Artifact
A product of human workmanship. [d]
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Auto-load
As a result of the collaborative process, change in flight profile, or auto-negotiation, the specific change is made digitally available to the operator (i.e., pilot, controller, dispatcher) for selection to be executed. It is consistent with the guiding principle that no action is executed without the explicit action/assent of the human. It is distinct from auto-execution. [c]
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Auto-negotiation
Describes the interaction between two or more systems to identify a specific operational response acceptable to the parties (e.g., user and service provider) served by the automated system. The automated systems would use the known operating constraints/user preferences to identify the preferred response. [c]
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Aviation System Technology Advanced Research (AvSTAR)
A conceptualization by NASA of potential future air transportation systems research scope and topics. The VAMS Project represents the operational concept and evaluation portion of the AvSTAR idea. Only the creation of decision support tools, which is part of AvSTAR, is not part of VAMS. [b]
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B
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Build
A word used to describe a level of non-real-time functionality within the Virtual Airspace Simulation Environment, usually used as in 'Build 1', 'Build 2', etc. [b]
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Build 1
State-of-the-art airspace models toolbox with the ability to assess economic impact of new technology and NAS operational performance, and the ability to model the dynamic effects of interactive agents. [b]
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Build 2
VAST toolbox enhanced with abilities to assess uncertainty within airspace system, model infrastructure and transitory constraints and their impacts on the system. [b]
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Build 3
VAST toolbox enhanced with cognitive human performance attributes and Communication, Navigation, and Surveillance models. [b]
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Build 4
VAST toolbox for advanced operational concept analysis. [b]
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C
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Calibration
The performance of VAST must be calibrated according to the existing NAS. Tools must be developed to show such comparison for each key parameter within acceptable criteria. Utilities must be developed to facilitate such calibration effort. [b]
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Capability(ies)
Qualities of a system that can be used or developed to provide functionality. In the case of VAST Real-Time, a system architecture will be created with the functionality to integrate real-time simulator facilities with real-time models and human interfaces. This capability should not have limitations on the types of facilities or models that can be included provided the facilities and models meet the system interface requirements. [b]
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Capacity
The amount of load that a given facility can successfully accommodate at a given time. Usually expressed as a scalar (e.g., 50 aircraft), sometimes as a rate (e.g., 50 aircraft per hour). [b]
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Collaborative Development Environment (CDE)
A package of software tools and utilities enabling a trained user to set up systems, monitor experiments, develop scenarios, modify configurations, and control the execution of simulations within the Virtual Airspace Simulation Environment. [b]
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Collaborative Decision-making
Generically refers to the information exchange and decision-making process for the purpose of collaboration between the user and service provider. [c]
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Collision Avoidance System
A device installed on aircraft for the purpose of:
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Detecting the presence of other aircraft
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Automatically assessing the potential collision hazard represented by other aircraft
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Providing advance warning to the pilot if a threat is predicted by the equipment
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Providing appropriate command signals indicating the proper evasive maneuver [e]
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Communication, Navigation, and Surveillance (CNS)
1. (In model terms) The ground based CNS components interact with the onboard CNS systems. It is projected that this functionality will only need to be simulated in order to provide proper vehicle inputs. However, these systems may need to be emulated closely to facilitate studies related to signal delay propagation or other system performance studies. [b]
2. (In functional terms)
A. Communication: NAS communication requirements encompass capabilities for providing voice data communication throughout the NAS with external facilities and government agencies. These requirements address the air-ground, ground-ground interfacility and ground-ground interfacility voice and data communications between aircraft and air traffic control and flight service facilities, between FAA and external facilities, and within NAS facilities. [g]
B. Navigation: Address the capabilities to provide en route and terminal navigation aids to assist the pilot of an aircraft in determining his position in the airspace at any given time and additionally, to provide assistance in locating terminal facilities. [g]
C. Surveillance: In order to detect all aircraft entering an ADIZ/DEWIZ within 13 seconds of penetration, the NAS must have a surveillance system capable of detecting these aircraft. The Air Route Surveillance Radars (ARSR) provide en route search coverage for air traffic control, as well as surveillance for air sovereignty and law enforcement within the ADIZ and DEWIZ areas. The ASRs provide positional information and height data on aircraft within its coverage area. This data is provided to the appropriate FAA, ACFs and to USAF air defense facilities and USN area control facilities. [g]
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Common Metric Set (CMS)
A comprehensive set of operational performance metrics that is related to the common scenario set. [b]
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Common Scenario Set (CSS)
A broad and integrated set of air transportation system operations scenarios used to evaluate operational concepts. Scenarios take many factors into consideration including time, location, participants, and tactical and strategic situations. [b]
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Constraint
Any limitation to the desired level of service. It includes the design limitations of the Air Traffic Management system (maximum capacity) and impact of transitory, anomalous events such as weather. Constraints recognize the finite quantum of NAS resources available at any point in time, regardless of how the resource limitation evolved. [c]
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Contract Task Order (CTO)
A contract instrument (NASA/Ames) used within the Air Traffic Management Systems Development and Integration (ATMSDI) contract process to identify a particular statement of objectives, for example CTO-7, that the contractors are being requested to implement. Two competing contractors can respond with a statement of work describing in detail work plans. [b]
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Controlled Airspace
Same as Mixed Airspace. It starts, in general, at some altitude above the ground and extends up to the Positive Control Airspace. In terminal area control zones, it extends to the ground. [e]
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Controlled Time of Arrival
The assignment and acceptance of an entry/use time for a specific NAS resource. Examples include point in space metering and assignment of a location and time for entry into the international oceanic route assignment. [c]
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Controller Interface
The Controller Interface is designed to accurately represent (via physical models or simulated behavior) the present day displays that are in use, primarily the FAA's Display System Replacement (DSR). The DSR will be used in all en route and terminal facilities. This interface has all the controls necessary to display and adjust parameters on the display, including range, maps and map center, data-block positions, brightness and contrast control, weather presentation, etc. Additionally, the interface has an input capability to enter data necessary to function as a controller position including, making and taking hand-offs, change altitude assignments (center), change/amend aircraft routing, etc. The Controller Interface position also has audio/voice control. This interface is used to connect to adjacent sector/facilities, as well as a "radio" interface to the pseudo-pilot positions. The controller interface should also permit a user to emulate or simulate controllers. A computer simulated interface is needed to provide voice recognition and speech synthesis for communication purposes, an intelligent agent for the decision making, as well as, the proper inputs and outputs for the controller simulation. [b]
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D
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Data Collection & Analysis Tools
(For simulations) Data may be of several types and can be intended for various purposes. Simulation data is collected for run-times and post-run analysis. Researcher data can be event oriented, time-historic, a combination of the two types, or even discrete screen snapshots collected during the course of a simulation run. Since the simulated models can be 'collection agents' for data, the data usually resides locally on the platform associated with the model generating the data. A means of consolidating and correlating the data from the other platforms is part of the data collection and analysis tool set. Tools can then be applied to process the raw data collection. The post-run capabilities include the ability to print or plot selected data sets. [b]
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Data Link
Any communication channel or circuit used to transmit data from a sensor to a computer, a readout device, or a storage device. [e]
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Decision Support System
Applications that make use of the information available via System Wide Information Management (SWIM) to achieve a specific objective. An application focused on an individual task or activity is referred to as a system. [c]
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Delay
1. The difference between an expected time of arrival of an aircraft at an airport and the actual time of arrival. 2. The difference between FAA's anticipated time of arrival plus 15 minutes and an aircraft's predicted time of arrival. 3. Delays to Instrument Flight Rules (IFR) traffic of 15 minutes or more, experienced by individual flights, which result from the ATC system detaining an aircraft at the gate, short of the runway, on the runway, on a taxiway, and/or in a holding configuration anywhere en route shall be reported. Facilities should make a cumulative delay calculation when an aircraft is held at more than one fix within a facility. The IFR controlling facility shall ensure delay reports are received and entered into the OpsNet. [a]
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Departure Delay
Refers to the amount of time that an aircraft's departure from an airport is delayed, usually by air traffic control procedures or weather. [b]
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Distributed ATC Management
System concept based on having some separation and/or traffic management functions controlled by airborne pilots and some controlled by a ground agency. [e]
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Down Link
Aircraft-to-ground data link. [e]
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E
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Electronic Flightbag
Refers to the aggregate availability of the information necessary to execute a flight (e.g., charts, approach plates) electronically for the flight deck. [c]
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En route
1. A portion of airspace generally considered starting at 18,000 feet and up covering an area. 2. Concepts dealing with the planning and implementation of aircraft paths between takeoff and landing. This includes creating more flexible aircraft paths, conflict detection and resolution, communication of environment and traffic monitoring, more accurate navigation methods, and prediction of traffic conditions. [b]
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En Route ATC Service
Air traffic control provided for aircraft by centers on an Instrument Flight Rules (IFR) flight plan while these aircraft are operating between departure and destination terminal areas. [e]
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En Route Delays
Refers to the amount of time that an aircraft is delayed between airports. The delay almost always occurs at the boundary between two centers and is reported by the Air Route Traffic Control Center. [b]
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Environment
The environment describes any and all aspects that vehicles will be traveling through. Historically these have been described in reference to the existing controlled entities such as: en route airspace, terminal airspace or Terminal Radar Approach Control (TRACON), airport or tower and ground. Additionally, other entities affecting the environment include, but are not limited to, the national command center and oceanic airspace. [b]
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Equitability
The provision of services of the Air Traffic Management system consistent with the rules of engagement and public policy established by the government. An example is the policy of first-come/first-serve vice the establishment of equipage requirements for service. [c]
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F
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Fail soft
Systems capability in which operations continue, but with some degradation in capacity, when a failure has occurred. [e]
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Fast Time
A type of simulation in which the passage of time is faster than found in the real world. It is a proper sub-set of Non-Real-Time type simulations where the passage of time is either slower or faster than that found in the real world. [b]
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Fidelity
1. The accuracy of the representation (model) when compared to the real world. The similarity, both physical and functional, between the simulation and that which it simulates. A measure of the realism of a simulation. The degree of similarity between a model and the system properties being modeled. [a] 2. Fidelity can be conceptualized as having two dimensions: Physical and functional. Physical fidelity is the degree to which the model or simulation includes important physical characteristics, such as those associated with visual, spatial, and kinesthetic sensory channels. For example, the physical fidelity of an aircraft simulator would be enhanced if the controls, visual displays, noise level and so on closely match those in the operational aircraft. Functional fidelity refers to the accurate representation of such elements as information flow and situational factors. [i]
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Fix
A geographical position determined by visual reference to the surface, by reference to one or more radio navigation aids, by celestial plotting, or by another navigational device. [e]
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Flight Deck Separation
Pilot conducted separation tasks requested by the flight crew and authorized by the service provider, or initiated by the service provider and accepted by the flight crew. In all cases, service providers continue to have discretion over when to apply these procedures, while pilots continue to have discretion over requesting or accepting the procedures. [c]
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Flight Intent
The future aircraft trajectory expressed as a 4D profile until destination, taking into account aircraft performance, weather and terrain, Air Traffic Management services constraints, and the calculated trajectory that is "owned" and agreed to by the pilot. [c]
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Flight Object
A data set of flight-specific information available throughout the duration of the flight both to the user and to service providers across the NAS via System Wide Information Management (SWIM). For an appropriately equipped aircraft operating under Visual Flight Rules (VFR), the flight object contains the flight path, a discrete identification code that provides precise location and identity information, and all necessary information to initiate SAR. For a flight operating under Instrument Flight Rules (IFR), the flight object can be a much larger data set, including a preferred trajectory coordinated individually by the user and supplemental information such as the aircraft's current weight, position, runway preference, or gate assignment. Flight object information can be updated by the user or service provider throughout the flight. [c]
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Flight Plan
Specified information relating to the intended flight of an aircraft; it is filed orally or in writing with an ATC facility. [e]
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Flight Path
The combination of altitude profile with horizontal track. [e]
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Flight Profile
Four-dimensional path that includes a complete set of user preferences for climb, descent, cruise settings, and other user operational preferences. [c]
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Flight Trajectory
Four-dimensional path of flight expressed at the level of performance the flight is capable of achieving. [c]
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G
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Gate Hold Delay
The difference between the time that departure of an aircraft is authorized by ATC to leave the gate and the time that the aircraft would have left the gate area in the absence of an ATC gate-hold. [b]
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H
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High Fidelity Model
1. Model that exhibits the functionality necessary for the simulation system to consistently portray the NAS for secondary level research objectives, infrastructure sensitivity analysis, and cost/benefit analysis. [b] 2. If a model has high fidelity, the interaction will be the same as in the real world. [a]
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Host
The host is the repository for flight plans, flight advisory amendments, handles radar hits, determines traffic shown on radar scopes, etc. A center's host also communicates with other center's hosts on handoffs. Initially, the requirement is to pursue understanding of this control element with the understanding that representations of the host may be included in other system models. Failures of the host system will not be simulated. [b]
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Human Performance
VAST must incorporate human behavior and response in areas where human interactions, e.g., controller to controller, controller to cockpit crew, where information exchange or execution are critical to the overall system's performance. Human interactions that require accuracy, response time, and decision-making, and have direct effects on air traffic management must be modeled and included appropriately. Human performance must be developed in proper form that is directly applicable to the process. [b]
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Human Team Modeling
A type of modeling that characterizes the behavior and performance of teams and their members and their interaction with other systems that they may or may not be part of. [b]
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Hyperbolic trees
A graphical technique for displaying large amounts of data by showing their direct connection. [b]
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I
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Implementation
Introduction of a capability or service into the Air Traffic Management system. It includes the necessary appropriate changes to airspace design, procedures, systems, logistics, labor negotiations, and certification, enabling NAS users and service providers to realize the intended benefits. [c]
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Implicit modeling
Specifically relates to the software construct. If not a discrete software component, the effects of a related or dependent model may be developed implicitly as part of a model. From the logical perspective, the implicit model may be represented internally, however only its meaningful effects will be represented outside of the larger software component. [b]
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Independent Implementation Review (IIR)
The NASA Program Management Council shall establish procedures to ensure that it remains cognizant of the status and performance of the programs and projects over which it has responsibility. An IIR provides a validation of conformance to the Program Commitment Authorization (PCA). An IIR provides: a. assessment of progress/milestone achievement against original baseline, b. review and evaluation of the cost, schedule, and technical content of the program over its entire life cycle, c. assessment of technical progress, risks remaining, and mitigation plans, and d. determination if any program deficiencies exist which result in revised projections exceeding predetermined thresholds. [j]
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Infrastructure Management
Refers to the monitoring, maintenance (both preventative and responsive), and general oversight of NAS infrastructure elements to ensure certified performance within acceptable/defined criteria. [c]
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Instrument Flight Rules (IFR)
Flight in which the ATC system assures collision avoidance between aircraft operating in accordance with IFR and CVR in Positive Controlled Airspace. When operating outside Positive Controlled Airspace, pilot responsibility with respect to collision avoidance differs according to flight weather conditions. Instrument Flight Rules may be defined differently in the 1980's than they are today. [e]
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Instrument Landing System
A runway approach system for unfavorable weather conditions consisting of equipment both on the aircraft and on the ground. There are three basic systems on the ground: The localizer, which broadcasts a 100-MHz signal that locates the far end of the runway: the glide slope, which broadcasts a 150 MHz signal from sides of the approach end of the runway and defines the limits within which the aircraft must be for proper approach; and the extended center marker, which broadcasts at 75 MHz from several antennas defining the center of the extended runway. [e]
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Intelligent agents
The use of software to emulate or simulate human processes will be desired for completing scenarios that do not require actual human intervention. These intelligent agents will need to make decisions in place of human pilots, controllers, and airline operations center (adc) dispatchers. These decisions may be of a tactical or strategic nature and the decision rate or amount of decisions per time period must be robust and allow for studies on workload. Also, varying levels of fidelity will be required from simple decision tree logic to advanced artificial intelligence. [b]
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Intent Information
The simulation will have the capability to augment the data contained in the flight plan of individual aircraft with information that the pilot enters to notify the system of his immediate intentions. This intent information can be considered "fine-tuning" of the flight plan data while the aircraft is en-route. Typical examples include changes in altitude or heading for traffic or weather considerations. This information provides the capability to optimize travel time and costs by predicting incursions based upon the filed flight plan and the specific intents of the pilot. [b]
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L
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Live Data
The simulation will be capable to download live data from the NAS to establish the initial condition for an experiment or to provide a baseline condition. The NAS aircraft feed will include all the flight plan data for each of the aircraft located in the area of concern as well as the location, speed, heading, altitude and identification. [b]
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Low Fidelity Model
Model that exhibits the functionality necessary for the simulation system to consistently portray the NAS for the primary research objectives in a high-level manner. [b]
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Loran
Originally standing for Long-Range Navigation, it is a form of hyperbolic navigation in which a system of signals is transmitted as pulses. There are master stations, each operating with one slave station. The difference in time of receipt of radio pulses from one such pair of stations is measured and the resultant time difference locates the aircraft on a hyperbolic line. When this is crossed with a second hyperbolic line from another pair of stations a fix is obtained. Letter designations such as A, C, and D denote different broadcasting operating frequencies. [e]
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M
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Medium Fidelity Model
Model that exhibits the functionality necessary for the simulation system to consistently portray the NAS for primary research objectives, infrastructure sensitivity analysis, and cost/benefit analysis. [b]
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Model
1. Any detailed reproduction. 2. The critical components of a simulation system. These would include, but not be limited to:
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Airspace/Map Overlay system - all airspace defined by boundary, airway, jetway, navigation fix/s files.
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Target Generator module/system - model the moving target behavior, both on the ground and in the air, for display on controller sector/s. These targets could be ground vehicles as well as aircraft including helicopters.
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Environment - used within system/scenario (wind model, temperature, barometer, etc.).
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System user interface - used to initiate system and scenario configuration/s, apply system timing for both local and remote systems.
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ATC display generator - present sector configuration and target representations to controller personnel.
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Connectivity - High Level Architecture (HLA).
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Communications - voice, both radio and land-line.
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Pseudo-Pilot stations and functionality - manipulate the aircraft (altitude, speed, direction changes, etc.) per controller command.
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A physical, mathematical, or otherwise logical representation of a system, entity, phenomenon, or process. A mathematical abstraction of the behavior of an object at a level appropriate for the planned simulation. Models are usually instantiated in simulation source code. The collective methods by which a simulation uses measurable characteristics to represent itself or other entities at a particular level of fidelity.
[b]
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Modeling
A set of mathematical constructs or equations and parameters that describe a phenomenon or concept. [b]
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Metric
1. A measure of some defined phenomena. 2. A measure of schedule, cost, or technical progress or performance. [b]
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Mixed Airspace
Airspace containing aircraft flying under Instrument Flight Rules (IFR) or Visual Flight Rules (VFR). [e]
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Mode C Interrogation
Civil transponder interrogation asking for aircraft altitude. [e]
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Model 3A Interrogation
Civil transponder interrogation asking for aircraft altitude. [e]
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N
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National Airspace System (NAS) and Automatic Radar Control Terminal System
The automation being implemented in the present Third Generation System. The committee feels that by expanding the semi-automation of NAS Stage A and ARTS III to include spacing, and conflict prediction and resolution, and by adding the data link, two or three times the present traffic, could probably be handled by the same controller work force. [e]
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National Airspace System (NAS) Common Reference
A method for registering all NAS components having location, volume, and time components into a common index. Items registered include the static (e.g., topographical features, obstructions); static with status (e.g., runways, Very High Frequency Omnidirectional Ranges (VOR), radars, radios, Letters of Agreement, Traffic Flow Management agreements); and the dynamic (e.g., weather cells, flight trajectories). NASCR is not a coordinate system; rather, it is a common and efficient means of identifying, accessing, and evaluating interactions between all such NAS components. As an example, flight information can be distributed to a facility or position based on a registered volume of interest within NASCR. [c]
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National Airspace System (NAS) Stage A and Stage B En Route System
An automated system of en route ATC providing alphanumeric information en route radar displays. The present system (Stage A) will serve as the basis for evolutionary growth of the future automated system (Stage B). Additional systems to be incorporated include flow control, conflict detection and resolution, and electronic tabular display. [e]
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National Airspace System (NAS) Wide Information Service
Analogous to System Wide Information Management (SWIM) in the international arena. See SWIM. [c]
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Navaid
Radio Navigation aid. [e]
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Near Midair Collision (NMAC)
A NMAC is considered to have taken place when two aircraft unintentionally pass within 250 feet of each other. [e]
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Non-Advocate Review (NAR)
(NASA usage) Provides an independent verification of a candidate program or project's plan, LLC status, and readiness to proceed to the next phase of the program's life cycle. A NAR is conducted by a team comprised of highly knowledgeable specialists from organizations outside of the advocacy chain of the program or project being reviewed. A NAR assesses 1) compatibility with NASA policy and baseline documentation. 2) Clarity of goals and objectives, 3) adequacy of management plans, including organizational structure and key personnel credentials, 4) technical complexity, risk assessment and risk mitigation plans, and, 5) thoroughness/realism of technical plans, schedules, and cost estimates (including reserves and descoping options). [b]
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Non-Real-Time
A type of simulation in which the passage of time is either slower or faster than the real world. [b]
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O
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Omni-System Supported Coordination (Omni-SYSCO)
SYSCO based on expert system type logic will exist both on and between airborne and ground elements of the NAS. The ground component will support automated negotiation for operations outside the normal operations between different facilities. The SYSCO between the airborne and ground will take the form of automated 4D trajectory negotiation via data link. System Wide Information Management (SWIM) ensures that all other elements that may be impacted by the negotiation are updated or included in the negotiation, as appropriate. [c]
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Ontologies
A specification of conceptualization.
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Operational Concept
An operational concept describes what a specific set of air transportation system capabilities does or will do to provide specific operational services to an identified set of system users. These operational services include: 1) Flight Planning, 2) Separation Assurance, 3) Situational Awareness & Advisory, 4) Navigation & Landing, 5) Traffic Management - Strategic Flow, 6) Traffic Management - Synchronization, 7) Airspace Management, 8) Emergency/Alerting, and 9) Infrastructure/Information Management. An operational concept may be limited to a sub-set of these services; for example, the operational concept might be "the air transportation system provides separation assurance between aircraft." [b]
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P
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Parabolic Profile
Aircraft operating in a manner described as continuous climb to top-of-descent and then continuous descent. (Cruise climb to cruise descent clearance.) [c]
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Part-task Analysis
An analysis, usually involving simulation, which examines only a portion of a person's duties and/or responsibilities. Usually part-task analysis will focus on a particular aspect of a person's tasking and examine, in detail, many parameters or aspects of that task, the human's behavior and movements in performing that task, and critical interfaces that are involved in that task. [b]
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Passenger Flow
A passenger flow model provides inputs for door-to-door mobility simulation studies. This flow model addresses a passenger's route and method of travel from the beginning of their trip (home or office) to their destination. This flow model interfaces with other models, such as terminal facility simulations, to place passengers at the appropriate gates for departure and again at arrival gates and then conducting simulated flights to the final destination. [b]
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Pilot Interface
The pilot interface should allow for the emulation or simulation of pilots and flight deck crewmembers. A computer simulated interface would likely need to provide some sort of voice recognition and speech synthesis for communication purposes, as well as, the proper inputs and outputs for the flight deck simulation. There may also be a need for pattern recognition or some simulated version of "seeing out the window". [b]
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Positive Controlled Airspace (PCA)
Exist above 18,000 feet in the Northeastern portion of the United States and above 24,000 feet in the remainder of the country. In PCA all aircraft are under IFR control and the ATC system provides separation service between all aircraft. [e]
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Point-to-Point (PTP)
Traveling from one destination to another without any intermediary stops. An example would be an aircraft flying from San Francisco to Washington D.C. without making a stopover in Chicago. [b]
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Preliminary Design Review (PDR)
(NASA usage) A formal review of the requirements and design work done to date presented to management and peers for technical review and comment. It should be expected that at the end [of a PDR that] all concerned parties will have a good idea of what has been done to date, what is planned for the future, how future aims will be accomplished and the technical, managerial, and cost risks associated with the planned approach, and how these risks will be mitigated. [k]
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Project Beacon
A scientific, engineering review of ATC conducted by the FAA at the request of President Kennedy in 1961. The review was also to prepare a practicable long-range plan to ensure efficient and safe ATC. [e]
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R
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Radar
A general term applying to both primary radar and transponder beacons. [e]
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Radar Beacon
A radar receiver-transmitter that transmits a strong coded signal whenever its receiver is triggered by an airborne interrogating radar. The coded reply can be used to determine position in terms of range and bearing from the beacon. Also called beacon, radar, and radar transponder. [e]
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Radar Identification
In ATC, radar identification is the process of ascertaining that a radar target is the radar return from a particular aircraft already in the ATC system or about to enter it. [e]
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Real-Time
A type of simulation in which the passage of time replicates the passage of time in the 'real' world. [b]
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Remotely Operated Aircraft
Pilotless aircraft, including a drone, which are remotely controlled by an external source either airborne or on the surface. [c]
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Representation of Systems
See Ontology.
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Required Navigation Performance (RNP)
Statement of the navigation performance accuracy necessary for operation within a defined airspace. (NOTE: There are additional requirements beyond navigation performance accuracy applied to a particular RNP type.) [c]
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Resectorization
A permanent reorganization of the geographic sectors controlled [e]
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Rho-Theta System
A navigation system based on azimuth (theta) and range (rho) relative to a properly equipped radar center. [e]
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Route
A defined path, consisting of one or more courses, which an aircraft travels in a horizontal plane over the surface of the earth. [e]
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Runway Number Designation
Numerical designation of runways, e.g., 4/22 runways denotes the compass heading of a runway to the nearest 10 degrees. For example the 4 stands for 40 degrees and 220 degrees, where the 4 would designate the south approach to the runway (heading of 40 degrees), and the 22 would designate the northeasterly approach (heading of 220 degrees). Further designations of L and R indicate the left or right sides of dual runway systems. [e]
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Runway Threshold
The physical beginning of a runway. [e]
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S
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Scenario
A description of an activity, in narrative form, as a sequence of actions showing how a transition from one state to another might occur. [b]
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Schema
A diagrammatic representation or framework. [d]
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System Evaluation and Assessment (SEA)
The primary goal of the System Evaluation and Assessment (SEA) sub-project of VAMS is to meet the requirement to develop evaluation methodologies, operational scenarios, metrics and to assess potential operational concepts and technologies to meet the forecasts across the trade space. The secondary goal of the SEA sub-project is to conduct system-level assessments of the VAMS concept sets by addressing potential benefits, identifying risks and limits, and evaluating performance, safety, operations, NAS infrastructure and transition challenges. [b]
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See and Avoid
That type of flight operation in which pilots are required by Civil Air Regulators to avoid collision with other aircraft by observing specific right of way and other rules of flight. This is usually referred to as Visual Flight Rules (VFR) flight. [e]
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Separation Minima
The minimum longitudinal, lateral, or vertical distances by which aircraft are spaced through application of ATC procedures. [e]
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Service Provider
Used generically to refer to any air traffic service employee or Department of Defense member who provides separation assurance, traffic management, information management, aviation information, navigation, landing, airspace management, SAR, or aviation assistance services for NAS users. [c]
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Simulation
1. The integration of models, usually as computer modules, that uses the passage of time as one parameter. 2. A method for implementing a model over time. Also a technique for testing, analysis, or training in which real-world systems is used, or where a model reproduces real-world and conceptual systems. [a]
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System-Level Integrated Concepts (SLIC)
The primary goal of the System-Level Integrated Concepts (SLIC) sub-project is to meet the project requirement to: "create operational concepts and conceptual architectures that can be used to define the next generation air transportation system." The secondary goal is to drive and validate the virtual airspace simulation and modeling capabilities coming out of the Virtual Airspace Simulation Technologies (VAST) sub-project and provide concept inputs for evaluation and assessment by the System Evaluation and Assessment (SEA) sub-project. Throughout the concept development process, the SLIC sub-project will also identify the necessary tools/technologies required to implement the envisioned next generation Air Traffic Management tools. [b]
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Stationkeeping
Stationkeeping helps maintain order in a structured aircraft population, as in military formation or pattern flying, and can do the same in high density landing and take-off conditions at busy civilian airports, or en-route in transatlantic air lines. The stationkeeping display is either a plan presentation of the relative position of all aircraft or a flight director display indicating how to fly in order to maintain proper longitudinal, lateral, and vertical position relative to selected reference aircraft. The use of airborne stationkeepers enables aircraft to maintain safe relative positions and flight direction without visual contact; Visual Flight Rules (VFR) spacings can be maintained more precisely with proper stationkeeeping equipment than without. Stationkeeping can also be provided from a control ground station. [e]
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Storyboard
A sequence of scenes within a scenario usually outlined by graphic images and descriptive dialogue. [b]
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Surface
1. That portion of the air traffic control system that describes an aircraft or other object of interest, as being on the surface of an airport, usually on a ramp, taxiway, or runway. 2. A type of operational concept that describes the rules and procedures associated with the behavior of airport surface traffic. This includes planning and monitoring of airport traffic, intra-airport communications, and availability of airport environmental data and aircraft state data as pertains to airport traffic. [b]
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Surface Traffic Management
Defined as a subset of Air Traffic Management activities that directly affects surface operations or that are directly influenced by surface movement. Surface Traffic Management includes the overall suite of surface management applications that provides NAS users and service providers with the ability to maximize airport capacity and throughput while maintaining the safety of airport operations. It also involves activities on and off the airport movement area and within the air traffic control tower, ramp tower, flight deck, FOC, and traffic management units. [c]
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System-level (gate-to-gate)
A type of Operational Concept that describes or discusses all aspects of operations and management of the NAS. [b]
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System Supported Coordination
The interaction of ground/ground automated systems. See Omni-SYSCO [b]
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System Wide Information Management (SWIM)
This functionality or service is analogous to NAS Wide Information System (NWIS). In addition to a pool of common information, SWIM provides context-sensitive information to NAS elements that may require it. (This includes flight deck access to the information, such as weather and resource status.) SWIM would serve as the mechanism to facilitate the development and use of automated intelligent agents on behalf of the independent processes across the NAS (and global system). Provides timely distribution of relevant, validated, up-to-date information to those who have the required authorization to access it. It is also consistent with the European concept of the same title. As such, it becomes the bridge to the global management of aviation information in support of the common operational concept elements. [c]
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T
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Tactical Air Navigation (TACAN)
A system of navigation in which a single Ultra High Frequency transmitter sends out signals that actuate airborne equipment and provides range and bearing indications with respect to the transmitter location when interrogated by another transmitter on the aircraft. Each TACAN station broadcasts a location identifying Morse code signal at regular intervals. [e]
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Taxi-In Delay
The difference between an aircraft touchdown time and its gate arrival time, minus a standard taxi-in time for a particular type of aircraft and airline at a specific airport. [b]
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Taxi-Out Delay
The difference between the time of lift-off and the time the aircraft departed the gate, minus a standard taxi-out time established for a particular type of aircraft and airline at a specific airport. [b]
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Taxonomies
A systematic classification, which is generally hierarchical. [b]
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Terminal
1. The portion of airspace that converts to en route airspace. 2. Concepts dealing with the planning and implementation of departures and arrivals. This includes predicting and implementing runway allocations for takeoff and landing, dissemination of environmental data to ease planning, and methods to increase navigation accuracy for better flow management. [b]
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Terminal Area
Airspace and surface area including airports within a pre-designated boundary and up to a pre-designated altitude above the surface. [e]
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Terrain
Terrain modeling will be included to represent accurate altitude information for airport movement as well as departure and arrival parameters. Additionally, terrain model will be used for navigational aid positioning. (Some VORs are located at high elevations, and are not co-located with an airport). Depending on the fidelity of the entire system, range and reception of navigational aids will depend on terrain (altitude) information to accurately model this utility. The terrain modeling will also affect weather movement, especially three-dimensional wind environments. [e]
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Testing
Testing of the VAST must include all individual subsystems and the fully integrated system. The performance of each subsystem must be representative to the existing NAS, and the performance of the fully integrated system must be consistent with subsystems and meet the design specifications. Testing must include full functional checks as well as maximum load checks to ensure the completeness and the integrity of the overall system. [b]
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Tool
Modules that reside along with Utility modules to allow for additional input or extraction of data to or from the core system, or monitor the system remotely. These may include but not limited to:
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V-Lab type monitor interface
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Weather input from remote location/files
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Data Collection - collection of all defined parameters with the capability of post-processing that data into desired formats.
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Routing tool - capability of creating "canned" primary routes and creating custom routes or modification due to scenario requirements (weather or traffic, etc.) [h]
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Toolset
VAST uses the term toolset to describe a collection of entities used for preparing, developing, configuring, executing, and analyzing a simulation. The toolset can included utilities to access information from data sources and data bases, to implement scenarios, to select and integrate models and agents representing elements of the simulation, to command and control the simulation, and to analyze simulation data. Additionally, toolset can refer to the collection of agents, models and simulations available for constructing larger scale simulations. [b]
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Track
The flight path of an aircraft over the surface of the earth. [e]
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Trade Space
The trades between specific parameters under consideration in an analysis, comparing experimental results against measures of merit. Only one or a few parameters may be optimized at the expense of others. [b]
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Traffic Flow Management Agreement
Refers to an interdependent response to a current or projected operational environment that is mutually acceptable to both the user and service provider. The agreements may be as broad as severe weather avoidance program (SWAP) initiatives or as narrowly focused as a specific aircraft as in the case of controlled time of arrival procedures. [c]
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Traffic Flow Management Interface
The traffic flow management interface allows emulation or simulation of the national command center located in Herndon, Virginia. This capability allows for national policy studies, as well as, interaction with airline traffic at the national level. [b]
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Traffic Pattern
The traffic flow that is prescribed for aircraft landing at, taxing on, and taking off from an airport. [e]
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Transition Airspace
The boundary within which exists terminal airspace. Transit on airspace lies 40 to 60 miles from the terminal and is the area where an en route controlled aircraft will normally be held, when necessary, prior to commencing approach. It is the area of transition from en route ATC to approach ATC. [e]
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Transponder
An airborne automated radar receiver-transmitter from which a coded response is triggered by interrogation from a ground transmitter. Response normally contains information on aircraft identification, altitude and airspeed, and occasionally, heading altitude rates and position. [e]
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Tube
Pre-designated three-dimensional path through airspace, normally assigned under high density and instrument flight conditions to aircraft having maximum equipment. [e]
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U
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Uncontrolled Airspace
Underlies controlled or mixed airspace. Aircraft operating solely in uncontrolled airspace are not presently required to carry navigation, communications, or transponder equipment; however, communications equipment meeting a limited channel capability requirement is needed for operations conducted at a tower-equipped field. [e]
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User
User and NAS user refer to any customer that uses the air traffic system, including commercial aviation, general aviation, commercial space transportation providers, and Department of Defense aviation and space. [c]
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User Preference
An unconstrained petition by the user based solely on his/her individual business objectives or operating procedures. [c]
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User Request
A petition made by the user of the Air Traffic Management system that incorporates expected system constraints. [c]
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Utilities
1. Software modules that are inherent to the core system to allow for basic data input that drives a particular model. These would include but not limited to:
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Navigational data - airways, jetways, standard instrument departures, standard terminal arrival routes, VORs, etc.
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Airspace definition - define all airspace utilized in a scenario, include sector type, sector center, default range, sector name and identification, radar positional information and update rate (sweep). This would also include the definition of Center boundaries, special use airspace, etc.
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Aircraft definitions - define aircraft with appropriate performance parameters [h]
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V
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Validation
VAST must demonstrate satisfactorily and match the existing NAS performance across a range of parameters including traffic flow, response time, and emergency handling of variations of each key parameters, (e.g., traffic flow, weather, and accident), in simulating the control and managing of airspace operations within scenario selected Centers, Terminal Radar Approach Control, and terminal. [b]
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Virtual Airspace Modeling and Simulation (VAMS)
The VAMS Project will identify advanced operational concepts, concepts of use and architectures for the air transportation system. It will establish and maintain a modeling and simulation capability that will enable the analysis and assessment along with the potential impact of these and other potential advances to the NAS to be continuously assessed, with a level of fidelity never before achieved. This project is part of the NASA Airspace Systems Program being conducted in cooperation with the Federal Aviation Administration (FAA). [b]
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Virtual Airspace Simulation Technologies (VAST)
The goals of the VAST Sub-project effort are to meet the requirement to "develop and validate modeling and simulation tools providing the multi-objective (cost, throughput, and safety) trade space to analyze Air Traffic Management concepts to meet forecasted demands of the 2020's" with the following overarching goals:
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Develop the capability to model and simulate the behavior of the air transportation system to never-before-achieved levels of fidelity.
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Develop an open, interoperable architecture that will serve as the foundation for the next generation simulation and analysis system for the NAS.
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Recommend NAS community-wide standards addressing critical aspects of simulation interoperability. [b]
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Vehicles
(In model terms) All the information regarding vehicles must be fully defined. This information must include, but not be limited to, the state vector or each aircraft, the physical geometry of the aircraft, the aircraft FAA type information and the on board Communication, Navigation, and Surveillance (CNS) equipment. [b]
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Verification
The process of determining the degree to which a model is an accurate representation of the real world from the perspective of the intended uses of the model. [b]
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Very High Frequency Radio Omnirange
A ground based radio station that propagates an unlimited number of "radials". On board an aircraft, the signals are converted to visual direction indications expressed as magnetic compass courses to and from the transmitter station. [e]
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Visual Flight Rules (VFR)
To perform the collision avoidance function, the rules take certain weather conditions into account and specify basic "rules of the air". [e]
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VORTAC
An air navigation system combining VHF omnirange (VOR) and tactical air navigation equipment. [e]
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W
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Weather
(In modeling terms) A weather environment will need to be provided to accurately represent real world conditions, in a three-dimensional arena. This will be primarily wind data and the effects the wind will have on all targets within the scenario setting, including aircraft simulators. Additionally, weather data/information, such as cloud conditions, visibility, etc., will need to be generated and displayed in a format that will suitable for visual presentation to external elements such as aircraft or tower simulators. Weather data could originate from many sources, both current and forecasted, but its input should be standardized to maintain repeatability within a scenario outline. This weather must be of high enough fidelity to allow both strategic and tactical decisions to be made by all the stakeholders. [b]
Category I Weather: Weather allowing a forward visibility of 1/2 mile. Under Category I, the pilot should be able to see the runway from an altitude not in excess of 200 feet. [e]
Category II Weather: Weather allowing a forward visibility of 1/4 mile. The pilot should be able to see the runway from an altitude not in excess of 100 feet. [e]
Category III Weather: Runway effectively not visible from any altitude and all landing decisions are left to the pilot. Category III breaks down into three subcategories.
III A Forward visibility is 700 feet, a distance sufficient for a landing abort.
III B Forward visibility is 150 feet, a distance sufficient to permit taxing.
III C Zero forward visibility. [e]
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[c] RTCA, Inc.
[i] Hays & Singer, 1989, p. 50
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