Defining and Measuring Aircraft Delay and Airport Capacity Thresholds (2014)

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61 TERM DEFINITION Actual Time of Arrival (ATA) The actual time an aircraft arrives at its parking position or gate; when the parking brake is set. Actual Time of Departure (ATD) The actual time an aircraft leaves its parking position or gate. Term used in flight planning/following to document time of departure from a point. Air Route Traffic Control Center (ARTCC) A facility responsible for controlling aircraft en route in a particular volume of airspace at high altitudes between airport approaches and departures. Air Traffic Control System Command Center (ATCSCC) The FAA command center that balances air traffic demand with system capacity in the National Airspace System (NAS). It is committed to managing the NAS in a safe, efficient, and cohesive manner. Air Traffic Control Tower (ATCT) The FAA tower(s) at an airport from which air traffic controllers track and direct flight operations at the airport and the surrounding airspace. Air Traffic Organization (ATO) The operations arm of the FAA. ATO is America’s air navigation service provider. The ATO is set up as a performance-based organization whose customers are commercial and private aviation and the military. Aircraft Communications Addressing and Reporting System (ACARS) A digital data link system for transmission of short, relatively simple messages between aircraft and ground stations via radio or satellite. Airfield The portion of the airport on which aircraft operate while on the ground. The airfield includes the runways, taxiways, ramp/apron, etc. Airline Service Quality Performance (ASQP) Operational flight database maintained by FAA that contains flight data reported by airlines that carry at least 1% of all domestic passengers. Airport Surface Detection Equipment (ASDE) A runway safety tool that enables air traffic controllers to detect potential runway conflicts by providing detailed coverage of movement on runways and taxiways. Airspace The space above the ground that planes use. Aircraft can fly in the airspace freely or on defined routes that are controlled by the FAA. For safety purposes, commercial and military aircraft almost always follow defined routes to travel from one airport to another. Annual Enplanements The number of passengers boarding an airplane including certified, commuter, air taxi, foreign, and in-transit planes annually. Annual Service Volume (ASV) A planning term that describes the number of annual aircraft operations possible at an airport with an acceptable amount of delay. The measure is specific to individual airports because it is derived from their own particular capacity characteristics. A P P E N D I X C Glossary of Terms

62 Apron The airfield facility where the loading and unloading of passengers and cargo, the refueling, servicing, maintenance and parking of aircraft, and any movement of aircraft, vehicles and pedestrians necessary for such purposes occurs. ARINC Global company that provides systems on-board aircraft for voice and data communications. Automatically records specific messages in flight useful for analyzing flight travel and delay. Aviation System Performance Metrics (ASPM) FAA database that contains detailed out, off, on, in times for flights at 77 U.S. airports. The system contains estimated nominal or unimpeded taxitimes for estimating flight delays. Benefit-Cost Analysis (BCA) A systematic process for calculating and comparing benefits and costs of a project. It involves comparing the total expected cost of each option against the total expected benefits, to see whether the benefits outweigh the costs, and by how much. Block Time The period from the moment the chocks are withdrawn and brakes released or moorings dropped, to the return to rest or take-up of moorings after the flight. Bureau of Transportation Statistics (BTS) Statistical agency of the U.S.DOT whose mission is to create, manage, and share transportation statistics’ knowledge. BTS is housed within RITA. Capacity Coverage Chart (CCC) A way to summarize the range of capacities at an airport and the frequency with which various levels of capacity are available. The chart shows how much capacity is available for what percentage of time. Concourse The area located in an air carrier’s terminal where the gates can be found. Connecting Hub An airport used by airlines to transfer/connect passengers from one airport/ origin to another airport/destination. En Route Airspace The airspace used by aircraft between airports that are tracked by regional control centers rather than by air traffic control towers at the airports. The en route airspace is comprised of en route airways that are predefined routes that aircraft typically follow. En Route Delays An en route delay is a delay at an airport, area, or geographical point en route before proceeding to the destination. En Route Service Delivery Point (SDP) The demarcation points between services and ground-based user systems. Federal Aviation Administration (FAA) An agency of the United States DOT that has authority to regulate and oversee all aspects of civil aviation in the United States. Ground Delay The number of minutes of waiting or stopping incurred by an arriving or departing aircraft during its transit to/from the runway. Ground delay is comprised of ramp delay, taxi delay, and departure queue delay. Hub FAA uses this term to refer to airports that board at least 0.05% of all annual passengers in the United States (large hub >1%, medium hub 0.25%–1%, small hub 0.05%–0.25%). Airlines typically use the term for a large airport at which a legacy carrier connects a large portion of passengers between arriving and departing flights. Typically at a hub, the major airline/airlines represent the majority of the flight activity. Hub-and-Spoke System A system of air transportation in which local airports offer air transportation to a central airport where long-distance flights are available. Instrument Flight Rules (IFR) The rules and regulations established by the FAA to govern flight under conditions in which flight by outside visual reference is not safe. IFR flights depend upon flying by reference to instruments in the flight deck, and navigation is accomplished by reference to electronic signals.

63 Instrument Meteorological Conditions (IMC) An aviation flight category that describes weather conditions that require pilots to fly primarily by reference to instruments, and therefore under instrument flight rules (IFR), rather than by outside visual references under visual flight rules (VFR). Typically, this means flying in low visibility, low ceiling, and/or bad weather. Level of Service A performance metric used in facility planning/evaluation. For terminals, LOS refers to the space provided to a passenger in various areas of the terminal; can also be applied to other areas such as highways/curbsides and may refer to a utilization, delay, travel time, wait, etc. Marginal VFR Air traffic rules that apply when the ceiling is 1,000 feet to 3,000 feet above ground and/or visibility of 3–5 miles such that VFR can no longer be flown. Maximum Throughput Capacity (or Saturation Capacity) The expected/or average number of operations (takeoffs and landings) that can be performed in 1 hour on a runway system without violating ATC rules, assuming continuous aircraft demand. Million Annual Passengers (MAP) The number of annual passengers at an airport in unit million. National Airspace System (NAS) The network of U.S. airspace: air navigation facilities, equipment, services, airports, rules, regulations, procedures, etc., that enables safe and expeditious air travel. Next Generation Air Transportation System (NextGen) The name given to a new National Airspace System due for implementation across the United States in stages between 2012 and 2025. To implement this, the FAA will undertake a wide-ranging transformation of the entire U.S. air transportation system. This transformation has the aim of reducing gridlock, both in the sky and at the airports. Official Airline Guide (OAG) Originally a source (for a fee) to obtain published flight schedules for airports around the world. Now, the company offers several different types of flight schedule, statistic, and operations data. On-to-In The time it takes for an aircraft to travel from landing on the runway until the aircraft has parking in its gate/parking position. Operations Network (OPSNET) The official source of NAS air traffic operations and delay data. The data collected through OPSNET is used to analyze the performance of the FAA’s ATC facilities. Out-to-Off The time it takes for an aircraft to travel out from a gate until the aircraft has lifted off the runway. Also known as taxi-out time. Overflight An aircraft traveling over an active airport whose presence may impact the capacity of that airport. In other words, an aircraft flying over an airport of interest, perhaps to travel to/from a nearby airport, for which separation and tracking must be taken into account for the airport of interest. Pareto Curves/Pareto Frontiers The set of choices that are Pareto efficient. The Pareto frontier is particularly useful in engineering: by restricting attention to the set of choices that are Pareto efficient, a designer can make tradeoffs within this set, rather than considering the full range of every parameter. In airport capacity terms, the Pareto curve displays the capacity at various tradeoffs of arrivals and departures. Performance Data Analysis and Reporting System (PDARS) Developed through collaboration with FAA and NASA, a database that collects real-time data from flights every 2 seconds. Data is captured for all IFR flights that fly through the en route airspace. Practical Hourly Capacity (PHCAP) The expected number of movements that can be performed during 1 hour on a runway system with an average delay per movement of 4 minutes. It is typically 80–90 percent of maximum throughput capacity.

64 Ramp The area around an airport terminal at which aircraft park, are serviced, and are loaded/unloaded. This area includes the gates and surrounding support area. This term is typically interchangeably used with apron and tarmac, although there may be operational subtleties that technically result in differences between these three areas. Research and Innovative Technology Administration (RITA) RITA is an office within the U.S.DOT that encompasses BTS and several other transportation research/data organizations. Runway Departure Queue Delay The queues of departure aircraft that form at runways and the delays aircraft incur while waiting in these queues. When the departure demand temporarily exceeds the capacity of the runway, aircraft will queue. Scheduled Time of Arrival (STA) The desired time that an aircraft should cross a certain point (landing or metering fix) or park at its gate. It takes other traffic and airspace configuration into account. Scheduled Time of Departure (STD) The time of departure from the gate according to the published schedule. SIMMOD The FAA Airport and Airspace Simulation Model, which is a discrete-event simulation model that tracks the movement of individual aircraft as they travel through the airspace and on the ground. Slot-Controlled/High Density Rule The High Density Rule (or slot rule) is a federal regulation, 14 CFR §93.123, which limits the aircraft operations (landings or takeoffs) occurring each hour. The FAA use it as a measure to reduce delays. Spoke An O&D airport for an airline that has other hubs or focus cities. Typically for a spoke, the airline has flights to/from only their hubs and other focus cities and uses a limited number of gates. For example, Dallas/Fort Worth is a spoke for all airlines except American, and Atlanta is spoke for all airlines except Delta and Southwest. Tarmac See ramp. Taxi-In/Taxi-Out The final phase (taxi-in) of a flight is a reverse of the first phase (taxi-out). The aircraft taxies under its own power onto the taxiway and to a gate. Or the aircraft taxies under its own power from its gate to the runway. Generally, taxi- out includes the time in departure queue. Terminal A building/facility at the airport that accommodates passenger processing facilities. A terminal may include gates but is typically defined by the fact that it includes the landside facilities (facilities used to process originating/terminating passengers) and curbsides. Total Airspace and Airport Modeler (TAAM) A large-scale, detailed fast-time simulation package for modeling entire air traffic systems. It is used to model airspace and airports to facilitate planning, analysis, and decisionmaking. TRACON (Terminal Radar Approach Control) FAA facility that generally guides air traffic approaching and departing airports within a 30- to 50-mile radius and up to 10,000 feet (exact dimensions will vary). Traffic Flow Management The craft of managing the flow of air traffic in the NAS based on capacity and demand. The goal of TFM is to control the overall flow of traffic in the National Airspace System. Traffic Flow Management System Counts (TFMSC) FAA database that contains aviation traffic and delay data for all IFR-filed aircraft in the United States. U.S. Department of Transportation (U.S.DOT) A federal Cabinet-level department of the United States government concerned with transportation. Its mission is to ensure a fast, safe, efficient, accessible, and convenient transportation system.

65 Visual Flight Rules (VFR) A set of regulations that allow a pilot to operate an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minimums, as specified in the rules of the relevant aviation authority. Visual Meteorological Conditions (VMC) An aviation flight category in which visual flight rules (VFR) are permitted; ceiling greater than 3,000 feet above ground and visibility greater than 5 miles. Conditions exist in which pilots have sufficient visibility to fly the aircraft maintaining visual separation from terrain and other aircraft. Visual meteorological conditions are usually defined by certain visibility minima, cloud ceilings (for takeoffs and landings), and cloud clearances. Wake Turbulence A turbulence that forms behind an aircraft as it passes through the air. Wake turbulence is especially hazardous during the landing and takeoff phases of flight.

Abbreviations and acronyms used without definitions in TRB publications: A4A Airlines for America AAAE American Association of Airport Executives AASHO American Association of State Highway Officials AASHTO American Association of State Highway and Transportation Officials ACI–NA Airports Council International–North America ACRP Airport Cooperative Research Program ADA Americans with Disabilities Act APTA American Public Transportation Association ASCE American Society of Civil Engineers ASME American Society of Mechanical Engineers ASTM American Society for Testing and Materials ATA American Trucking Associations CTAA Community Transportation Association of America CTBSSP Commercial Truck and Bus Safety Synthesis Program DHS Department of Homeland Security DOE Department of Energy EPA Environmental Protection Agency FAA Federal Aviation Administration FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration FRA Federal Railroad Administration FTA Federal Transit Administration HMCRP Hazardous Materials Cooperative Research Program IEEE Institute of Electrical and Electronics Engineers ISTEA Intermodal Surface Transportation Efficiency Act of 1991 ITE Institute of Transportation Engineers MAP-21 Moving Ahead for Progress in the 21st Century Act (2012) NASA National Aeronautics and Space Administration NASAO National Association of State Aviation Officials NCFRP National Cooperative Freight Research Program NCHRP National Cooperative Highway Research Program NHTSA National Highway Traffic Safety Administration NTSB National Transportation Safety Board PHMSA Pipeline and Hazardous Materials Safety Administration RITA Research and Innovative Technology Administration SAE Society of Automotive Engineers SAFETEA-LU Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) TCRP Transit Cooperative Research Program TEA-21 Transportation Equity Act for the 21st Century (1998) TRB Transportation Research Board TSA Transportation Security Administration U.S.DOT United States Department of Transportation