A-Weighted Sound (dBA) − A system for measuring sound energy that is designed to
    represent the response of the human ear to sound. Energy at frequencies more readily
    detected by the human ear is more heavily weighted in the measurement, while
    frequencies less well detected are assigned lower weights. A-weighted sound
    measurements are commonly used in studies where the human response to sound
    is the object of the analysis.

    Air Route Traffic Control Center (ARTCC or Center) − A FAA facility established to
    provide air traffic control service to aircraft operating on Instrument Flight Rules (IFR)
    flight plans within controlled airspace during the en route portion of flight.

    Air Traffic Control (ATC) − A service operated to promote the safe, orderly, and
    expeditious flow of air traffic.

    Airman’s Information Manual (AIM) − A publication containing basic flight information
    and ATC procedures, designed primarily as a pilot’s information and instructional manual
    for use in the National Airspace System.

    Airport Elevation − The highest point on an airport’s usable runways, expressed in feet
    above mean sea level (MSL).

    Airport Improvement Program (AIP) − A Federal funding program for airport
    improvements. Congress periodically reauthorizes AIP with funding appropriated from
    the Aviation Trust Fund. Proceeds to the Trust Fund are derived from excise taxes on
    airline tickets, aviation fuel, etc.

    Airport Layout Plan (ALP) − A scaled drawing of existing and proposed land and f
    acilities necessary for the operation and development of the airport. The ALP shows
    boundaries and proposed additions to all areas owned or controlled by the airport
    operator for airport purposes, the location and nature of existing and proposed airport
    facilities and structures, and the location on the airport of existing and proposed
    non-aviation areas and improvements thereon.

    Airport Operations − Landings (arrivals) and takeoffs (departures) from an airport.
    Airport Surveillance Radar (ASR) − A radar system which allows air traffic controllers to
    identify an arriving or departing aircraft’s distance and direction from an airport.

    Airport Traffic Control Tower (ATCT) − The airport traffic control facility located on

    an airport that is responsible for traffic separation within the immediate vicinity of the
    airport and on the surface of the airport.

    Airway − A corridor of controlled airspace whose centerline is established by radio
    navigational aids (NAVAIDs). Low altitude airways (between 3,000 and 18,000 feet MSL)
    are identified by number with the letter V as a prefix. High altitude airways (above 18,000
    feet MSL) are known as Jet airways and are identified by number with the letter J as a

    Ambient Noise − The total sum of noise from all sources in a given place and time.

    ANCA - Airport Noise and Capacity Act (1990)

    Approach Light Systems (ALS) – A series of lights that assists the pilot when
    aligning aircraft with the extended runway centerline on final approach.

    Attenuation − Acoustical phenomenon whereby sound energy is reduced between the
    noise source and the receiver. This energy loss can be attributed to atmospheric
    conditions, terrain, vegetation, other natural features, and man-made features (e.g.,
    sound insulation).

    Automated Radar Terminal System (ARTS) − Computer-aided radar display
    subsystems capable of associating alphanumeric data − such as aircraft identification,
    altitude, and airspeed − with aircraft radar returns.

    Azimuth − An arc of the horizon measured between a fixed point (such as true north)
    and the vertical circle passing through the center of an object.

    Bank – (1) A cluster of arrivals or departures in a short period of time, characteristic
    of an airline hub operation; (2) to turn, as in to bank left or right along a flight course; (3)
    to put away for later use, as in to bank land for future airport development.

    Base leg – A flight path at right angles to the approach of a runway end. It usually
    extends from the downwind leg to the intersection of the extended runway centerline.
    See “traffic pattern.”

    Baseline Condition − The existing condition or conditions prior to future development
    or the enactment of additional noise abatement procedures, which serve as a foundation
    for analysis.

    Building Restriction Line (BRL) − A line drawn on an airport layout plan which
    distinguishes between areas that are suitable for buildings and areas that are unsuitable.
    The BRL is drawn to exclude the runway protection zones, the runway visibility zones
    required for clear line of sight from the airport traffic control tower, and all airport areas
    with a clearance of less than 35 feet (10.5 meters) beneath the FAR Part 77 surfaces.

    Commuter Aircraft – Commuters are commercial operators that provide regularly
    scheduled passenger or cargo service with aircraft seating less than 60 passengers.
    A typical commuter flight operates over a trip distance of less than 300 miles.

    Connecting Passenger – An airline passenger who transfers from an arriving aircraft
    to a departing aircraft in order to reach his or her ultimate destination.

    Controlled Airspace − Airspace of defined dimensions within which air traffic control
    service is provided to IFR flights and to VFR flights in accordance with the airspace
    classification. Controlled airspace is designated as Class A, Class B, Class C, Class D,
    or Class E. Aircraft operators are subject to certain pilot qualifications, operating rules,
    and equipment requirements as specified in FAR Part 91, depending upon the class of
    airspace in which they are operating.

    Crosswind Leg – A flight path at right angles to the approach runway end off of its
    upwind end.

    Day-Night Average Sound Level (DNL) − A noise measure used to describe the
    average sound level over a 24-hour period, typically an average day over the course
    of a year. In computing DNL, an extra weight of 10 decibels is assigned to noise
    occurring between the hours of 10 p.m. and 7 a.m. to account for increased annoyance
    when ambient noise levels are lower and people are trying to sleep. DNL may be
    determined for individual locations or expressed in noise contours.

    Decibel (dB) − Sound is measured by its pressure or energy in terms of decibels.
    The decibel scale is logarithmic. A 10-decibel increase in sound is equal to a tenfold
    increase in sound energy.

    Displaced Threshold − A threshold that is located at a point on the runway other than
    the designated beginning of the runway. The portion of pavement behind a displaced
    threshold may be available for takeoffs in both directions and landings from the opposite

    Distance Measuring Equipment (DME) − A flight instrument that measures the
    line-of-sight distance of an aircraft from a navigational radio station in nautical miles.

    Easement – The legal right of one party to use part of the rights of a piece of real
    estate belonging to another party. This may include, but is not limited to, the right of
    passage over, on or below the property; certain air rights above the property, including
    view rights; and the rights to any specified form of development or activity.

    Enplanements −The number of passengers boarding an aircraft at an airport. Does
    not include arriving or through passengers.

    Enroute System − That part of the National Airspace System where aircraft are
    operating between origin and destination airports.

    Enroute Control − The control of IFR traffic in route between two or more adjacent
    approach control facilities.

    Environmental Assessment (EA) − A concise document that assesses the
    environmental impacts of a proposed Federal Action. It discusses the need for, and
    environmental impacts of, the proposed action and alternatives. An environmental
    assessment should provide sufficient evidence and analysis for a Federal
    determination whether to prepare an Environmental Impact Statement (EIS) or a
    Finding of No
    Significant Impact (FONSI). Public participation and consultation with other Federal,
    state, and local agencies is a cornerstone of the EA process.

    Environmental Impact Statement (EIS) − An EIS is a document that provides a
    discussion of the significant environmental impacts which would occur as a result of
    a proposed project, and informs decision-makers and the public of the reasonable
    alternatives which would avoid or minimize adverse impacts. Public participation and
    consultation with other Federal, state, and local agencies is a cornerstone of the EIS
    process. DEIS -draft document. FEIS for final document

    Equivalent Sound Level (Leq) − The average A-weighted sound level over any
    specified time period.

    Federal Aviation Administration (FAA) −The FAA is the Federal agency responsible
    for insuring the safe and efficient use of the nation’s airspace, for fostering civil
    aeronautics and air commerce, and for supporting the requirements of national defense.
    The activities required to carry out these responsibilities include: safety regulations;
    airspace management and the establishment, operation, and maintenance of a system
    of air traffic control and navigation facilities; research and development in support of the
    fostering of a national system of airports, promulgation of standards and specifications
    for civil airports, and administration of Federal grants-in-aid for developing public airports;
    various joint and cooperative activities with the Department of Defense; and technical
    assistance (under State Department auspices) to other countries.

    Federal Aviation Regulations (FAR) − The body of Federal regulations relating to
    aviation. Published as Title 14 of the Code of Federal Regulations.

    Final Approach – A flight path that follows the extended runway centerline. It usually
    extends from the base leg to the runway.

    Finding of No Significant Impact (FONSI) − If, following the preparation of an
    environmental assessment, the Federal Agency determines a proposed project will
    not result in any significant environmental impact, a finding of no significant impact
    (FONSI) is issued by the Federal Agency. A FONSI is a document briefly explaining
    the reasons why an action will not have a significant effect on the human environment
    and for which an EIS, therefore, is not necessary.

    Fixed Base Operator (FBO) – A business located on the airport that provides services
    such as hangar space, fuel, flight training, repair, and maintenance to airport users.

    Flight Track Utilization − The use of established routes for arrival and departure by
    aircraft to and from the runways at the airport.

    Glide Slope (GS) − Provides vertical guidance for aircraft during approach and landing.
    The glide slope consists of the following:
    •        Electronic components emitting signals which provide vertical guidance by reference
    to airborne instruments during instrument approaches such as ILS, or
    •        Visual ground aids, such as VASI, which provide vertical guidance for VFR approach
    or for the visual portion of an instrument approach and landing.

    Global Positioning System (GPS) − A system of 24 satellites used as reference points
    to enable navigators equipped with GPS receivers to determine their latitude, longitude,
    and altitude. The accuracy of the system can be further refined by using a ground receiver
    at a known location to calculate the error in the satellite range data. This is known as
    differential GPS (DGPS).

    Grid Analysis − A type of aircraft noise analysis that evaluates the noise levels at
    individual points rather than through generation of noise contours.

    Ground Effect − Noise attenuation attributed to absorption or reflection of noise by
    man-made or natural features on the ground surface.

    Hourly Noise Level (HNL) – A noise summation metric including primarily those
    single events that exceed a specific threshold or duration during one hour.

    Hub − An airport that services airlines that have hubbing operations.

    Hubbing − A method of airline scheduling that times the arrival and departure of
    several aircraft in a close period of time in order to allow the transfer of passengers
    between different flights of the same airline in order to reach their ultimate destination.
    Several airlines may conduct hubbing operations at an airport.

    Infill – Urban development occurring on vacant lots in substantially developed areas.
    May also include the redevelopment of areas to a greater density.

    Instrument Approach − A series of predetermined maneuvers for the orderly transfer
    of an aircraft under instrument flight conditions from the beginning of the initial approach
    to a landing, or to a point from which a landing may be made visually.
    Instrument Flight Rules (IFR) − That portion of the Federal Aviation Regulations
    (14 CFR 91) specifying the procedures to be used by aircraft during flight in Instrument
    Meteorological Conditions. These procedures may also be used under visual conditions
    and provide for positive control by ATC. (See also VFR).

    Instrument Landing System (ILS) − An electronic system installed at some airports
    which helps to guide pilots to runways for landing during periods of limited visibility or
    adverse weather.

    Instrument Meteorological Conditions (IMC) −Weather conditions expressed in
    terms of visibility, distance from clouds, and cloud ceilings during which all aircraft are
    required to operate using instrument flight rules (IFR).

    Integrated Noise Model (INM) − A computer model developed, updated and
    maintained by the FAA to predict the noise exposure generated by aircraft operations
    at an airport.

    Knots − Airspeed measured as the distance in nautical miles (6,076.1 feet) covered
    in one hour. (Approximately equal to 1.15 miles per hour.)

    Land and Hold Short Operations (LAHSO) – An air traffic control procedure intended
    to increase overall airport capacity without compromising safety. LAHSO include landing
    and holding short of an intersecting runway, taxiway, or some other designated point on a
    runway or taxiway.

    Land Use Compatibility − The ability of land uses surrounding the airport to coexist with
    airport-related activities with minimum conflict.

    Landing and Takeoff (LTO) Cycle −The time that an aircraft is in operation at or near
    an airport. An LTO cycle begins when an aircraft starts its final approach (arrival) and
    ends after the aircraft has made its climb-out (departure).

    Ldn − See DNL. Ldn is used in place of DNL in mathematical equations only.

    Leq  Equivalent Sound Level. The steady A-weighted sound level over any specified
    period of time (not necessarily 24 hours) that has the same acoustic energy as the
    fluctuating noise during that period (with no consideration of nighttime weighting). It is a
    measure of cumulative acoustical energy. Because the time interval may vary, it should
    be specified by a subscript (such as Leq 8 for an 8-hour exposure to noise) or be clearly
    understood from the context.

    Local Passenger −A passenger who either enters or exits a metropolitan area on
    flights serviced by the area’s airport. A local passenger is the opposite of a connecting

    Localizer − The component of an ILS which provides lateral course guidance to the

    Loudness −The subjective assessment of the intensity of sound.

    Mean Sea Level (MSL) − The average height of the surface of the sea for all stages
    of the tide; used as a reference for elevations. Also called sea level datum.

    Merge – Combining noise events that exceed a given threshold level and occur within
    a selected period of time.

    Missed Approach −A prescribed procedure to be followed by aircraft that cannot
    complete an attempted landing at an airport.

    Narrow-body Aircraft − A commercial passenger jet having a single aisle and maximum
    of three seats on each side of the aisle. Common narrow-body aircraft include A320,
    B717, B727, B737, B757, DC9, MD80, and MD90.

    National Airspace System (NAS) − The common network of U.S. airspace; air
    navigation facilities, equipment, services, airports, or landing areas; aeronautical
    charts, information, and services; rules, regulations, and procedures; technical
    information, manpower, and materials, all of which are used in aerial navigation.

    National Environmental Policy Act of 1969 (NEPA) − The original legislation
    establishing the environmental review process for proposed Federal actions.

    Nautical Mile − A measure of distance equal to one minute of arc on the earth’s
    surface (6,076.1 feet or 1,852 meters).

    NAVAIDs (Navigational Aids) − Any facility used by an aircraft for navigation.

    Noise Abatement − A measure or action that minimizes the amount of impact of
    noise on the environs of an airport. Noise abatement measures include aircraft
    operating procedures and use or disuse of certain runways or flight tracks.

    Noise Berm – A manmade soil structure designed to interrupt the direct transmission
    of noise from a source to a noise-sensitive area.

    Noise Contour Map − A map representing average annual noise levels summarized
    by lines connecting points of equal noise exposure.

    Nondirectional Beacon (NDB) − A beacon transmitting nondirectional signals whereby
    the pilot of an aircraft equipped with direction finding equipment can determine his
    bearing to and from the station. When the radio beacon is installed in conjunction with
    the ILS marker, it is normally called a compass locator.

    Nonprecision Approach − A standard instrument approach procedure providing
    runway alignment but no glide slope or descent information.

    Operation – A takeoff or landing by an aircraft.

    Outer Fix − An air traffic control term for a point in the airspace from which aircraft
    are normally cleared to the approach fix or final approach course.

    Part 150 StudyA voluntary process initiated by an airport to
    develop, evaluate and recommend actions that an airport, local municipalities, airlines,
    and/or the Federal Aviation Administration (FAA) could take to help reduce the impact
    of aircraft noise in communities surrounding an airport.

    Part 161 Study of the Federal Aviation Regulations specifies procedures that must be
    followed by any airport intending to implement a proposed noise rule:
    Part 161 requirements include:
  • Cost and benefit analyses of the proposed rule
  • Examination of alternatives
  • Public notice and opportunity for comment by affected parties
  • Establishment of a public docket
  • FAA Headquarters must approve the study before the proposed rule can be put
    into effect.
    FAA requires that the proposed restriction:
  • is reasonable, nonarbitrary and nondiscriminatory
  • would not create an undue burden on interstate or foreign commerce
  • would maintain safe and efficient use of navigable airspace
  • would not conflict with any existing federal statute or regulation
  • was given adequate opportunity for the public to comment on
  • does not create an undue burden on the national aviation system

    Positive Control −The separation of all air traffic within designated airspace as
    directed by air traffic controllers.

    Precision Approach Path Indicator (PAPI) – Provides visual approach slope
    guidance to aircraft during an approach. It is similar to a VASI but provides a sharper
    transition between the colored indicator lights.

    Precision Approach Procedure −A standard instrument approach procedure in
    which an electronic glideslope/glidepath is provided (e.g., ILS and PAR).

    Precision Approach Radar (PAR) – Navigational equipment located on the ground
    adjacent to the runway, and consisting of one antenna which scans the vertical plane
    and a second antenna which scans the horizontal plane. The PAR provides the controller
    with a picture of the descending aircraft in azimuth, distance, and elevation, permitting
    an accurate determination of the aircraft’s alignment relative to the runway centerline
    and the glide slope.

    Primary Commercial Service Airport − A commercial airport which enplanes 0.01
    percent or more of the total annual U.S. enplanements.

    Primary Runway − The runway on which the majority of operations take place.

    Profile −The position of the aircraft during an approach or departure in terms of altitude
    above the runway and distance from the runway end.

    Propagation – Sound propagation is the spreading or radiating of sound energy from
    the noise source. It usually involves a reduction in sound energy with increased distance
    from the source. Atmospheric conditions, terrain, natural objects, and manmade objects
    affect sound propagation.

    Public Use Airport − An airport open to public use without prior permission, and
    without restrictions within the physical capabilities of the facility. It may or may not be
    publicly owned.

    Reliever Airport −An airport which, when certain criteria are met, relieves the
    aeronautical demand on a busier air carrier airport.

    Run-Up − A routine procedure for testing aircraft systems by running one or more
    engines at a high power setting. Engine run-ups are normally conducted by airline
    maintenance personnel checking an engine or other on board systems following

    Runway End Identifier Lights (REIL) – Two synchronized flashing lights, one on
    each side of the runway threshold, which identify the approach end of the runway.

    Runway Protection Zone (RPZ) − An area, trapezoidal in shape and centered
    about the extended runway centerline, designated to enhance the safety of aircraft
    operations. It begins 200 feet (60 M) beyond the end of the area usable for takeoff
    or landing. The RPZ dimensions are functions of the aircraft, type of operation and
    visibility minimums. (Formerly known as the clear zone).

    Runway Safety Area (RSA) − A defined surface surrounding the runway prepared
    or suitable for reducing the risk or damage to airplanes in the event of an undershoot,
    overshoot, or excursion from the runway.

    Runway Threshold − The beginning of that portion of the runway usable for landing.

    Runway Use Program – A noise abatement runway selection plan crafted to further
    noise abatement efforts for communities around airports. A runway selection plan is
    developed into a runway use program. It typically applies to all turbojet aircraft 12,500
    pounds or heavier. Turbojet aircraft less than 12,500 pounds are included only if the
    airport proprietor determines that the aircraft creates a noise problem. These programs
    are coordinated with the FAA in accordance with FAA Order 8400.9, National Safety
    and Operational Criteria for Runway Use Programs, and are administered as either
    “formal” or “informal” programs.

    Runway Use Program (formal) – An approved runway use program outlined in a
    Letter of Understanding between the FAA–Flight Standards, FAA–Air Traffic Service,
    the airport proprietor, and the users. It is mandatory for aircraft operators and pilots
    as provided for in FAR Section 91.87.

    Runway Use Program (informal) - An approved runway use program that does not
    require a Letter of Understanding. Participation in the program by aircraft operators and
    pilots is voluntary.

    Single event – One noise event. For many kinds of analysis, the sound from single
    events is expressed using the Sound Exposure Level (SEL) metric.

    Slant-range distance – The distance along a straight line between an aircraft and a
    point on the ground.

    Sound − Sound is the result of vibration in the air. The vibration produces alternating
    bands of relatively dense and sparse particles of air, spreading outward from the source
    in the same way as ripples do on water after a stone is thrown into it. The result of the
    movement is fluctuation in the normal atmospheric pressure or sound waves.

    Sound Exposure Level (SEL) − A standardized measure of a single sound event,
    expressed in A-weighted decibels, that takes into account all sound above a specified
    threshold set at least 10 decibels below the maximum level. All sound energy in the
    event is integrated over one second.

    Special Use Airspace −Airspace of defined dimensions identified by an area on the
    earth’s surface wherein activities must be confined because of their nature and/or
    wherein limitations may be imposed upon aircraft operations which are not part of
    those activities.

    Stage 2 Aircraft − Aircraft that meet the noise levels prescribed by FAR Part 36 which
    is less stringent than those established for the quieter Stage 3 designation. The Airport
    Noise and Capacity Act required the phase-out of all Stage 2 aircraft over 75,000 pounds
    by December 31, 1999, with the potential for case-by-case exceptions through the
    year 2003.

    Stage 3 Aircraft − Aircraft that meet the most stringent noise levels set in FAR Part 36.

    Standard Instrument Departure Procedure (SID or DP) − A planned IFR air traffic
    ontrol departure procedure published for pilot use in graphic and textual form. SIDs
    provides transition from the terminal to the en route air traffic control structure.

    Standard Terminal Arrival Route (STAR) − A planned IFR air traffic control arrival
    procedure published for pilot use in graphic and textual form. STARs provide transition
    from the en route air traffic control structure to an outer fix or an instrument approach
    fix in the terminal area.

    Statute Mile − A measure of distance equal to 5,280 feet.

    Tactical Air Navigation (TACAN) -- A navigational system used by the military.
    TACAN provides both azimuth and distance information to a receiver on board an a

    Terminal Radar Approach Control (TRACON) − An FAA Air Traffic Control Facility
    which uses radar and two-way communication to provide separation of air traffic
    within a specified geographic area in the vicinity of one or more airports.

    Terminal Radar Service Area (TRSA) – Airspace surrounding certain airports
    where ATC provides radar vectoring, sequencing, and separation on a full-time basis
    for all IFR and participating VFR aircraft.

    Through Passenger − An airline passenger who arrives at an airport and departs
    without deplaning the aircraft.

    Time Above (TA) − The amount of time that sound exceeds a given decibel level
    during a 24-hour period (e.g., time in minutes that the sound level is above 75 dBA).

    Touchdown Zone Lighting (TDZ) – A system of two rows of transverse light bars
    located symmetrically about the runway centerline, usually at 100-foot intervals and
    extending 3,000 feet along the runway.

    Traffic Pattern – The traffic flow for aircraft landing and departure at an airport. Typical
    components of the traffic pattern include upwind leg, crosswind leg, downwind leg,
    base leg, and final approach.

    UNICOM – A nongovernment communication facility which may provide airport
    information at certain airports. Aeronautical charts and publications show the locations
    and frequencies of UNICOMs.

    Upwind Leg – A flight path parallel to the approach runway in the direction of approach.
    Vector − Compass heading instructions issued by ATC in providing navigational
    guidance by radar.

    Very High Frequency Omnidirectional Range (VOR) Station − A ground-based
    radio navigation aid transmitting signals in all directions. A VOR provides azimuth
    guidance to pilots by reception of electronic signals.

    Very High Frequency Omnidirectional Range Station with Tactical Air Navigation
    (VORTAC) -A navigational aid providing VOR azimuth and TACAN distance measuring
    equipment (DME) at one site.

    Visual Approach − An approach conducted on an IFR flight plan that authorizes the
    pilot to proceed visually and clear of clouds to the airport.

    Visual Approach Slope Indicator (VASI) −A visual aid to final approach to the
    runway threshold, consisting of two wing bars of lights on either side of the runway. Each
    bar produces a split beam of light – the upper segment is white, the lower is red.

    Visual Flight Rules (VFR) − Rules and procedures specified in 14 CFR 91 for aircraft
    operations under visual conditions. Aircraft operations under VFR are not generally
    under positive control by ATC. The term VFR is also used in the United States to
    indicate weather conditions that are equal to or greater than minimum VFR requirements.
    In addition, it is used by pilots and controllers to indicate a type of flight plan.

    Visual Meteorological Conditions (VMC) −Weather conditions expressed in terms
    of visibility, distance from cloud, and cloud ceiling equal to or greater than those
    specified in 14 CFR 91.155 for aircraft operations under Visual Flight Rules (VFR).

    Wide-Body Aircraft - A commercial jet with a wingspan generally greater than 155
    feet and, in passenger configuration, having two aisles with 8 to 11 seats across in
    a row. Common wide-body aircraft include the A300, A310, B747, B767, B777, DC-10,
    and MD-11.

    Yearly Day-Night Average Sound Level – see DNL.

    Source: PHL-Citizens Aviation Watch Association: info@phl-caw.org

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