A-Weighted Sound (dBA) -- A measurement representing a
sound generally as the human ear hears it by filtering out as much as 20 to 40
decibels of sound below 100 hertz (Hz). Used for aircraft noise evaluations.
Air Route Traffic Control Center (ARTCC) -- An FAA facility established
to provide air traffic control service to aircraft operating on an IFR flight
plan within controlled airspace during the en route portion of a flight.
Air Traffic Control (ATC) -- A service operated by appropriate authority
to promote the safe orderly, and expeditious flow of air traffic.
Airman's Information Manual -- 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 Elevations -- The highest point on an airport's usable runways
expressed in feet above mean sea level (MSL).
Airport Improvement Plan (AIP) -- A Federal funding program for airport
improvements. Funds are derived from sources such as airline tickets, aviation
fuel, etc.
Airport Layout Plan (ALP) -- An airport layout plan is a scaled drawing
of existing and proposed land and facilities necessary for the operation and
development of the airport. Any airport will benefit from a carefully developed
plan that reflects current FAA design standards and planning criteria. The ALP
shows boundaries and proposed additions to all areas owned or controlled by the
sponsor 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 -- The total number of movements in landings
(arrivals) plus 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 air traffic control facility
located on an airport and responsible for traffic separation within the
immediate vicinity of an airport as well as on the surface of the airport.
Airway -- A corridor of controlled airspace whose centerline is
established by radio navaids. Low altitude airways (between 3,000 and 18,000
feet AGL) are identified by the letter V. High altitude airways (above 18,000
feet MSL) are known as Jet airways and are identified with the letter J.
Ambient Noise -- The totality of noise in a given place and time -
usually a composite of sounds from varying sources at varying distances from
the observer.
Annual Service Volume (ASV) -- A planning term which describes the
number of annual aircraft operations which is 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.
Attenuation -- Acoustical phenomenon whereby a reduction of sound energy
is experienced between the noise source and the receiver. This energy loss can
be attributed to atmospheric conditions, terrain, vegetation, man-made features
(e.g., sound insulation) and natural features.
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 (as true
north) and the vertical circle passing through the center of an object.
Baseline Condition -- The existing conditions or conditions prior to
future development, which serve as a foundation for analysis.
Building Restriction Line (BRL) -- A line which identifies suitable
building area locations on airports. The BRL encompasses the runway protection
zones, the runway visibility zone areas required for airport traffic control
tower clean line of sight and all airport areas with less than 35 foot (10.5)
clearance under the FAR Part 77 surfaces.
Capacity -- The number of aircraft that can land or depart from an
airport under specific conditions during a particular time. Capacity is
determined by a number of complex factors including the length of runways in
use, air traffic rules, the mix of airplanes using the airport, the current
weather and visibility, the number of available gates, and other limiting
factors such as getting to and from the airport.
Class A Airspace -- Generally, that airspace from 18,000 feet MSL up to
and including FL600, including the airspace overlying the waters within 12
nautical miles of the coast of the 48 contiguous States and Alaska; and
designated international airspace beyond 12 nautical miles of the coast of the
48 contiguous States and Alaska within areas of domestic radio navigational
signal or ATC radar coverage, and within which domestic procedures are applied.
Class B Airspace -- That 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), and is
designed to contain all published instrument procedures once an aircraft enters
the airspace. An ATC clearance is required for all aircraft to operate in the
area, and all aircraft that are so cleared receive separation services within
the airspace. The cloud clearance requirement for VFR operations is "clear
of clouds."
Class C Airspace -- That airspace from the surface to 4,000 feet above
the airport elevation (charted in MSL) surrounding those airports that have an
operational control tower, are serviced by a radar approach control, and that
have a certain number of IFR operations or passenger enplanements. Although the
configuration of each Class C airspace area is individually tailored, the
airspace usually consists of a 5 NM radius core surface area that extends from
the surface up to 4,000 feet above the airport elevation, and a 10 NM radius
shelf area that extends from 1,200 feet to 4,000 feet above the airport
elevation.
Class D Airspace -- That airspace from the surface to 2,500 feet above
the airport elevation (charted in MSL) surrounding those airports that have an
operational control tower. The configuration of each Class D airspace area is
individually tailored and when instrument procedures are published, the
airspace will normally be designed to contain the procedures.
Commuter Aircraft -- Commuters are those operators that provide
regularly scheduled passenger or cargo service with aircraft seating 72
passengers or less. 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 their ultimate
destination.
Constructive Use -- Refers to the possible indirect impacts to DOT Section
303(c) properties such as parks. Constructive use is considered to occur when a
transportation project does not incorporate land from a Section 303(c) resource
but the projects proximity impacts are so severe that the protected activities
feature or attributes that qualify a resource for protection under section
303(c) are substantially impaired. Substantial impairment occurs only when the
protected activities, features or attributes of the resource are substantially
diminished. For example, a substantial increase in noise levels at a park due
to transportation project may represent a constructive use, even though the
park is not directly affected through acquisition or development.
Controlled Airspace -- An 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 airspace. Aircraft operators
are subject to certain pilot qualifications, operating rules, and equipment
requirements as specified in FAR Part 91, depending upon the class airspace in
which they are operating.
Day-Night Average Sound Level (DNL) -- A noise measure used to describe
the average aircraft noise levels over a 24-hour period, typically an average
day over the course of a year. DNL considers aircraft operations that occur
between the hours of 10 p.m. and 7 p.m. to be 10 decibels louder than they
actually are 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. DNL is currently the accepted measure
for aircraft noise analysis.
Decibel (dB) -- Sound is measured by its pressure or energy in terms of
decibels. The decibel scale is logarithmic; when the scale goes up by ten, the
perceived sound is two times as loud.
Delay -- The difference, in minutes, between the scheduled time and
actual time of an aircraft arrival or departure. For airport planning purposes,
it is often expressed as an annual average delay per aircraft operation (in
minutes).
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 either
direction and landings from the opposite direction.
Distance Measuring Equipment (DME) -- A flight instrument which measures
the distance from a navigational radio station in nautical miles.
Enplanements -- The total number of departure passengers boarding an
aircraft.
En route System -- That part of the National Airspace System where
aircraft are operating between departure and destination airports.
Equivalent Sound Level (Leq) -- The steady A-weighted sound level over
any specified time period. It is used to identify the average sound level over
a period of time.
Federal Aviation Administration (FAA) -- The FAA is 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.
Fix -- A geographical position determined by reference to one or more
radio NAVAIDS; celestial plotting; or by some other means such as satellite
navigation. Examples for Dayton International Airport include BRUNY, DANEI,
KEKEE, and BUCKE.
Flight Level -- A level of constant atmospheric pressure related to a
reference datum of 29.92 inches of mercury. Each Flight level is expressed in
three digits representing hundreds of feet. For example FL 250 represents a
barometric altitude of 25,000 feet. Aircraft operating at altitudes greater
than 18,000 feet MSL use Flight levels as their altitude reference.
Flight Track Utilization -- The use of established routes for arrival
and departure by aircraft to and from the existing runways at the airport.
Glide Slope (GS) -- Provides vertical guidance for aircraft during
approach and landing. The glide scope 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 which 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.
Hub -- An airport which service airlines that have hubbing operations.
Hubbing -- A method of airline scheduling that times the arrival and
departure of several aircraft in 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.
Hubbing Complex -- The period of time in which an airline times the
arrival and departure of several aircraft to accomplish hubbing. An airline may
operate several complexes at an airport each day.
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 Air
Regulations (14 CFR 91) specifying the procedures to be used by aircraft during
flight in IMC. 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 and
maintained by the FAA to predict the noise impacts generated by aircraft
operations.
Knots -- Airspeed measured as the distance in nautical miles covered in
1 hour.
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 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 used in place for DNL in mathematical equations
only.
Leq -- Equivalent Sound Level. The steady A-weighted sound level over
any specified period of time (examples: 24 hours, 8 hours). This metric is used
to identify the average sound level over a specified period of time.
Local Passenger -- A passenger who either enters or exits a metropolitan
area on flights serviced by the area's airport. The opposite of a connecting
passenger.
Localizer -- The component of an ILS which provides lateral course
guidance to the runway
Location Impact Analysis -- An analysis conducted to determine if noise level
increases associated with projected development would approach the FAA
threshold of a 1.5 DNL increase within the 65 DNL or greater noise contours
over any noise-sensitive land use.
Loudness -- The subjective intensity of sound.
Master Plan Update -- An update to the long-range airport development
requirements. These plans are typically updated every 5-7 years.
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.
Missed Approach -- A prescribed procedure to be followed by aircraft
that cannot complete an attempted landing at an airport.
Mitigation -- The avoidance or minimization of an adverse impact.
Mitigation Measure -- An action take to alleviate adverse impacts.
Narrowbody Aircraft -- A commercial passenger jet having a single aisle
and maximum of three seats on each side of the aisle. Narrowbody aircraft
include B727, B737, B757, DC9, MD80, MD90 and A320.
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 material which are used in
aerial navigation.
National Environmental Policy Act of 1969 (NEPA) -- The original legislation
establishing the environmental review process.
Nautical Mile -- A measure of distance equal to 1 minute of arc on the
earth's surface (approximately 6,076 feet).
NAVAIDS (Navigation Aids) -- Any facility used by an aircraft for
navigation.
Noise -- Unwanted Sound
Noise Abatement -- A measure or action that minimizes the 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 Contour Map -- A map representing average annual noise levels
summarized by lines connecting points of equal noise exposure.
Noise Exposure Map (NEM) -- A map of an airport and its environs which
identifies the area impacted by various aircraft noise levels. The FAA has
specified criteria for presentation of Noise Exposure Maps, which is governed
by FAR Part 150.
Noise Impact Routing System (NIRS) -- A computer simulation model that
evaluates noise impacts in a defined study area from the ground up to 18,000
feet AGL. This model replaces the FAA's Checklist Analysis 7210.360.
Noise Level Reduction (NLR) -- The amount of noise level reduction
achieved through incorporation of noise attenuation (between outdoor and indoor
levels) in the design and construction of a facility.
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
Compass Locator.
Nonprecision Approach -- A standard instrument approach procedure
providing runway alignment but no glide slope or descent information.
Outer Fix -- A general air traffic control term to describe the fixes in
the terminal area from which aircraft are normally cleared to the approach fix
or final approach course.
Positive Control --The separation of all air traffic within designated
airspace.
Precision Approach Procedure/Precision Approach -- A standard instrument
approach procedure in which an electronic glideslope/glidepath is provided,
e.g.. ILS and PAR.
Primary Runway -- The runway on which the majority of operations take
place. At large, busy airports, there may be two or more parallel primary
runways.
Profile -- The physical position of the aircraft during landings or
takeoffs in term of altitude in feet above the runway and distance from the
runway end.
Quadrant -- A quarter part of a circle, centered on a NAVAID oriented
clockwise from magnetic north.
Radial -- A magnetic bearing extending from a VOR, VORTAC or TACAN
facility.
Rotational Runway Use -- Variance in use of runways over a specific time
period to prevent constant use of one runway.
Run-Up -- A routine procedure for testing an aircraft engine at a high
power setting. Engine run-ups are normally conducted by airline maintenance
personnel checking an engine following the conduct of maintenance.
Runway -- A defined rectangular area on an airport for the purpose of
landing and takeoff of aircraft. Runways are normally numbered in relation to
their magnetic direction rounded off to the nearest 10 degrees, e.g., Runway 14,
Runway 32.
Runway Protection Zone (RPZ) -- An area (formally the clear zone)
trapezoidal in shape and centered about the extended runway centerline, is used
to enhance the safety or aircraft operations. It begins 200 feet (60M) beyond
the end of the area usable for takeoff or landing. The RPZ dimensions are
functions of the design aircraft, type of operation and visibility minimums.
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.
Single Event -- An occurrence of audible noise usually above a specified
minimum noise level caused by an intrusive source such as an aircraft
overflight, passing train or ship's horn.
Slant-Range Distance -- The straight-line distance between an aircraft
and a point on the ground.
Sound -- Sound is the result of a sound source 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
measure of the physical energy of the noise event which takes into account both
intensity and duration. By definition SEL values are referenced to a duration
of one second and should not be confused with either the average or maximum
noise levels associated with a specific event. People do not hear SEL. SEL is
always higher than the average and the maximum as long as the event is longer
than one second. Expressed in dB.
Special Use Airspace -- Six types of airspace designated to special uses
and defined in the Airman's Information Manual. It includes 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 which meet the noise levels prescribed by
FAR Part 36 and are less stringent than those established for the quieter
designation (State 3). The Airport Noise and Capacity Act requires
the phase-out of all Stage 2 aircraft by December 31, 1999, with 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) -- A preplanned IFR air
traffic control departure procedure printed for pilot use in graphic and/or
textual form. SID's provide transition from the terminal to the en route structure.
Standard Terminal Arrival Routes (STARS) -- A preplanned IFR air traffic
control arrival procedure printed for pilot use in graphic and/or textual form.
STAR's provide transition from the en route 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.
S-Turns -- Turns issued to pilots by air traffic controllers such that
aircraft follow the path of the letter "S". These turns are issued
when necessary to delay aircraft, or to ensure proper aircraft separation and
sequencing .
TACAN -- Tactical Air Navigation. A navigational system used by the
military. TACAN provides both azimuth and distance information to a receiver on
board an aircraft.
Taxiway -- A defined path established for the taxiing of aircraft from
one part of an airport to another.
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.
Threshold -- The beginning of that portion of the runway usable for
landing.
Through Passenger-- An airline passenger who arrives at an airport and
departs without deplaning the aircraft.
Time Above (TA) -- Time above indicates the time in minutes that a given
dB(A) level is exceeded during a 24-hour period. The time in minutes at a
specific location that a preselected sound level is exceeded due to aircraft
operations (e.g., time in minutes that the sound level is above 75 dB(A).
Tower En-Route Control -- The control of IFR traffic en route between
two or more adjacent approach control facilities.
Transitional Airspace -- That portion of controlled airspace wherein
aircraft change from one phase of flight or flight condition to another.
Vector -- Compass heading instructions issued by ATC to provide
navigational guidance by radar.
Very High Frequency Omnidirectional Range Station (VOR) -- A
ground-based radio navigation aid transmitting signals in all directions. A VOR
provides azimuth guidance to pilots by reception of electronic signals.
Visual Approach -- An approach conducted on an IFR flight plan which
authorizes the pilot to proceed visually and clear of clouds to the
airport.
Visual Flight Rules (VFR) -- Rules and procedures specified in 14 CFR 91
for aircraft operations under visual conditions. Aircraft operation 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 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).
VORTAC -- Very High Frequency Omnidirectional Range with Tactical Air
Navigation. A navigational aid providing VOR azimuth and TACAN distance measuring equipment (DME) at one site.