abandoned runway: A runway permanently closed to aircraft operations which may be marked in accordance with current FAA standards for marking and lighting of deceptive, closed, and hazardous area on airports.
access taxiway: A taxiway that provides access to a particular location or area. (FAA Order 1000.15A)
active aircraft: Aircraft registered with the FAA and reported or estimated to have been flown at least one hour during the preceding year.
actual runway length: The length of full-width usable runway from end to end of full strength pavement where those runways are paved. (FAA Order 1000.15A)
administrative building: A building or buildings accommodating airport administration activity and public facilities for itinerant and local flying, usually associated with general aviation fixed-based operations. (FAA Order 1000.15A)
Advisory Circular (AC): A series of external FAA publications consisting of all non-regulatory material of a policy, guidance, and informational nature. (FAA Order 1000.15A)
AGL: Above ground level. (FAA Order 1000.15A)
air carrier: A scheduled operator carrying passengers, mail, or cargo for revenue in accordance with FAR Part 121 or 127. (FAA Order 1000.15A)
aircraft: A device that is used or intended to be used for flight in the air. (FAR Part 1)
aircraft mix: The number of aircraft movements categorized by capacity group or operational group, and specified as a percentage of total aircraft movements. (FAA Order 1000.15A)
aircraft operations: The airborne movement of aircraft in controlled or noncontrolled airport terminal areas and about given en-route fixes or at other points where counts can be made. There are two types of operations-local and itinerant.
(1) Local operations are performed by aircraft which:
(a) Operate in the local traffic pattern or within sight of the airport.
(b) Are known to be departing for, or arriving from, flight in local practice areas within a 20-mile radius of the airport.
(c) Execute simulated instrument approaches or low passes at the airport.
(2) Itinerant operations are all aircraft operations other than local operations. (FAA Order 1000.15A)
aircraft tiedown: Positions on the ground surface that are available for securing aircraft.
(FAA Order 1000.15A)
airport capacity: The rate of aircraft movements on the runway/taxiway system which results in a given level of delay.
air navigation facility (NAVAID): Any facility used in, available for use in, or designed for use in aid of air navigation, including landing areas, lights, any apparatus or equipment for disseminating weather information, for signaling, for radio direction-finding, or for radio or other electronic communication, and any other structure or mechanism having a similar purpose for guiding and controlling flight in the air or the landing or takeoff of aircraft.
airport: An area of land or water that is used or intended to be used for the landing and takeoff of aircraft, and includes its buildings and facilities, if any. (FAR Part 1)
Airport and Airway Development Act Amendments of 1976: Extended the 1970 Act for five years and included a number of amendments including the types of airport development projects eligible for ADAP funding, increased the federal share for ADAP and PGP grants, and initiated a number of studies concerning the National Airport System Plan (NASP)
Airport and Airway Development Act of 1970: A federal aid to airports program administered by the FAA for the 10-year period ending in 1980. Over $4.1 billion was invested in the airport system during this period.
Airport and Airway Improvement Act of 1982: Re-established the operation of the Airport and Airway Trust Fund with a slightly revised schedule of user taxes.
Airport and Airway Revenue Act of 1970: Created an airport and airway trust fund to generate revenues for airport aid. Taxes included an 8 percent surcharge on domestic passenger fares, a $3 surcharge on international passenger tickets, a 7 cents surcharge on fuel, a 5 percent surcharge on airfreight waybills, and an annual registration fee of $25 on all civil aircraft.
airport beacon: A visual navigation aid displaying alternating white and green flashes to indicate a lighted airport or white flashes only for an unlighted airport. (FAA Order 1000.15A)
airport configuration: The relative layout of component parts of an airport such as the runway-taxiway-terminal arrangement. (FAA Order 1000.15A)
Airport Reference Code (ARC): Includes Aircraft Approach Category and Airplane Design Group (ADG). The aircraft approach category is a grouping of aircraft based on 1.3 times their stall speed in their landing configuration at their maximum certificated landing weight. The ADG is a grouping of airplanes based on wingspan.
airport director: Sometimes referred to as airport manager or supervisor, the person responsible for the overall day-to-day operation of the airport.
airport elevation: The highest point of an airport's usable runways measured in feet above mean sea level.
airport imaginary surfaces: Imaginary surfaces established at an airport for obstruction determination purposes and consisting of primary, approach-departure, horizontal, vertical, conical, and transitional surfaces. (FAA Order 1000.15A)
Airport Improvement Program (AIP): The Airport Improvement Program of the Airport and Airways Improvement Act of 1982 as amended by the Airport and Airway Safety and Capacity Expansion Act of 1987. Under this program, the FAA provides funding assistance for the planning, design and development of airports and airport facilities.
airport layout plan (ALP): A graphic presentation, to scale, of existing and proposed airport facilities, their location on the airport, and the pertinent clearance and dimensional information required to show conformance with applicable standards. To be eligible for AIP funding assistance, an airport must have an FAA-approved Airport Layout Plan. (FAA Order 1000.15A)
Airport Master Plan: Presents the planner's conception of the ultimate development of a specific airport. It presents the research and logic from which the plan was evolved and displays the plan in a graphic and written report. The ALP is part of this plan.
airport reference point (ARP): A point having equal relationship to all existing and proposed landing and take-off areas.
airport requirements: First phase of the airport master plan which specifies new or expanded facilities that will be needed during the planning period. This involves cataloging existing facilities and forecasting future traffic demand. The planner compares the capacity of existing facilities with future demand, identifying where demand will exceed capacity, and what new facilities will be necessary.
airport sponsor: A public agency or tax-supported organization such as an airport authority, that is authorized to own and operate the airport, to obtain property interests, to obtain funds, and to be legally, financially, and otherwise able to meet all applicable requirements of current laws and regulations. (FAA Order 1000.15A)
air route: Navigable airspace between two points which is identifiable. (FAA Order 1000.15A)
Air Route Traffic Control Center (ARTCC): A facility established to provide positive air traffic control service to aircraft operating on IFR flight plans within controlled airspace. Controls only traffic en-route between airports. (FAA Order 1000.15A)
airspace: Space in the air above the surface of the Earth, or a particular portion of such space, usually defined by the boundaries of an area on the surface projected upward. (FAA Order 1000.15A)
airside facilities: The airfield on which aircraft operations are carried out, including runways and taxiways.
airspace capacity: Includes the proximity of airports to one another, the relationship of runway alignments, and the nature of operations. (IFR or VFR) in the area.
air taxi: Scheduled and/or nonscheduled aircraft operations carrying passengers and/or cargo for compensation. The capacity of air taxi aircraft is limited by Part 135 of the Federal Aviation Regulations. (FAA Order 1000.15A)
air taxi aircraft: Aircraft operated by the holder of an Air Taxi Operating Certificate, which authorizes the carriage of passengers, mail or cargo for revenue in accordance with FAR Parts 135 and 121. (FAA Order 1000.15A)
air taxi operator: An operator providing either scheduled or unscheduled air taxi service or mail service (FAA Order 1000.15A), and operate by FAR Part 135 using small aircraft (under 35 seats or a maximum payload of less than 7,500 pounds) (FAA Order 1000.15A)
air traffic: Aircraft operating in the air or on an airport surface, exclusive of loading ramps and parking areas. (FAR Part 1)
air transportation: Interstate, overseas, or foreign air transportation, or the transportation, or the transportation of mail by aircraft. (FAR Part 1)
airway: A path through the navigable airspace designated by appropriate authority within which air traffic service is provided.
ALP: Airport Layout Plan (see airport master plan).
ALS: Approach Lighting System.
alternate airport: An airport at which an aircraft may land if a landing at the intended airport becomes inadvisable. (FAR Part 1)
approach and clear zone layout: A graphic presentation to scale of the imaginary surfaces defined in FAR Part 77.
approach area: The defined area the dimensions of which are measured horizontally beyond the threshold over which the landing and takeoff operations are made. (FAA Order 1000.15A)
Approach Lighting System (ALS): An airport lighting facility which provides visual guidance to landing aircraft by radiating light beams in a directional pattern by which the pilot aligns the aircraft with the extended centerline of the runway on his final approach and landing. (FAA Order 1000.15A)
approach path: A specific flight course laid out in the vicinity of an airport and designed to bring aircraft in to safe landings; usually delineated by suitable navigational aids. (FAA Order 1000.15A)
approach slope ratio: The ratio of horizontal to vertical distance indicating the degree of inclination of the approach surface. (FAA Order 1000.15A)
approach surface: An imaginary surface longitudinally centered on the extended centerline of the runway, beginning at the end of the primary surface and rising outward and upward to a specified height above the established airport elevation. (FAA Order 1000.15A)
apron: A defined area, on a land airport, intended to accommodate aircraft for purposes of loading or unloading passengers or cargo, refueling, parking, or maintenance. (FAA Order 1000.15A)
apron/ramp: An area designated for aircraft use, other than taxiways and runways. Example uses for an apron include loading and unloading, parking, maintenance, refueling, before take-off engine runup, and as a temporary traffic holding area.
approved instrument approach: An instrument approach approved for general use and publication by the FAA. It must meet design, accuracy, and equipment requirements set by the FAA, and is subject to periodic FAA flight checks.
ARP: Airport Reference Point.
ARTCC: Air Route Traffic Control Center.
ASDE: Airport Surface Detection Equipment.
ASR: Airport Surveillance Radar.
ATC: Air Traffic Control.
ATIS: Automated Terminal Information Service.
ATCT: Air Traffic Control Tower.
Automated Weather Observing System (AWOS): This equipment automatically gathers weather data from various locations on an airport and transmits the information directly to pilots by means of computer generated voice messages over a discrete frequency. (FAA Order 1000.15A)
Aviation Safety and Noise Abatement Act of 1979: Provides assistance to airport operators to prepare and carry out noise compatibility programs. Authorizes the FAA to help airport operators develop noise abatement programs and makes them eligible for grants under ADAP.
avigation easement: A grant of a property interest in land over which a right of unobstructed flight in the airspace is established. (FAA Order 1000.15A)
based aircraft: The total number of active general aviation aircraft which use or may be expected to use an airport as a "home base."
base leg: (See traffic pattern).
basic data table: Shown on the airport layout plan drawing, it includes the airport elevation, runway identification and gradient, percent of wind coverage by principal runway, ILS runway when designated, normal or mean maximum daily temperature of the hottest month, pavement strength of each runway, and plan for obstruction removal, relocation of facilities.
basic runway length: Runway length resulting when actual length is corrected to mean seal level, standard atmospheric, and no gradient conditions. (FAA Order 1000.15A)
basic transport airport (or runway): An airport (or runway) that accommodates turbojet-powered aircraft up to 60,000 pounds gross weight. (FAA Order 1000.15A)
Basic Utility - Stage I: This type of airport serves about 75 percent of the single-engine and small twin-engine airplanes used for personal and business purposes. Precision approach operations are not usually anticipated. This airport is designed to serve small airplanes with a wingspan not exceeding 9 feet.
Basic Utility - Stage II: This type of airport serves all the airplanes of Stage I, plus some small business and air taxi-type twin-engine airplanes. Precision approach operations are not usually anticipated. This airport is designed to serve small airplanes with wingspans not to exceed 79 feet.
budgets: The planned dollar amounts needed to operate and maintain the airport during a definite period of time such as a year. There are capital budgets for major capital expenditures (such as runway resurfacing) and operating budgets to meet daily expenses.
building area: An area on an airport to be used, considered, or intended to be used, for airport buildings or other airport facilities or rights-of-way, together with all airport buildings and facilities located thereon.
building restriction line: A line shown on the airport layout plan beyond which airport buildings must not be positioned in order to limit their proximity to aircraft movement areas.
busy-hour operations: The total number of aircraft operations expected to occur at an airport at its busiest hour, computed by averaging two adjacent busiest hours of a typically high activity day.
by-pass taxiway: A taxiway located adjacent to an area which accommodates moving or parked aircraft specifically designed to achieve efficient aircraft passing movements.. (FAA Order 1000.15A)
capacity: The ability of an airport to handle a given volume of traffic (demand). It is a limit that cannot be exceeded without incurring an operational penalty.
ceiling: The height above the earth's surface of the lowest layer of clouds or other phenomena which obscure vision.
CIP: Capital Improvement Plan.
Civil Aeronautics Board (CAB): Responsible for the economic regulation of the certificated air carriers during the period from 1940 to 1985.
civil airport user categories: As used by airport planners, refers to the four major types of airports: certificated air carrier, commuter, general aviation, and military.
closed airport: An airport temporarily closed to aircraft operations for maintenance, construction, or some other purpose while the operator is still in business. (FAA Order 1000.15A)
closed field marking: Panels placed in the center of the segmented circle, or in the center of the field, in the form of a cross which will signify that the field is closed to all traffic. (FAA Order 1000.15A)
closed runway marking: Panels placed on the ends of the runway and at regular intervals in the form of a cross, signifying that a runway is closed to all traffic. (FAA Order 1000.15A)
commercial service: Commercial service airports are public use airports which receive scheduled passenger service aircraft, and which annually enplane 2,500 or more passengers, but do not qualify for primary service classification. (FAA Order 1000.15A)
conical surface: A surface extending from the periphery of the horizontal surface outward and upward at a slope of 20 to 1 for the horizontal distances and the elevations above the airport elevation as prescribed by FAR Part 77. (FAA Order 1000.15A)
controlled airspace: Airspace within which some or all aircraft may be subject to air traffic control to promote safe and expeditious flow of air traffic. (FAA Order 1000.15A)
controlling obstruction: The highest obstruction relative to a prescribed plane within a specific area. (FAA Order 1000.15A)
criteria for inclusion in the NASP: The principal criteria are: 1) that the airport has (or is forecast to have within five years) at least 10 based aircraft (or engines); 2) that it be at least a 30-minute drive from the nearest existing or proposed airport currently in the NASP; and 3) that there is an eligible sponsor willing to undertake ownership and development of the airport.
crosswind: A wind blowing across the line of flight of an aircraft. (FAA Order 1000.15A)
crosswind component: A wind component that is at a right angle to the longitudinal axis of the runway or the flight path of the aircraft. (FAA Order 1000.15A)
crosswind leg: A flight path at right angles to the landing runway off its upwind leg. (FAA Order 1000.15A)
crosswind runway: A runway additional to the primary runway to provide for wind coverage not adequately provided by the primary runway. (FAA Order 1000.15A)
dBA: A-weighted sound pressure level.
decibel (dB): A unit of noise level representing a relative quantity. This reference value is a sound pressure of 20 micronewtons per square meter. (FAA Order 1000.15A)
decision height (DH): With respect to the operation of aircraft, means the height specified in M.S.L. above the highest runway elevations in the touchdown zone at which a missed approach shall be initiated if the required visual reference has not been established (during the ILS or PAR instrument approach, to either continue the approach or to execute a missed approach). (FAR Part 1)
Department of Transportation (DOT): Established in 1966 to promote coordination of existing federal programs and to act as a focal point for future research and development efforts in transportation.
depreciable investment: The annual cost of capital invested in plant and equipment.
directional marker: An airway marker located on the ground used to give visual direction to an aircraft; consists of an arrow indicating true North and arrows indicating names and states of the nearest town.
discrete address beacon system (DABS): A sophisticated air traffic control surveillance system capable of interrogating each airborne DABS transponder in an "all-call" mode or with a discrete address signal encoded for each specific aircraft operating in the system. The data acquired upon response from each transponder are then processed to provide range, azimuth, altitude, and identity of each aircraft in the system on an individual basis but in sequence on a programmed interrogating schedule. Since aircraft are addressed individually in DABS, the surveillance system automatically provides a natural vehicle for a data link between ground and aircraft which can be used for ATC control purposes including the proposed intermittent positive control (IPC) concepts (FAA Order 1000.15A)
displaced threshold: A threshold that is located at a point on the runway other than the beginning. (FAA Order 1000.15A)
Distance Measuring Equipment (DME): A navigation ground station capable of receiving interrogations from aircraft and transmitting signals which allow time, speed, and distance computations to be made. The station is usually sited with a VOR and at times an ILS.
downwind leg: A flight path in the traffic pattern parallel to the landing runway in the direction opposite to landing. It extends to the intersection of the base leg. (FAA Order 1000.15A)
effective perceived noise level (EPNL): Time-integrated perceived noise level calculated with adjustments for irregularities in the sound spectrum, such as that caused by discrete-frequency components (tone-correction) The unit of effective perceived noise level is the decibel, with identifying prefix for clarification, EPNdB. (FAA Order 1000.15A)
effective runway length: (a) Effective runway length for takeoff means the distance from the end of the runway at which the takeoff is started to the point at which the obstruction clearance plane associated with the other end of the runway intersects the runway center-line. (FAR Part 121.171b) (b) Effective runway length for landing means the distance from the point at which the obstruction clearance plane associated with the approach end of the runway intersects the centerline of the runway to the far end thereof. (FAR Part 121.171b) (FAA Order 1000.15A)
entrance taxiway: A taxiway that provides entrance for aircraft to the takeoff end of the runway.
executive aircraft operator: A corporation, company, or individual which operates owned or leased aircraft, flown by pilot(s) whose primary duties involve pilotage of aircraft, as a means of transportation or personnel or cargo in the conduct of company business. (FAA Order 1000.15A)
exit taxiway: A taxiway used as an exit from a runway to the apron or other aircraft operating area. (FAA Order 1000.15A)
enplaned passengers: The total number of revenue passengers boarding aircraft, including originating, stopover and transfer passengers, in scheduled and non-scheduled services. (FAA Order 1000.15A)
FAA: Federal Aviation Administration.
FAA high-density rule: Quotas imposed at selected airports based on estimated limits of the air traffic control (ATC) system and airport runway capacity.
FAR: Federal Aviation Regulation.
FAR Part 77: A definition of the protected airspace required for the safe navigation of aircraft. (FAA Order 1000.15A)
FAR Part 107, Airport Security: Prescribes security rules for airport operators serving certificated air carriers.
FAR Part 91: General operating and flight rules.
FAR Part 150, Airport-Land Use Compatibility Planning: Designed to assist airport operators in determining the extent and nature of the noise problem at a given airport.
FAR Part 121: Certification and operations; domestic, flag, and supplemental air carriers and commercial operators of large aircraft. (FAA Order 1000.15A)
Federal Airport Act of 1946: A federal aid to airports program administered by the CAA (later the FAA) to give the United States a comprehensive system of airports. Over $1.2 billion in airport development aid funds were disbursed by the Federal Government during its 24-year history.
FAR Part 135: Air Taxi Operators and Commercial Operators.
Federal Aviation Act of 1958: Created the Federal Aviation Agency (FAA) with an administrator responsible to the President. The law retained the CAB as an independent agency and transferred the safety-rule-making powers to the FAA along with the functions of the CAA and the Airways Modernization Board.
Federal Aviation Administration (FAA): Created by the act that established the Department of Transportation. Assumed all of the responsibilities of the former Federal Aviation Agency.
federal government-operated airports: Two commercial airports serving the District of Columbia and surrounding area which were once managed by the FAA. They are Washington National and Washington-Dulles International.
final approach area(s): Areas of defined dimensions protected for aircraft executing instrument approaches. (FAA Order 1000.15A)
final approach (IFR): The flight path of an aircraft which is inbound to the airport on an approved final instrument approach course, beginning at the final approach fix (AIM, Part 1) and extending to the airport or the point where circling for landing or missed approach is executed.
final approach (VFR): A flight path, in the traffic pattern, of a landing aircraft in the direction of landing along the extended runway centerline from the base leg to the runway (AIM, Part 1).
final controller: That controller providing final approach guidance utilizing radar equipment (AIM, Part 1).
fixed base operator: An individual or company located at an airport, and providing commercial general aviation services. (FAA Order 1000.15A)
flareout: That portion of a landing maneuver in which the rate of descent is reduced to lessen the impact of landing. (FAA Order 1000.15A)
flight advisory service: Advice and information provided by a facility to assist pilots in the safe conduct of flight and aircraft movement. (FAA Order 1000.15A)
flight plan: Specified information relating to the intended flight of an aircraft, which is filed orally or in writing with air traffic control. (FAR Part 1)
Flight Service Station (FSS): A central operations facility in the national flight advisory system utilizing data interchange facilities for the collection and dissemination of NOTAMS, weather, administrative date; and providing preflight and inflight advisory service, and other services to pilot, via air/ground communication facilities. (FAA Order 1000.15A)
flight time: The time from the moment the aircraft first moves under its own power for the purpose of flight until the moment it comes to rest at the next point of landing ("block-to-block" time). (FAR Part 1)
fuel flowage fees: Fees levied by the airport operator per gallon of aviation gasoline and jet fuel sold at the airport.
general aviation: That portion of civil aviation which encompasses all facets of aviation except air carriers holding a certificate of convenience and necessity from the Civil Aeronautics Board, and commercial operators of large aircraft. (FAA Order 1000.15A)
general aviation airports: Those airports with fewer than 2,500 annual enplaned passengers and those used exclusively by private and business aircraft not providing common-carrier passenger service.
general aviation itinerant operations: Takeoffs and landings of civil aircraft (exclusive of air carrier) operating on other than local flights. (FAA Order 1000.15A)
glideslope transmitter (GS): An ILS navigation facility in the terminal area electronic navigation system, providing vertical guidance for aircraft during approach and landing by radiating a directional pattern of VHF radio waves modulated by two signals which, when received with equal intensity, are displayed by compatible airborne equipment as an "on-path" indication. (FAA Order 1000.15A)
handoff: Passing of control of an aircraft from one controller to another, either within the same facility or interfacility. (FAA Order 1000.15A)
hangar: A building used to store one or more aircraft, and/or conduct aircraft maintenance.
heliport: An area of land, water, or structure used or intended to be used for the landing and takeoff of helicopters. (FAR Part 1)
high-intensity light: A runway or threshold light whose main beam provides a minimum intensity of 12,000 candlepower in white light through a vertical angle of 3 degrees and a horizontal angle of 6 degrees.
HIRL: High intensity runway lighting. (FAA Order 1000.15A)
holding areas: Run-up areas located at or very near the ends of runways for pilots to make final checks and await final clearance for takeoff.
holding bay: An area where aircraft can be held, or bypassed, to facilitate efficient ground traffic movement. (FAA Order 1000.15A)
horizontal surface: A specified portion of a horizontal plane located 150 feet above the established airport elevation which establishes the height above which an object is determined to be an obstruction to air navigation. (FAA Order 1000.15A)
IFR: Instrument Flight Rules (FAR Part 91).
IFR airport: An airport with an authorized instrument approach procedure. (FAA Order 1000.15A)
IFR conditions: Weather conditions below the minimum for flight under visual flight rules. (FAR Part 1)
ILS: Instrument Landing System.
ILS Category I: An ILS which provides acceptable guidance information from the coverage limits of the ILS to the point at which the localizer course line intersects the glide path at a height of 100 feet above the horizontal plane containing the runway threshold. A Category I ILS supports landing minima as low as
200 ft. HAT and 1800 RVR. (FAA Order 1000.15A)
ILS Category II: An ILS which provides acceptable guidance information from the coverage limits of the ILS to the point at which the localizer course line intersects the glide path at a height of 50 feet above the horizontal plane containing the runway threshold. A Category II ILS supports landing minima as low as
100 feet HAT and 1200 RVR. (FAA Order 1000.15A)
ILS Category III: An ILS which provides acceptable guidance information from the coverage limits of the ILS with no decision height specified above the horizontal plane containing the runway threshold.
See ILS-CAT III A-B-C operations . (FAA Order 1000.15A)
ILS-CAT III A operation: Operation, with no decision height limitation, to and along the surface of the runway with a runway visual range not less than 700 feet. (FAA Order 1000.15A)
ILS-CAT III B operation: Operation, with no decision height limitation, to and along the surface of the runway without reliance on external visual reference; and, subsequently, taxiing with external visual reference with a runway visual range not less than 150 feet. (FAA Order 1000.15A)
ILS CAT III C operation: Operation, with no decision height limitation, to and along the surface of the runway and taxiways without reliance on external visual reference. (FAA Order 1000.15A)
inactive airport: An airport where all flying activities have ceased yet has remained in an acceptable state of repair for civil use and is identifiable from the air as an airport. (FAA Order 1000.15A)
INM: Integrated Noise Model; FAA computer program used to generate noise contours of equal sound levels.
inner marker (IM): An ILS navigational facility in the terminal area navigation system located between the middle marker and the end of the ILS runway, transmitting a 75 megahertz fan shaped radiation pattern modulated at 3000 Hz, keyed at six dots per second and received by compatible airborne equipment indicating to the pilot, both aurally and visually, that he is directly over the facility at an altitude of 100 feet on his final ILS approach, providing he is on the glide path. (FAA Order 1000.15A)
in-runway lighting: A lighting system consisting of flush or semi-flush lights placed in the runway pavement in specified patterns. (FAA Order 1000.15A)
instrument approach aids: An approach to an airport during which the pilot navigates solely by instruments for some period of time.
instrument approach: An approach to an airport, with intent to land, by an aircraft flying in accordance with an IFR flight plan, when the visibility is less than 3 miles and/or when the ceiling is at or below the minimum initial altitude. (FAA Order 1000.15A)
instrument approach runway: A runway served by an electronic aid providing at least directional guidance adequate for a straight-in approach. (FAA Order 1000.15A)
Instrument Flight Rules (IFR): Rules governing the procedures for conducting instrument flight. Pilots are required to follow these rules when operating in controlled airspace with a visibility of less than three miles and/or a ceiling lower than 1,000 feet.
instrument landing system (ILS): A system which provides in the aircraft, the lateral, longitudinal, and vertical guidance necessary for a landing. (FAA Order 1000.15A)
instrument meteorological conditions (IMC): Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling less than the minima specified for visual meteorological conditions.
(FAA Order 1000.15A)
instrument operation: A take-off or landing of an aircraft that has an instrument flight clearance.
instrument runway: A runway equipped with electronic and visual navigation aids and for which a straight-in (precision or non-precision) approach procedure has been approved or is planned.
intersecting runways: Two or more runways which cross or meet within their lengths. (FAA Order 1000.15A)
itinerant operations: All aircraft arrivals and departures other than local operations. (FAA Order 1000.15A)
jet noise: The noise generated externally to a jet engine in the turbulent jet exhaust. (FAA Order 1000.15A)
Joint Automated Weather Observation System (JAWOS): Automatically gathers local weather data and distributes it to other air traffic control facilities and to the National Weather Service.
joint-use airport: An airport owned by the military, a public body, or both, where an agreement exists for joint civil-military fixed-based aviation operations. (FAA Order 1000.15A)
landing area: any locality, either on land or water, including airports, heliports and STOLports, which is used or intended to be used for the landing and takeoff or surface maneuvering of aircraft, whether or not facilities are provided for the shelter, servicing, or repair of aircraft, or for receiving or discharging of passengers or cargo. (FAA Order 1000.15A)
landing gear: That part of an aircraft which is required for landing. Gear may be configured as Single Wheel Gear (SWG), Dual Wheel Gear (DWG), or Dual Tandem Wheel Gear (DTWG).
landing roll: The distance from the point of touchdown to the point where the aircraft can be brought to a stop, or exit the runway. (FAA Order 1000.15A)
landing strip: A term formerly used to designate: (1) the graded area upon which the runway was symmetrically located and, (2) the graded area suitable for the takeoff and land of airplanes where a paved runway was not provided. (FAA Order 1000.15A)
landside operations: Those parts of the airport designed to serve passengers including the terminal buildings, vehicular circular drive, and parking facilities.
land use plan: Shows on-airport land uses as developed by the airport sponsor under the master plan effort and off-airport land uses as developed by surrounding communities.
large aircraft: Aircraft of more than 12,500 pounds maximum certificated takeoff weight. (FAR Part 1)
Ldn: The Ldn is the 24-hour average sound level, in decibels, for the period from midnight to midnight, obtained after the addition of ten decibels to sound levels for the periods between midnight and 7 a.m. and between 19 o.m. and midnight, local time, as averaged over a span of one year. It is the FAA standard metric for determining the cumulative exposure of individuals to noise.
lighted airport: An airport where runway and associated obstruction lighting is available from sunset to sunrise or during periods of reduced visibility or on request of the pilot. (FAA Order 1000.15A)
localizer: A non-precision NAVAID which gives electronic directional guidance to a specific runway to pilots approaching for a landing. (FAA Order 1000.15A)
localizer beacon: An ILS navigation facility in the terminal area electronic navigation system, providing horizontal guidance to the runway centerline for aircraft during approach and landing by radiating a directional pattern of VHF radio waves modulated by two signals which, when received with equal intensity, are displayed by compatible airborne equipment as an "on-course" indication, and when received in unequal intensity are displayed as an "off-course" indication. (FAA Order 1000.15A)
local operations: As pertaining to air traffic operations, aircraft operating in the local traffic pattern or within sight of the tower; aircraft known to be departing for, or arriving from, flight in local practice areas located within a 20-mile radius of the control tower; aircraft executing simulated instrument approaches or low passes at the airport. (FAA Order 1000.15A)
local traffic: Aircraft operating in the local traffic pattern or within sight of the tower, or aircraft known to be departing for or arriving from flight in local practice areas, or aircraft executing simulated instrument approaches at the airport. (FAA Order 1000.15A)
local VFR flight plan: Specific information provided to air traffic service units, relative to the intended flight of an aircraft under visual flight rules within a specific local area. (FAA Order 1000.15A)
location map: Shown on the airport layout plan drawing, it depicts the airport, cities, railroads, major highways, and roads within 20 to 50 miles of the airport.
low-intensity light: A runway or threshold light from which the light distribution through 360 degrees of azimuth and a selected 6 degrees in the vertical is not less than 10 candlepower in white light. (FAA Order 1000.15A)
Low Level Wind Shear Alert System (LLWSAS): Provides the air traffic control tower with information on wind conditions near the runway. It consists of an array of anemometers that read wind velocity and direction around the airport and signal the sudden changes that indicate wind shear.
MALSR: A medium intensity approach lighting system with runway alignment indicator lights.
marking: On airports, a pattern of contrasting colors placed on the pavement, turf, or other usable surface by paint or other means to provide specific information to aircraft pilots and sometimes to operators of ground vehicles, on the movement areas. (FAA Order 1000.15A)
metering: Regulating the arrival time of aircraft in the terminal area so as not to exceed a given acceptance rate.
Microwave Landing System (MLS): An advanced form of precision approach system (MLS) equipment with improved accuracy and fewer siting problems than current ILS. An MLS also can permit curved path approaches to the runway instead of requiring a straight path as an ILS and PAR do (FAA Order 1000.15A)
middle marker (MM): An ILS navigation facility in the terminal area navigation system located approximately 3,500 feet from the runway edge on the extended centerline, transmitting a 75 MHz fan-shaped radiation pattern, modulated at 1,300 Hz, keyed alternately dot and dash, and received by compatible airborne equipment, indicating to the pilot both aurally and visually, that he is passing over the fac