PILOT/CONTROLLER GLOSSARY This glossary was compiled to promote a common understanding of the terms used in the Air Traffic Control system. It includes those terms which are intended for pilot/controller communications. Those terms most frequently used in pilot/controller communications are printed in bold italics. The definitions are primarily defined in an operational sense applicable to both users and operators of the National Airspace System. Use of the glossary will preclude any misunderstandings concerning the system's design, function, and purpose. Because of the international nature of flying, terms used in the Lexicon, published by the International Civil Aviation Organization (ICAO), are included when they differ from FAA definitions. These terms are followed by ``[ICAO]''. For the reader's convenience, there are also cross references to related terms in other parts of the Glossary and to other documents, such as the Federal Aviation Regulations (FAR's) and the Airman's Information Manual (AIM). This glossary was compiled from electronic data made available by the FAA. It will be revised, as necessary, to maintain a common understanding of the system. AAI (See ARRIVAL AIRCRAFT INTERVAL). AAR (See AIRPORT ACCEPTANCE RATE). ABBREVIATED IFR FLIGHT PLANS An authorization by ATC requiring pilots to submit only that information needed for the purpose of ATC. It includes only a small portion of the usual IFR flight plan information. In certain instances, this may be only aircraft identification, location, and pilot request. Other information may be requested if needed by ATC for separation/control purposes. It is frequently used by aircraft which are airborne and desire an instrument approach or by aircraft which are on the ground and desire a climb to VFR on top. ABEAM An aircraft is ``abeam'' a fix, point, or object when that fix, point, or object is approximately 90 degrees to the right or left of the aircraft track. Abeam indicates a general position rather than a precise point. ABORT To terminate a preplanned aircraft maneuver; e.g., an aborted takeoff. ACC [ICAO] (See AREA CONTROL CENTER). ACCELERATE-STOP DISTANCE AVAILABLE The runway plus stopway length declared available and suitable for the acceleration and deceleration of an airplane aborting a takeoff ACCELERATE-STOP DISTANCE AVAILABLE [ICAO] The length of the take-off run available plus the length of the stopway if provided. ACDO (See AIR CARRIER DISTRICT OFFICE). ACKNOWLEDGE Let me know that you have received my message. ACKNOWLEDGE [ICAO] Let me know that you have received and understood this message. ACLS (See AUTOMATIC CARRIER LANDING SYSTEM). ACLT (See ACTUAL CALCULATED LANDING TIME). ACROBATIC FLIGHT An intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration not necessary for normal flight. ACROBATIC FLIGHT [ICAO] Manoeuvres intentionally performed by an aircraft involving an abrupt change in its attitude, an abnormal attitude, or an abnormal variation in speed. ACTIVE RUNWAY (See RUNWAY IN USE/ACTIVE RUNWAY/DUTY RUNWAY). ACTUAL CALCULATED LANDING TIME ACLT is a flight's frozen calculated landing time. An actual time determined at freeze calculated landing time (FCLT) or meter list display interval (MLDI) for the adapted vertex for each arrival aircraft based upon runway configuration, airport acceptance rate, airport arrival delay period, and other metered arrival aircraft. This time is either the vertex time of arrival (VTA) of the aircraft or the tentative calculated landing time (TCLT)/ACLT of the previous aircraft plus the arrival aircraft interval (AAI), whichever is later. This time will not be updated in response to the aircraft's progress. ADDITIONAL SERVICES Advisory information provided by ATC which includes but is not limited to the following: Traffic advisories. Vectors, when requested by the pilot, to assist aircraft receiving traffic advisories to avoid observed traffic. Altitude deviation information of 300 feet or more from an assigned altitude as observed on a verified (reading correctly) automatic altitude readout (Mode C). Advisories that traffic is no longer a factor. Weather and chaff information. Weather assistance. Bird activity information. Holding pattern surveillance. Additional services are provided to the extent possible contingent only upon the controller's capability to fit them into the performance of higher priority duties and on the basis of limitations of the radar, volume of traffic, frequency congestion, and controller workload. The controller has complete discretion for determining if he is able to provide or continue to provide a service in a particular case. The controller's reason not to provide or continue to provide a service in a particular case is not subject to question by the pilot and need not be made known to him. ADF (See AUTOMATIC DIRECTION FINDER). ADIZ (See AIR DEFENSE IDENTIFICATION ZONE). ADLY (See ARRIVAL DELAY). ADMINISTRATOR The Federal Aviation Administrator or any person to whom he has delegated his authority in the matter concerned. ADVISE INTENTIONS Tell me what you plan to do. ADVISORY Advice and information provided to assist pilots in the safe conduct of flight and aircraft movement. ADVISORY FREQUENCY The appropriate frequency to be used for Airport Advisory Service. ADVISORY SERVICE Advice and information provided by a facility to assist pilots in the safe conduct of flight and aircraft movement. AERIAL REFUELING A procedure used by the military to transfer fuel from one aircraft to another during flight. AERODROME A defined area on land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure, and movement of aircraft. AERODROME BEACON [ICAO] Aeronautical beacon used to indicate the location of an aerodrome from the air. AERODROME CONTROL SERVICE [ICAO] Air traffic control service for aerodrome traffic. AERODROME CONTROL TOWER [ICAO] A unit established to provide air traffic control service to aerodrome traffic. AERODROME ELEVATION [ICAO] The elevation of the highest point of the landing area. AERODROME TRAFFIC CIRCUIT [ICAO] The specified path to be flown by aircraft operating in the vicinity of an aerodrome. AERONAUTICAL BEACON A visual NAVAID displaying flashes of white and/or colored light to indicate the location of an airport, a heliport, a landmark, a certain point of a Federal airway in mountainous terrain, or an obstruction. AERONAUTICAL CHART A map used in air navigation containing all or part of the following: Topographic features, hazards and obstructions, navigation aids, navigation routes, designated airspace, and airports. Commonly used aeronautical charts are: Sectional Aeronautical Charts (1:500,000). Designed for visual navigation of slow or medium speed aircraft. Topographic information on these charts features the portrayal of relief and a judicious selection of visual check points for VFR flight. Aeronautical information includes visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions, and related data. VFR Terminal Area Charts (1:250,000). Depict Class B airspace which provides for the control or segregation of all the aircraft within Class B airspace. The chart depicts topographic information and aeronautical information which includes visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions, and related data. World Aeronautical Charts (WAC) (1:1,000,000). Provide a standard series of aeronautical charts covering land areas of the world at a size and scale convenient for navigation by moderate speed aircraft. Topographic information includes cities and towns, principal roads, railroads, distinctive landmarks, drainage, and relief. Aeronautical information includes visual and radio aids to navigation, airports, airways, restricted areas, obstructions, and other pertinent data. En Route Low Altitude Charts. Provide aeronautical information for en route instrument navigation (IFR) in the low altitude stratum. Information includes the portrayal of airways, limits of controlled airspace, position identification and frequencies of radio aids, selected airports, minimum en route and minimum obstruction clearance altitudes, airway distances, reporting points, restricted areas, and related data. Area charts, which are a part of this series, furnish terminal data at a larger scale in congested areas. En Route High Altitude Charts. Provide aeronautical information for en route instrument navigation (IFR) in the high altitude stratum. Information includes the portrayal of jet routes, identification and frequencies of radio aids, selected airports, distances, time zones, special use airspace, and related information. Instrument Approach Procedures (IAP) Charts. Portray the aeronautical data which is required to execute an instrument approach to an airport. These charts depict the procedures, including all related data, and the airport diagram. Each procedure is designated for use with a specific type of electronic navigation system including NDB, TACAN, VOR, ILS/MLS, and RNAV. These charts are identified by the type of navigational aid(s) which provide final approach guidance. Standard Instrument Departure (SID) Charts. Designed to expedite clearance delivery and to facilitate transition between takeoff and en route operations. Each SID procedure is presented as a separate chart and may serve a single airport or more than one airport in a given geographical location. Standard Terminal Arrival (STAR) Charts. Designed to expedite air traffic control arrival procedures and to facilitate transition between en route and instrument approach operations. Each STAR procedure is presented as a separate chart and may serve a single airport or more than one airport in a given geographical location. Airport Taxi Charts. Designed to expedite the efficient and safe flow of ground traffic at an airport. These charts are identified by the official airport name; e.g., Washington National Airport. AERONAUTICAL CHART [ICAO] A representation of a portion of the earth, its culture and relief, specifically designated to meet the requirements of air navigation. AERONAUTICAL INFORMATION PUBLICATION [AIP] [ICAO] A publication issued by or with the authority of a State and containing aeronautical information of a lasting character essential to air navigation. A/FD (See AIRPORT/FACILITY DIRECTORY). AFFIRMATIVE Yes. AIM (See AIRMAN'S INFORMATION MANUAL). AIP [ICAO] (See AERONAUTICAL INFORMATION PUBLICATION). AIRBORNE DELAY Amount of delay to be encountered in airborne holding. AIR CARRIER DISTRICT OFFICE An FAA field office serving an assigned geographical area, staffed with Flight Standards personnel serving the aviation industry and the general public on matters related to the certification and operation of scheduled air carriers and other large aircraft operations. AIRCRAFT Device(s) that are used or intended to be used for flight in the air, and when used in air traffic control terminology, may include the flight crew. AIRCRAFT [ICAO] Any machine that can derive support in the atmosphere from the reactions of the air other than the reactions of the air against the earth's surface. AIRCRAFT APPROACH CATEGORY A grouping of aircraft based on a speed of 1.3 times the stall speed in the landing configuration at maximum gross landing weight. An aircraft shall fit in only one category. If it is necessary to maneuver at speeds in excess of the upper limit of a speed range for a category, the minimums for the next higher category should be used. For example, an aircraft which falls in Category A, but is circling to land at a speed in excess of 91 knots, should use the approach Category B minimums when circling to land. The categories are as follows: Category A. Speed less than 91 knots. Category B. Speed 91 knots or more but less than 121 knots. Category C. Speed 121 knots or more but less than 141 knots. Category D. Speed 141 knots or more but less than 166 knots. Category E. Speed 166 knots or more. AIRCRAFT CLASSES For the purposes of Wake Turbulence Separation Minima, ATC classifies aircraft as Heavy, Large, and Small as follows: Heavy. Aircraft capable of takeoff weights of 300,000 pounds or more whether or not they are operating at this weight during a particular phase of flight. Large. Aircraft of more than 12,500 pounds, maximum certificated takeoff weight, up to 300,000 pounds. Small. Aircraft of 12,500 pounds or less maximum certificated takeoff weight. AIRCRAFT SITUATION DISPLAY ASD is a computer system that receives radar track data from all 20 CONUS ARTCC's, organizes this data into a mosaic display, and presents it on a computer screen. The display allows the traffic management coordinator multiple methods of selection and high lighting of individual aircraft or groups of aircraft. The user has the option of superimposing these aircraft positions over any number of background displays. These background options include ARTCC boundaries, any stratum of en route sector boundaries, fixes, airways, military and other special use airspace, airports, and geopolitical boundaries. By using the ASD, a coordinator can monitor any number of traffic situations or the entire systemwide traffic flows. AIRCRAFT SURGE LAUNCH AND RECOVERY Procedures used at USAF bases to provide increased launch and recovery rates in instrument flight rules conditions. ASLAR is based on: Reduced separation between aircraft which is based on time or distance. Standard arrival separation applies between participants including multiple flights until the DRAG point. The DRAG point is a published location on an ASLAR approach where aircraft landing second in a formation slows to a predetermined airspeed. The DRAG point is the reference point at which MARSA applies as expanding elements effect separation within a flight or between subsequent participating flights. ASLAR procedures shall be covered in a Letter of Agreement between the responsible USAF military ATC facility and the concerned Federal Aviation Administration facility. Initial Approach Fix spacing requirements are normally addressed as a minimum. AIR DEFENSE EMERGENCY A military emergency condition declared by a designated authority. This condition exists when an attack upon the continental U.S., Alaska, Canada, or U.S. installations in Greenland by hostile aircraft or missiles is considered probable, is imminent, or is taking place. AIR DEFENSE IDENTIFICATION ZONE The area of airspace over land or water, extending upward from the surface, within which the ready identification, the location, and the control of aircraft are required in the interest of national security. Domestic Air Defense Identification Zone. An ADIZ within the United States along an international boundary of the United States. Coastal Air Defense Identification Zone. An ADIZ over the coastal waters of the United States. Distant Early Warning Identification Zone (DEWIZ). An ADIZ over the coastal waters of the State of Alaska. AIRMAN'S INFORMATION MANUAL A primary FAA publication whose purpose is to instruct airmen about operating in the National Airspace System of the U.S. It provides basic flight information, ATC Procedures and general instructional information concerning health, medical facts, factors affecting flight safety, accident and hazard reporting, and types of aeronautical charts and their use. AIRMAN'S METEOROLOGICAL INFORMATION (See AIRMET). AIRMET In flight weather advisories issued only to amend the area forecast concerning weather phenomena which are of operational interest to all aircraft and potentially hazardous to aircraft having limited capability because of lack of equipment, instrumentation, or pilot qualifications. AIRMET's concern weather of less severity than that covered by SIGMET's or Convective SIGMET's. AIRMET's cover moderate icing, moderate turbulence, sustained winds of 30 knots or more at the surface, widespread areas of ceilings less than 1,000 feet and/or visibility less than 3 miles, and extensive mountain obscurement. AIR NAVIGATION FACILITY 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 directional finding, or for radio or other electrical communication, and any other structure or mechanism having a similar purpose for guiding or controlling flight in the air or the landing and take off of aircraft. AIRPORT An area on 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. AIRPORT ACCEPTANCE RATE A dynamic input parameter specifying the number of arriving aircraft which an airport or airspace can accept from the ARTCC per hour. The AAR is used to calculate the desired interval between successive arrival aircraft. AIRPORT ADVISORY AREA The area within ten miles of an airport without a control tower or where the tower is not in operation, and on which a Flight Service Station is located. AIRPORT ELEVATION The highest point of an airport's usable runways measured in feet from mean sea level. AIRPORT/FACILITY DIRECTORY A publication designed primarily as a pilot's operational manual containing all airports, seaplane bases, and heliports open to the public including communications data, navigational facilities, and certain special notices and procedures. This publication is issued in seven volumes according to geographical area. AIRPORT INFORMATION AID (See AIRPORT INFORMATION DESK). AIRPORT INFORMATION DESK An airport unmanned facility designed for pilot self service briefing, flight planning, and filing of flight plans. AIRPORT LIGHTING Various lighting aids that may be installed on an airport. Types of airport lighting include: Approach Light 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 for landing. Condenser Discharge Sequential Flashing Lights/Sequenced Flashing Lights may be installed in conjunction with the ALS at some airports. Types of Approach Light Systems are: ALSF-1. Approach Light System with Sequenced Flashing Lights in ILS Cat I configuration. ALSF-2. Approach Light System with Sequenced Flashing Lights in ILS Cat II configuration. The ALSF-2 may operate as an SSALR when weather conditions permit. SSALF. Simplified Short Approach Light System with Sequenced Flashing Lights. SSALR. Simplified Short Approach Light System with Runway Alignment Indicator Lights. MALSF. Medium Intensity Approach Light System with Sequenced Flashing Lights. MALSR. Medium Intensity Approach Light System with Runway Alignment Indicator Lights. LDIN. Lead in light system: Consists of one or more series of flashing lights installed at or near ground level that provides positive visual guidance along an approach path, either curving or straight, where special problems exist with hazardous terrain, obstructions, or noise abatement procedures. RAIL. Runway Alignment Indicator Lights (Sequenced Flashing Lights which are installed only in combination with other light systems). ODALS. Omnidirectional Approach Lighting System consists of seven omnidirectional flashing lights located in the approach area of a nonprecision runway. Five lights are located on the runway centerline extended with the first light located 300 feet from the threshold and extending at equal intervals up to 1,500 feet from the threshold. The other two lights are located, one on each side of the runway threshold, at a lateral distance of 40 feet from the runway edge, or 75 feet from the runway edge when installed on a runway equipped with a VASI. Runway Lights/Runway Edge Lights. Lights having a prescribed angle of emission used to define the lateral limits of a runway. Runway lights are uniformly spaced at intervals of approximately 200 feet, and the intensity may be controlled or preset. Touchdown Zone Lighting. Two rows of tranverse light bars located symmetrically about the runway centerline normally at 100 foot intervals. The basic system extends 3,000 feet along the runway. Runway Centerline Lighting. Flush centerline lights spaced at 50-foot intervals beginning 75 feet from the landing threshold and extending to within 75 feet of the opposite end of the runway. Threshold Lights. Fixed green lights arranged symmetrically left and right of the runway centerline, identifying the runway threshold. Runway End Identifier Lights (REIL). Two synchronized flashing lights, one on each side of the runway threshold, which provide rapid and positive identification of the approach end of a particular runway. Visual Approach Slope Indicator (VASI). An airport lighting facility providing vertical visual approach slope guidance to aircraft during approach to landing by radiating a directional pattern of high intensity red and white focused light beams which indicate to the pilot that he is ``on path'' if he sees red/white, ``above path` if white/white, and ``below path'' if red/red. Some airports serving large aircraft have three bar VASIs which provide two visual glide paths to the same runway. Boundary Lights. Lights defining the perimeter of an airport or landing area. AIRPORT MARKING AIDS Markings used on runway and taxiway surfaces to identify a specific runway, a runway threshold, a centerline, a hold line, etc. A runway should be marked in accordance with its present usage such as: Visual. Nonprecision instrument. Precision instrument. AIRPORT RESERVATION OFFICE Office responsible for monitoring the operation of the high density rule. Receives and processes requests for IFR operations at high density traffic airports. AIRPORT ROTATING BEACON A visual NAVAID operated at many airports. At civil airports, alternating white and green flashes indicate the location of the airport. At military airports, the beacons flash alternately white and green, but are differentiated from civil beacons by dualpeaked (two quick) white flashes between the green flashes. AIRPORT SURFACE DETECTION EQUIPMENT Radar equipment specifically designed to detect all principal features on the surface of an airport, including aircraft and vehicular traffic, and to present the entire image on a radar indicator console in the control tower. Used to augment visual observation by tower personnel of aircraft and/or vehicular movements on runways and taxiways. AIRPORT SURVEILLANCE RADAR Approach control radar used to detect and display an aircraft's position in the terminal area. ASR provides range and azimuth information but does not provide elevation data. Coverage of the ASR can extend up to 60 miles. AIRPORT TAXI CHARTS (See AERONAUTICAL CHART). AIRPORT TRAFFIC CONTROL SERVICE A service provided by a control tower for aircraft operating on the movement area and in the vicinity of an airport. AIRPORT TRAFFIC CONTROL TOWER (See TOWER). AIR ROUTE SURVEILLANCE RADAR Air route traffic control center (ARTCC) radar used primarily to detect and display an aircraft's position while en route between terminal areas. The ARSR enables controllers to provide radar air traffic control service when aircraft are within the ARSR coverage. In some instances, ARSR may enable an ARTCC to provide terminal radar services similar to but usually more limited than those provided by a radar approach control. AIR ROUTE TRAFFIC CONTROL CENTER A facility established to provide air traffic control service to aircraft operating on IFR flight plans within controlled airspace and principally during the en route phase of flight. When equipment capabilities and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft. AIRSPACE HIERARCHY Within the airspace classes, there is a heirarchy and, in the event of an overlap of airspace: Class A preempts Class B, Class B preempts Class C, Class C preempts Class D, Class D preempts Class E, and Class E preempts Class G. AIRSPEED The speed of an aircraft relative to its surrounding air mass. The unqualified term ``airspeed` means one of the following: Indicated Airspeed. The speed shown on the aircraft airspeed indicator. This is the speed used in pilot/controller communications under the general term ``airspeed.'' True Airspeed. The airspeed of an aircraft relative to undisturbed air. Used primarily in flight planning and en route portion of flight. When used in pilot/controller communications, it is referred to as ``true airspeed'' and not shortened to ``airspeed.'' AIRSTART The starting of an aircraft engine while the aircraft is airborne, preceded by engine shutdown during training flights or by actual engine failure. AIR TAXI Used to describe a helicopter/VTOL aircraft movement conducted above the surface but normally not above 100 feet AGL. The aircraft may proceed either via hover taxi or flight at speeds more than 20 knots. The pilot is solely responsible for selecting a safe airspeed/altitude for the operation being conducted. AIR TRAFFIC Aircraft operating in the air or on an airport surface, exclusive of loading ramps and parking areas. AIR TRAFFIC [ICAO] All aircraft in flight or operating on the manoeuvring area of an aerodrome. AIR TRAFFIC CLEARANCE An authorization by air traffic control, for the purpose of preventing collision between known aircraft, for an aircraft to proceed under specified traffic conditions within controlled airspace. The pilot-in-command of an aircraft may not deviate from the provisions of a visual flight rules (VFR) or instrument flight rules (IFR) air traffic clearance unless an amended clearance has been obtained. Additionally, the pilot may request a different clearance from that which has been issued by air traffic control (ATC) if information available to the pilot makes another course of action more practicable or if aircraft equipment limitations or company procedures forbid compliance with the clearance issued. Pilots may also request clarification or amendment, as appropriate, any time a clearance is not fully understood, or considered unacceptable because of safety of flight. Controllers should, in such instances and to the extent of operational practicality and safety, honor the pilot's request. AIR TRAFFIC CONTROL A service operated by appropriate authority to promote the safe, orderly and expeditious flow of air traffic. AIR TRAFFIC CONTROL CLEARANCE [ICAO] Authorization for an aircraft to proceed under conditions specified by an air traffic control unit. AIR TRAFFIC CONTROL SERVICE (See AIR TRAFFIC CONTROL). AIR TRAFFIC CONTROL SERVICE [ICAO] A service provided for the purpose of: Preventing collisions: Between aircraft; and On the maneuvering area between aircraft and obstructions; and Expediting and maintaining an orderly flow of air traffic. AIR TRAFFIC CONTROL SPECIALIST A person authorized to provide air traffic control service. AIR TRAFFIC CONTROL SYSTEM COMMAND CENTER An Air Traffic Operations Service facility consisting of four operational units. Central Flow Control Function (CFCF). Responsible for coordination and approval of all major intercenter flow control restrictions on a system basis in order to obtain maximum utilization of the airspace. Central Altitude Reservation Function (CARF). Responsible for coordinating, planning, and approving special user requirements under the Altitude Reservation (ALTRV) concept. Airport Reservation Office (ARO). Responsible for approving IFR flights at designated high density traffic airports (John F. Kennedy, LaGuardia, O'Hare, and Washington National) during specified hours. ATC Contingency Command Post. A facility which enables the FAA to manage the ATC system when significant portions of the system's capabilities have been lost or are threatened. AIR TRAFFIC SERVICE A generic term meaning: Flight Information Service: Alerting Service: Air Traffic Advisory Service: Air Traffic Control Service: Area Control Service, Approach Control Service, or Airport Control Service. AIRWAY A Class E airspace area established in the form of a corridor, the centerline of which is defined by radio navigational aids. AIRWAY [ICAO] A control area or portion thereof established in the form of corridor equipped with radio navigational aids. AIRWAY BEACON Used to mark airway segments in remote mountain areas. The light flashes Morse Code to identify the beacon site. AIT (See AUTOMATED INFORMATION TRANSFER). ALERFA (Alert Phase) [ICAO] A situation wherein apprehension exists as to the safety of an aircraft and its occupants. ALERT AREA (See SPECIAL USE AIRSPACE). ALERT NOTICE A request originated by a flight service station (FSS) or an air route traffic control center (ARTCC) for an extensive communication search for overdue, unreported, or missing aircraft. ALERTING SERVICE A service provided to notify appropriate organizations regarding aircraft in need of search and rescue aid and assist such organizations as required. ALNOT (See ALERT NOTICE). ALPHANUMERIC DISPLAY Letters and numerals used to show identification, altitude, beacon code, and other information concerning a target on a radar display. ALTERNATE AERODROME [ICAO] An aerodrome to which an aircraft may proceed when it becomes either impossible or inadvisable to proceed to or to land at the aerodrome of intended landing. ALTERNATE AIRPORT An airport at which an aircraft may land if a landing at the intended airport becomes inadvisable. ALTIMETER SETTING The barometric pressure reading used to adjust a pressure altimeter for variations in existing atmospheric pressure or to the standard altimeter setting (29.92). ALTITUDE The height of a level, point, or object measured in feet Above Ground Level (AGL) or from Mean Sea Level (MSL). MSL Altitude. Altitude expressed in feet measured from mean sea level. AGL Altitude. Altitude expressed in feet measured above ground level. Indicated Altitude. The altitude as shown by an altimeter. On a pressure or barometric altimeter it is altitude as shown uncorrected for instrument error and uncompensated for variation from standard atmospheric conditions. ALTITUDE [ICAO] The vertical distance of a level, a point or an object considered as a point, measured from mean sea level (MSL). ALTITUDE READOUT An aircraft's altitude, transmitted via the Mode C transponder feature, that is visually displayed in 100-foot increments on a radar scope having readout capability. ALTITUDE RESERVATION Airspace utilization under prescribed conditions normally employed for the mass movement of aircraft or other special user requirements which cannot otherwise be accomplished. ALTRVs are approved by the appropriate FAA facility. ALTITUDE RESTRICTION An altitude or altitudes, stated in the order flown, which are to be maintained until reaching a specific point or time. Altitude restrictions may be issued by ATC due to traffic, terrain, or other airspace considerations. ALTITUDE RESTRICTIONS ARE CANCELED Adherence to previously imposed altitude restrictions is no longer required during a climb or descent. ALTRV (See ALTITUDE RESERVATION). AMVER (See AUTOMATED MUTUAL-ASSISTANCE VESSEL RESCUE SYSTEM APPROACH CLEARANCE Authorization by ATC for a pilot to conduct an instrument approach. The type of instrument approach for which a clearance and other pertinent information is provided in the approach clearance when required. APPROACH CONTROL FACILITY A terminal ATC facility that provides approach control service in a terminal area. APPROACH CONTROL SERVICE Air traffic control service provided by an approach control facility for arriving and departing VFR/IFR aircraft and, on occasion, en route aircraft. At some airports not served by an approach control facility, the ARTCC provides limited approach control service. APPROACH CONTROL SERVICE [ICAO] Air traffic control service for arriving or departing controlled flights. APPROACH GATE An imaginary point used within ATC as a basis for vectoring aircraft to the final approach course. The gate will be established along the final approach course 1 mile from the outer marker (or the fix used in lieu of the outer marker) on the side away from the airport for precision approaches and 1 mile from the final approach fix on the side away from the airport for nonprecision approaches. In either case when measured along the final approach course, the gate will be no closer than 5 miles from the landing threshold. APPROACH LIGHT SYSTEM (See AIRPORT LIGHTING). APPROACH SEQUENCE The order in which aircraft are positioned while on approach or awaiting approach clearance. APPROACH SEQUENCE [ICAO] The order in which two or more aircraft are cleared to approach to land at the aerodrome. APPROACH SPEED The recommended speed contained in aircraft manuals used by pilots when making an approach to landing. This speed will vary for different segments of an approach as well as for aircraft weight and configuration. APPROPRIATE ATS AUTHORITY [ICAO] The relevant authority designated by the State responsible for providing air traffic services in the airspace concerned. In the United States, the ``appropriate ATS authority'' is the Director, Office of Air Traffic System Management, ATM-1. APPROPRIATE AUTHORITY Regarding flight over the high seas: the relevant authority is the State of Registry. Regarding flight over other than the high seas: the relevant authority is the State having sovereignty over the territory being overflown. APPROPRIATE OBSTACLE CLEARANCE MINIMUM ALTITUDE Any of the following: (See Minimum IFR Altitude) (See Minimum En Route Altitude) (See Minimum Obstruction Clearance Altitude) (See Minimum Vectoring Altitude) APPROPRIATE TERRAIN CLEARANCE MINIMUM ALTITUDE Any of the following: (See Minimum IFR Altitude) (See Minimum En Route Altitude) (See Minimum Obstruction Clearance Altitude) (See Minimum Vectoring Altitude) APRON A defined area on an airport or heliport intended to accommodate aircraft for purposes of loading or unloading passengers or cargo, refueling, parking, or maintenance. With regard to seaplanes, a ramp is used for access to the apron from the water. APRON [ICAO] A defined area, on a land aerodrome, intended to accommodate aircraft for purposes of loading or unloading passengers, mail or cargo, refuelling, parking or maintenance. ARC The track over the ground of an aircraft flying at a constant distance from a navigational aid by reference to distance measuring equipment (DME). AREA CONTROL CENTER [ICAO] An ICAO term for an air traffic control facility primarily responsible for ATC services being provided IFR aircraft during the en route phase of flight. The U.S. equivalent facility is an air route traffic control center (ARTCC). AREA NAVIGATION A method of navigation that permits aircraft operation on any desired course within the coverage of station referenced navigation signals or within the limits of a self contained system capability. Random area navigation routes are direct routes, based on area navigation capability, between waypoints defined in terms of latitude/longitude coordinates, degree/distance fixes, or offsets from published or established routes/airways at a specified distance and direction. The major types of equipment are: VORTAC referenced or Course Line Computer (CLC) systems, which account for the greatest number of RNAV units in use. To function, the CLC must be within the service range of a VORTAC. OMEGA/VLF, although two separate systems, can be considered as one operationally. A long range navigation system based upon Very Low Frequency radio signals transmitted from a total of 17 stations worldwide. Inertial (INS) systems, which are totally self contained and require no information from external references. They provide aircraft position and navigation information in response to signals resulting from inertial effects on components within the system. MLS Area Navigation (MLS/RNAV), which provides area navigation with reference to an MLS ground facility. LORAN C is a long range radio navigation system that uses ground waves transmitted at low frequency to provide user position information at ranges of up to 600 to 1,200 nautical miles at both en route and approach altitudes. The usable signal coverage areas are determined by the signal to noise ratio, the envelope to cycle difference, and the geometric relationship between the positions of the user and the transmitting stations. AREA NAVIGATION [ICAO] A method of navigation which permits aircraft operation on any desired flight path within the coverage of station referenced navigation aids or within the limits of the capability of self contained aids, or a combination of these. ARINC An acronym for Aeronautical Radio, Inc., a corporation largely owned by a group of airlines. ARINC is licensed by the FCC as an aeronautical station and contracted by the FAA to provide communications support for air traffic control and meteorological services in portions of international airspace. ARMY AVIATION FLIGHT INFORMATION BULLETIN A bulletin that provides air operation data covering Army, National Guard, and Army Reserve aviation activities. ARO (See AIRPORT RESERVATION OFFICE). ARRESTING SYSTEM A safety device consisting of two major components, namely, engaging or catching devices and energy absorption devices for the purpose of arresting both tailhook and/or nontailhook equipped aircraft. It is used to prevent aircraft from overrunning runways when the aircraft cannot be stopped after landing or during aborted takeoff. Arresting systems have various names; e.g., arresting gear, hook device, wire barrier cable. ARRIVAL AIRCRAFT INTERVAL An internally generated program in hundredths of minutes based upon the AAR. AAI is the desired optimum interval between successive arrival aircraft over the vertex. ARRIVAL CENTER The ARTCC having jurisdiction for the impacted airport. ARRIVAL DELAY A parameter which specifies a period of time in which no aircraft will be metered for arrival at the specified airport. ARRIVAL SECTOR An operational control sector containing one or more meter fixes. ARRIVAL SECTOR ADVISORY LIST An ordered list of data on arrivals displayed at the PVD of the sector which controls the meter fix. ARRIVAL SEQUENCING PROGRAM The automated program designed to assist in sequencing aircraft destined for the same airport. ARRIVAL TIME The time an aircraft touches down on arrival. ARSR (See AIR ROUTE SURVEILLANCE RADAR). ARTCC (See AIR ROUTE TRAFFIC CONTROL CENTER). ARTS (See AUTOMATED RADAR TERMINAL SYSTEMS). ASD (See AIRCRAFT SITUATION DISPLAY). ASDA (See ACCELERATE-STOP DISTANCE AVAILABLE). ASDA [ICAO] (See ICAO Term ACCELERATE-STOP DISTANCE AVAILABLE). ASDE (See AIRPORT SURFACE DETECTION EQUIPMENT). ASLAR (See AIRCRAFT SURGE LAUNCH AND RECOVERY). ASP (See ARRIVAL SEQUENCING PROGRAM). ASR (See AIRPORT SURVEILLANCE RADAR). ASR APPROACH (See SURVEILLANCE APPROACH). ATC (See AIR TRAFFIC CONTROL). ATCAA (See ATC ASSIGNED AIRSPACE). ATC ADVISES Used to prefix a message of noncontrol information when it is relayed to an aircraft by other than an air traffic controller. ATC ASSIGNED AIRSPACE Airspace of defined vertical/lateral limits, assigned by ATC, for the purpose of providing air traffic segregation between the specified activities being conducted within the assigned airspace and other IFR air traffic. ATC CLEARANCE (See AIR TRAFFIC CLEARANCE). ATC CLEARS Used to prefix an ATC clearance when it is relayed to an aircraft by other than an air traffic controller. ATC INSTRUCTIONS Directives issued by air traffic control for the purpose of requiring a pilot to take specific actions; e.g., ``Turn left heading two five zero,'' ``Go around,'' ``Clear the runway.'' ATCRBS (See RADAR). ATC REQUESTS Used to prefix an ATC request when it is relayed to an aircraft by other than an air traffic controller. ATCSCC (See AIR TRAFFIC CONTROL SYSTEM COMMAND CENTER). ATCSCC DELAY FACTOR The amount of delay calculated to be assigned prior to departure. ATCT (See TOWER). ATIS (See AUTOMATIC TERMINAL INFORMATION SERVICE). ATIS [ICAO] (See ICAO Term AUTOMATIC TERMINAL INFORMATION SERVICE). ATS Route [ICAO] A specified route designed for channelling the flow of traffic as necessary for the provision of air traffic services. AUTOLAND APPROACH An autoland approach is a precision instrument approach to touchdown and, in some cases, through the landing rollout. An autoland approach is performed by the aircraft autopilot which is receiving position information and/or steering commands from onboard navigation equipment AUTOMATED INFORMATION TRANSFER A precoordinated process, specifically defined in facility directives, during which a transfer of altitude control and/or radar identification is accomplished without verbal coordination between controllers using information communicated in a full data block. AUTOMATED MUTUAL-ASSISTANCE VESSEL RESCUE SYSTEM A facility which can deliver, in a matter of minutes, a surface picture (SURPIC) of vessels in the area of a potential or actual search and rescue incident, including their predicted positions and their characteristics. AUTOMATED RADAR TERMINAL SYSTEMS The generic term for the ultimate in functional capability afforded by several automation systems. Each differs in functional capabilities and equipment. ARTS plus a suffix roman numeral denotes a specific system. A following letter indicates a major modification to that system. In general, an ARTS displays for the terminal controller aircraft identification, flight plan data, other flight associated information; e.g., altitude, speed, and aircraft position symbols in conjunction with his radar presentation. Normal radar co exists with the alphanumeric display. In addition to enhancing visualization of the air traffic situation, ARTS facilitate intra/inter facility transfer and coordination of flight information. These capabilities are enabled by specially designed computers and subsystems tailored to the radar and communications equipments and operational requirements of each automated facility. Modular design permits adoption of improvements in computer software and electronic technologies as they become available while retaining the characteristics unique to each system. ARTS II. A programmable nontracking, computer aided display subsystem capable of modular expansion. ARTS II systems provide a level of automated air traffic control capability at terminals having low to medium activity. Flight identification and altitude may be associated with the display of secondary radar targets. The system has the capability of communicating with ARTCC's and other ATRS II, IIA, III, and IIIA facilities. ARTS IIA. A programmable radar tracking computer subsystem capable of modular expansion. The ARTS IIA detects, tracks, and predicts secondary radar targets. The targets are displayed by means of computer generated symbols, ground speed, and flight plan data. Although it does not track primary radar targets, they are displayed coincident with the secondary radar as well as the symbols and alphanumerics. The system has the capability of communicating with ARTCC's and other ARTS II, IIA, III, and IIIA facilities. ARTS III. The Beacon Tracking Level of the modular programmable automated radar terminal system in use at medium to high activity terminals. ARTS III detects, tracks, and predicts secondary radar derived aircraft targets. These are displayed by means of computer generated symbols and alphanumeric characters depicting flight identification, aircraft altitude, ground speed, and flight plan data. Although it does not track primary targets, they are displayed coincident with the secondary radar as well as the symbols and alphanumerics. The system has the capability of communicating with ARTCC's and other ARTS III facilities. ARTS IIIA. The Radar Tracking and Beacon Tracking Level (RT&BTL) of the modular, programmable automated radar terminal system. ARTS IIIA detects, tracks, and predicts primary as well as secondary radar derived aircraft targets. This more sophisticated computer driven system upgrades the existing ARTS III system by providing improved tracking, continuous data recording, and fail soft capabilities. AUTOMATIC ALTITUDE REPORT (See ALTITUDE READOUT). AUTOMATIC ALTITUDE REPORTING That function of a transponder which responds to Mode C interrogations by transmitting the aircraft's altitude in 100-foot increments. AUTOMATIC CARRIER LANDING SYSTEM U.S. Navy final approach equipment consisting of precision tracking radar coupled to a computer data link to provide continuous information to the aircraft, monitoring capability to the pilot, and a backup approach system. AUTOMATIC DIRECTION FINDER An aircraft radio navigation system which senses and indicates the direction to a L/MF nondirectional radio beacon (NDB) ground transmitter. Direction is indicated to the pilot as a magnetic bearing or as a relative bearing to the longitudinal axis of the aircraft depending on the type of indicator installed in the aircraft. In certain applications, such as military, ADF operations may be based on airborne and ground transmitters in the VHF/UHF frequency spectrum. AUTOMATIC TERMINAL INFORMATION SERVICE The continuous broadcast of recorded noncontrol information in selected terminal areas. Its purpose is to improve controller effectiveness and to relieve frequency congestion by automating the repetitive transmission of essential but routine information; e.g., ``Los Angeles information Alfa. One three zero zero Coordinated Universal Time. Weather, measured ceiling two thousand overcast, visibility three, haze, smoke, temperature seven one, dew point five seven, wind two five zero at five, altimeter two niner niner six. I L S Runway Two Five Left approach in use, Runway Two Five Right closed, advise you have Alfa.'' AUTOMATIC TERMINAL INFORMATION SERVICE [ICAO] The provision of current, routine information to arriving and departing aircraft by means of continuous and repetitive broadcasts throughout the day or a specified portion of the day. AUTOROTATION A rotorcraft flight condition in which the lifting rotor is driven entirely by action of the air when the rotorcraft is in motion. Autorotative Landing/Touchdown Autorotation. Used by a pilot to indicate that he will be landing without applying power to the rotor. Low Level Autorotation. Commences at an altitude well below the traffic pattern, usually below 100 feet AGL and is used primarily for tactical military training. 180 degrees Autorotation. Initiated from a downwind heading and is commenced well inside the normal traffic pattern. ``Go around'' may not be possible during the latter part of this maneuver. AVIATION WEATHER SERVICE A service provided by the National Weather Service (NWS) and FAA which collects and disseminates pertinent weather information for pilots, aircraft operators, and ATC. Available aviation weather reports and forecasts are displayed at each NWS office and FAA FSS. AWW (See SEVERE WEATHER FORECAST ALERTS). AZIMUTH (MLS) A magnetic bearing extending from an MLS navigation facility. BASE LEG (See TRAFFIC PATTERN). BEACON (See RADAR). BEARING The horizontal direction to or from any point, usually measured clockwise from true north, magnetic north, or some other reference point through 360 degrees. BELOW MINIMUMS Weather conditions below the minimums prescribed by regulation for the particular action involved; e.g., landing minimums, takeoff minimums. BLAST FENCE A barrier that is used to divert or dissipate jet or propeller blast. BLIND SPEED The rate of departure or closing of a target relative to the radar antenna at which cancellation of the primary radar target by moving target indicator (MTI) circuits in the radar equipment causes a reduction or complete loss of signal. BLIND SPOT An area from which radio transmissions and/or radar echoes cannot be received. The term is also used to describe portions of the airport not visible from the control tower. BLIND TRANSMISSION (See TRANSMITTING IN THE BLIND). BLIND VELOCITY [ICAO] The radial velocity of a moving target such that the target is not seen on primary radars fitted with certain forms of fixed echo suppression. BLIND ZONE (See BLIND SPOT). BLOCKED Phraseology used to indicate that a radio transmission has been distorted or interrupted due to multiple simultaneous radio transmissions. BOUNDARY LIGHTS (See AIRPORT LIGHTING). BRAKING ACTION (GOOD, FAIR, POOR, OR NIL) A report of conditions on the airport movement area providing a pilot with a degree/quality of braking that he might expect. Braking action is reported in terms of good, fair, poor, or nil. BRAKING ACTION ADVISORIES When tower controllers have received runway braking action reports which include the terms ``poor'' or ``nil,'' or whenever weather conditions are conducive to deteriorating or rapidly changing runway braking conditions, the tower will include on the ATIS broadcast the statement, ``BRAKING ACTION ADVISORIES ARE IN EFFECT.'' During the time Braking Action Advisories are in effect, ATC will issue the latest braking action report for the runway in use to each arriving and departing aircraft. Pilots should be prepared for deteriorating braking conditions and should request current runway condition information if not volunteered by controllers. Pilots should also be prepared to provide a descriptive runway condition report to controllers after landing. BROADCAST Transmission of information for which an acknowledgement is not expected. BROADCAST [ICAO] A transmission of information relating to air navigation that is not addressed to a specific station or stations. CALCULATED LANDING TIME A term that may be used in place of tentative or actual calculated landing time, whichever applies. CALL UP Initial voice contact between a facility and an aircraft, using the identification of the unit being called and the unit initiating the call. CALL FOR RELEASE Wherein the overlying ARTCC requires a terminal facility to initiate verbal coordination to secure ARTCC approval for release of a departure into the en route environment. CANADIAN MINIMUM NAVIGATION PERFORMANCE SPECIFICATION AIRSPACE That portion of Canadian domestic airspace within which MNPS separation may be applied. CARDINAL ALTITUDES ``Odd'' or ``Even'' thousand foot altitudes or flight levels; e.g., 5,000, 6,000, 7,000, FL 250, FL 260, FL 270. CARDINAL FLIGHT LEVELS (See CARDINAL ALTITUDES). CAT (See CLEAR AIR TURBULENCE). CDT PROGRAMS (See CONTROLLED DEPARTURE TIME PROGRAMS). CEILING The heights above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as ``broken,'' ``overcast,'' or ``obscuration,'' and not classified as ``thin'' or ``partial''. CEILING [ICAO] The height above the ground or water of the base of the lowest layer of cloud below 6,000 metres (20,000 feet) covering more than half the sky. CENRAP (See CENTER RADAR ARTS PRESENTATION/PROCESSING). CENRAP-PLUS (See CENTER RADAR ARTS PRESENTATION/PROCESSING-PLUS). CENTER (See AIR ROUTE TRAFFIC CONTROL CENTER). CENTER'S AREA The specified airspace within which an air route traffic control center (ARTCC) provides air traffic control and advisory service. CENTER RADAR ARTS PRESENTATION/PROCESSING A computer program developed to provide a back up system for airport surveillance radar in the event of a failure or malfunction. The program uses air route traffic control center radar for the processing and presentation of data on the ARTS IIA or IIIA displays. CENTER RADAR ARTS PRESENTATION/PROCESSING PLUS A computer program developed to provide a back up system for airport surveillance radar in the event of a terminal secondary radar system failure. The program uses a combination of Air Route Traffic Control Center Radar and terminal airport surveillance radar primary targets displayed simultaneously for the processing and presentation of data on the ARTS IIA or IIIA displays. CENTER WEATHER ADVISORY An unscheduled weather advisory issued by Center Weather Service Unit meteorologists for ATC use to alert pilots of existing or anticipated adverse weather conditions within the next 2 hours. A CWA may modify or redefine a SIGMET. CENTRAL EAST PACIFIC An organized route system between the U.S. West Coast and Hawaii. CEP (See CENTRAL EAST PACIFIC). CERAP (See COMBINED CENTER RAPCON). CFR (See CALL FOR RELEASE). CHAFF Thin, narrow metallic reflectors of various lengths and frequency responses, used to reflect radar energy. These reflectors when dropped from aircraft and allowed to drift downward result in large targets on the radar display. CHARTED VFR FLYWAYS Charted VFR Flyways are flight paths recommended for use to bypass areas heavily traversed by large turbine powered aircraft. Pilot compliance with recommended flyways and associated altitudes is strictly voluntary. VFR Flyway Planning charts are published on the back of existing VFR Terminal Area charts. CHARTED VISUAL FLIGHT PROCEDURE APPROACH An approach wherein a radar controlled aircraft on an IFR flight plan, operating in VFR conditions and having an ATC authorization, may proceed to the airport of intended landing via visual landmarks and altitudes depicted on a charted visual flight procedure. CHASE An aircraft flown in proximity to another aircraft normally to observe its performance during training or testing. CHASE AIRCRAFT (See CHASE). CIRCLE TO LAND MANEUVER A maneuver initiated by the pilot to align the aircraft with a runway for landing when a straight in landing from an instrument approach is not possible or is not desirable. This maneuver is made only after ATC authorization has been obtained and the pilot has established required visual reference to the airport CIRCLE TO RUNWAY (RUNWAY NUMBER) Used by ATC to inform the pilot that he must circle to land because the runway in use is other than the runway aligned with the instrument approach procedure. When the direction of the circling maneuver in relation to the airport/runway is required, the controller will state the direction (eight cardinal compass points) and specify a left or right downwind or base leg as appropriate; e.g., ``Cleared VOR Runway Three Six Approach circle to Runway Two Two,'' or ``Circle northwest of the airport for a right downwind to Runway Two Two.'' CIRCLING APPROACH (See CIRCLE TO LAND MANEUVER). CIRCLING MANEUVER (See CIRCLE TO LAND MANEUVER). CIRCLING MINIMA (See LANDING MINIMUMS). CLASS A AIRSPACE (See Controlled Airspace CLASS A AIRSPACE) CLASS B AIRSPACE (See Controlled Airspace CLASS B AIRSPACE) CLASS C AIRSPACE (See Controlled Airspace CLASS C AIRSPACE) CLASS D AIRSPACE (See Controlled Airspace CLASS D AIRSPACE) CLASS E AIRSPACE (See Controlled Airspace CLASS E AIRSPACE) CLASS G AIRSPACE That airspace not designated as Class A, B, C, D or E. CLEAR AIR TURBULENCE Turbulence encountered in air where no clouds are present. This term is commonly applied to high level turbulence associated with wind shear. CAT is often encountered in the vicinity of the jet stream. CLEAR OF THE RUNWAY A taxiing aircraft, which is approaching a runway, is clear of the runway when all parts of the aircraft are held short of the applicable holding position marking. A pilot or controller may consider an aircraft, which is exiting or crossing a runway, to be clear of the runway when all parts of the aircraft are beyond the runway edge and there is no ATC restriction to its continued movement beyond the applicable holding position marking. Pilots and controllers shall exercise good judgement to ensure that adequate separation exists between all aircraft on runways and taxiways at airports with inadequate runway edge lines or holding position markings. CLEARANCE (See AIR TRAFFIC CLEARANCE). CLEARANCE LIMIT The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance. CLEARANCE LIMIT [ICAO] The point of which an aircraft is granted an air traffic control clearance. CLEARANCE VOID IF NOT OFF BY (TIME) Used by ATC to advise an aircraft that the departure clearance is automatically canceled if takeoff is not made prior to a specified time. The pilot must obtain a new clearance or cancel his IFR flight plan if not off by the specified time. CLEARANCE VOID TIME [ICAO] A time specified by an air traffic control unit at which a clearance ceases to be valid unless the aircraft concerned has already taken action to comply therewith. CLEARED AS FILED Means the aircraft is cleared to proceed in accordance with the route of flight filed in the flight plan. This clearance does not include the altitude, SID, or SID Transition. CLEARED (Type Of) APPROACH ATC authorization for an aircraft to execute a specific instrument approach procedure to an airport; e.g., ``Cleared ILS Runway Three Six Approach.'' CLEARED APPROACH ATC authorization for an aircraft to execute any standard or special instrument approach procedure for that airport. Normally, an aircraft will be cleared for a specific instrument approach procedure. CLEARED FOR TAKEOFF ATC authorization for an aircraft to depart. It is predicated on known traffic and known physical airport conditions. CLEARED FOR THE OPTION ATC authorization for an aircraft to make a touch and go, low approach, missed approach, stop and go, or full stop landing at the discretion of the pilot. It is normally used in training so that an instructor can evaluate a student's performance under changing situations. CLEARED THROUGH ATC authorization for an aircraft to make intermediate stops at specified airports without refiling a flight plan while en route to the clearance limit. CLEARED TO LAND ATC authorization for an aircraft to land. It is predicated on known traffic and known physical airport conditions. CLEARWAY An area beyond the takeoff runway under the control of airport authorities within which terrain or fixed obstacles may not extend above specified limits. These areas may be required for certain turbine powered operations and the size and upward slope of the clearway will differ depending on when the aircraft was certificated. CLIMBOUT That portion of flight operation between takeoff and the initial cruising altitude. CLIMB TO VFR ATC authorization for an aircraft to climb to VFR conditions within Class B, C, D, and E surface areas when the only weather limitation is restricted visibility. The aircraft must remain clear of clouds while climbing to VFR. CLOSED RUNWAY A runway that is unusable for aircraft operations. Only the airport management/military operations office can close a runway. CLOSED TRAFFIC Successive operations involving takeoffs and landings or low approaches where the aircraft does not exit the traffic pattern. CLT (See CALCULATED LANDING TIME). CLUTTER In radar operations, clutter refers to the reception and visual display of radar returns caused by precipitation, chaff, terrain, numerous aircraft targets, or other phenomena. Such returns may limit or preclude ATC from providing services based on radar. CMNPS (See CANADIAN MINIMUM NAVIGATION PERFORMANCE SPECIFICATION AIRSPACE). COASTAL FIX A navigation aid or intersection where an aircraft transitions between the domestic route structure and the oceanic route structure. CODES The number assigned to a particular multiple pulse reply signal transmitted by a transponder. COMBINED CENTER RAPCON An air traffic facility which combines the functions of an ARTCC and a radar approach control facility. COMMON POINT A significant point over which two or more aircraft will report passing or have reported passing before proceeding on the same or diverging tracks. To establish/maintain longitudinal separation, a controller may determine a common point not originally in the aircraft's flight plan and then clear the aircraft to fly over the point. See significant point. COMMON PORTION (See COMMON ROUTE). COMMON ROUTE That segment of a North American Route between the inland navigation facility and the coastal fix. COMMON TRAFFIC ADVISORY FREQUENCY A frequency designed for the purpose of carrying out airport advisory practices while operating to or from an uncontrolled airport. The CTAF may be a UNICOM, Multicom, FSS, or tower frequency and is identified in appropriate aeronautical publications. COMPASS LOCATOR A low power, low or medium frequency (L/MF) radio beacon installed at the site of the outer or middle marker of an instrument landing system (ILS). It can be used for navigation at distances of approximately 15 miles or as authorized in the approach procedure. Outer Compass Locator (LOM). A compass locator installed at the site of the outer marker of an instrument landing system. Middle Compass Locator (LMM). A compass locator installed at the site of the middle marker of an instrument landing system. COMPASS ROSE A circle, graduated in degrees, printed on some charts or marked on the ground at an airport. It is used as a reference to either true or magnetic direction. COMPOSITE FLIGHT PLAN A flight plan which specifies VFR operation for one portion of flight and IFR for another portion. It is used primarily in military operations. COMPOSITE ROUTE SYSTEM An organized oceanic route structure, incorporating reduced lateral spacing between routes, in which composite separation is authorized. COMPOSITE SEPARATION A method of separating aircraft in a composite route system where, by management of route and altitude assignments, a combination of half the lateral minimum specified for the area concerned and half the vertical minimum is applied. COMPULSORY REPORTING POINTS Reporting points which must be reported to ATC. They are designated on aeronautical charts by solid triangles or filed in a flight plan as fixes selected to define direct routes. These points are geographical locations which are defined by navigation aids/fixes. Pilots should discontinue position reporting over compulsory reporting points when informed by ATC that their aircraft is in ``radar contact.'' CONFLICT ALERT A function of certain air traffic control automated systems designed to alert radar controllers to existing or pending situations between tracked targets (known IFR or VFR aircraft) that require his immediate attention/action. CONFLICT RESOLUTION The resolution of potential conflictions between aircraft that are radar identified and in communication with ATC by ensuring that radar targets do not touch. Pertinent traffic advisories shall be issued when this procedure is applied. CONSOLAN A low frequency, long distance NAVAID used principally for transoceanic navigations. CONTACT Establish communication with (followed by the name of the facility and, if appropriate, the frequency to be used). A flight condition wherein the pilot ascertains the attitude of his aircraft and navigates by visual reference to the surface. CONTACT APPROACH An approach wherein an aircraft on an IFR flight plan, having an air traffic control authorization, operating clear of clouds with at least 1 mile flight visibility and a reasonable expectation of continuing to the destination airport in those conditions, may deviate from the instrument approach procedure and proceed to the destination airport by visual reference to the surface. This approach will only be authorized when requested by the pilot and the reported ground visibility at the destination airport is at least 1 statute mile. CONTERMINOUS U.S. The 48 adjoining States and the District of Columbia. CONTINENTAL UNITED STATES The 49 States located on the continent of North America and the District of Columbia. CONTROL AREA [ICAO] A controlled airspace extending upwards from a specified limit above the earth. 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. Note 1 - Controlled airspace is a generic term that covers Class A, Class B, Class C, Class D, and Class E airspace. Note 2 - Controlled airspace is also that airspace within which all aircraft operators are subject to certain pilot qualifications, operating rules, and equipment requirements in Part 91 (for specific operating requirements, please refer to Part 91). For IFR operations in any class of controlled airspace, a pilot must file an IFR flight plan and receive an appropriate ATC clearance. Each Class B, Class C, and Class D airspace area designated for an airport contains at least one primary airport around which the airspace is designated (for specific designations and descriptions of the airspace classes, please refer to Part 71). Controlled airspace in the United States is designated as follows: CLASS A: 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. Unless otherwise authorized, all persons must operate their aircraft under IFR. CLASS B: Generally, that airspace from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of airport 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 airspaces 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: Generally, 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 surface area with a 5 nm radius, and an outer area with a 10 nm radius that extends from 1,200 feet to 4,000 feet above the airport elevation. Each person must establish two-way radio communications with the ATC facility providing air traffic services prior to entering the airspace and thereafter maintain those communications while within the airspace. VFR aircraft are only separated from IFR aircraft within the airspace. CLASS D: Generally, 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. Arrival extensions for instrument approach procedures may be Class D or Class E airspace. Unless otherwise authorized, each person must establish two-way radio communications with the ATC facility providing air traffic services prior entering the airspace and thereafter maintain those communications while in the airspace. No separation services are provided to VFR aircraft. CLASS E: Generally, if the airspace is not Class A, Class B, Class C, or Class D, and it is controlled airspace, it is Class E airspace. Class E airspace extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace. When designated as a surface area, the airspace will be configured to contain all instrument procedures. Also in this class are Federal airways, airspace beginning at either 700 or 1,200 feet AGL used to transition to/from the terminal or enroute environment, enroute domestic, and offshore airspace areas designated below 18,000 feet MSL. Unless designated at a lower altitude, Class E airspace begins at 14,500 MSL over the United States, including that airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous States and Alaska, up to, but not including 18,000 feet MSL, and the airspace above FL 600. CONTROLLED AIRSPACE [ICAO] 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. Note-Controlled airspace is a generic term which covers ATS airspace Classes A, B, C, D, and E. CONTROLLED DEPARTURE TIME PROGRAMS These programs are the flow control process whereby aircraft are held on the ground at the departure airport when delays are projected to occur in either the en route system or the terminal of intended landing. The purpose of these programs is to reduce congestion in the air traffic system or to limit the duration of airborne holding in the arrival center or terminal area. A CDT is a specific departure slot shown on the flight plan as an expected departure clearance time (EDCT). CONTROLLED TIME OF ARRIVAL The original estimated time of arrival adjusted by the ATCSCC ground delay factor. CONTROLLER (See AIR TRAFFIC CONTROL SPECIALIST). CONTROLLER [ICAO] A person authorized to provide air traffic control services. CONTROL SECTOR An airspace area of defined horizontal and vertical dimensions for which a controller or group of controllers has air traffic control responsibility, normally within an air route traffic control center or an approach control facility. Sectors are established based on predominant traffic flows, altitude strata, and controller workload. Pilot communications during operations within a sector are normally maintained on discrete frequencies assigned to the sector. CONTROL SLASH A radar beacon slash representing the actual position of the associated aircraft. Normally, the control slash is the one closest to the interrogating radar beacon site. When ARTCC radar is operating in narrowband (digitized) mode, the control slash is converted to a target symbol. CONVECTIVE SIGMET A weather advisory concerning convective weather significant to the safety of all aircraft. Convective SIGMET's are issued for tornadoes, lines of thunderstorms, embedded thunderstorms of any intensity level, areas of thunderstorms greater than or equal to VIP level 4 with an area coverage of 4/10 (40%) or more, and hail 3/4 inch or greater. CONVECTIVE SIGNIFICANT METEOROLOGICAL INFORMATION (See CONVECTIVE SIGMET). COORDINATES The intersection of lines of reference, usually expressed in degrees/minutes/seconds of latitude and longitude, used to determine position or location. COORDINATION FIX The fix in relation to which facilities will handoff, transfer control of an aircraft, or coordinate flight progress data. For terminal facilities, it may also serve as a clearance for arriving aircraft. COPTER (See HELICOPTER). CORRECTION An error has been made in the transmission and the correct version follows. COUPLED APPROACH A coupled approach is an instrument approach performed by the aircraft autopilot which is receiving position information and/or steering commands from onboard navigation equipment. In general, coupled nonprecision approaches must be discontinued and flown manually at altitudes lower than 50 feet below the minimum descent altitude, and coupled precision approaches must be flown manually below 50 feet ALG COURSE The intended direction of flight in the horizontal plane measured in degrees from north. The ILS localizer signal pattern usually specified as the front course or the back course. The intended track along a straight, curved, or segmented MLS path. CPL [ICAO] (See CURRENT FLIGHT PLAN) CRITICAL ENGINE The engine which, upon failure, would most adversely affect the performance or handling qualities of an aircraft. CROSS (FIX) AT (ALTITUDE) Used by ATC when a specific altitude restriction at a specified fix is required. CROSS (FIX) AT OR ABOVE (ALTITUDE) Used by ATC when an altitude restriction at a specified fix is required. It does not prohibit the aircraft from crossing the fix at a higher altitude than specified; however, the higher altitude may not be one that will violate a succeeding altitude restriction or altitude assignment. CROSS (FIX) AT OR BELOW (ALTITUDE) Used by ATC when a maximum crossing altitude at a specific fix is required. It does not prohibit the aircraft from crossing the fix at a lower altitude; however, it must be at or above the minimum IFR altitude. CROSSWIND When used concerning the traffic pattern, the word means ``crosswind leg.'' When used concerning wind conditions, the word means a wind not parallel to the runway or the path of an aircraft. CROSSWIND COMPONENT The wind component measured in knots at 90 degrees to the longitudinal axis of the runway. CRUISE Used in an ATC clearance to authorize a pilot to conduct flight at any altitude from the minimum IFR altitude up to and including the altitude specified in the clearance. The pilot may level off at any intermediate altitude within this block of airspace. Climb/descent within the block is to be made at the discretion of the pilot. However, once the pilot starts descent and verbally reports leaving an altitude in the block, he may not return to that altitude without additional ATC clearance. Further, it is approval for the pilot to proceed to and make an approach at destination airport and can be used in conjunction with: An airport clearance limit at locations with a standard/special instrument approach procedure. The FAR's require that if an instrument letdown to an airport is necessary, the pilot shall make the letdown in accordance with a standard/special instrument approach procedure for that airport, or An airport clearance limit at locations that are within/below/outside controlled airspace and without a standard/special instrument approach procedure. Such a clearance is NOT AUTHORIZATION for the pilot to descend under IFR conditions below the applicable minimum IFR altitude nor does it imply that ATC is exercising control over aircraft in Class G airspace; however, it provides a means for the aircraft to proceed to destination airport, descend, and land in accordance with applicable FAR's governing VFR flight operations. Also, this provides search and rescue protection until such time as the IFR flight plan is closed. CRUISING ALTITUDE An altitude or flight level maintained during en route level flight. This is a constant altitude and should not be confused with a cruise clearance. CRUISING LEVEL [ICAO] A level maintained during a significant portion of a flight. CRUISE CLIMB A climb technique employed by aircraft, usually at a constant power setting, resulting in an increase of altitude as the aircraft weight decreases. CRUISING LEVEL (See CRUISING ALTITUDE). CT MESSAGE An EDCT time generated by the ATCSCC to regulate traffic at arrival airports. Normally, a CT message is automatically transferred from the Traffic Management System computer to the NAS en route computer and appears as an EDCT. In the event of a communication failure between the TMS and the NAS, the CT message can be manually entered by the TMC at the en route facility. CTA (See CONTROLLED TIME OF ARRIVAL). CTA (See CONTROL AREA [ICAO]). CTAF (See COMMON TRAFFIC ADVISORY FREQUENCY). CURRENT FLIGHT PLAN [ICAO] The flight plan, including changes, CVFP APPROACH (See CHARTED VISUAL FLIGHT PROCEDURE APPROACH). CWA (See CENTER WEATHER ADVISORY). DA [ICAO] (See ICAO Term DECISION ALTITUDE/DECISION HEIGHT). DAIR (See DIRECT ALTITUDE AND IDENTITY READOUT). DANGER AREA [ICAO] An airspace of defined dimensions within which activities dangerous to the flight of aircraft may exist at specified times. DATA BLOCK (See ALPHANUMERIC DISPLAY). DEAD RECKONING Dead reckoning, as applied to flying, is the navigation of an airplane solely by means of computations based on airspeed, course, heading, wind direction, and speed, groundspeed, and elapsed time. DECISION ALTITUDE/DECISION HEIGHT [ICAO] A specified altitude or height (A/H) in the precision approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. DECISION HEIGHT With respect to the operation of aircraft, means the height at which a decision must be made during an ILS, MLS, or PAR instrument approach to either continue the approach or to execute a missed approach. DECODER The device used to decipher signals received from ATCRBS transponders to effect their display as select codes. DEFENSE VISUAL FLIGHT RULES Rules applicable to flights within an ADIZ conducted under the visual flight rules in Part 91. DELAY INDEFINITE (REASON IF KNOWN) EXPECT FURTHER CLEARANCE (TIME) Used by ATC to inform a pilot when an accurate estimate of the delay time and the reason for the delay cannot immediately be determined; e.g., a disabled aircraft on the runway, terminal or center area saturation, weather below landing minimums, etc. DELAY TIME The amount of time that the arrival must lose to cross the meter fix at the assigned meter fix time. This is the difference between ACLT and VTA. DEPARTURE CENTER The ARTCC having jurisdiction for the airspace that generates a flight to the impacted airport. DEPARTURE CONTROL A function of an approach control facility providing air traffic control service for departing IFR and, under certain conditions, VFR aircraft. DEPARTURE SEQUENCING PROGRAM A program designed to assist in achieving a specified interval over a common point for departures. DEPARTURE TIME The time an aircraft becomes airborne. DESCENT SPEED ADJUSTMENTS Speed deceleration calculations made to determine an accurate VTA. These calculations start at the transition point and use arrival speed segments to the vertex. DETRESFA (DISTRESS PHASE) [ICAO] The code word used to designate an emergency phase wherein there is reasonable certainty that an aircraft and its occupants are threatened by grave and imminent danger or require immediate assistance. DEVIATIONS A departure from a current clearance, such as an off course maneuver to avoid weather or turbulence. Where specifically authorized in the FAR's and requested by the pilot, ATC may permit pilots to deviate from certain regulations. DF (See DIRECTION FINDER). DF APPROACH PROCEDURE Used under emergency conditions where another instrument approach procedure cannot be executed. DF guidance for an instrument approach is given by ATC facilities with DF capability. DF FIX The geographical location of an aircraft obtained by one or more direction finders. DF GUIDANCE Headings provided to aircraft by facilities equipped with direction finding equipment. These headings, if followed, will lead the aircraft to a predetermined point such as the DF station or an airport. DF guidance is given to aircraft in distress or to other aircraft which request the service. Practice DF guidance is provided when workload permits. DF STEER (See DF GUIDANCE). DH (See DECISION HEIGHT). DH [ICAO] (See ICAO Term DECISION ALTITUDE/DECISION HEIGHT). DIRECT Straight line flight between two navigational aids, fixes, points, or any combination thereof. When used by pilots in describing off airway routes, points defining direct route segments become compulsory reporting points unless the aircraft is under radar contact. DIRECT ALTITUDE AND IDENTITY READOUT The DAIR System is a modification to the AN/TPX-42 Interrogator System. The Navy has two adaptations of the DAIR System Carrier Air Traffic Control Direct Altitude and Identification Readout System for Aircraft Carriers and Radar Air Traffic Control Facility Direct Altitude and Identity Readout System for land based terminal operations. The DAIR detects, tracks, and predicts secondary radar aircraft targets. Targets are displayed by means of computer generated symbols and alphanumeric characters depicting flight identification, altitude, ground speed, and flight plan data. The DAIR System is capable of interfacing with ARTCC's. DIRECTION FINDER A radio receiver equipped with a directional sensing antenna used to take bearings on a radio transmitter. Specialized radio direction finders are used in aircraft as air navigation aids. Others are ground based, primarily to obtain a ``fix'' on a pilot requesting orientation assistance or to locate downed aircraft. A location ``fix'' is established by the intersection of two or more bearing lines plotted on a navigational chart using either two separately located Direction Finders to obtain a fix on an aircraft or by a pilot plotting the bearing indications of his DF on two separately located ground based transmitters, both of which can be identified on his chart. UDF's receive signals in the ultra high frequency radio broadcast band; VDF's in the very high frequency band; and UVDF's in both bands. ATC provides DF service at those air traffic control towers and flight service stations listed in the Airport/Facility Directory and the DOD FLIP IFR En Route Supplement. DISCRETE BEACON CODE (See DISCRETE CODE). DISCRETE CODE As used in the Air Traffic Control Radar Beacon System (ATCRBS), any one of the 4096 selectable Mode 3/A aircraft transponder codes except those ending in zero zero; e.g., discrete codes: 0010, 1201, 2317, 7777; nondiscrete codes: 0100, 1200, 7700. Nondiscrete codes are normally reserved for radar facilities that are not equipped with discrete decoding capability and for other purposes such as emergencies (7700), VFR aircraft (1200), etc. DISCRETE FREQUENCY A separate radio frequency for use in direct pilot controller communications in air traffic control which reduces frequency congestion by controlling the number of aircraft operating on a particular frequency at one time. Discrete frequencies are normally designated for each control sector in en route/terminal ATC facilities. Discrete frequencies are listed in the Airport/Facility Directory and the DOD FLIP IFR En Route Supplement. DISPLACED THRESHOLD A threshold that is located at a point on the runway other than the designated beginning of the runway. DISTANCE MEASURING EQUIPMENT Equipment (airborne and ground) used to measure, in nautical miles, the slant range distance of an aircraft from the DME navigational aid. DISTRESS A condition of being threatened by serious and/or imminent danger and of requiring immediate assistance. DIVE BRAKES (See SPEED BRAKES). DIVERSE VECTOR AREA In a radar environment, that area in which a prescribed departure route is not required as the only suitable route to avoid obstacles. The area in which random radar vectors below the MVA/MIA, established in accordance with the TERPS criteria for diverse departures obstacles and terrain avoidance, may be issued to departing aircraft. DME (See DISTANCE MEASURING EQUIPMENT). DME FIX A geographical position determined by reference to a navigational aid which provides distance and azimuth information. It is defined by a specific distance in nautical miles and a radial, azimuth, or course (i.e., localizer) in degrees magnetic from that aid. DME SEPARATION Spacing of aircraft in terms of distances (nautical miles) determined by reference to distance measuring equipment (DME). DOD FLIP Department of Defense Flight Information Publications used for flight planning, en route, and terminal operations. FLIP is produced by the Defense Mapping Agency for world wide use. United States Government Flight Information Publications (en route charts and instrument approach procedure charts) are incorporated in DOD FLIP for use in the National Airspace System (NAS). DOMESTIC AIRSPACE Airspace which overlies the continental land mass of the United States plus Hawaii and U.S. possessions. Domestic airspace extends to 12 miles offshore. DOWNBURST A strong downdraft which induces an outburst of damaging winds on or near the ground. Damaging winds, either straight or curved, are highly divergent. The sizes of downbursts vary from 1/2 mile or less to more than 10 miles. An intense down burst often causes widespread damage. Damaging winds, lasting 5 to 30 minutes, could reach speeds as high as 120 knots. DOWNWIND LEG (See TRAFFIC PATTERN). DRAG CHUTE A parachute device installed on certain aircraft which is deployed on landing roll to assist in deceleration of the aircraft. DSP (See DEPARTURE SEQUENCING PROGRAM). DT (See DELAY TIME). DUE REGARD A phase of flight wherein an aircraft commander of a State operated aircraft assumes responsibility to separate his aircraft from all other aircraft. DUTY RUNWAY (See RUNWAY IN USE/ACTIVE RUNWAY/DUTY RUNWAY). DVA (See DIVERSE VECTOR AREA). DVFR (See DEFENSE VISUAL FLIGHT RULES). DVFR FLIGHT PLAN A flight plan filed for a VFR aircraft which intends to operate in airspace within which the ready identification, location, and control of aircraft are required in the interest of national security. DYNAMIC Continuous review, evaluation, and change to meet demands. DYNAMIC RESTRICTIONS Those restrictions imposed by the local facility on an ~``as needed'' basis to manage unpredictable fluctuations in traffic demands. EARTS (See EN ROUTE AUTOMATED RADAR TRACKING SYSTEM). EDCT (See EXPECTED DEPARTURE CLEARANCE TIME). EFC (See EXPECT FURTHER CLEARANCE (TIME)). ELT (See EMERGENCY LOCATOR TRANSMITTER). EMERGENCY A distress or an urgency condition. EMERGENCY LOCATOR TRANSMITTER A radio transmitter attached to the aircraft structure which operates from its own power source on 121.5 mHz and 243.0 mHz. It aids in locating downed aircraft by radiating a downward sweeping audio tone, 2-4 times per second. It is designed to function without human action after an accident. EMERGENCY SAFE ALTITUDE (See MINIMUM SAFE ALTITUDE). ERMSAW (See EN ROUTE MINIMUM SAFE ALTITUDE WARNING). ENTRY POINT The point at which an aircraft transitions from an offshore control area to oceanic airspace. ENGINEERED PERFORMANCE STANDARDS A mathematically derived runway capacity standard. EPS's are calculated for each airport on an individual basis and reflect that airport's aircraft mix, operating procedures, runway layout, and specific weather conditions. EPS's do not give consideration to staffing, experience levels, equipment outages, and in trail restrictions as does the AAR. EN ROUTE AIR TRAFFIC CONTROL SERVICES Air traffic control service provided aircraft on IFR flight plans, generally by centers, when these aircraft are operating between departure and destination terminal areas. When equipment, capabilities, and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft. EN ROUTE AUTOMATED RADAR TRACKING SYSTEM An automated radar and radar beacon tracking system. Its functional capabilities and design are essentially the same as the terminal ARTS IIIA system except for the EARTS capability of employing both short range (ASR) and long range (ARSR) radars, use of full digital radar displays, and fail safe design. EN ROUTE CHARTS (See AERONAUTICAL CHART). EN ROUTE DESCENT Descent from the en route cruising altitude which takes place along the route of flight. EN ROUTE FLIGHT ADVISORY SERVICE A service specifically designed to provide, upon pilot request, timely weather information pertinent to his type of flight, intended route of flight, and altitude. The FSS's providing this service are listed in the Airport/Facility Directory. EN ROUTE HIGH ALTITUDE CHARTS (See AERONAUTICAL CHART). EN ROUTE LOW ALTITUDE CHARTS (See AERONAUTICAL CHART). EN ROUTE MINIMUM SAFE ALTITUDE WARNING A function of the NAS Stage A en route computer that aids the controller by alerting him when a tracked aircraft is below or predicted by the computer to go below a predetermined minimum IFR altitude (MIA). EN ROUTE SPACING PROGRAM A program designed to assist the exit sector in achieving the required in trail spacing. EPS (See ENGINEERED PERFORMANCE STANDARDS). ESP (See EN ROUTE SPACING PROGRAM). ESTIMATED ELAPSED TIME [ICAO] The estimated time required to proceed from one significant point to another. ESTIMATED OFF BLOCK TIME [ICAO] The estimated time at which the aircraft will commence movement associated with departure. ESTIMATED TIME OF ARRIVAL The time the flight is estimated to arrive at the gate (scheduled operators) or the actual runway on times for nonscheduled operators. ESTIMATED TIME EN ROUTE The estimated flying time from departure point to destination (lift off to touchdown). ETA (See ESTIMATED TIME OF ARRIVAL). ETE (See ESTIMATED TIME EN ROUTE). EXECUTE MISSED APPROACH Instructions issued to a pilot making an instrument approach which means continue inbound to the missed approach point and execute the missed approach procedure as described on the Instrument Approach Procedure Chart or as previously assigned by ATC. The pilot may climb immediately to the altitude specified in the missed approach procedure upon making a missed approach. No turns should be initiated prior to reaching the missed approach point. When conducting an ASR or PAR approach, execute the assigned missed approach procedure immediately upon receiving instructions to ``execute missed approach.'' EXPECT (ALTITUDE) AT (TIME) or (FIX) Used under certain conditions to provide a pilot with an altitude to be used in the event of two way communications failure. It also provides altitude information to assist the pilot in planning. EXPECTED DEPARTURE CLEARANCE TIME The runway release time assigned to an aircraft in a controlled departure time program and shown on the flight progress strip as an EDCT. EXPECT FURTHER CLEARANCE (TIME) The time a pilot can expect to receive clearance beyond a clearance limit. EXPECT FURTHER CLEARANCE VIA (AIRWAYS, ROUTES OR FIXES) Used to inform a pilot of the routing he can expect if any part of the route beyond a short range clearance limit differs from that filed. EXPEDITE Used by ATC when prompt compliance is required to avoid the development of an imminent situation. FAF (See FINAL APPROACH FIX). FA MESSAGE The data entered into the ARTCC computers that activates delay processing for an impacted airport. The FA data includes the delay factor for flight plans that have not been assigned delays under CT message processing. The delay factor appears on flight progress strips in the form of an EDCT (e.g., EDCT 1820). FA processing assigns delays in 15-minute time blocks. FA's control numbers of aircraft within a specified time block but do not spread aircraft out evenly throughout the time block. FAP (See FINAL APPROACH POINT). FAST FILE A system whereby a pilot files a flight plan via telephone that is tape recorded and then transcribed for transmission to the appropriate air traffic facility. Locations having a fast file capability are contained in the Airport/Facility Directory. FCLT (See FREEZE CALCULATED LANDING TIME). FEATHERED PROPELLER A propeller whose blades have been rotated so that the leading and trailing edges are nearly parallel with the aircraft flight path to stop or minimize drag and engine rotation. Normally used to indicate shutdown of a reciprocating or turboprop engine due to malfunction. FEDERAL AIRWAYS (See LOW ALTITUDE AIRWAY STRUCTURE). FEEDER FIX The fix depicted on Instrument Approach Procedure Charts which establishes the starting point of the feeder route. FEEDER ROUTE A route depicted on instrument approach procedure charts to designate routes for aircraft to proceed from the en route structure to the initial approach fix (IAF). FERRY FLIGHT A flight for the purpose of: Returning an aircraft to base. Delivering an aircraft from one location to another. Moving an aircraft to and from a maintenance base. Ferry flights, under certain conditions, may be conducted under terms of a special flight permit. FIELD ELEVATION (See AIRPORT ELEVATION). FILED Normally used in conjunction with flight plans, meaning a flight plan has been submitted to ATC. FILED EN ROUTE DELAY Any of the following preplanned delays at points/areas along the route of flight which require special flight plan filing and handling techniques. Terminal Area Delay. A delay within a terminal area for touch and go, low approach, or other terminal area activity. Special Use Airspace Delay. A delay within a Military Operating Area, Restricted Area, Warning Area, or ATC Assigned Airspace. Aerial Refueling Delay. A delay within an Aerial Refueling Track or Anchor. FILED FLIGHT PLAN The flight plan as filed with an ATS unit by the pilot or his designated representative without any subsequent changes or clearances. FINAL Commonly used to mean that an aircraft is on the final approach course or is aligned with a landing area. FINAL APPROACH [ICAO] That part of an instrument approach procedure which commences at the specified final approach fix or point, or where such a fix or point is not specified, a) At the end of the last procedure turn, base turn or inbound turn of a racetrack procedure, if specified; or b) At the point of interception of the last track specified in the approach procedure; and ends at a point in the vicinity of an aerodrome from which: 1)A landing can be made; or 2)A missed approach procedure is initiated. FINAL APPROACH COURSE A published MLS course, a straight line extension of a localizer, a final approach radial/bearing, or a runway centerline all without regard to distance. FINAL APPROACH FIX The fix from which the final approach (IFR) to an airport is executed and which identifies the beginning of the final approach segment. It is designated on Government charts by the Maltese Cross symbol for nonprecision approaches and the lightning bolt symbol for precision approaches; or when ATC directs a lower than published Glideslope/path Intercept Altitude, it is the resultant actual point of the glideslope/path intercept. FINAL APPROACH IFR The flight path of an aircraft which is inbound to an airport on a final instrument approach course, beginning at the final approach fix or point and extending to the airport or the point where a circle to land maneuver or a missed approach is executed. FINAL APPROACH POINT The point, applicable only to a nonprecision approach with no depicted FAF (such as an on airport VOR), where the aircraft is established inbound on the final approach course from the procedure turn and where the final approach descent may be commenced. The FAP serves as the FAF and identifies the beginning of the final approach segment. FINAL APPROACH SEGMENT (See SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE). FINAL APPROACH SEGMENT [ICAO] That segment of an instrument approach procedure in which alignment and descent for landing are accomplished. FINAL APPROACH VFR (See TRAFFIC PATTERN). FINAL CONTROLLER The controller providing information and final approach guidance during PAR and ASR approaches utilizing radar equipment. FINAL MONITOR AID A high resolution color display that is equipped with the controller alert system hardware/software which is used in the precision runway monitor (PRM) system. The display includes alert algorithms providing the target predictors, a color change alert when a target penetrates or is predicted to penetrate the no transgression zone (NTZ), a color change alert if the aircraft transponder becomes inoperative, synthesized voice alerts, digital mapping, and like features contained in the PRM system. FIR (See FLIGHT INFORMATION REGION). FIRST TIER CENTER The ARTCC immediately adjacent to the impacted center. FIX A geographical position determined by visual reference to the surface, by reference to one or more radio NAVAIDs, by celestial plotting, or by another navigational device. FIX BALANCING A process whereby aircraft are evenly distributed over several available arrival fixes reducing delays and controller workload. FLAG A warning device incorporated in certain airborne navigation and flight instruments indicating that: Instruments are inoperative or otherwise not operating satisfactorily, or Signal strength or quality of the received signal falls below acceptable values. FLAG ALARM (See FLAG). FLAMEOUT Unintended loss of combustion in turbine engines resulting in the loss of engine power. FLIGHT CHECK A call sign prefix used by FAA aircraft engaged in flight inspection/certification of navigational aids and flight procedures. The word ``recorded'' may be added as a suffix; e.g., ``Flight Check 320 recorded'' to indicate that an automated flight inspection is in progress in terminal areas. FLIGHT FOLLOWING (See TRAFFIC ADVISORIES). FLIGHT INFORMATION REGION An airspace of defined dimensions within which Flight Information Service and Alerting Service are provided. Flight Information Service. A service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights. Alerting Service. A service provided to notify appropriate organizations regarding aircraft in need of search and rescue aid and to assist such organizations as required. FLIGHT INFORMATION SERVICE A service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights. FLIGHT INSPECTION Inflight investigation and evaluation of a navigational aid to determine whether it meets established tolerances. FLIGHT LEVEL A level of constant atmospheric pressure related to a reference datum of 29.92 inches of mercury. Each is stated in three digits that represent hundreds of feet. For example, flight level 250 represents a barometric altimeter indication of 25,000 feet; flight level 255, an indication of 25,500 feet. FLIGHT LEVEL [ICAO] A surface of constant atmospheric pressure which is related to a specific pressure datum, 1013.2 hPa (1013.2 mb), and is separated from other such surfaces by specific pressure intervals. a)When set to a QNH altimeter setting, will indicate altitude; b)When set to a QFE altimeter setting, will indicate height above the QFE reference datum; and c)When set to a pressure of 1013.2 hPa (1013.2 mb), may be used to indicate flight levels. FLIGHT LINE A term used to describe the precise movement of a civil photogrammetric aircraft along a predetermined course(s) at a predetermined altitude during the actual photographic run. FLIGHT MANAGEMENT SYSTEMS A computer system that uses a large data base to allow routes to be preprogrammed and fed into the system by means of a data loader. The system is constantly updated with respect to position accuracy by reference to conventional navigation aids. The sophisticated program and its associated data base insures that the most appropriate aids are automatically selected during the information update cycle. FLIGHT PATH A line, course, or track along which an aircraft is flying or intended to be flown. FLIGHT PLAN Specified information relating to the intended flight of an aircraft that is filed orally or in writing with an FSS or an ATC facility. FLIGHT PLAN AREA The geographical area assigned by regional air traffic divisions to a flight service station for the purpose of search and rescue for VFR aircraft, issuance of notams, pilot briefing, in flight services, broadcast, emergency services, flight data processing, international operations, and aviation weather services. Three letter identifiers are assigned to every flight service station and are annotated in AFD's and Order 7350.6 as tie in facilities. FLIGHT RECORDER A general term applied to any instrument or device that records information about the performance of an aircraft in flight or about conditions encountered in flight. Flight recorders may make records of airspeed, outside air temperature, vertical acceleration, engine RPM, manifold pressure, and other pertinent variables for a given flight. FLIGHT RECORDER [ICAO] Any type of recorder installed in the aircraft for the purpose of complementing accident/incident investigation. FLIGHT SERVICE STATION Air traffic facilities which provide pilot briefing, en route communications and VFR search and rescue services, assist lost aircraft and aircraft in emergency situations, relay ATC clearances, originate Notices to Airmen, broadcast aviation weather and NAS information, receive and process IFR flight plans, and monitor NAVAID's. In addition, at selected locations, FSS's provide Enroute Flight Advisory Service (Flight Watch), take weather observations, issue airport advisories, and advise Customs and Immigration of transborder flights. FLIGHT STANDARDS DISTRICT OFFICE An FAA field office serving an assigned geographical area and staffed with Flight Standards personnel who serve the aviation industry and the general public on matters relating to the certification and operation of air carrier and general aviation aircraft. Activities include general surveillance of operational safety, certification of airmen and aircraft, accident prevention, investigation, enforcement, etc. FLIGHT TEST A flight for the purpose of: Investigating the operation/flight characteristics of an aircraft or aircraft component. Evaluating an applicant for a pilot certificate or rating. FLIGHT VISIBILITY (See VISIBILITY). FLIGHT WATCH A shortened term for use in air ground contacts to identify the flight service station providing En Route Flight Advisory Service; e.g., ``Oakland Flight Watch.'' FLIP (See DOD FLIP). FLOW CONTROL Measures designed to adjust the flow of traffic into a given airspace, along a given route, or bound for a given aerodrome (airport) so as to ensure the most effective utilization of the airspace. FLY HEADING (DEGREES) Informs the pilot of the heading he should fly. The pilot may have to turn to, or continue on, a specific compass direction in order to comply with the instructions. The pilot is expected to turn in the shorter direction to the heading unless otherwise instructed by ATC. FMA (See FINAL MONITOR AID). FMS (See FLIGHT MANAGEMENT SYSTEM). FORMATION FLIGHT More than one aircraft which, by prior arrangement between the pilots, operate as a single aircraft with regard to navigation and position reporting. Separation between aircraft within the formation is the responsibility of the flight leader and the pilots of the other aircraft in the flight. This includes transition periods when aircraft within the formation are maneuvering to attain separation from each other to effect individual control and during join up and breakaway. A standard formation is one in which a proximity of no more than 1 mile laterally or longitudinally and within 100 feet vertically from the flight leader is maintained by each wingman. Nonstandard formations are those operating under any of the following conditions: When the flight leader has requested and ATC has approved other than standard formation dimensions. When operating within an authorized altitude reservation (ALTRV) or under the provisions of a letter of agreement. When the operations are conducted in airspace specifically designed for a special activity. FRC (See REQUEST FULL ROUTE CLEARANCE). FREEZE/FROZEN Terms used in referring to arrivals which have been assigned ACLT's and to the lists in which they are displayed. FREEZE CALCULATED LANDING TIME A dynamic parameter number of minutes prior to the meter fix calculated time of arrival for each aircraft when the TCLT is frozen and becomes an ACLT (i.e., the VTA is updated and consequently the TCLT is modified as appropriate until FCLT minutes prior to meter fix calculated time of arrival, at which time updating is suspended and an ACLT and a frozen meter fix crossing time (MFT) is assigned). FREEZE SPEED PARAMETER A speed adapted for each aircraft to determine fast and slow aircraft. Fast aircraft freeze on parameter FCLT and slow aircraft freeze on parameter MLDI. FSDO (See FLIGHT STANDARDS DISTRICT OFFICE). FSPD (See FREEZE SPEED PARAMETER). FSS (See FLIGHT SERVICE STATION). FUEL DUMPING Airborne release of usable fuel. This does not include the dropping of fuel tanks. FUEL REMAINING A phrase used by either pilots or controllers when relating to the fuel remaining on board until actual fuel exhaustion. When transmitting such information in response to either a controller question or pilot initiated cautionary advisory to air traffic control, pilots will state the APPROXIMATE NUMBER OF MINUTES the flight can continue with the fuel remaining. All reserve fuel SHOULD BE INCLUDED in the time stated, as should an allowance for established fuel gauge system error. FUEL SIPHONING Unintentional release of fuel caused by overflow, puncture, loose cap, etc. FUEL VENTING (See FUEL SIPHONING). GADO (See GENERAL AVIATION DISTRICT OFFICE). GATE HOLD PROCEDURES Procedures at selected airports to hold aircraft at the gate or other ground location whenever departure delays exceed or are anticipated to exceed 15 minutes. The sequence for departure will be maintained in accordance with initial call up unless modified by flow control restrictions. Pilots should monitor the ground control/clearance delivery frequency for engine start/taxi advisories or new proposed start/taxi time if the delay changes. GCA (See GROUND CONTROLLED APPROACH). GENERAL AVIATION That portion of civil aviation which encompasses all facets of aviation except air carriers holding a certificate of public convenience and necessity from the Civil Aeronautics Board and large aircraft commercial operators. GENERAL AVIATION [ICAO] All civil aviation operations other than scheduled air services and nonscheduled air transport operations for remuneration or hire. GENERAL AVIATION DISTRICT OFFICE An FAA field office serving a designated geographical area and staffed with Flight Standards personnel who have the responsibility for serving the aviation industry and the general public on all matters relating to the certification and operation of general aviation aircraft. GEO MAP The digitized map markings associated with the ASR-9 Radar System. GLIDEPATH (See GLIDESLOPE). GLIDEPATH INTERCEPT ALTITUDE (See GLIDESLOPE INTERCEPT ALTITUDE). GLIDESLOPE Provides vertical guidance for aircraft during approach and landing. The glideslope/glidepath is based on the following: Electronic components emitting signals which provide vertical guidance by reference to airborne instruments during instrument approaches such as ILS/MLS, or Visual ground aids, such as VASI, which provide vertical guidance for a VFR approach or for the visual portion of an instrument approach and landing. PAR. Used by ATC to inform an aircraft making a PAR approach of its vertical position (elevation) relative to the descent profile. GLIDEPATH [ICAO] A descent profile determined for vertical guidance during a final approach. GLIDESLOPE INTERCEPT ALTITUDE The minimum altitude to intercept the glideslope/path on a precision approach. The intersection of the published intercept altitude with the glideslope/path, designated on Government charts by the lightning bolt symbol, is the precision FAF; however, when ATC directs a lower altitude, the resultant lower intercept position is then the FAF. GLOBAL POSITIONING SYSTEM A space base radio positioning, navigation, and time transfer system being developed by Department of Defense. When fully deployed, the system is intended to provide highly accurate position and velocity information, and precise time, on a continuous global basis, to an unlimited number of properly equipped users. The system will be unaffected by weather, and will provide a worldwide common grid reference system. The GPS concept is predicated upon accurate and continuous knowledge of the spatial position of each satellite in the system with respect to time and distance from a transmitting satellite to the user. The GPS receiver automatically selects appropriate signals from the satellites in view and translates these into a three dimensional position, velocity, and time. Predictable system accuracy for civil users is projected to be 100 meters horizontally. Performance standards and certification criteria have not yet been established. GO AHEAD Proceed with your message. Not to be used for any other purpose. GO AROUND Instructions for a pilot to abandon his approach to landing. Additional instructions may follow. Unless otherwise advised by ATC, a VFR aircraft or an aircraft conducting visual approach should overfly the runway while climbing to traffic pattern altitude and enter the traffic pattern via the crosswind leg. A pilot on an IFR flight plan making an instrument approach should execute the published missed approach procedure or proceed as instructed by ATC; e.g., ``Go around'' (additional instructions if required). GPS (See Global Positioning System). GROUND CLUTTER A pattern produced on the radar scope by ground returns which may degrade other radar returns in the affected area. The effect of ground clutter is minimized by the use of moving target indicator (MTI) circuits in the radar equipment resulting in a radar presentation which displays only targets which are in motion. GROUND CONTROLLED APPROACH A radar approach system operated from the ground by air traffic control personnel transmitting instructions to the pilot by radio. The approach may be conducted with surveillance radar (ASR) only or with both surveillance and precision approach radar (PAR). Usage of the term ``GCA'' by pilots is discouraged except when referring to a GCA facility. Pilots should specifically request a ``PAR'' approach when a precision radar approach is desired or request an ``ASR'' or ``surveillance'' approach when a nonprecision radar approach is desired. GROUND DELAY The amount of delay attributed to ATC, encountered prior to departure, usually associated with a CDT program. GROUND SPEED The speed of an aircraft relative to the surface of the earth. GROUND STOP Normally, the last initiative to be utilized; this method mandates that the terminal facility will not allow any departures to enter the ARTCC airspace until further notified. GROUND VISIBILITY (See VISIBILITY). HAA (See HEIGHT ABOVE AIRPORT). HAL (See HEIGHT ABOVE LANDING). HANDOFF An action taken to transfer the radar identification of an aircraft from one controller to another if the aircraft will enter the receiving controller's airspace and radio communications with the aircraft will be transferred. HAT (See HEIGHT ABOVE TOUCHDOWN). HAVE NUMBERS Used by pilots to inform ATC that they have received runway, wind, and altimeter information only. HAZARDOUS INFLIGHT WEATHER ADVISORY SERVICE Continuous recorded hazardous inflight weather forecasts broadcasted to airborne pilots over selected VOR outlets defined as an HIWAS BROADCAST AREA. HAZARDOUS WEATHER INFORMATION Summary of significant meteorological information (SIGMET/WS), convective significant meteorological information (convective SIGMET/WST), urgent pilot weather reports (urgent PIREP/UUA), center weather advisories (CWA), airmen's meteorological information (AIRMET/WA) and any other weather such as isolated thunderstorms that are rapidly developing and increasing in intensity, or low ceilings and visibilities that are becoming widespread which is considered significant and are not included in a current hazardous weather advisory. HEAVY (AIRCRAFT) (See AIRCRAFT CLASSES). HEIGHT ABOVE AIRPORT The height of the Minimum Descent Altitude above the published airport elevation. This is published in conjunction with circling minimums. HEIGHT ABOVE LANDING The height above a designated helicopter landing area used for helicopter instrument approach procedures. HEIGHT ABOVE TOUCHDOWN The height of the Decision Height or Minimum Descent Altitude above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway). HAT is published on instrument approach charts in conjunction with all straight in minimums. HELICOPTER Rotorcraft that, for its horizontal motion, depends principally on its engine driven rotors. HELICOPTER [ICAO] A heavier than air aircraft supported in flight chiefly by the reactions of the air on one or more power driven rotors on substantially vertical axes. HELIPAD A small, designated area, usually with a prepared surface, on a heliport, airport, landing/takeoff area, apron/ramp, or movement area used for takeoff, landing, or parking of helicopters. HELIPORT An area of land, water, or structure used or intended to be used for the landing and takeoff of helicopters and includes its buildings and facilities if any. HERTZ The standard radio equivalent of frequency in cycles per second of an electromagnetic wave. Kilohertz (kHz) is a frequency of one thousand cycles per second. Megahertz (mHz) is a frequency of one million cycles per second. HF (See HIGH FREQUENCY). HF COMMUNICATIONS (See HIGH FREQUENCY COMMUNICATIONS). HIGH FREQUENCY The frequency band between 3 and 30 mHz. HIGH FREQUENCY COMMUNICATIONS High radio frequencies (HF) between 3 and 30 mHz used for air to ground voice communication in overseas operations. HIGH SPEED EXIT (See HIGH SPEED TAXIWAY). HIGH SPEED TAXIWAY A long radius taxiway designed and provided with lighting or marking to define the path of aircraft, traveling at high speed (up to 60 knots), from the runway center to a point on the center of a taxiway. Also referred to as long radius exit or turn off taxiway. The high speed taxiway is designed to expedite aircraft turning off the runway after landing, thus reducing runway occupancy time. HIGH SPEED TURNOFF (See HIGH SPEED TAXIWAY). HIWAS (See HAZARDOUS INFLIGHT WEATHER ADVISORY SERVICE). HIWAS AREA (See HAZARDOUS INFLIGHT WEATHER ADVISORY SERVICE). HIWAS BROADCAST AREA A geographical area of responsibility including one or more HIWAS outlet areas assigned to an AFSS/FSS for hazardous weather advisory broadcasting. HIWAS OUTLET AREA An area defined as a 150 NM radius of a HIWAS outlet, expanded as necessary to provide coverage. HOLDING PROCEDURE (See HOLD PROCEDURE). HOLD PROCEDURE A predetermined maneuver which keeps aircraft within a specified airspace while awaiting further clearance from air traffic control. Also used during ground operations to keep aircraft within a specified area or at a specified point while awaiting further clearance from air traffic control. HOLDING FIX A specified fix identifiable to a pilot by NAVAID's or visual reference to the ground used as a reference point in establishing and maintaining the position of an aircraft while holding. HOLDING POINT [ICAO] A specified location, identified by visual or other means, in the vicinity of which the position of an aircraft in flight is maintained in accordance with air traffic control clearances. HOLD FOR RELEASE Used by ATC to delay an aircraft for traffic management reasons; i.e., weather, traffic volume, etc. Hold for release instructions (including departure delay information) are used to inform a pilot or a controller (either directly or through an authorized relay) that an IFR departure clearance is not valid until a release time or additional instructions have been received. HOMING Flight toward a NAVAID, without correcting for wind, by adjusting the aircraft heading to maintain a relative bearing of zero degrees. HOMING [ICAO] The procedure of using the direction finding equipment of one radio station with the emission of another radio station, where at least one of the stations is mobile, and whereby the mobile station proceeds continuously towards the other station. HOVER CHECK Used to describe when a helicopter/VTOL aircraft requires a stabilized hover to conduct a performance/power check prior to hover taxi, air taxi, or takeoff. Altitude of the hover will vary based on the purpose of the check. HOVER TAXI Used to describe a helicopter/VTOL aircraft movement conducted above the surface and in ground effect at airspeeds less than approximately 20 knots. The actual height may vary, and some helicopters may require hover taxi above 25 feet AGL to reduce ground effect turbulence or provide clearance for cargo slingloads. HOW DO YOU HEAR ME? A question relating to the quality of the transmission or to determine how well the transmission is being received. HZ (See HERTZ). IAF (See INITIAL APPROACH FIX). IAP (See INSTRUMENT APPROACH PROCEDURE). ICAO (See INTERNATIONAL CIVIL AVIATION ORGANIZATION). ICAO [ICAO] (See ICAO Term INTERNATIONAL CIVIL AVIATION ORGANIZATION). IDENT A request for a pilot to activate the aircraft transponder identification feature. This will help the controller to confirm an aircraft identity or to identify an aircraft. IDENT FEATURE The special feature in the Air Traffic Control Radar Beacon System (ATCRBS) equipment. It is used to immediately distinguish one displayed beacon target from other beacon targets. IF (See INTERMEDIATE FIX). IFIM (See INTERNATIONAL FLIGHT INFORMATION MANUAL). IF NO TRANSMISSION RECEIVED FOR (TIME) Used by ATC in radar approaches to prefix procedures which should be followed by the pilot in event of lost communications. IFR (See INSTRUMENT FLIGHT RULES). IFR AIRCRAFT An aircraft conducting flight in accordance with instrument flight rules. IFR CONDITIONS Weather conditions below the minimum for flight under visual flight rules. IFR DEPARTURE PROCEDURE (See IFR TAKEOFF MINIMUMS AND DEPARTURE PROCEDURES). IFR FLIGHT (See IFR AIRCRAFT). IFR LANDING MINIMUMS (See LANDING MINIMUMS). IFR MILITARY TRAINING ROUTES (IR) Routes used by the Department of Defense and associated Reserve and Air Guard units for the purpose of conducting low altitude navigation and tactical training in both IFR and VFR weather conditions below 10,000 feet MSL at airspeeds in excess of 250 knots IAS. IFR TAKEOFF MINIMUMS AND DEPARTURE PROCEDURES Federal Aviation Regulations, Part 91, prescribes standard takeoff rules for certain civil users. At some airports, obstructions or other factors require the establishment of nonstandard takeoff minimums, departure procedures, or both to assist pilots in avoiding obstacles during climb to the minimum en route altitude. Those airports are listed in NOS/DOD Instrument Approach Charts (IAP's) under a section entitled ``IFR Takeoff Minimums and Departure Procedures.'' The NOS/DOD IAP chart legend illustrates the symbol used to alert the pilot to nonstandard takeoff minimums and departure procedures. When departing IFR from such airports or from any airports where there are no departure procedures, SID's, or ATC facilities available, pilots should advise ATC of any departure limitations. Controllers may query a pilot to determine acceptable departure directions, turns, or headings after takeoff. Pilots should be familiar with the departure procedures and must assure that their aircraft can ILS (See INSTRUMENT LANDING SYSTEM). ILS CATEGORIES 1.ILS Category I. An ILS approach procedure which provides for approach to a height above touchdown of not less than 200 feet and with runway visual range of not less than 1,800 feet. 2.ILS Category II. An ILS approach procedure which provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet. 3.ILS Category III: IIIA. An ILS approach procedure which provides for approach without a decision height minimum and with runway visual range of not less than 700 feet. IIIB. An ILS approach procedure which provides for approach without a decision height minimum and with runway visual range of not less than 150 feet. IIIC. An ILS approach procedure which provides for approach without a decision height minimum and without runway visual range minimum. IM (See INNER MARKER). IMC (See INSTRUMENT METEOROLOGICAL CONDITIONS). IMMEDIATELY Used by ATC when such action compliance is required to avoid an imminent situation. INCERFA Uncertainty Phase) [ICAO] A situation wherein uncertainty exists as to the safety of an aircraft and its occupants. INCREASE SPEED TO (SPEED) (See SPEED ADJUSTMENT). INERTIAL NAVIGATION SYSTEM An RNAV system which is a form of self contained navigation. Q02 INFLIGHT REFUELING (See AERIAL REFUELING). INFLIGHT WEATHER ADVISORY (See WEATHER ADVISORY). INFORMATION REQUEST A request originated by an FSS for information concerning an overdue VFR aircraft. INITIAL APPROACH FIX The fixes depicted on instrument approach procedure charts that identify the beginning of the initial approach segment(s). INITIAL APPROACH SEGMENT (See SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE). INITIAL APPROACH SEGMENT [ICAO] That segment of an instrument approach procedure between the initial approach fix and the intermediate approach fix or, where applicable, the final approach fix or point. INLAND NAVIGATION FACILITY A navigation aid on a North American Route at which the common route and/or the noncommon route begins or ends. INNER MARKER A marker beacon used with an ILS (CAT II) precision approach located between the middle marker and the end of the ILS runway, transmitting a radiation pattern keyed at six dots per second and indicating to the pilot, both aurally and visually, that he is at the designated decision height (DH), normally 100 feet above the touchdown zone elevation, on the ILS CAT II approach. It also marks progress during a CAT III approach. INNER MARKER BEACON (See INNER MARKER). INREQ (See INFORMATION REQUEST). INS (See INERTIAL NAVIGATION SYSTEM). INSTRUMENT APPROACH (See INSTRUMENT APPROACH PROCEDURE). INSTRUMENT APPROACH PROCEDURE 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. It is prescribed and approved for a specific airport by competent authority. U.S. civil standard instrument approach procedures are approved by the FAA as prescribed under Part 97 and are available for public use. U.S. military standard instrument approach procedures are approved and published by the Department of Defense. Special instrument approach procedures are approved by the FAA for individual operators but are not published in Part 97 for public use. INSTRUMENT APPROACH PROCEDURE [ICAO] A series of predetermined manoeuvres by reference to flight instruments with specified protection from obstacles from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point from which a landing can be completed and thereafter, if a landing is not completed, to a position at which holding or en route obstacle clearance criteria apply. INSTRUMENT APPROACH PROCEDURES CHARTS (See AERONAUTICAL CHART). INSTRUMENT FLIGHT RULES Rules governing the procedures for conducting instrument flight. Also a term used by pilots and controllers to indicate type of flight plan. INSTRUMENT FLIGHT RULES [ICAO] A set of rules governing the conduct of flight under instrument meteorological conditions. INSTRUMENT LANDING SYSTEM A precision instrument approach system which normally consists of the following electronic components and visual aids: Localizer. Glideslope. Outer Marker. Middle Marker. Approach Lights. INSTRUMENT METEOROLOGICAL CONDITIONS Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling less than the minima specified for visual meteorological conditions. INSTRUMENT RUNWAY A runway equipped with electronic and visual navigation aids for which a precision or nonprecision approach procedure having straight in landing minimums has been approved. INSTRUMENT RUNWAY [ICAO] One of the following types of runways intended for the operation of aircraft using instrument approach procedures: a)Nonprecision Approach Runway. An instrument runway served by visual aids and a nonvisual aid providing at least directional guidance adequate for a straight in approach. b)Precision Approach Runway, Category I. An instrument runway served by ILS and visual aids intended for operations down to 60 m (200 feet) decision height and down to an RVR of the order of 800 m. c)Precision Approach Runway, Category II. An instrument runway served by ILS and visual aids intended for operations down to 30 m (100 feet) decision height and down to an RVR of the order of 400 m. d)Precision Approach Runway, Category III. An instrument runway served by ILS to and along the surface of the runway and: A. Intended for operations down to an RVR of the order of 200 m (no decision height being applicable) using visual aids during the final phase of landing; B. Intended for operations down to an RVR of the order of 50 m (no decision height being applicable) using visual aids for taxiing; C. Intended for operations without reliance on visual reference for landing or taxiing. INTERMEDIATE APPROACH SEGMENT (See SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE). INTERMEDIATE APPROACH SEGMENT [ICAO] That segment of an instrument approach procedure between either the intermediate approach fix and the final approach fix or point, or between the end of a reversal, race track or dead reckoning track procedure and the final approach fix or point, as appropriate. INTERMEDIATE FIX The fix that identifies the beginning of the intermediate approach segment of an instrument approach procedure. The fix is not normally identified on the instrument approach chart as an intermediate fix (IF). INTERMEDIATE LANDING On the rare occasion that this option is requested, it should be approved. The departure center, however, must advise the ATCSCC so that the appropriate delay is carried over and assigned at the intermediate airport. An intermediate landing airport within the arrival center will not be accepted without coordination with and the approval of the ATCSCC. INTERNATIONAL AIRPORT Relating to international flight, it means: An airport of entry which has been designated by the Secretary of Treasury or Commissioner of Customs as an international airport for customs service. A landing rights airport at which specific permission to land must be obtained from customs authorities in advance of contemplated use. Airports designated under the Convention on International Civil Aviation as an airport for use by international commercial air transport and/or international general aviation. INTERNATIONAL AIRPORT [ICAO] Any airport designated by the Contracting State in whose territory it is situated as an airport of entry and departure for international air traffic, where the formalities incident to customs, immigration, public health, animal and plant quarantine and similar procedures are carried out. INTERNATIONAL CIVIL AVIATION ORGANIZATION [ICAO] A specialized agency of the United Nations whose objective is to develop the principles and techniques of international air navigation and to foster planning and development of international civil air transport. ICAO Regions include: AFI African Indian Ocean Region CAR Caribbean Region EUR European Region MID/ASIA Middle East/Asia Region NAM North American Region NAT North Atlantic Region PAC Pacific Region SAM South American Region INTERNATIONAL FLIGHT INFORMATION MANUAL A publication designed primarily as a pilot's preflight planning guide for flights into foreign airspace and for flights returning to the U.S. from foreign locations. INTERROGATOR The ground based surveillance radar beacon transmitter receiver, which normally scans in synchronism with a primary radar, transmitting discrete radio signals which repetitiously request all transponders on the mode being used to reply. The replies received are mixed with the primary radar returns and displayed on the same plan position indicator (radar scope). Also, applied to the airborne element of the TACAN/DME system. INTERSECTING RUNWAYS Two or more runways which cross or meet within their lengths. INTERSECTION A point defined by any combination of courses, radials, or bearings of two or more navigational aids. Used to describe the point where two runways, a runway and a taxiway, or two taxiways cross or meet. INTERSECTION DEPARTURE A departure from any runway intersection except the end of the runway. INTERSECTION TAKEOFF (See INTERSECTION DEPARTURE). IR (See IFR MILITARY TRAINING ROUTES). I SAY AGAIN The message will be repeated. JAMMING Electronic or mechanical interference which may disrupt the display of aircraft on radar or the transmission/reception of radio communications/navigation. JET BLAST Jet engine exhaust (thrust stream turbulence). JET ROUTE A route designed to serve aircraft operations from 18,000 feet MSL up to and including flight level 450. The routes are referred to as ``J'' routes with numbering to identify the designated route; e.g., J105. JET STREAM A migrating stream of high speed winds present at high altitudes. JETTISONING OF EXTERNAL STORES Airborne release of external stores; e.g., tiptanks, ordnance. JOINT USE RESTRICTED AREA (See RESTRICTED AREA). KNOWN TRAFFIC With respect to ATC clearances, means aircraft whose altitude, position, and intentions are known to ATC. LAA (See LOCAL AIRPORT ADVISORY). LAAS (See LOW ALTITUDE ALERT SYSTEM). LANDING AREA Any locality either on land, water, or structures, including airports/heliports and intermediate landing fields, which is used, or intended to be used, for the landing and takeoff of aircraft whether or not facilities are provided for the shelter, servicing, or for receiving or discharging passengers or cargo. LANDING AREA [ICAO] That part of a movement area intended for the landing or takeoff of aircraft. LANDING DIRECTION INDICATOR A device which visually indicates the direction in which landings and takeoffs should be made. LANDING DISTANCE AVAILABLE [ICAO] The length of runway which is declared available and suitable for the ground run of an aeroplane landing. LANDING MINIMUMS The minimum visibility prescribed for landing a civil aircraft while using an instrument approach procedure. The minimum applies with other limitations set forth in Part 91 with respect to the Minimum Descent Altitude (MDA) or Decision Height (DH) prescribed in the instrument approach procedures as follows: Straight in landing minimums. A statement of MDA and visibility, or DH and visibility, required for a straight in landing on a specified runway, or Circling minimums. A statement of MDA and visibility required for the circle to land maneuver. 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. LANDING SEQUENCE The order in which aircraft are positioned for landing. LAST ASSIGNED ALTITUDE The last altitude/flight level assigned by ATC and acknowledged by the pilot. LATERAL SEPARATION The lateral spacing of aircraft at the same altitude by requiring operation on different routes or in different geographical locations. LDA (See LOCALIZER TYPE DIRECTIONAL AID). LDA [ICAO] (See ICAO Term LANDING DISTANCE AVAILABLE). LF (See LOW FREQUENCY). LIGHTED AIRPORT An airport where runway and obstruction lighting is available. LIGHT GUN A handheld directional light signaling device which emits a brilliant narrow beam of white, green, or red light as selected by the tower controller. The color and type of light transmitted can be used to approve or disapprove anticipated pilot actions where radio communication is not available. The light gun is used for controlling traffic operating in the vicinity of the airport and on the airport movement area. LOCALIZER The component of an ILS which provides course guidance to the runway. LOCALIZER COURSE [ICAO] The locus of points, in any given horizontal plane, at which the DDM (difference in depth of modulation) is zero. LOCALIZER TYPE DIRECTIONAL AID A NAVAID used for nonprecision instrument approaches with utility and accuracy comparable to a localizer but which is not a part of a complete ILS and is not aligned with the runway. LOCALIZER USABLE DISTANCE The maximum distance from the localizer transmitter at a specified altitude, as verified by flight inspection, at which reliable course information is continuously received. LOCAL AIRPORT ADVISORY [LAA] A service provided by flight service stations or the military at airports not serviced by an operating control tower. This service consists of providing information to arriving and departing aircraft concerning wind direction and speed, favored runway, altimeter setting, pertinent known traffic, pertinent known field conditions, airport taxi routes and traffic patterns, and authorized instrument approach procedures. This information is advisory in nature and does not constitute an ATC clearance. LOCAL TRAFFIC Aircraft operating in the traffic pattern or within sight of the tower, or aircraft known to be departing or arriving from flight in local practice areas, or aircraft executing practice instrument approaches at the airport. LOCATOR [ICAO] An LM/MF NDB used as an aid to final approach. LONGITUDINAL SEPARATION The longitudinal spacing of aircraft at the same altitude by a minimum distance expressed in units of time or miles. LONG RANGE NAVIGATION (See LORAN). LORAN An electronic navigational system by which hyperbolic lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from two fixed transmitters. Loran A operates in the 1750-1950 kHz frequency band. Loran C and D operate in the 100-110 kHz frequency band. LOST COMMUNICATIONS Loss of the ability to communicate by radio. Aircraft are sometimes referred to as NORDO (No Radio). Standard pilot procedures are specified in Part 91. Radar controllers issue procedures for pilots to follow in the event of lost communications during a radar approach when weather reports indicate that an aircraft will likely encounter IFR weather conditions during the approach. LOW ALTITUDE AIRWAY STRUCTURE The network of airways serving aircraft operations up to but not including 18,000 feet MSL. LOW ALTITUDE ALERT, CHECK YOUR ALTITUDE IMMEDIATELY (See SAFETY ALERT). LOW ALTITUDE ALERT SYSTEM An automated function of the TPX-42 that alerts the controller when a Mode C transponder equipped aircraft on an IFR flight plan is below a predetermined minimum safe altitude. If requested by the pilot, LAAS monitoring is also available to VFR Mode C transponder equipped aircraft. LOW APPROACH An approach over an airport or runway following an instrument approach or a VFR approach including the go around maneuver where the pilot intentionally does not make contact with the runway. LOW FREQUENCY The frequency band between 30 and 300 kHz. MAA (See MAXIMUM AUTHORIZED ALTITUDE). MACH NUMBER The ratio of true airspeed to the speed of sound; e.g., MACH .82, MACH 1.6. MACH TECHNIQUE [ICAO] Describes a control technique used by air traffic control whereby turbojet aircraft operating successively along suitable routes are cleared to maintain appropriate MACH numbers for a relevant portion of the en route phase of flight. The principle objective is to MAINTAIN Concerning altitude/flight level, the term means to remain at the altitude/flight level specified. The phrase ``climb and'' or ``descend and'' normally precedes ``maintain'' and the altitude assignment; e.g., ``descend and maintain 5,000.'' Concerning other ATC instructions, the term is used in its literal sense; e.g., maintain VFR. MAKE SHORT APPROACH Used by ATC to inform a pilot to alter his traffic pattern so as to make a short final approach. MANDATORY ALTITUDE An altitude depicted on an instrument Approach Procedure Chart requiring the aircraft to maintain altitude at the depicted value. MAP (See MISSED APPROACH POINT). MARKER BEACON An electronic navigation facility transmitting a 75 mHz vertical fan or boneshaped radiation pattern. Marker beacons are identified by their modulation frequency and keying code, and when received by compatible airborne equipment, indicate to the pilot, both aurally and visually, that he is passing over the facility. MARSA (See MILITARY AUTHORITY ASSUMES RESPONSIBILITY FOR SEPARATION OF AIRCRAFT). MAXIMUM AUTHORIZED ALTITUDE A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment. It is the highest altitude on a Federal airway, jet route, area navigation low or high route, or other direct route for which an MEA is designated in Part 95 at which adequate reception of navigation aid signals is assured. MAYDAY The international radiotelephony distress signal. When repeated three times, it indicates imminent and grave danger and that immediate assistance is requested. MCA (See MINIMUM CROSSING ALTITUDE). MDA (See MINIMUM DESCENT ALTITUDE). MEA (See MINIMUM EN ROUTE IFR ALTITUDE). METEOROLOGICAL IMPACT STATEMENT An unscheduled planning forecast describing conditions expected to begin within 4 to 12 hours which may impact the flow of air traffic in a specific center's (ARTCC) area. METER FIX TIME/SLOT TIME A calculated time to depart the meter fix in order to cross the vertex at the ACLT. This time reflects descent speed adjustment and any applicable time that must be absorbed prior to crossing the meter fix. METER LIST DISPLAY INTERVAL A dynamic parameter which controls the number of minutes prior to the flight plan calculated time of arrival at the meter fix for each aircraft, at which time the TCLT is frozen and becomes an ACLT; i.e., the VTA is updated and consequently the TCLT modified as appropriate until frozen at which time updating is suspended and an ACLT is assigned. When frozen, the flight entry is inserted into the arrival sector's meter list for display on the sector PVD. MLDI is used if filed true airspeed is less than or equal to freeze speed parameters (FSPD). METERING A method of time regulating arrival traffic flow into a terminal area so as not to exceed a predetermined terminal acceptance rate. METERING AIRPORTS Airports adapted for metering and for which optimum flight paths are defined. A maximum of 15 airports may be adapted. METERING FIX A fix along an established route from over which aircraft will be metered prior to entering terminal airspace. Normally, this fix should be established at a distance from the airport which will facilitate a profile descent 10,000 feet above airport elevation [AAE] or above. METERING POSITION(S) Adapted PVD's and associated ``D'' positions eligible for display of a metering position list. A maximum of four PVD's may be adapted. METERING POSITION LIST An ordered list of data on arrivals for a selected metering airport displayed on a metering position PVD. MFT (See METER FIX TIME/SLOT TIME). MHA (See MINIMUM HOLDING ALTITUDE). MIA (See MINIMUM IFR ALTITUDES). MICROBURST A small downburst with outbursts of damaging winds extending 2.5 miles or less. In spite of its small horizontal scale, an intense microburst could induce wind speeds as high as 150 knots MICROWAVE LANDING SYSTEM A precision instrument approach system operating in the microwave spectrum which normally consists of the following components: Azimuth Station. Elevation Station. Precision Distance Measuring Equipment. MIDDLE COMPASS LOCATOR (See COMPASS LOCATOR). MIDDLE MARKER A marker beacon that defines a point along the glideslope of an ILS normally located at or near the point of decision height (ILS Category I). It is keyed to transmit alternate dots and dashes, with the alternate dots and dashes keyed at the rate of 95 dot/dash combinations per minute on a 1300 Hz tone, which is received aurally and visually by compatible airborne equipment. MID RVR (See VISIBILITY). MILES IN TRAIL A specified distance between aircraft, normally, in the same stratum associated with the same destination or route of flight. MILITARY AUTHORITY ASSUMES RESPONSIBILITY FOR SEPARATION OF AIRCRAFT A condition whereby the military services involved assume responsibility for separation between participating military aircraft in the ATC system. It is used only for required IFR operations which are specified in letters of agreement or other appropriate FAA or military documents. MILITARY OPERATIONS AREA (See SPECIAL USE AIRSPACE). MILITARY TRAINING ROUTES Airspace of defined vertical and lateral dimensions established for the conduct of military flight training at airspeeds in excess of 250 knots IAS. MINIMA (See MINIMUMS). MINIMUM CROSSING ALTITUDE The lowest altitude at certain fixes at which an aircraft must cross when proceeding in the direction of a higher minimum en route IFR altitude (MEA). MINIMUM DESCENT ALTITUDE The lowest altitude, expressed in feet above mean sea level, to which descent is authorized on final approach or during circle to land maneuvering in execution of a standard instrument approach procedure where no electronic glideslope is provided. MINIMUM EN ROUTE IFR ALTITUDE The lowest published altitude between radio fixes which assures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes. The MEA prescribed for a Federal airway or segment thereof, area navigation low or high route, or other direct route applies to the entire width of the airway, segment, or route between the radio fixes defining the airway, segment, or route. MINIMUM FUEL Indicates that an aircraft's fuel supply has reached a state where, upon reaching the destination, it can accept little or no delay. This is not an emergency situation but merely indicates an emergency situation is possible should any undue delay occur. MINIMUM HOLDING ALTITUDE The lowest altitude prescribed for a holding pattern which assures navigational signal coverage, communications, and meets obstacle clearance requirements. MINIMUM IFR ALTITUDES Minimum altitudes for IFR operations as prescribed in Part 91. These altitudes are published on aeronautical charts and prescribed in Part 95 for airways and routes, and in Part 97 for standard instrument approach procedures. If no applicable minimum altitude is prescribed in FAR 95 or FAR 97, the following minimum IFR altitude applies: In designated mountainous areas, 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or Other than mountainous areas, 1,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles from the course to be flown; or As otherwise authorized by the Administrator or assigned by ATC. MINIMUM NAVIGATION PERFORMANCE SPECIFICATION A set of standards which require aircraft to have a minimum navigation performance capability in order to operate in MNPS designated airspace. In addition, aircraft must be certified by their State of Registry for MNPS operation. MINIMUM NAVIGATION PERFORMANCE SPECIFICATIONS AIRSPACE Designated airspace in which MNPS procedures are applied between MNPS certified and equipped aircraft. Under certain conditions, non MNPS aircraft can operate in MNPSA. However, standard oceanic separation minima is provided between the non MNPS aircraft and other traffic. Currently, the only designated MNPSA is described as follows: Between FL 275 and FL 400; Between latitudes 27- N and the North Pole; In the east, the eastern boundaries of the CTA's Santa Maria Oceanic, Shanwick Oceanic, and Reykjavik; In the west, the western boundaries of CTA's Reykjavik and Gander Oceanic and New York Oceanic excluding the area west of 60- W and south of 38- 30' N. MINIMUM OBSTRUCTION CLEARANCE ALTITUDE The lowest published altitude in effect between radio fixes on VOR airways, off airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which assures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR. MINIMUM RECEPTION ALTITUDE The lowest altitude at which an intersection can be determined. MINIMUM SAFE ALTITUDE The minimum altitude specified in Part 91 for various aircraft operations. Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the navigation facility upon which a procedure is predicated. These altitudes will be identified as Minimum Sector Altitudes or Emergency Safe Altitudes and are established as follows: a. Minimum Sector Altitudes. Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance within a 25-mile radius of the navigation facility upon which the procedure is predicated. Sectors depicted on approach charts must be at least 90 degrees in scope. These altitudes are for emergency use only and do not necessarily assure acceptable navigational signal coverage. b. Emergency Safe Altitudes. Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance in nonmountainous areas and 2,000 feet of obstacle clearance in designated mountainous areas within a 100-mile radius of the navigation facility upon which the procedure is predicated and normally used only in military procedures. These altitudes are identified on published procedures as ``Emergency Safe Altitudes.'' MINIMUM SAFE ALTITUDE WARNING A function of the ARTS III computer that aids the controller by alerting him when a tracked Mode C equipped aircraft is below or is predicted by the computer to go below a predetermined minimum safe altitude. MINIMUM SECTOR ALTITUDE [ICAO] The lowest altitude which may be used under emergency conditions which will provide a minimum clearance of 300 m (1,000 feet) above all obstacles located in an area contained within a sector of a circle of 46 km (25 NM) radius centered on a radio aid to navigation. MINIMUMS Weather condition requirements established for a particular operation or type of operation; e.g., IFR takeoff or landing, alternate airport for IFR flight plans, VFR flight, etc. MINIMUM VECTORING ALTITUDE The lowest MSL altitude at which an IFR aircraft will be vectored by a radar controller, except as otherwise authorized for radar approaches, departures, and missed approaches. The altitude meets IFR obstacle clearance criteria. It may be lower than the published MEA along an airway or J route segment. It may be utilized for radar vectoring only upon the controller's determination that an adequate radar return is being received from the aircraft being controlled. Charts depicting minimum vectoring altitudes are normally available only to the controllers and not to pilots. MINUTES IN TRAIL A specified interval between aircraft expressed in time. This method would more likely be utilized regardless of altitude. MIS (See METEOROLOGICAL IMPACT STATEMENT). MISSED APPROACH A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing. The route of flight and altitude are shown on instrument approach procedure charts. A pilot executing a missed approach prior to the Missed Approach Point (MAP) must continue along the final approach to the MAP. The pilot may climb immediately to the altitude specified in the missed approach procedure. A term used by the pilot to inform ATC that he is executing the missed approach. At locations where ATC radar service is provided, the pilot should conform to radar vectors when provided by ATC in lieu of the published missed approach procedure. MISSED APPROACH POINT A point prescribed in each instrument approach procedure at which a missed approach procedure shall be executed if the required visual reference does not exist. MISSED APPROACH PROCEDURE [ICAO] The procedure to be followed if the approach cannot be continued. MISSED APPROACH SEGMENT (See SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE). MLDI (See METER LIST DISPLAY INTERVAL). MLS (See MICROWAVE LANDING SYSTEM). MLS CATEGORIES MLS Category I. An MLS approach procedure which provides for an approach to a height above touchdown of not less than 200 feet and a runway visual range of not less than 1,800 feet. MLS Category II. Undefined until data gathering/analysis completion. MLS Category III. Undefined until data gathering/analysis completion. MM (See MIDDLE MARKER). MNPS (See MINIMUM PERFORMANCE SPECIFICATION). MNPSA (See MINIMUM PERFORMANCE SPECIFICATIONS AIRSPACE). MOA (See MILITARY OPERATIONS AREA). MOCA (See MINIMUM OBSTRUCTION CLEARANCE ALTITUDE). MODE The letter or number assigned to a specific pulse spacing of radio signals transmitted or received by ground interrogator or airborne transponder components of the Air Traffic Control Radar Beacon System (ATCRBS). Mode A (military Mode 3) and Mode C (altitude reporting) are used in air traffic control. MODE (SSR MODE) [ICAO] The letter or number assigned to a specific pulse spacing of the interrogation signals transmitted by an interrogator. There are 4 modes, A, B, C and D specified in Annex 10, corresponding to four different interrogation pulse spacings. MODE C INTRUDER ALERT A function of certain air traffic control automated systems designed to alert radar controllers to existing or pending situations between a tracked target (known IFR or VFR aircraft) and an untracked target (unknown IFR or VFR aircraft) that requires immediate attention/action. MONITOR (When used with communication transfer) listen on a specific frequency and stand by for instructions. Under normal circumstances do not establish communications. MOVEMENT AREA The runways, taxiways, and other areas of an airport/heliport which are utilized for taxiing/hover taxiing, air taxiing, takeoff, and landing of aircraft, exclusive of loading ramps and parking areas. At those airports/heliports with a tower, specific approval for entry onto the movement area must be obtained from ATC. MOVEMENT AREA [ICAO] That part of an aerodrome to be used for the takeoff, landing and taxiing of aircraft, consisting of the manoeuvring area and the apron(s). MOVING TARGET INDICATOR An electronic device which will permit radar scope presentation only from targets which are in motion. A partial remedy for ground clutter. MRA (See MINIMUM RECEPTION ALTITUDE). MSA (See MINIMUM SAFE ALTITUDE). MSAW (See MINIMUM SAFE ALTITUDE WARNING). MTI (See MOVING TARGET INDICATOR). MTR (See MILITARY TRAINING ROUTES). MULTICOM A mobile service not open to public correspondence used to provide communications essential to conduct the activities being performed by or directed from private aircraft. MULTIPLE RUNWAYS The utilization of a dedicated arrival runway(s) for departures and a dedicated departure runway(s) for arrivals when feasible to reduce delays and enhance capacity. MVA (See MINIMUM VECTORING ALTITUDE). NAS (See NATIONAL AIRSPACE SYSTEM). NAS STAGE A The en route ATC system's radar, computers and computer programs, controller plan view displays (PVDs/Radar Scopes), input/output devices, and the related communications equipment which are integrated to form the heart of the automated IFR air traffic control system. This equipment performs Flight Data Processing (FDP) and Radar Data Processing (RDP). It interfaces with automated terminal systems and is used in the control of en route IFR aircraft. NATIONAL AIRSPACE SYSTEM The common network of U.S. airspace; air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and procedures, technical information, and manpower and material. Included are system components shared jointly with the military. NATIONAL BEACON CODE ALLOCATION PLAN AIRSPACE Airspace over United States territory located within the North American continent between Canada and Mexico, including adjacent territorial waters outward to about boundaries of oceanic control areas (CTA)/Flight Information Regions (FIR). NATIONAL FLIGHT DATA CENTER A facility in Washington D.C., established by FAA to operate a central aeronautical information service for the collection, validation, and dissemination of aeronautical data in support of the activities of government, industry, and the aviation community. The information is published in the National Flight Data Digest. NATIONAL FLIGHT DATA DIGEST A daily (except weekends and Federal holidays) publication of flight information appropriate to aeronautical charts, aeronautical publications, Notices to Airmen, or other media serving the purpose of providing operational flight data essential to safe and efficient aircraft operations. NATIONAL SEARCH AND RESCUE PLAN An interagency agreement which provides for the effective utilization of all available facilities in all types of search and rescue missions. NAVAID (See NAVIGATIONAL AID). NAVAID CLASSES VOR, VORTAC, and TACAN aids are classed according to their operational use. The three classes of NAVAID's are: Terminal. Low altitude. High altitude. NAVIGABLE AIRSPACE Airspace at and above the minimum flight altitudes prescribed in the FAR's including airspace needed for safe takeoff and landing. NAVIGATIONAL AID Any visual or electronic device airborne or on the surface which provides point to point guidance information or position data to aircraft in flight. NBCAP AIRSPACE (See NATIONAL BEACON CODE ALLOCATION PLAN AIRSPACE). NDB (See NONDIRECTIONAL BEACON). NEGATIVE ``No,'' or ``permission not granted,'' or ``that is not correct.'' NEGATIVE CONTACT Used by pilots to inform ATC that: Previously issued traffic is not in sight. It may be followed by the pilot's request for the controller to provide assistance in avoiding the traffic. They were unable to contact ATC on a particular frequency. NFDC (See NATIONAL FLIGHT DATA CENTER). NFDD (See NATIONAL FLIGHT DATA DIGEST). NIGHT The time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the American Air Almanac, converted to local time. NIGHT [ICAO] The hours between the end of evening civil twilight and the beginning of morning civil twilight or such other period between sunset and sunrise as may be specified by the appropriate authority. NO GYRO APPROACH A radar approach/vector provided in case of a malfunctioning gyro compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions ``turn right/left'' or ``stop turn'' as appropriate. NO GYRO VECTOR (See NO GYRO APPROACH). NONAPPROACH CONTROL TOWER Authorizes aircraft to land or takeoff at the airport controlled by the tower or to transit the Class D airspace. The primary function of a nonapproach control tower is the sequencing of aircraft in the traffic pattern and on the landing area. Nonapproach control towers also separate aircraft operating under instrument flight rules clearances from approach controls and centers. They provide ground control services to aircraft, vehicles, personnel, and equipment on the airport movement area. NONCOMMON ROUTE/PORTION That segment of a North American Route between the inland navigation facility and a designated North American terminal. NONCOMPOSITE SEPARATION Separation in accordance with minima other than the composite separation minimum specified for the area concerned. NONDIRECTIONAL BEACON An L/MF or UHF radio beacon transmitting nondirectional signals whereby the pilot of an aircraft equipped with direction finding equipment can determine his bearing to or from the radio beacon and ``home'' on or track to or from the station. When the radio beacon is installed in conjunction with the Instrument Landing System marker, it is normally called a Compass Locator. NONMOVEMENT AREAS Taxiways and apron (ramp) areas not under the control of air traffic. NONPRECISION APPROACH (See NONPRECISION APPROACH PROCEDURE). NONPRECISION APPROACH PROCEDURE A standard instrument approach procedure in which no electronic glideslope is provided; e.g., VOR, TACAN, NDB, LOC, ASR, LDA, or SDF approaches. NONRADAR Precedes other terms and generally means without the use of radar, such as: Nonradar Approach. Used to describe instrument approaches for which course guidance on final approach is not provided by ground based precision or surveillance radar. Radar vectors to the final approach course may or may not be provided by ATC. Examples of nonradar approaches are VOR, NDB, TACAN, and ILS/MLS approaches. Nonradar Approach Control. An ATC facility providing approach control service without the use of radar. Nonradar Arrival. An aircraft arriving at an airport without radar service or at an airport served by a radar facility and radar contact has not been established or has been terminated due to a lack of radar service to the airport. Nonradar Route. A flight path or route over which the pilot is performing his own navigation. The pilot may be receiving radar separation, radar monitoring, or other ATC services while on a nonradar route. Nonradar Separation. The spacing of aircraft in accordance with established minima without the use of radar; e.g., vertical, lateral, or longitudinal separation. NONRADAR SEPARATION [ICAO] The separation used when aircraft position information is derived from sources other than radar. NOPAC (See NORTH PACIFIC). NORDO (See LOST COMMUNICATIONS). NORTH AMERICAN ROUTE A numerically coded route preplanned over existing airway and route systems to and from specific coastal fixes serving the North Atlantic. North American Routes consist of the following: Common Route/Portion. That segment of a North American Route between the inland navigation facility and the coastal fix. NonCommon Route/Portion. That segment of a North American Route between the inland navigation facility and a designated North American terminal. Inland Navigation Facility. A navigation aid on a North American Route at which the common route and/or the noncommon route begins or ends. Coastal Fix. A navigation aid or intersection where an aircraft transitions between the domestic route structure and the oceanic route structure. NORTH MARK A beacon data block sent by the host computer to be displayed by the ARTS on a 360 degree bearing at a locally selected radar azimuth and distance. The North Mark is used to ensure correct range/azimuth orientation during periods of CENRAP. NORTH PACIFIC An organized route system between the Alaskan west coast and Japan. NOTAM (See NOTICE TO AIRMEN). NOTICE TO AIRMEN A notice containing information (not known sufficiently in advance to publicize by other means) concerning the establishment, condition, or change in any component (facility, service, or procedure of, or hazard in the National Airspace System) the timely knowledge of which is essential to personnel concerned with flight operations. NOTAM(D). A NOTAM given (in addition to local dissemination) distant dissemination beyond the area of responsibility of the Flight Service Station. These NOTAM's will be stored and available until canceled. NOTAM(L). A NOTAM given local dissemination by voice and other means, such as telautograph and telephone, to satisfy local user requirements. FDC NOTAM. A NOTAM regulatory in nature, transmitted by USNOF and given system wide dissemination. NOTAM [ICAO] A notice containing information concerning the establishment, condition or change in any aeronautical facility, service, procedure or hazard, the timely knowledge of which is essential to personnel concerned with flight operations. Class I Distribution. Distribution by means of telecommunication. Class II Distribution. Distribution by means other than telecommunications. NOTICES TO AIRMEN PUBLICATION A publication issued every 14 days, designed primarily for the pilot, which contains current NOTAM information considered essential to the safety of flight as well as supplemental data to other aeronautical publications. The contraction NTAP is used in NOTAM text. NTAP (See NOTICES TO AIRMEN PUBLICATION). NUMEROUS TARGETS VICINITY (LOCATION) A traffic advisory issued by ATC to advise pilots that targets on the radar scope are too numerous to issue individually. OALT (See OPERATIONAL ACCEPTABLE LEVEL OF TRAFFIC). OBSTACLE An existing object, object of natural growth, or terrain at a fixed geographical location or which may be expected at a fixed location within a prescribed area with reference to which vertical clearance is or must be provided during flight operation. OBSTACLE FREE ZONE The OFZ is a three dimensional volume of airspace which protects for the transition of aircraft to and from the runway. The OFZ clearing standard precludes taxiing and parked airplanes and object penetrations, except for frangible NAVAID locations that are fixed by function. Additionally, vehicles, equipment, and personnel may be authorized by air traffic control to enter the area using the provisions of Order 7110.65, Air Traffic Control, paragraph 3-5. The runway OFZ and when applicable, the inner-approach OFZ, and the inner-transitional OFZ, comprise the OFZ. Runway OFZ. The runway OFZ is a defined volume of airspace centered above the runway. The runway OFZ is the airspace above a surface whose elevation at any point is the same as the elevation of the nearest point on the runway centerline. The runway OFZ extends 200 feet beyond each end of the runway. The width is as follows: (a)For runways serving large airplanes, the greater of: (1)400 feet, or (2)180 feet, plus the wingspan of the most demanding airplane, plus 20 feet per 1,000 feet of airport elevation. (b))For runways serving only small airplanes: (1)300 feet for precision instrument runways. (2)250 feet for other runways serving small airplanes with approach speeds of 50 knots, or more. (3)120 feet for other runways serving small airplanes with approach speeds of less than 50 knots. Inner-approach OFZ. The inner-approach OFZ is a defined volume of airspace centered on the approach area. The inner-approach OFZ applies only to runways with an approach lighting system. The inner-approach OFZ begins 200 feet from the runway threshold at the same elevation as the runway threshold and extends 200 feet beyond the last light unit in the approach lighting system. The width of the inner-approach OFZ is the same as the runway OFZ and rises at a slope of 50 (horizontal) to 1 (vertical) from the beginning. Inner-transitional OFZ. The inner transitional surface OFZ is a defined volume of airspace along the sides of the runway and inner-approach OFZ and applies only to precision instrument runways. OBSTRUCTION Any object/obstacle exceeding the obstruction standards specified by Part 77, Subpart C. OBSTRUCTION LIGHT A light or one of a group of lights, usually red or white, frequently mounted on a surface structure or natural terrain to warn pilots of the presence of an obstruction. OCEANIC AIRSPACE Airspace over the oceans of the world, considered international airspace, where oceanic separation and procedures per the International Civil Aviation Organization are applied. Responsibility for the provisions of air traffic control service in this airspace is delegated to various countries, based generally upon geographic proximity and the availability of the required resources. OCEANIC DISPLAY AND PLANNING SYSTEM An automated digital display system which provides flight data processing, conflict probe, and situation display for oceanic air traffic control. OCEANIC NAVIGATIONAL ERROR REPORT A report filed when an aircraft exiting oceanic airspace has been observed by radar to be off course. ONER reporting parameters and procedures are contained in Order 7110.82, Monitoring of Navigational Performance In Oceanic Areas. OCEANIC PUBLISHED ROUTE A route established in international airspace and charted or described in flight information publications, such as Route Charts, DOD Enroute Charts, Chart Supplements, NOTAM's, and Track Messages. OCEANIC TRANSITION ROUTE An ATS route established for the purpose of transitioning aircraft to/from an organized track system. ODAPS (See OCEANIC DISPLAY AND PLANNING SYSTEM). OFF COURSE A term used to describe a situation where an aircraft has reported a position fix or is observed on radar at a point not on the ATC approved route of flight. OFFSHORE CONTROL AREA That portion of airspace between the U.S 12-mile limit and the oceanic CTA/FIR boundary within which air traffic control is exercised. These areas are established to permit the application of domestic procedures in the provision of air traffic control services. Offshore control area is generally synonymous with Federal Aviation Regulations, Part 71, Subpart E, ``Control Areas and Control Area Extensions.'' OFF ROUTE VECTOR A vector by ATC which takes an aircraft off a previously assigned route. Altitudes assigned by ATC during such vectors provide required obstacle clearance. OFFSET PARALLEL RUNWAYS Staggered runways having centerlines which are parallel. OFT (See OUTER FIX TIME). OM (See OUTER MARKER). OMEGA An RNAV system designed for long range navigation based upon ground based electronic navigational aid signals. ONER (See OCEANIC NAVIGATIONAL ERROR REPORT). OPERATIONAL (See DUE REGARD). ON COURSE Used to indicate that an aircraft is established on the route centerline. Used by ATC to advise a pilot making a radar approach that his aircraft is lined up on the final approach course. ON COURSE INDICATION An indication on an instrument, which provides the pilot a visual means of determining that the aircraft is located on the centerline of a given navigational track, or an indication on a radar scope that an aircraft is on a given track. OPERATIONAL ACCEPTABLE LEVEL OF TRAFFIC An air traffic activity level associated with the designed capacity for a sector or airport. The OALT considers dynamic changes in staffing, personnel experience levels, equipment outages, operational configurations, weather, traffic complexity, aircraft performance mixtures, transitioning flights, adjacent airspace, handoff/point out responsibilities, and other factors that may affect an air traffic operational position or system element. The OALT is normally considered to be the total number of aircraft that any air traffic functional position can accommodate for a defined period of time under a given set of circumstances. OPPOSITE DIRECTION AIRCRAFT Aircraft are operating in opposite directions when: They are following the same track in reciprocal directions; or Their tracks are parallel and the aircraft are flying in reciprocal directions; or Their tracks intersect at an angle of more than 135«. OPTION APPROACH An approach requested and conducted by a pilot which will result in either a touch and go, missed approach, low approach, stop and go, or full stop landing. ORGANIZED TRACK SYSTEM A movable system of oceanic tracks that traverses the North Atlantic between Europe and North America the physical position of which is determined twice daily taking the best advantage of the winds aloft. ORGANIZED TRACK SYSTEM A series of ATS routes which are fixed and charted; i.e., CEP, NOPAC, or flexible and described by NOTAM; i.e., NAT TRACK MESSAGE. OTR (See OCEANIC TRANSITION ROUTE). OTS (See ORGANIZED TRACK SYSTEM). OUT The conversation is ended and no response is expected. OUTER AREA (associated with Class C airspace) Nonregulatory airspace surrounding designated Class C airspace airports wherein ATC provides radar vectoring and sequencing on a full time basis for all IFR and participating VFR aircraft. The service provided in the outer area is called Class C service which includes: IFR/IFR standard IFR separation; IFR/VFR traffic advisories and conflict resolution; and VFR/VFR traffic advisories and, as appropriate, safety alerts. The normal radius will be 20 nautical miles with some variations based on site specific requirements. The outer area extends outward from the primary Class C airspace airport and extends from the lower limits of radar/radio coverage up to the ceiling of the approach control's delegated airspace excluding the Class C charted area and other airspace as appropriate. OUTER COMPASS LOCATOR (See COMPASS LOCATOR). OUTER FIX A general term used within ATC to describe fixes in the terminal area, other than the final approach fix. Aircraft are normally cleared to these fixes by an Air Route Traffic Control Center or an Approach Control Facility. Aircraft are normally cleared from these fixes to the final approach fix or final approach course. OUTER FIX An adapted fix along the converted route of flight, prior to the meter fix, for which crossing times are calculated and displayed in the metering position list. OUTER FIX TIME A calculated time to depart the outer fix in order to cross the vertex at the ACLT. The time reflects descent speed adjustments and any applicable delay time that must be absorbed prior to crossing the meter fix. OUTER MARKER A marker beacon at or near the glideslope intercept altitude of an ILS approach. It is keyed to transmit two dashes per second on a 400 Hz tone, which is received aurally and visually by compatible airborne equipment. The OM is normally located four to seven miles from the runway threshold on the extended centerline of the runway. OVER My transmission is ended; I expect a response. OVERHEAD MANEUVER A series of predetermined maneuvers prescribed for aircraft (often in formation) for entry into the visual flight rules (VFR) traffic pattern and to proceed to a landing. An overhead maneuver is not an instrument flight rules (IFR) approach procedure. An aircraft executing an overhead maneuver is considered VFR and the IFR flight plan is cancelled when the aircraft reaches the ``initial point'' on the initial approach portion of the maneuver. The pattern usually specifies the following: The radio contact required of the pilot. The speed to be maintained. An initial approach 3 to 5 miles in length. An elliptical pattern consisting of two 180 degree turns. A break point at which the first 180 degree turn is started. The direction of turns. Altitude (at least 500 feet above the conventional pattern). A ``Roll out'' on final approach not less than 1/4 mile from the landing threshold and not less than 300 feet above the ground. OVERLYING CENTER The ARTCC facility that is responsible for arrival/departure operations at a specific terminal. P TIME (See PROPOSED DEPARTURE TIME). PAN PAN The international radio telephony urgency signal. When repeated three times, indicates uncertainty or alert followed by the nature of the urgency. PAR (See PRECISION APPROACH RADAR). PAR [ICAO] (See ICAO Term PRECISION APPROACH RADAR). PARALLEL ILS APPROACHES Approaches to parallel runways by IFR aircraft which, when established inbound toward the airport on the adjacent final approach courses, are radar separated by at least 2 miles. PARALLEL MLS APPROACHES (See PARALLEL ILS APPROACHES). PARALLEL OFFSET ROUTE A parallel track to the left or right of the designated or established airway/route. Normally associated with Area Navigation (RNAV) operations. PARALLEL RUNWAYS Two or more runways at the same airport whose centerlines are parallel. In addition to runway number, parallel runways are designated as L (left) and R (right) or, if three parallel runways exist, L (left), C (center), and R (right). PATWAS (See PILOTS AUTOMATIC TELEPHONE WEATHER ANSWERING SERVICE). PBCT (See PROPOSED BOUNDARY CROSSING TIME). PERMANENT ECHO Radar signals reflected from fixed objects on the earth's surface; e.g., buildings, towers, terrain. Permanent echoes are distinguished from ``ground clutter'' by being definable locations rather than large areas. Under certain conditions they may be used to check radar alignment. PHOTO RECONNAISSANCE Military activity that requires locating individual photo targets and navigating to the targets at a preplanned angle and altitude. The activity normally requires a lateral route width of 16 NM and altitude range of 1,500 feet to 10,000 feet AGL. PIDP (See PROGRAMMABLE INDICATOR DATA PROCESSOR). PILOT BRIEFING A service provided by the FSS to assist pilots in flight planning. Briefing items may include weather information, NOTAMS, military activities, flow control information, and other items as requested. PILOT IN COMMAND The pilot responsible for the operation and safety of an aircraft during flight time. PILOTS AUTOMATIC TELEPHONE WEATHER ANSWERING SERVICE A continuous telephone recording containing current and forecast weather information for pilots. PILOT'S DISCRETION When used in conjunction with altitude assignments, means that ATC has offered the pilot the option of starting climb or descent whenever he wishes and conducting the climb or descent at any rate he wishes. He may temporarily level off at any intermediate altitude. However, once he has vacated an altitude, he may not return to that altitude. PILOT WEATHER REPORT A report of meteorological phenomena encountered by aircraft in flight. PIREP (See PILOT WEATHER REPORT). POINT OUT (See RADAR POINT OUT). POLAR TRACK STRUCTURE A system of organized routes between Iceland and Alaska which overlie Canadian MNPS Airspace. POSITION REPORT A report over a known location as transmitted by an aircraft to ATC. POSITION SYMBOL A computer generated indication shown on a radar display to indicate the mode of tracking. POSITIVE CONTROL The separation of all air traffic within designated airspace by air traffic control. PRACTICE INSTRUMENT APPROACH An instrument approach procedure conducted by a VFR or an IFR aircraft for the purpose of pilot training or proficiency demonstrations. PREARRANGED COORDINATION A standardized procedure which permits an air traffic controller to enter the airspace assigned to another air traffic controller without verbal coordination. The procedures are defined in a facility directive which ensures standard separation between aircraft. PRECIPITATION Any or all forms of water particles (rain, sleet, hail, or snow) that fall from the atmosphere and reach the surface. PRECISION APPROACH (See PRECISION APPROACH PROCEDURE). PRECISION APPROACH PROCEDURE A standard instrument approach procedure in which an electronic glideslope/glidepath is provided; e.g., ILS/MLS and PAR. PRECISION APPROACH RADAR Radar equipment in some ATC facilities operated by the FAA and/or the military services at joint use civil/military locations and separate military installations to detect and display azimuth, elevation, and range of aircraft on the final approach course to a runway. This equipment may be used to monitor certain nonradar approaches, but is primarily used to conduct a precision instrument approach (PAR) wherein the controller issues guidance instructions to the pilot based on the aircraft's position in relation to the final approach course (azimuth), the glidepath (elevation), and the distance (range) from the touchdown point on the runway as displayed on the radar scope. The abbreviation ``PAR'' is also used to denote preferential arrival routes in ARTCC computers. PRECISION APPROACH RADAR [ICAO] Primary radar equipment used to determine the position of an aircraft during final approach, in terms of lateral and vertical deviations relative to a nominal approach path, and in range relative to touchdown. PRECISION RUNWAY MONITOR Provides air traffic controllers with high precision secondary surveillance data for aircraft on final approach to closely spaced parallel runways. High resolution color monitoring displays (FMA) are required to present surveillance track data to controllers along with detailed maps depicting approaches and no transgression zone. PREFERENTIAL ROUTES Preferential routes (PDR's, PAR's, and PDAR's) are adapted in ARTCC computers to accomplish inter/intrafacility controller coordination and to assure that flight data is posted at the proper control positions. Locations having a need for these specific inbound and outbound routes normally publish such routes in local facility bulletins, and their use by pilots minimizes flight plan route amendments. When the workload or traffic situation permits, controllers normally provide radar vectors or assign requested routes to minimize circuitous routing. Preferential routes are usually confined to one ARTCC's area and are referred to by the following names or acronyms: Preferential Departure Route (PDR). A specific departure route from an airport or terminal area to an en route point where there is no further need for flow control. It may be included in a Standard Instrument Departure (SID) or a Preferred IFR Route. Preferential Arrival Route (PAR). A specific arrival route from an appropriate en route point to an airport or terminal area. It may be included in a Standard Terminal Arrival (STAR) or a Preferred IFR Route. The abbreviation ``PAR'' is used primarily within the ARTCC and should not be confused with the abbreviation for Precision Approach Radar. Preferential Departure and Arrival Route (PDAR). A route between two terminals which are within or immediately adjacent to one ARTCC's area. PDAR's are not synonymous with Preferred IFR Routes but may be listed as such as they do accomplish essentially the same purpose. PREFERRED IFR ROUTES Routes established between busier airports to increase system efficiency and capacity. They normally extend through one or more ARTCC areas and are designed to achieve balanced traffic flows among high density terminals. IFR clearances are issued on the basis of these routes except when severe weather avoidance procedures or other factors dictate otherwise. Preferred IFR Routes are listed in the Airport/Facility Directory. If a flight is planned to or from an area having such routes but the departure or arrival point is not listed in the Airport/Facility Directory, pilots may use that part of a Preferred IFR Route which is appropriate for the departure or arrival point that is listed. Preferred IFR Routes are correlated with SID's and STAR's and may be defined by airways, jet routes, direct routes between NAVAID's, Waypoints, NAVAID radials/DME, or any combinations thereof. PRE FLIGHT PILOT BRIEFING (See PILOT BRIEFING). PREVAILING VISIBILITY (See VISIBILITY). PRM (See PRECISION RUNWAY MONITOR). PROCEDURE TURN The maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course. The outbound course, direction of turn, distance within which the turn must be completed, and minimum altitude are specified in the procedure. However, unless otherwise restricted, the point at which the turn may be commenced and the type and rate of turn are left to the discretion of the pilot. PROCEDURE TURN [ICAO] A manoeuvre in which a turn is made away from a designated track followed by a turn in the opposite direction to permit the aircraft to intercept and proceed along the reciprocal of the designated track. PROCEDURE TURN INBOUND That point of a procedure turn maneuver where course reversal has been completed and an aircraft is established inbound on the intermediate approach segment or final approach course. A report of ``procedure turn inbound'' is normally used by ATC as a position report for separation purposes. PROFILE DESCENT An uninterrupted descent (except where level flight is required for speed adjustment; e.g., 250 knots at 10,000 feet MSL) from cruising altitude/level to interception of a glideslope or to a minimum altitude specified for the initial or intermediate approach segment of a nonprecision instrument approach. The profile descent normally terminates at the approach gate or where the glideslope or other appropriate minimum altitude is intercepted. PROGRAMMABLE INDICATOR DATA PROCESSOR The PIDP is a modification to the AN/TPX-42 interrogator system currently installed in fixed RAPCON's. The PIDP detects, tracks, and predicts secondary radar aircraft targets. These are displayed by means of computer generated symbols and alphanumeric characters depicting flight identification, aircraft altitude, ground speed, and flight plan data. Although primary radar targets are not tracked, they are displayed coincident with the secondary radar targets as well as with the other symbols and alphanumerics. The system has the capability of interfacing with ARTCC's. PROGRESS REPORT (See POSITION REPORT). PROGRESSIVE TAXI Precise taxi instructions given to a pilot unfamiliar with the airport or issued in stages as the aircraft proceeds along the taxi route. PROHIBITED AREA (See SPECIAL USE AIRSPACE). PROHIBITED AREA [ICAO] An airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of aircraft is prohibited. PROPOSED BOUNDARY CROSSING TIME Each center has a PBCT parameter for each internal airport. Proposed internal flight plans are transmitted to the adjacent center if the flight time along the proposed route from the departure airport to the center boundary is less than or equal to the value of PBCT or if airport adaptation specifies transmission regardless of PBCT. PROPOSED DEPARTURE TIME The time a scheduled flight will depart the gate (scheduled operators) or the actual runway off time for nonscheduled operators. For EDCT purposes, the ATCSCC adjusts the ``P'' time for scheduled operators to reflect the runway off times. PROTECTED AIRSPACE The airspace on either side of an oceanic route/track that is equal to one half the lateral separation minimum except where reduction of protected airspace has been authorized. PT (See PROCEDURE TURN). PTS (See POLAR TRACK STRUCTURE). PUBLISHED ROUTE A route for which an IFR altitude has been established and published; e.g., Federal Airways, Jet Routes, Area Navigation Routes, Specified Direct Routes. QUEUING (See STAGING/QUEUING). QLOW (See QUOTA FLOW CONTROL). QNE The barometric pressure used for the standard altimeter setting (29.92 inches Hg.). QNH The barometric pressure as reported by a particular station. QUADRANT A quarter part of a circle, centered on a NAVAID, oriented clockwise from magnetic north as follows: NE quadrant 000-089, SE quadrant 090-179, SW quadrant 180-269, NW quadrant 270-359. QUICK LOOK A feature of NAS Stage A and ARTS which provides the controller the capability to display full data blocks of tracked aircraft from other control positions. QUOTA FLOW CONTROL A flow control procedure by which the Central Flow Control Function (CFCF) restricts traffic to the ARTC Center area having an impacted airport, thereby avoiding sector/area saturation. RADAR A device which, by measuring the time interval between transmission and reception of radio pulses and correlating the angular orientation of the radiated antenna beam or beams in azimuth and/or elevation, provides information on range, azimuth, and/or elevation of objects in the path of the transmitted pulses. Primary Radar. A radar system in which a minute portion of a radio pulse transmitted from a site is reflected by an object and then received back at that site for processing and display at an air traffic control facility. Secondary Radar/Radar Beacon (ATCRBS). A radar system in which the object to be detected is fitted with cooperative equipment in the form of a radio receiver/transmitter (transponder). Radar pulses transmitted from the searching transmitter/receiver (interrogator) site are received in the cooperative equipment and used to trigger a distinctive transmission from the transponder. This reply transmission, rather than a reflected signal, is then received back at the transmitter/receiver site for processing and display at an air traffic control facility. RADAR [ICAO] A radio detection device which provides information on range, azimuth and/or elevation of objects. Primary Radar. Radar system which uses reflected radio signals. Secondary Radar. Radar system wherein a radio signal transmitted from a radar station initiates the transmission of a radio signal from another station. RADAR ADVISORY The provision of advice and information based on radar observations. RADAR ALTIMETER (See RADIO ALTIMETER). RADAR APPROACH An instrument approach procedure which utilizes Precision Approach Radar (PAR) or Airport Surveillance Radar (ASR). RADAR APPROACH [ICAO] An approach, executed by an aircraft, under the direction of a radar controller. RADAR APPROACH CONTROL FACILITY A terminal ATC facility that uses radar and nonradar capabilities to provide approach control services to aircraft arriving, departing, or transiting airspace controlled by the facility I20(See APPROACH CONTROL SERVICE). Provides radar ATC services to aircraft operating in the vicinity of one or more civil and/or military airports in a terminal area. The facility may provide services of a ground controlled approach (GCA); i.e., ASR and PAR approaches. A radar approach control facility may be operated by FAA, USAF, US Army, USN, USMC, or jointly by FAA and a military service. Specific facility nomenclatures are used for administrative purposes only and are related to the physical location of the facility and the operating service generally as follows: Army Radar Approach Control (ARAC) (Army). Radar Air Traffic Control Facility (RATCF) (Navy/FAA). Radar Approach Control (RAPCON) (Air Force/FAA). Terminal Radar Approach Control (TRACON) (FAA). Tower/Airport Traffic Control Tower (ATCT) (FAA). (Only those towers delegated approach control authority.). RADAR ARRIVAL An aircraft arriving at an airport served by a radar facility and in radar contact with the facility. RADAR BEACON (See RADAR). RADAR CONTACT Used by ATC to inform an aircraft that it is identified on the radar display and radar flight following will be provided until radar identification is terminated. Radar service may also be provided within the limits of necessity and capability. When a pilot is informed of ``radar contact,'' he automatically discontinues reporting over compulsory reporting points. The term used to inform the controller that the aircraft is identified and approval is granted for the aircraft to enter the receiving controllers airspace. RADAR CONTACT LOST Used by ATC to inform a pilot that radar data used to determine the aircraft's position is no longer being received, or is no longer reliable and radar service is no longer being provided. The loss may be attributed to several factors including the aircraft merging with weather or ground clutter, the aircraft operating below radar line of sight coverage, the aircraft entering an area of poor radar return, failure of the aircraft transponder, or failure of the ground radar equipment. (See Clutter) (See Radar Contact) RADAR CLUTTER [ICAO] The visual indication on a radar display of unwanted signals. RADAR CONTACT [ICAO] The situation which exists when the radar blip or radar position symbol of a particular aircraft is seen and identified on a radar display. RADAR ENVIRONMENT An area in which radar service may be provided. RADAR FLIGHT FOLLOWING The observation of the progress of radar identified aircraft, whose primary navigation is being provided by the pilot, wherein the controller retains and correlates the aircraft identity with the appropriate target or target symbol displayed on the radar scope. RADAR IDENTIFICATION The process of ascertaining that an observed radar target is the radar return from a particular aircraft. RADAR IDENTIFICATION [ICAO] The process of correlating a particular radar blip or radar position symbol with a specific aircraft. RADAR IDENTIFIED AIRCRAFT An aircraft, the position of which has been correlated with an observed target or symbol on the radar display. RADAR MONITORING (See RADAR SERVICE). RADAR NAVIGATIONAL GUIDANCE (See RADAR SERVICE). RADAR POINT OUT An action taken by a controller to transfer the radar identification of an aircraft to another controller if the aircraft will or may enter the airspace or protected airspace of another controller and radio communications will not be transferred. RADAR REQUIRED A term displayed on charts and approach plates and included in FDC Notams to alert pilots that segments of either an instrument approach procedure or a route are not navigable because of either the absence or unusability of a NAVAID. The pilot can expect to be provided radar navigational guidance while transiting segments labeled with this term. RADAR ROUTE A flight path or route over which an aircraft is vectored. Navigational guidance and altitude assignments are provided by ATC. RADAR SEPARATION (See RADAR SERVICE). RADAR SERVICE A term which encompasses one or more of the following services based on the use of radar which can be provided by a controller to a pilot of a radar identified aircraft. Radar Monitoring. The radar flight following of aircraft, whose primary navigation is being performed by the pilot, to observe and note deviations from its authorized flight path, airway, or route. When being applied specifically to radar monitoring of instrument approaches; i.e., with precision approach radar (PAR) or radar monitoring of simultaneous ILS/MLS approaches, it includes advice and instructions whenever an aircraft nears or exceeds the prescribed PAR safety limit or simultaneous ILS/MLS no transgression zone. Radar Navigational Guidance. Vectoring aircraft to provide course guidance. Radar Separation. Radar spacing of aircraft in accordance with established minima. RADAR SERVICE [ICAO] Term used to indicate a service provided directly by means of radar. Radar Monitoring. The use of radar for the purpose of providing aircraft with information and advice relative to significant deviations from nominal flight path. Radar Separation. The separation used when aircraft position information is derived from radar sources. RADAR SERVICE TERMINATED Used by ATC to inform a pilot that he will no longer be provided any of the services that could be received while in radar contact. Radar service is automatically terminated, and the pilot is not advised in the following cases: An aircraft cancels its IFR flight plan, except within Class B airspace, Class C airspace, a TRSA, or where Basic Radar service is provided. An aircraft conducting an instrument, visual, or contact approach has landed or has been instructed to change to advisory frequency. An arriving VFR aircraft, receiving radar service to a tower controlled airport within Class B airspace, Class C airspace, a TRSA, or where sequencing service is provided, has landed; or to all other airports, is instructed to change to tower or advisory frequency. An aircraft completes a radar approach. RADAR SURVEILLANCE The radar observation of a given geographical area for the purpose of performing some radar function. RADAR TRAFFIC ADVISORIES Advisories issued to alert pilots to known or observed radar traffic which may affect the intended route of flight of their aircraft. RADAR TRAFFIC INFORMATION SERVICE (See TRAFFIC ADVISORIES). RADAR VECTORING [ICAO] Provision of navigational guidance to aircraft in the form of specific headings, based on the use of radar. RADAR WEATHER ECHO INTENSITY LEVELS Existing radar systems cannot detect turbulence. However, there is a direct correlation between the degree of turbulence and other weather features associated with thunderstorms and the radar weather echo intensity. The National Weather Service has categorized radar weather echo intensity for precipitation into six levels. These levels are sometimes expressed during communications as ``VIP LEVEL'' 1 through 6 (derived from the component of the radar that produces the information Video Integrator and Processor). The following list gives the ``VIP LEVELS'' in relation to the precipitation intensity within a thunderstorm: Level 1. WEAK Level 2. MODERATE Level 3. STRONG Level 4. VERY STRONG Level 5. INTENSE Level 6. EXTREME RADIAL A magnetic bearing extending from a VOR/VORTAC/TACAN navigation facility. RADIO A device used for communication. Used to refer to a flight service station; e.g., ``Seattle Radio'' is used to call Seattle FSS. RADIO ALTIMETER Aircraft equipment which makes use of the reflection of radio waves from the ground to determine the height of the aircraft above the surface. RADIO BEACON (See NONDIRECTIONAL BEACON). RADIO DETECTION AND RANGING (See RADAR). RADIO MAGNETIC INDICATOR An aircraft navigational instrument coupled with a gyro compass or similar compass that indicates the direction of a selected NAVAID and indicates bearing with respect to the heading of the aircraft. RAMP (See APRON). RANDOM ALTITUDE An altitude inappropriate for direction of flight and/or not in accordance with paragraph 4-60. RANDOM ROUTE Any route not established or charted/published or not otherwise available to all users. RC (See ROAD RECONNAISSANCE). RCAG (See REMOTE COMMUNICATIONS AIR/GROUND FACILITY). RCC (See RESCUE COORDINATION CENTER). RCO (See REMOTE COMMUNICATIONS OUTLET). RCR (See RUNWAY CONDITION READING). READ BACK Repeat my message back to me. RECEIVING CONTROLLER A controller/facility receiving control of an aircraft from another controller/facility. RECEIVING FACILITY (See RECEIVING CONTROLLER). REDUCE SPEED TO (SPEED) (See SPEED ADJUSTMENT). REIL (See RUNWAY END IDENTIFIER LIGHTS). RELEASE TIME A departure time restriction issued to a pilot by ATC (either directly or through an authorized relay) when necessary to separate a departing aircraft from other traffic. RELEASE TIME [ICAO] Time prior to which an aircraft should be given further clearance or prior to which it should not proceed in case of radio failure. REMOTE COMMUNICATIONS AIR/GROUND FACILITY An unmanned VHF/UHF transmitter/receiver facility which is used to expand ARTCC air/ground communications coverage and to facilitate direct contact between pilots and controllers. RCAG facilities are sometimes not equipped with emergency frequencies 121.5 mHz and 243.0 mHz. REMOTE COMMUNICATIONS OUTLET An unmanned communications facility remotely controlled by air traffic personnel. RCO's serve FSS's. RTR's serve terminal ATC facilities. An RCO or RTR may be UHF or VHF and will extend the communication range of the air traffic facility. There are several classes of RCO's and RTR's. The class is determined by the number of transmitters or receivers. Classes A through G are used primarily for air/ground purposes. RCO and RTR class O facilities are nonprotected outlets subject to undetected and prolonged outages. RCO (O's) and RTR (O's) were established for the express purpose of providing ground to ground communications between air traffic control specialists and pilots located at a satellite airport for delivering en route clearances, issuing departure authorizations, and acknowledging instrument flight rules cancellations or departure/landing times. As a secondary function, they may be used for advisory purposes whenever the aircraft is below the coverage of the primary air/ground frequency. REMOTE TRANSMITTER/RECEIVER (See REMOTE COMMUNICATIONS OUTLET). REPORT Used to instruct pilots to advise ATC of specified information; e.g., ``Report passing Hamilton VOR.'' REPORTING POINT A geographical location in relation to which the position of an aircraft is reported. REPORTING POINT [ICAO] A specified geographical location in relation to which the position of an aircraft can be reported. REQUEST FULL ROUTE CLEARANCE Used by pilots to request that the entire route of flight be read verbatim in an ATC clearance. Such request should be made to preclude receiving an ATC clearance based on the original filed flight plan when a filed IFR flight plan has been revised by the pilot, company, or operations prior to departure. RESCUE COORDINATION CENTER A search and rescue (SAR) facility equipped and manned to coordinate and control SAR operations in an area designated by the SAR plan. The U.S. Coast Guard and the U.S. Air Force have responsibility for the operation of RCC's. RESCUE CO ORDINATION CENTRE [ICAO] A unit responsible for promoting efficient organization of search and rescue service and for co ordinating the conduct of search and rescue operations within a search and rescue region. RESTRICTED AREA (See SPECIAL USE AIRSPACE). RESTRICTED AREA [ICAO] An airspace of defined dimensions, above the land areas or territorial waters of a State, within which the flight of aircraft is restricted in accordance with certain specified conditions. RESUME OWN NAVIGATION Used by ATC to advise a pilot to resume his own navigational responsibility. It is issued after completion of a radar vector or when radar contact is lost while the aircraft is being radar vectored. RMI (See RADIO MAGNETIC INDICATOR). RNAV (See AREA NAVIGATION). RNAV [ICAO] (See ICAO Term AREA NAVIGATION). RNAV APPROACH An instrument approach procedure which relies on aircraft area navigation equipment for navigational guidance. ROAD RECONNAISSANCE Military activity requiring navigation along roads, railroads, and rivers. Reconnaissance route/route segments are seldom along a straight line and normally require a lateral route width of 10 NM to 30 NM and an altitude range of 500 feet to 10,000 feet AGL. ROGER I have received all of your last transmission. It should not be used to answer a question requiring a yes or a no answer. ROLLOUT RVR (See VISIBILITY). ROUTE A defined path, consisting of one or more courses in a horizontal plane, which aircraft traverse over the surface of the earth. ROUTE SEGMENT As used in Air Traffic Control, a part of a route that can be defined by two navigational fixes, two NAVAID's, or a fix and a NAVAID. ROUTE SEGMENT [ICAO] A portion of a route to be flown, as defined by two consecutive significant points specified in a flight plan. RSA (See RUNWAY SAFETY AREA). RTR (See REMOTE TRANSMITTER/RECEIVER). RUNWAY A defined rectangular area on a land airport prepared for the landing and takeoff run of aircraft along its length. Runways are normally numbered in relation to their magnetic direction rounded off to the nearest 10 degrees; e.g., Runway 01, Runway 25. RUNWAY [ICAO] A defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft. RUNWAY CENTERLINE LIGHTING (See AIRPORT LIGHTING). RUNWAY CONDITION READING Numerical decelerometer readings relayed by air traffic controllers at USAF and certain civil bases for use by the pilot in determining runway braking action. These readings are routinely relayed only to USAF and Air National Guard Aircraft. RUNWAY END IDENTIFIER LIGHTS (See AIRPORT LIGHTING). RUNWAY GRADIENT The average slope, measured in percent, between two ends or points on a runway. Runway gradient is depicted on Government aerodrome sketches when total runway gradient exceeds 0.3%. RUNWAY HEADING The magnetic direction that corresponds with the runway centerline extended, not the painted runway number. When cleared to ``fly or maintain runway heading,'' pilots are expected to fly or maintain the heading that corresponds with the extended centerline of the departure runway. Drift correction shall not be applied; e.g., Runway 4, actual magnetic heading of the runway centerline 044, fly 044. RUNWAY IN USE/ACTIVE RUNWAY/DUTY RUNWAY Any runway or runways currently being used for takeoff or landing. When multiple runways are used, they are all considered active runways. In the metering sense, a selectable adapted item which specifies the landing runway configuration or direction of traffic flow. The adapted optimum flight plan from each transition fix to the vertex is determined by the runway configuration for arrival metering processing purposes. RUNWAY LIGHTS (See AIRPORT LIGHTING). RUNWAY MARKINGS (See AIRPORT MARKING AIDS). RUNWAY OVERRUN In military aviation exclusively, a stabilized or paved area beyond the end of a runway, of the same width as the runway plus shoulders, centered on the extended runway centerline. RUNWAY PROFILE DESCENT An instrument flight rules (IFR) air traffic control arrival procedure to a runway published for pilot use in graphic and/or textual form and may be associated with a STAR. Runway Profile Descents provide routing and may depict crossing altitudes, speed restrictions, and headings to be flown from the en route structure to the point where the pilot will receive clearance for and execute an instrument approach procedure. A Runway Profile Descent may apply to more than one runway if so stated on the chart. RUNWAY SAFETY AREA A defined surface surrounding the runway prepared, or suitable, for reducing the risk of damage to airplanes in the event of an undershoot, overshoot, or excursion from the runway. The dimensions of the RSA vary and can be determined by using the criteria contained within Advisory Circular 150/5300-13, Chapter 3. Figure 3-1 in Advisory Circular 150/5300-13 depicts the RSA. The design standards dictate that the RSA shall be: Cleared, graded, and have no potentially hazardous ruts, humps, depressions, or other surface variations; Drained by grading or storm sewers to prevent water accumulation; Capable, under dry conditions, of supporting snow removal equipment, aircraft rescue and firefighting equipment, and the occasional passage of aircraft without causing structural damage to the aircraft; and, Free of objects, except for objects that need to be located in the runway safety area because of their function. These objects shall be constructed on low impact resistant supports (frangible mounted structures) to the lowest practical height with the frangible point no higher than 3 inches above grade. RUNWAY USE PROGRAM A noise abatement runway selection plan designed to enhance noise abatement efforts with regard to airport communities for arriving and departing aircraft. These plans are developed into runway use programs and apply 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. Runway use programs are coordinated with FAA offices, and safety criteria used in these programs are developed by the Office of Flight Operations. Runway use programs are administered by the Air Traffic Service as ``Formal'' or ``Informal'' programs. Formal Runway Use Program. An approved noise abatement program which is defined and acknowledged in a Letter of Understanding between Flight Operations, Air Traffic Service, the airport proprietor, and the users. Once established, participation in the program is mandatory for aircraft operators and pilots as provided for in Part 91.129. Informal Runway Use Program. An approved noise abatement program which does not require a Letter of Understanding, and participation in the program is voluntary for aircraft operators/pilots. RUNWAY VISIBILITY VALUE (See VISIBILITY). RUNWAY VISUAL RANGE (See VISIBILITY). SAFETY ALERT A safety alert issued by ATC to aircraft under their control if ATC is aware the aircraft is at an altitude which, in the controller's judgment, places the aircraft in unsafe proximity to terrain, obstructions, or other aircraft. The controller may discontinue the issuance of further alerts if the pilot advises he is taking action to correct the situation or has the other aircraft in sight. Terrain/Obstruction Alert. A safety alert issued by ATC to aircraft under their control if ATC is aware the aircraft is at an altitude which, in the controller's judgment, places the aircraft in unsafe proximity to terrain/obstructions; e.g., ``Low Altitude Alert, check your altitude immediately.'' Aircraft Conflict Alert. A safety alert issued by ATC to aircraft under their control if ATC is aware of an aircraft that is not under their control at an altitude which, in the controller's judgment, places both aircraft in unsafe proximity to each other. With the alert, ATC will offer the pilot an alternate course of action when feasible; e.g., ``Traffic Alert, advise you turn right heading zero niner zero or climb to eight thousand immediately.'' SAIL BACK A maneuver during high wind conditions (usually with power off) where float plane movement is controlled by water rudders/opening and closing cabin doors. SAME DIRECTION AIRCRAFT Aircraft are operating in the same direction when: They are following the same track in the same direction; or Their tracks are parallel and the aircraft are flying in the same direction; or Their tracks intersect at an angle of less than 45 degrees. SAR (See SEARCH AND RESCUE). SAY AGAIN Used to request a repeat of the last transmission. Usually specifies transmission or portion thereof not understood or received; e.g., ``Say again all after ABRAM VOR.'' SAY ALTITUDE Used by ATC to ascertain an aircraft's specific altitude/flight level. When the aircraft is climbing or descending, the pilot should state the indicated altitude rounded to the nearest 100 feet. SAY HEADING Used by ATC to request an aircraft heading. The pilot should state the actual heading of the aircraft. SDF (See SIMPLIFIED DIRECTIONAL FACILITY). SEA LANE A designated portion of water outlined by visual surface markers for and intended to be used by aircraft designed to operate on water. SEARCH AND RESCUE A service which seeks missing aircraft and assists those found to be in need of assistance. It is a cooperative effort using the facilities and services of available Federal, state and local agencies. The U.S. Coast Guard is responsible for coordination of search and rescue for the Maritime Region, and the U.S. Air Force is responsible for search and rescue for the Inland Region. Information pertinent to search and rescue should be passed through any air traffic facility or be transmitted directly to the Rescue Coordination Center by telephone. SEARCH AND RESCUE FACILITY A facility responsible for maintaining and operating a search and rescue (SAR) service to render aid to persons and property in distress. It is any SAR unit, station, NET, or other operational activity which can be usefully employed during an SAR Mission; e.g., a Civil Air Patrol Wing, or a Coast Guard Station. SECTIONAL AERONAUTICAL CHARTS (See AERONAUTICAL CHART). SECTOR LIST DROP INTERVAL A parameter number of minutes after the meter fix time when arrival aircraft will be deleted from the arrival sector list. SEE AND AVOID A visual procedure wherein pilots of aircraft flying in visual meteorological conditions (VMC), regardless of type of flight plan, are charged with the responsibility to observe the presence of other aircraft and to maneuver their aircraft as required to avoid the other aircraft. Right of way rules are contained in Part 91. SEGMENTED CIRCLE A system of visual indicators designed to provide traffic pattern information at airports without operating control towers. SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE An instrument approach procedure may have as many as four separate segments depending on how the approach procedure is structured. Initial Approach. The segment between the initial approach fix and the intermediate fix or the point where the aircraft is established on the intermediate course or final approach course. Intermediate Approach. The segment between the intermediate fix or point and the final approach fix. Final Approach. The segment between the final approach fix or point and the runway, airport, or missed approach point. Missed Approach. The segment between the missed approach point or the point of arrival at decision height and the missed approach fix at the prescribed altitude. SELECTED GROUND DELAYS A traffic management procedure whereby selected flights are issued ground delays to better regulate traffic flows over a particular fix or area. SEPARATION In air traffic control, the spacing of aircraft to achieve their safe and orderly movement in flight and while landing and taking off. SEPARATION [ICAO] Spacing between aircraft, levels or tracks. SEPARATION MINIMA The minimum longitudinal, lateral, or vertical distances by which aircraft are spaced through the application of air traffic control procedures. SERVICE A generic term that designates functions or assistance available from or rendered by air traffic control. For example, Class C service would denote the ATC services provided within a Class C airspace area. SEVERE WEATHER AVOIDANCE PLAN An approved plan to minimize the affect of severe weather on traffic flows in impacted terminal and/or ARTCC areas. SWAP is normally implemented to provide the least disruption to the ATC system when flight through portions of airspace is difficult or impossible due to severe weather. SEVERE WEATHER FORECAST ALERTS Preliminary messages issued in order to alert users that a Severe Weather Watch Bulletin (WW) is being issued. These messages define areas of possible severe thunderstorms or tornado activity. The messages are unscheduled and issued as required by the National Severe Storm Forecast Center at Kansas City, Missouri. SFA (See SINGLE FREQUENCY APPROACH). SFO (See SIMULATED FLAMEOUT). SHF (See SUPER HIGH FREQUENCY). SHORT RANGE CLEARANCE A clearance issued to a departing IFR flight which authorizes IFR flight to a specific fix short of the destination while air traffic control facilities are coordinating and obtaining the complete clearance. SHORT TAKEOFF AND LANDING AIRCRAFT AIRCRAFT An aircraft which, at some weight within its approved operating weight, is capable of operating from a STOL runway in compliance with the applicable STOL characteristics, airworthiness, operations, noise, and pollution standards. SIAP (See STANDARD INSTRUMENT APPROACH PROCEDURE). SIDESTEP MANEUVER A visual maneuver accomplished by a pilot at the completion of an instrument approach to permit a straight in landing on a parallel runway not more than 1,200 feet to either side of the runway to which the instrument approach was conducted. SIGMET A weather advisory issued concerning weather significant to the safety of all aircraft. SIGMET advisories cover severe and extreme turbulence, severe icing, and widespread dust or sandstorms that reduce visibility to less than 3 miles. SIGMET INFORMATION [ICAO] Information issued by a meteorological watch office concerning the occurrence or expected occurrence of specified en route weather phenomena which may affect the safety of aircraft operations. SIGNIFICANT METEOROLOGICAL INFORMATION (See SIGMET). SIGNIFICANT POINT A point, whether a named intersection, a NAVAID, a fix derived from a NAVAID(s), or geographical coordinate expressed in degrees of latitude and longitude, which is established for the purpose of providing separation, as a reporting point, or to delineate a route of flight. SIMPLIFIED DIRECTIONAL FACILITY A NAVAID used for nonprecision instrument approaches. The final approach course is similar to that of an ILS localizer except that the SDF course may be offset from the runway, generally not more than 3 degrees, and the course may be wider than the localizer, resulting in a lower degree of accuracy. SIMULATED FLAMEOUT A practice approach by a jet aircraft (normally military) at idle thrust to a runway. The approach may start at a relatively high altitude over a runway (high key) and may continue on a relatively high and wide downwind leg with a high rate of descent and a continuous turn to final. It terminates in a landing or low approach. The purpose of this approach is to simulate a flameout. SIMULTANEOUS ILS APPROACHES An approach system permitting simultaneous ILS/MLS approaches to airports having parallel runways separated by at least 4,300 feet between centerlines. Integral parts of a total system are ILS/MLS, radar, communications, ATC procedures, and appropriate airborne equipment. SIMULTANEOUS MLS APPROACHES (See SIMULTANEOUS ILS APPROACHES). SIMULTANEOUS OPERATIONS ON INTERSECTING RUNWAYS Operations which include simultaneous takeoffs and landings and/or simultaneous landings when a landing aircraft is able and is instructed by the controller to hold short of the intersecting runway or designated hold short point. Pilots are expected to promptly inform the controller if the hold short clearance cannot be accepted. SINGLE DIRECTION ROUTES Preferred IFR Routes which are sometimes depicted on high altitude en route charts and which are normally flown in one direction only. SINGLE FREQUENCY APPROACH A service provided under a letter of agreement to military single piloted turbojet aircraft which permits use of a single UHF frequency during approach for landing. Pilots will not normally be required to change frequency from the beginning of the approach to touchdown except that pilots conducting an en route descent are required to change frequency when control is transferred from the air route traffic control center to the terminal facility. The abbreviation ``SFA'' in the DOD FLIP IFR Supplement under ``Communications'' indicates this service is available at an aerodrome. SINGLE PILOTED AIRCRAFT A military turbojet aircraft possessing one set of flight controls, tandem cockpits, or two sets of flight controls but operated by one pilot is considered single piloted by ATC when determining the appropriate air traffic service to be applied. SLASH A radar beacon reply displayed as an elongated target. SLDI (See SECTOR LIST DROP INTERVAL). SLOT TIME (See METER FIX TIME/SLOT TIME). SLOW TAXI To taxi a float plane at low power or low RPM. SN (See SYSTEM STRATEGIC NAVIGATION). SPEAK SLOWER Used in verbal communications as a request to reduce speech rate. SPECIAL EMERGENCY A condition of air piracy or other hostile act by a person(s) aboard an aircraft which threatens the safety of the aircraft or its passengers. SPECIAL INSTRUMENT APPROACH PROCEDURE (See INSTRUMENT APPROACH PROCEDURE). SPECIAL USE AIRSPACE Airspace of defined dimensions identified by an area on the surface of the earth wherein activities must be confined because of their nature and/or wherein limitations may be imposed upon aircraft operations that are not a part of those activities. Types of special use airspace are: Alert Area. Airspace which may contain a high volume of pilot training activities or an unusual type of aerial activity, neither of which is hazardous to aircraft. Alert Areas are depicted on aeronautical charts for the information of nonparticipating pilots. All activities within an Alert Area are conducted in accordance with Federal Aviation Regulations, and pilots of participating aircraft as well as pilots transiting the area are equally responsible for collision avoidance. Controlled Firing Area. Airspace wherein activities are conducted under conditions so controlled as to eliminate hazards to nonparticipating aircraft and to ensure the safety of persons and property on the ground. Military Operations Area (MOA). An MOA is an airspace assignment of defined vertical and lateral dimensions established outside Class A airspace to separate/segregate certain military activities from IFR traffic and to identify for VFR traffic where these activities are conducted. Prohibited Area. Designated airspace within which the flight of aircraft is prohibited. Restricted Area. Airspace designated under Part 73, within which the flight of aircraft, while not wholly prohibited, is subject to restriction. Most restricted areas are designated joint use and IFR/VFR operations in the area may be authorized by the controlling ATC facility when it is not being utilized by the using agency. Restricted areas are depicted on en route charts. Where joint use is authorized, the name of the ATC controlling facility is also shown. Warning Area. Airspace which may contain hazards to nonparticipating aircraft in international airspace. SPECIAL VFR CONDITIONS Meteorlogical conditions that are less than those required for basic VFR flight in Class B, C, D, or E surface areas and in which some aircraft are permitted flight under visual flight rules. SPECIAL VFR FLIGHT [ICAO] A VFR flight cleared by air traffic control to operate within Class B, C, D, and E surface areas in meterological conditions below VMC. SPECIAL VFR OPERATIONS Aircraft operating in accordance with clearances within Class B, C, D, and E surface areas in weather conditions less than the basic VFR weather minima. Such operations must be requested by the pilot and approved by ATC. SPEED (See AIRSPEED). SPEED ADJUSTMENT An ATC procedure used to request pilots to adjust aircraft speed to a specific value for the purpose of providing desired spacing. Pilots are expected to maintain a speed of plus or minus 10 knots or 0.02 mach number of the specified speed. Examples of speed adjustments are: ``Increase/reduce speed to mach point (number).'' ``Increase/reduce speed to (speed in knots)'' or ``Increase/reduce speed (number of knots) knots.'' SPEED BRAKES Moveable aerodynamic devices on aircraft that reduce airspeed during descent and landing. SPEED SEGMENTS Portions of the arrival route between the transition point and the vertex along the optimum flight path for which speeds and altitudes are specified. There is one set of arrival speed segments adapted from each transition point to each vertex. Each set may contain up to six segments. SQUAWK (Mode, Code, Function) Activate specific modes/codes/functions on the aircraft transponder; e.g., ``Squawk three/alpha, two one zero five, low.'' STAGING/QUEUING The placement, integration, and segregation of departure aircraft in designated movement areas of an airport by departure fix, EDCT, and/or restriction. STANDARD INSTRUMENT APPROACH PROCEDURE (See INSTRUMENT APPROACH PROCEDURE). STANDARD INSTRUMENT DEPARTURE A preplanned instrument flight rule (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 appropriate en route structure. STANDARD INSTRUMENT DEPARTURE CHARTS (See AERONAUTICAL CHART). STANDARD RATE TURN A turn of three degrees per second. STANDARD TERMINAL ARRIVAL A preplanned instrument flight rule (IFR) air traffic control arrival procedure published 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/arrival waypoint in the terminal area. STANDARD TERMINAL ARRIVAL CHARTS (See AERONAUTICAL CHART). STAND BY Means the controller or pilot must pause for a few seconds, usually to attend to other duties of a higher priority. Also means to wait as in ``stand by for clearance.'' The caller should reestablish contact if a delay is lengthy. ``Stand by'' is not an approval or denial. STAR (See STANDARD TERMINAL ARRIVAL). STATE AIRCRAFT Aircraft used in military, customs and police service, in the exclusive service of any government, or of any political subdivision, thereof including the government of any state, territory, or possession of the United States or the District of Columbia, but not including any government owned aircraft engaged in carrying persons or property for commercial purposes. STATIC RESTRICTIONS Those restrictions that are usually not subject to change, fixed, in place, and/or published. STATIONARY RESERVATIONS Altitude reservations which encompass activities in a fixed area. Stationary reservations may include activities, such as special tests of weapons systems or equipment, certain U.S. Navy carrier, fleet, and anti submarine operations, rocket, missile and drone operations, and certain aerial refueling or similar operations. STEPDOWN FIX A fix permitting additional descent within a segment of an instrument approach procedure by identifying a point at which a controlling obstacle has been safely overflown. STEP TAXI To taxi a float plane at full power or high RPM. STEP TURN A maneuver used to put a float plane in a planing configuration prior to entering an active sea lane for takeoff. The STEP TURN maneuver should only be used upon pilot request. STEREO ROUTE A routinely used route of flight established by users and ARTCC's identified by a coded name; e.g., ALPHA 2.These routes minimize flight plan handling and communications. STOL AIRCRAFT (See SHORT TAKEOFF AND LANDING AIRCRAFT). STOP ALTITUDE SQUAWK Used by ATC to inform an aircraft to turn off the automatic altitude reporting feature of its transponder. It is issued when the verbally reported altitude varies 300 feet or more from the automatic altitude report. STOP AND GO A procedure wherein an aircraft will land, make a complete stop on the runway, and then commence a takeoff from that point. STOP BURST (See STOP STREAM). STOP BUZZER (See STOP STREAM). STOPOVER FLIGHT PLAN A flight plan format which permits in a single submission the filing of a sequence of flight plans through interim full stop destinations to a final destination. STOP SQUAWK (Mode or Code) Used by ATC to tell the pilot to turn specified functions of the aircraft transponder off. STOP STREAM Used by ATC to request a pilot to suspend electronic countermeasure activity. STOPWAY An area beyond the takeoff runway no less wide than the runway and centered upon the extended centerline of the runway, able to support the airplane during an aborted takeoff, without causing structural damage to the airplane, and designated by the airport authorities for use in decelerating the airplane during an aborted takeoff. STRAIGHT IN APPROACH IFR An instrument approach wherein final approach is begun without first having executed a procedure turn, not necessarily completed with a straight in landing or made to straight in landing minimums. STRAIGHT IN APPROACH VFR Entry into the traffic pattern by interception of the extended runway centerline (final approach course) without executing any other portion of the traffic pattern. STRAIGHT IN LANDING A landing made on a runway aligned within 30« of the final approach course following completion of an instrument approach. STRAIGHT IN LANDING MINIMUMS (See LANDING MINIMUMS). STRAIGHT IN MINIMUMS (See STRAIGHT IN LANDING MINIMUMS). SUBSTITUTIONS Users are permitted to exchange CTA's. Normally, the airline dispatcher will contact the ATCSCC with this request. The ATCSCC shall forward approved substitutions to the TMU's who will notify the appropriate terminals. Permissible swapping must not change the traffic load for any given hour of an EQF program. SUBSTITUTE ROUTE A route assigned to pilots when any part of an airway or route is unusable because of NAVAID status. These routes consist of: Substitute routes which are shown on U.S. Government charts. Routes defined by ATC as specific NAVAID radials or courses. Routes defined by ATC as direct to or between NAVAID's. SUNSET AND SUNRISE The mean solar times of sunset and sunrise as published in the Nautical Almanac, converted to local standard time for the locality concerned. Within Alaska, the end of evening civil twilight and the beginning of morning civil twilight, as defined for each locality. SUPER HIGH FREQUENCY The frequency band between 3 and 30 gigahertz (gHz). The elevation and azimuth stations of the microwave landing system operate from 5031 mHz to 5091 mHz in this spectrum. SUPPLEMENTAL WEATHER SERVICE LOCATION Airport facilities staffed with contract personnel who take weather observations and provide current local weather to pilots via telephone or radio. (All other services are provided by the parent FSS). SUPPS Refers to ICAO Document 7030 Regional Supplementary Procedures. SUPPS contain procedures for each ICAO Region which are unique to that Region and are not covered in the worldwide provisions identified in the ICAO Air Navigation Plan. Procedures contained in chapter 8 are based in part on those published in SUPPS. SURFACE AREA The airspace contained by the lateral boundary of the Class B, C, D, or E airspace designated for an airport that begins at the surface and extends upward. SURPIC A description of surface vessels in the area of a Search and Rescue incident including their predicted positions and their characteristics. SURVEILLANCE APPROACH An instrument approach wherein the air traffic controller issues instructions, for pilot compliance, based on aircraft position in relation to the final approach course (azimuth), and the distance (range) from the end of the runway as displayed on the controller's radar scope. The controller will provide recommended altitudes on final approach if requested by the pilot. SWAP (See SEVERE WEATHER AVOIDANCE PLAN). SWSL (See SUPPLEMENTAL WEATHER SERVICE LOCATION). SYSTEM STRATEGIC NAVIGATION Military activity accomplished by navigating along a preplanned route using internal aircraft systems to maintain a desired track. This activity normally requires a lateral route width of 10 NM and altitude range of 1,000 feet to 6,000 feet AGL with some route segments that permit terrain following. TACAN (See TACTICAL AIR NAVIGATION). TACAN ONLY AIRCRAFT An aircraft, normally military, possessing TACAN with DME but no VOR navigational system capability. Clearances must specify TACAN or VORTAC fixes and approaches. TACTICAL AIR NAVIGATION An ultra high frequency electronic rho theta air navigation aid which provides suitably equipped aircraft a continuous indication of bearing and distance to the TACAN station. TAILWIND Any wind more than 90 degrees to the longitudinal axis of the runway. The magnetic direction of the runway shall be used as the basis for determining the longitudinal axis. TAKEOFF AREA (See LANDING AREA). TAKE-OFF DISTANCE AVAILABLE [ICAO] The length of the take-off run available plus the length of the clearway, if provided. TAKE-OFF RUN AVAILABLE [ICAO] The length of runway declared available and suitable for the ground run of an aeroplane take-off. TARGET The indication shown on a radar display resulting from a primary radar return or a radar beacon reply. TARGET [ICAO] In radar: 1. Generally, any discrete object which reflects or retransmits energy back to the radar equipment. 2. Specifically, an object of radar search or surveillance. TARGET RESOLUTION A process to ensure that correlated radar targets do not touch. Target resolution shall be applied as follows: Between the edges of two primary targets or the edges of the ASR-9 primary target symbol. Between the end of the beacon control slash and the edge of a primary target. Between the ends of two beacon control slashes. MANDATORY TRAFFIC ADVISORIES AND SAFETY ALERTS SHALL BE ISSUED WHEN THIS PROCEDURE IS USED. TARGET SYMBOL A computer generated indication shown on a radar display resulting from a primary radar return or a radar beacon reply. TAXI The movement of an airplane under its own power on the surface of an airport (Part 135.100-Note). Also, it describes the surface movement of helicopters equipped with wheels. TAXI INTO POSITION AND HOLD Used by ATC to inform a pilot to taxi onto the departure runway in takeoff position and hold. It is not authorization for takeoff. It is used when takeoff clearance cannot immediately be issued because of traffic or other reasons. TAXI PATTERNS Patterns established to illustrate the desired flow of ground traffic for the different runways or airport areas available for use. TCAS (See TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEM). TCH (See THRESHOLD CROSSING HEIGHT). TCLT (See TENTATIVE CALCULATED LANDING TIME). TDZE (See TOUCHDOWN ZONE ELEVATION). TELEPHONE INFORMATION BRIEFING SERVICE A continuous telephone recording of meteorological and/or aeronautical information. TENTATIVE CALCULATED LANDING TIME A projected time calculated for adapted vertex for each arrival aircraft based upon runway configuration, airport acceptance rate, airport arrival delay period, and other metered arrival aircraft. This time is either the VTA of the aircraft or the TCLT/ACLT of the previous aircraft plus the AAI, whichever is later. This time will be updated in response to an aircraft's progress and its current relationship to other arrivals. TERMINAL AREA A general term used to describe airspace in which approach control service or airport traffic control service is provided. TERMINAL AREA FACILITY A facility providing air traffic control service for arriving and departing IFR, VFR, Special VFR, and on occasion en route aircraft. TERMINAL VFR RADAR SERVICE A national program instituted to extend the terminal radar services provided instrument flight rules (IFR) aircraft to visual flight rules (VFR) aircraft. The program is divided into four types service referred to as basic radar service, terminal radar service area (TRSA) service, Class B service and Class C service. The type of service provided at a particular location is contained in the Airport/Facility Directory. 1.Basic Radar Service: These services are provided for VFR aircraft by all commissioned terminal radar facilities. Basic radar service includes safety alerts, traffic advisories, limited radar vectoring when requested by the pilot, and sequencing at locations where procedures have been established for this purpose and/or when covered by a letter of agreement. The purpose of this service is to adjust the flow of arriving IFR and VFR aircraft into the traffic pattern in a safe and orderly manner and to provide traffic advisories to departing VFR aircraft. 2.TRSA Service: This service provides, in addition to basic radar service, sequencing of all IFR and participating VFR aircraft to the primary airport and separation between all participating VFR aircraft. The purpose of this service is to provide separation between all participating VFR aircraft and all IFR aircraft operating within the area defined as a TRSA. 3.Class C Service: This service provides, in addition to basic radar service, approved separation between IFR and VFR aircraft, and sequencing of VFR aircraft, and sequencing of VFR arrivals to the primary airport. 4.Class B Service: This service provides, in addition to basic radar service, approved separation of aircraft based on IFR, VFR, and/or weight, and sequencing of VFR arrivals to the primary airport(s). TERMINAL RADAR SERVICE AREA Airspace surrounding designated airports wherein ATC provides radar vectoring, sequencing, and separation on a full time basis for all IFR and participating VFR aircraft. Service provided in a TRSA is called Stage III Service. The AIM contains an explanation of TRSA. TRSA's are depicted on VFR aeronautical charts. Pilot participation is urged but is not mandatory. TERMINAL VERY HIGH FREQUENCY OMNIDIRECTIONAL RANGE STATION A very high frequency terminal omnirange station located on or near an airport and used as an approach aid. TERRAIN FOLLOWING The flight of a military aircraft maintaining a constant AGL altitude above the terrain or the highest obstruction. The altitude of the aircraft will constantly change with the varying terrain and/or obstruction. TETRAHEDRON A device normally located on uncontrolled airports and used as a landing direction indicator. The small end of a tetrahedron points in the direction of landing. At controlled airports, the tetrahedron, if installed, should be disregarded because tower instructions supersede the indicator. TF (See TERRAIN FOLLOWING). THAT IS CORRECT The understanding you have is right. 360 OVERHEAD (See OVERHEAD APPROACH). THRESHOLD The beginning of that portion of the runway usable for landing. THRESHOLD CROSSING HEIGHT The theoretical height above the runway threshold at which the aircraft's glideslope antenna would be if the aircraft maintains the trajectory established by the mean ILS glideslope or MLS glidepath. THRESHOLD LIGHTS (See AIRPORT LIGHTING). TIBS (See TELEPHONE INFORMATION BRIEFING SERVICE). TIME GROUP Four digits representing the hour and minutes from the 24-hour clock. Time groups without time zone indicators are understood to be UTC (Coordinated Universal Time); e.g., ``0205.'' The term ``Zulu'' is used when ATC procedures require a reference to UTC. A time zone designator is used to indicate local time; e.g., ``0205M.'' The end and the beginning of the day are shown by ``2400'' and ``0000,'' respectively. TMPA (See TRAFFIC MANAGEMENT PROGRAM ALERT). TMU (See TRAFFIC MANAGEMENT UNIT). TODA [ICAO] (See ICAO Term TAKE-OFF DISTANCE AVAILABLE). TORA [ICAO] (See ICAO Term TAKE-OFF RUN AVAILABLE). TORCHING The burning of fuel at the end of an exhaust pipe or stack of a reciprocating aircraft engine, the result of an excessive richness in the fuel air mixture. TOTAL ESTIMATED ELAPSED TIME [ICAO] For IFR flights, the estimated time required from take off to arrive over that designated point, defined by reference to navigation aids, from which it is intended that an instrument approach procedure will be commenced, or, if no navigation aid is associated with the destination aerodrome, to arrive over the destination aerodrome. For VFR flights, the estimated time required from takeoff to arrive over the destination aerodrome. TOUCH AND GO An operation by an aircraft that lands and departs on a runway without stopping or exiting the runway. TOUCH AND GO LANDING (See TOUCH AND GO). TOUCHDOWN The point at which an aircraft first makes contact with the landing surface. Concerning a precision radar approach (PAR), it is the point where the glide path intercepts the landing surface. TOUCHDOWN [ICAO] The point where the nominal glide path intercepts the runway. TOUCHDOWN RVR (See VISIBILITY). TOUCHDOWN ZONE The first 3,000 feet of the runway beginning at the threshold. The area is used for determination of Touchdown Zone Elevation in the development of straight in landing minimums for instrument approaches. TOUCHDOWN ZONE [ICAO] The portion of a runway, beyond the threshold, where it is intended landing aircraft first contact the runway. TOUCHDOWN ZONE ELEVATION The highest elevation in the first 3,000 feet of the landing surface. TDZE is indicated on the instrument approach procedure chart when straight in landing minimums are authorized. TOUCHDOWN ZONE LIGHTING (See AIRPORT LIGHTING). TOWER A terminal facility that uses air/ground communications, visual signaling, and other devices to provide ATC services to aircraft operating in the vicinity of an airport or on the movement area. Authorizes aircraft to land or takeoff at the airport controlled by the tower or to transit the Class D airspace area regardless of flight plan or weather conditions (IFR or VFR). A tower may also provide approach control services (radar or nonradar). TOWER EN ROUTE CONTROL SERVICE The control of IFR en route traffic within delegated airspace between two or more adjacent approach control facilities. This service is designed to expedite traffic and reduce control and pilot communication requirements. TOWER TO TOWER (See TOWER EN ROUTE CONTROL SERVICE). TPX-42 A numeric beacon decoder equipment/system. It is designed to be added to terminal radar systems for beacon decoding. It provides rapid target identification, reinforcement of the primary radar target, and altitude information from Mode C. TRACK The actual flight path of an aircraft over the surface of the earth. TRACK [ICAO] The projection on the earth's surface of the path of an aircraft, the direction of which path at any point is usually expressed in degrees from North (True, Magnetic, or Grid). TRAFFIC A term used by a controller to transfer radar identification of an aircraft to another controller for the purpose of coordinating separation action. Traffic is normally issued: (a) in response to a handoff or point out, (b) in anticipation of a handoff or point out, or (c) in conjunction with a request for control of an aircraft. A term used by ATC to refer to one or more aircraft. TRAFFIC ADVISORIES Advisories issued to alert pilots to other known or observed air traffic which may be in such proximity to the position or intended route of flight of their aircraft to warrant their attention. Such advisories may be based on: Visual observation. Observation of radar identified and nonidentified aircraft targets on an ATC radar display, or Verbal reports from pilots or other facilities. (Identification), TRAFFIC ALERT. ADVISE YOU TURN LEFT/RIGHT (specific heading if appropriate), AND/OR CLIMB/DESCEND (specific altitude if appropriate) IMMEDIATELY. (See SAFETY ALERT). TRAFFIC ALERT AND COLLISION AVOIDANCE SYSTEM An airborne collision avoidance system based on radar beacon signals which operates independent of ground based equipment. TCAS I generates traffic advisories only. TCAS II generates traffic advisories, and resolution (collision avoidance) advisories in the vertical plane. TRAFFIC INFORMATION (See TRAFFIC ADVISORIES). TRAFFIC IN SIGHT Used by pilots to inform a controller that previously issued traffic is in sight. TRAFFIC MANAGEMENT PROGRAM ALERT A term used in a Notice to Airmen (NOTAM) issued in conjunction with a special traffic management program to alert pilots to the existence of the program and to refer them to either the Notices to Airmen publication or a special traffic management program advisory message for program details. The contraction TMPA is used in NOTAM text. TRAFFIC MANAGEMENT UNIT The entity in ARTCC's and designated terminals responsible for direct involvement in the active management of facility traffic. Usually under the direct supervision of an assistant manager for traffic management. TRAFFIC NO FACTOR Indicates that the traffic described in a previously issued traffic advisory is no factor. TRAFFIC NO LONGER OBSERVED Indicates that the traffic described in a previously issued traffic advisory is no longer depicted on radar, but may still be a factor. TRAFFIC PATTERN The traffic flow that is prescribed for aircraft landing at, taxiing on, or taking off from an airport. The components of a typical traffic pattern are upwind leg, crosswind leg, downwind leg, base leg, and final approach. Upwind Leg. A flight path parallel to the landing runway in the direction of landing. Crosswind Leg. A flight path at right angles to the landing runway off its upwind end. Downwind Leg. A flight path parallel to the landing runway in the direction opposite to landing. The downwind leg normally extends between the crosswind leg and the base leg. Base Leg. A flight path at right angles to the landing runway off its approach end. The base leg normally extends from the downwind leg to the intersection of the extended runway centerline. Final Approach. A flight path in the direction of landing along the extended runway centerline. The final approach normally extends from the base leg to the runway. An aircraft making a straight in approach VFR is also considered to be on final approach. TRANSCRIBED WEATHER BROADCAST A continuous recording of meteorological and aeronautical information that is broadcast on L/MF and VOR facilities for pilots. TRANSFER OF CONTROL That action whereby the responsibility for the separation of an aircraft is transferred from one controller to another. TRANSFER OF CONTROL [ICAO] Transfer of responsibility for providing air traffic control service. TRANSFERRING CONTROLLER A controller/facility transferring control of an aircraft to another controller/facility. TRANSFERRING FACILITY (See TRANSFERRING CONTROLLER). TRANSFERRING UNIT/CONTROLLER [ICAO] Air traffic control unit/air traffic controller in the process of transferring the responsibility for providing air traffic control service to an aircraft to the next air traffic control unit/air traffic controller along the route of flight. TRANSITION The general term that describes the change from one phase of flight or flight condition to another; e.g., transition from en route flight to the approach or transition from instrument flight to visual flight. A published procedure (SID Transition) used to connect the basic SID to one of several en route airways/jet routes, or a published procedure (STAR Transition) used to connect one of several en route airways/jet routes to the basic STAR. TRANSITIONAL AIRSPACE That portion of controlled airspace wherein aircraft change from one phase of flight or flight condition to another. TRANSITION POINT A point at an adapted number of miles from the vertex at which an arrival aircraft would normally commence descent from its en route altitude. This is the first fix adapted on the arrival speed segments. TRANSMISSOMETER An apparatus used to determine visibility by measuring the transmission of light through the atmosphere. It is the measurement source for determining runway visual range (RVR) and runway visibility value (RVV). TRANSMITTING IN THE BLIND A transmission from one station to other stations in circumstances where two way communication cannot be established, but where it is believed that the called stations may be able to receive the transmission. TRANSPONDER The airborne radar beacon receiver/transmitter portion of the Air Traffic Control Radar Beacon System (ATCRBS) which automatically receives radio signals from interrogators on the ground, and selectively replies with a specific reply pulse or pulse group only to those interrogations being received on the mode to which it is set to respond. TRANSPONDER [ICAO] A receiver/transmitter which will generate a reply signal upon proper interrogation; the interrogation and reply being on different frequencies. TRANSPONDER CODES (See CODES). TRSA (See TERMINAL RADAR SERVICE AREA). TURBOJET AIRCRAFT An aircraft having a jet engine in which the energy of the jet operates a turbine which in turn operates the air compressor. TURBOPROP AIRCRAFT An aircraft having a jet engine in which the energy of the jet operates a turbine which drives the propeller. TWEB (See TRANSCRIBED WEATHER BROADCAST). TVOR (See TERMINAL VERY HIGH FREQUENCY OMNIDIRECTIONAL RANGE STATION). TWO WAY RADIO COMMUNICATIONS FAILURE (See LOST COMMUNICATIONS). UDF (See DIRECTION FINDER). UHF (See ULTRAHIGH FREQUENCY). ULTRAHIGH FREQUENCY The frequency band between 300 and 3,000 mHz. The bank of radio frequencies used for military air/ground voice communications. In some instances this may go as low as 225 mHz and still be referred to as UHF. ULTRALIGHT VEHICLE An aeronautical vehicle operated for sport or recreational purposes which does not require FAA registration, an airworthiness certificate, nor pilot certification. They are primarily single occupant vehicles, although some two place vehicles are authorized for training purposes. Operation of an ultralight vehicle in certain airspace requires authorization from ATC. UNABLE Indicates inability to comply with a specific instruction, request, or clearance. UNDER THE HOOD Indicates that the pilot is using a hood to restrict visibility outside the cockpit while simulating instrument flight. An appropriately rated pilot is required in the other control seat while this operation is being conducted. UNICOM A nongovernment communication facility which may provide airport information at certain airports. Locations and frequencies of UNICOMs are shown on aeronautical charts and publications. UNPUBLISHED ROUTE A route for which no minimum altitude is published or charted for pilot use. It may include a direct route between NAVAIDS, a radial, a radar vector, or a final approach course beyond the segments of an instrument approach procedure. UPWIND LEG (See TRAFFIC PATTERN). URGENCY A condition of being concerned about safety and of requiring timely but not immediate assistance; a potential distress condition. URGENCY [ICAO] A condition concerning the safety of an aircraft or other vehicle, or of person on board or in sight, but which does not require immediate assistance. USAFIB (See ARMY AVIATION FLIGHT INFORMATION BULLETIN). UVDF (See DIRECTION FINDER). VASI (See VISUAL APPROACH SLOPE INDICATOR). VDF (See DIRECTION FINDER). VDP (See VISUAL DESCENT POINT). VECTOR A heading issued to an aircraft to provide navigational guidance by radar. VERIFY Request confirmation of information; e.g., ``verify assigned altitude.'' VERIFY SPECIFIC DIRECTION OF TAKEOFF (OR TURNS AFTER TAKEOFF) Used by ATC to ascertain an aircraft's direction of takeoff and/or direction of turn after takeoff. It is normally used for IFR departures from an airport not having a control tower. When direct communication with the pilot is not possible, the request and information may be relayed through an FSS, dispatcher, or by other means. VERTEX The last fix adapted on the arrival speed segments. Normally, it will be the outer marker of the runway in use. However, it may be the actual threshold or other suitable common point on the approach path for the particular runway configuration. VERTEX TIME OF ARRIVAL A calculated time of aircraft arrival over the adapted vertex for the runway configuration in use. The time is calculated via the optimum flight path using adapted speed segments. VERTICAL SEPARATION Separation established by assignment of different altitudes or flight levels. VERTICAL SEPARATION [ICAO] Separation between aircraft expressed in units of vertical distance. VERTICAL TAKEOFF AND LANDING AIRCRAFT Aircraft capable of vertical climbs and/or descents and of using very short runways or small areas for takeoff and landings. These aircraft include, but are not limited to, helicopters. VERY HIGH FREQUENCY The frequency band between 30 and 300 mHz. Portions of this band, 108 to 118 mHz, are used for certain NAVAIDS; 118 to 136 mHz are used for civil air/ground voice communications. Other frequencies in this band are used for purposes not related to air traffic control. VERY HIGH FREQUENCY OMNIDIRECTIONAL RANGE STATION (See VOR). VERY LOW FREQUENCY The frequency band between 3 and 30 kHz. VFR (See VISUAL FLIGHT RULES). VFR AIRCRAFT An aircraft conducting flight in accordance with visual flight rules. VFR CONDITIONS Weather conditions equal to or better than the minimum for flight under visual flight rules. The term may be used as an ATC clearance/instruction only when: An IFR aircraft requests a climb/descent in VFR conditions. The clearance will result in noise abatement benefits where part of the IFR departure route does not conform to an FAA approved noise abatement route or altitude. A pilot has requested a practice instrument approach and is not on an IFR flight plan. All pilots receiving this authorization must comply with the VFR visibility and distance from cloud criteria in Part 91. Use of the term does not relieve controllers of their responsibility to separate aircraft in Class B and Class C airspace or TRSA's as required by FAA Order 7110.65. When used as an ATC clearance/instruction, the term may be abbreviated ``VFR;'' e.g., ``MAINTAIN VFR,'' ``CLIMB/DESCEND VFR,'' etc. VFR FLIGHT (See VFR AIRCRAFT). VFR MILITARY TRAINING ROUTES Routes used by the Department of Defense and associated Reserve and Air Guard units for the purpose of conducting low altitude navigation and tactical training under VFR below 10,000 feet MSL at airspeeds in excess of 250 knots IAS. VFR NOT RECOMMENDED An advisory provided by a flight service station to a pilot during a preflight or inflight weather briefing that flight under visual flight rules is not recommended. To be given when the current and/or forecast weather conditions are at or below VFR minimums. It does not abrogate the pilot's authority to make his own decision. VFR ON TOP ATC authorization for an IFR aircraft to operate in VFR conditions at any appropriate VFR altitude (as specified in FAR and as restricted by ATC). A pilot receiving this authorization must comply with the VFR visibility, distance from cloud criteria, and the minimum IFR altitudes specified in Part 91. The use of this term does not relieve controllers of their responsibility to separate aircraft in Class B and Class C airspace or TRSA's as required by FAA Order 7110.65. VFR TERMINAL AREA CHARTS (See AERONAUTICAL CHART). VHF (See VERY HIGH FREQUENCY). VHF OMNIDIRECTIONAL RANGE/TACTICAL AIR NAVIGATION (See VORTAC). VIDEO MAP An electronically displayed map on the radar display that may depict data such as airports, heliports, runway centerline extensions, hospital emergency landing areas, NAVAID's and fixes, reporting points, airway/route centerlines, boundaries, handoff points, special use tracks, obstructions, prominent geographic features, map alignment indicators, range accuracy marks, minimum vectoring altitudes. VISIBILITY The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night. Visibility is reported as statute miles, hundreds of feet or meters. Flight Visibility. The average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night. Ground Visibility. Prevailing horizontal visibility near the earth's surface as reported by the United States National Weather Service or an accredited observer. Prevailing Visibility. The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle which need not necessarily be continuous. Runway Visibility Value (RVV). The visibility determined for a particular runway by a transmissometer. A meter provides a continuous indication of the visibility (reported in miles or fractions of miles) for the runway. RVV is used in lieu of prevailing visibility in determining minimums for a particular runway. Runway Visual Range (RVR). An instrumentally derived value, based on standard calibrations, that represents the horizontal distance a pilot will see down the runway from the approach end. It is based on the sighting of either high intensity runway lights or on the visual contrast of other targets whichever yields the greater visual range. RVR, in contrast to prevailing or runway visibility, is based on what a pilot in a moving aircraft should see looking down the runway. RVR is horizontal visual range, not slant visual range. It is based on the measurement of a transmissometer made near the touchdown point of the instrument runway and is reported in hundreds of feet. RVR is used in lieu of RVV and/or prevailing visibility in determining minimums for a particular runway. a. Touchdown RVR. The RVR visibility readout values obtained from RVR equipment serving the runway touchdown zone. b. Mid RVR. The RVR readout values obtained from RVR equipment located midfield of the runway. c. Rollout RVR. The RVR readout values obtained from RVR equipment located nearest the rollout end of the runway. VISIBILITY [ICAO] The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night. Flight Visibility. The visibility forward from the cockpit of an aircraft in flight. Ground Visibility. The visibility at an aerodrome as reported by an accredited observer. Runway Visual Range [RVR]. The range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the lights delineating the runway or identifying its centre line. VISUAL APPROACH An approach wherein an aircraft on an IFR flight plan, operating in VFR conditions under the control of an air traffic control facility and having an air traffic control authorization, may proceed to the airport of destination in VFR conditions. VISUAL APPROACH [ICAO] An approach by an IFR flight when either part or all of an instrument approach procedure is not completed and the approach is executed in visual reference to terrain. VISUAL APPROACH SLOPE INDICATOR (See AIRPORT LIGHTING). VISUAL DESCENT POINT A defined point on the final approach course of a nonprecision straight in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided the approach threshold of that runway, or approach lights, or other markings identifiable with the approach end of that runway are clearly visible to the pilot. VISUAL FLIGHT RULES Rules that govern the procedures for conducting flight under visual conditions. 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 HOLDING The holding of aircraft at selected, prominent geographical fixes which can be easily recognized from the air. VISUAL METEOROLOGICAL CONDITIONS Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling equal to or better than specified minima. VISUAL SEPARATION A means employed by ATC to separate aircraft in terminal areas. There are two ways to effect this separation: The tower controller sees the aircraft involved and issues instructions, as necessary, to ensure that the aircraft avoid each other. A pilot sees the other aircraft involved and upon instructions from the controller provides his own separation by maneuvering his aircraft as necessary to avoid it. This may involve following another aircraft or keeping it in sight until it is no longer a factor. VLF (See VERY LOW FREQUENCY). VMC (See VISUAL METEOROLOGICAL CONDITIONS). VOR A ground based electronic navigation aid transmitting very high frequency navigation signals, 360 degrees in azimuth, oriented from magnetic north. Used as the basis for navigation in the National Airspace System. The VOR periodically identifies itself by Morse Code and may have an additional voice identification feature. Voice features may be used by ATC or FSS for transmitting instructions/information to pilots. VORTAC A navigation aid providing VOR azimuth, TACAN azimuth, and TACAN distance measuring equipment (DME) at one site. VORTICES Circular patterns of air created by the movement of an airfoil through the air when generating lift. As an airfoil moves through the atmosphere in sustained flight, an area of area of low pressure is created above it. The air flowing from the high pressure area to the low pressure area around and about the tips of the airfoil tends to roll up into two rapidly rotating vortices, cylindrical in shape. These vortices are the most predominant parts of aircraft wake turbulence and their rotational force is dependent upon the wing loading, gross weight, and speed of the generating aircraft. The vortices from medium to heavy aircraft can be of extremely high velocity and hazardous to smaller aircraft. VOR TEST SIGNAL (See VOT). VOT A ground facility which emits a test signal to check VOR receiver accuracy. Some VOT's are available to the user while airborne, and others are limited to ground use only. VR (See VFR MILITARY TRAINING ROUTES). VTA (See VERTEX TIME OF ARRIVAL). VTOL AIRCRAFT (See VERTICAL TAKEOFF AND LANDING AIRCRAFT). WA (See AIRMET). WAKE TURBULENCE Phenomena resulting from the passage of an aircraft through the atmosphere. The term includes vortices, thrust stream turbulence, jet blast, jet wash, propeller wash, and rotor wash both on the ground and in the air. WARNING AREA (See SPECIAL USE AIRSPACE). WAYPOINT A predetermined geographical position used for route/instrument approach definition, or progress reporting purposes, that is defined relative to a VORTAC station or in terms of latitude/longitude coordinates. WEATHER ADVISORY In aviation weather forecast practice, an expression of hazardous weather conditions not predicted in the area forecast, as they affect the operation of air traffic and as prepared by the NWS. WHEN ABLE When used in conjunction with ATC instructions, gives the pilot the latitude to delay compliance until a condition or event has been reconciled. Unlike ``pilot discretion,'' when instructions are prefaced ``when able,'' the pilot is expected to seek the first opportunity to comply. Once a maneuver has been initiated, the pilot is expected to continue until the specifications of the instructions have been met. ``When able,'' should not be used when expeditious compliance is required. WILCO I have received your message, understand it, and will comply with it. WIND SHEAR A change in wind speed and/or wind direction in a short distance resulting in a tearing or shearing effect. It can exist in a horizontal or vertical direction and occasionally in both. WING TIP VORTICES (See VORTICES). WORDS TWICE As a request: ``Communication is difficult. Please say every phrase twice.'' As information: ``Since communications are difficult, every phrase in this message will be spoken twice.'' WORLD AERONAUTICAL CHARTS (See AERONAUTICAL CHART). WS (See SIGMET). WST (See CONVECTIVE SIGMET).