AIRPORT WAYPOINT (WP) - A waypoint located on the final approach course at or abeam the first usable landing surface, which is used for construction of the final approach area for an RNAV circling-only approach. 

 ALONGTRACK DISTANCE (ATD) FIX - The ADT fix is an alongtrack position defined as a distance in NM, with reference to the next waypoint.

 ALTERNATE AERODROME (ICAO) - An aerodrome specified in the flight plan to which a flight may proceed when it becomes inadvisable to land at the aerodrome of intended landing.

 ALTERNATE AIRFIELD (JCS, NATO) - An airfield specified in the flight plan to which a flight may proceed when a landing at the intended destination becomes inadvisable.  An alternate airfield may be the airfield of departure.

 ALTERNATE AIRPORT (P / CG) -  An airfield at which an aircraft may land if a landing at the intended airport becomes inadvisable.

 APPROACH CLEARANCE -  Authorization by Air Traffic Control (ATC) for a pilot to conduct an instrument approach.  The type of instrument approach for which cleared and other pertinent information is provided in the approach clearance when required.

 AREA NAVIGATION / RNAV (P / CG) - A method of navigation that permits aircraft operations of any desired course within the coverage of station- referenced navigation signals or within the limits of self- contained system capability.  Random Area Navigation 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.

Major types of equipment are: 

            (1) 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 the VORTAC. 

            (2) 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.   

            (3) 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. 

            (4)  MLS Area Navigation (MLS/RNAV), which provides area navigation with reference to an MLS ground facility. 

            (5)  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 enroute and approach altitudes.  The usable signal coverage areas are determined by the signal-to-cycle ratio, the envelope-to cycle difference, and the geometric relationship between the positions of the user and the transmitting stations. 

AREA NAVIGATION/RNAV (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. 

APPROACH SEQUENCE (P/CG)-  The order in which aircraft are positioned while on approach or awaiting approach clearance. 

BELOW MINIMUMS-  Weather conditions below the minimums prescribed by regulations or the particular action involved, e.g., landing minimums, takeoff minimums. 

CEILING (P/CG)-  The height 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.” 

CIRCLE TO LAND MANEUVER / CIRCLING 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 36 approach, circle to runway 22” or “Circle northwest of the airport for a right downwind to runway 22.”  

CLEARANCE LIMIT (P/CG)-  The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance. 

CLEARED FOR (Type of) APPROACH-  ATC authorization for an aircraft to execute a specific instrument approach to an airport, e.g., “Cleared for ILS runway 36 approach.”  (See instrument approach clearance.) (Refer to FAR Part 91). 

CLEARED FOR 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. 

COMMON TRAFFIC ADVISORY FREQUENCY/CTAF (NIMA)-  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.   

DEAD RECKONING-  The estimating or determining of position by advancing an earlier known position by the application of direction and speed data. 

DECISION ALTITUDE/DA (NATO)-  An altitude related to the highest elevation in the touchdown zone, specified for a glideslope approach, at which a missed approach procedure must be initiated if the required visual reference has not been established.  (See also DECISION HEIGHT) 

DECISION HEIGHT/DH (P/CG)-  With respect to the operation of aircraft means, 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. 

DECISION HEIGHT (NATO)-  A height in MSL above the highest elevation in the touchdown zone, specified for a glideslope approach, at which a missed approach procedure must be initiated if the required visual reference has not been established. 

DECISION HEIGHT/DH (ICAO)-  A specified height at which a missed approach must be initiated if the required visual reference to continue the approach to land has not been established. 

DME ARC-  A course, indicated as a constant DME distance, around a navigational facility which provides distance information. 

DME DISTANCE-  The line-of-site distance (slant range) from the source of the DME signal to the receiving antenna. 

DEPARTURE PROCEDURES (DP)- A preplanned instrument flight rule (IFR) ATC departure procedure published for pilot use in graphic and/or textual form.  DPs provide transition form the terminal to the appropriate enroute structure.  

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 (FAF)-  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 denoted  on government  (DOD and NOS) charts by the Maltese Cross symbol for nonprecision approaches.  The Lightning Bolt symbol is used for precision approaches to designate the approximate point where glideslope/path is intercepted at published intercept altitude.  

FINAL APPROACH POINT (FAP)- The point, applicable only to a non-precision 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 WAYPOINT (FAWP)-  A fly-by waypoint that marks the beginning of final approach segment. 

FIX (P/CP)-  A geographical position determined by a visual reference to the surface, by reference to one or more radio NAVAIDS, by celestial plotting, or by another navigational device. 

GLS -  The acronym for Global Navigation Satellite System (GNSS) Landing System 

GLIDESLOPE/INTERCEPT ALTITUDE-  The minimum altitude of the intermediate approach segment prescribed for a precision which assures required obstacle clearance.  It is depicted on instrument approach procedure charts. 

HEIGHT ABOVE AIRPORT (HAA)-  The height  of the Minimum Descent Altitude above the published airport elevation.  This is published in conjunction with circling minimums. 

HEIGHT ABOVE LANDING (HAL)-  The height above a designated helicopter landing area used for helicopter instrument approach procedures. 

HEIGHT ABOVE SURFACE (HAS) (TERPS)-  The height of the MDA above the highest terrain/surface within a 5200 feet radius of the MAP in Point in Space procedures.  (Helicopter only procedures) 

HEIGHT ABOVE TOUCHDOWN (HAT)-  The height of the Decision Height or Minimum Descent Altitude above the highest runway elevation in the touchdown zone (First 3000 feet of the runway).  HAT is published on instrument approach charts in conjunction with all straight-in minimums. 

INITIAL APPROACH WAYPOINT (IAWP)-    Normally a fly-by waypoint that marks the beginning of the initial segment and end of the feeder, if applicable. 

INTERMEDIATE WAYPOINT (IWP)-  A fly-by waypoint that marks the end of an initial segment and the beginning of the ntermediate segment. 

INSTRUMENT APPROACH PROCEDURE (IAP) (P/CG)-  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 point from which a landing may be made visually.  It is prescribed and approved for a specific airport by competent authority. 

            (1)  US civil standard instrument approach procedures are approved by the FAA as prescribed under FAR Part 97, and are available for public use. 

            (2)  US military standard instrument approach procedures are approved and published by the Department of Defense (DOD). 

            (3)  Special instrument approach procedures are approved by the FAA for individual operators, but are not published in FAR Part 97, and are not available for public use. 

INSTRUMENT APPROACH PROCEDURES (NATO), ICAO)-  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 a point from which a landing may be made visually. 

INSTRUMENT APPROACH WAYPOINT-  Fixes used in defining RNAV instrument approach procedures, including the feeder waypoint (FWP), the initial  approach waypoint (IAWP), the intermediate waypoint (IWP), the final approach waypoint (FAWP), the runway waypoint (RWY WP), and the airport waypoint (APT WP), when required. 

LNAV - LNAV means lateral navigation. A function of RNAV equipment which calculates, displays, and provides horizontal guidance to a profile or path. Note: use of the word horizontal in lieu of lateral. This was used as LNAV affects the entire horizontal plane and to avoid the interpretation of lateral as meaning to the left or right of the profile and/or path. 

LANDING MINIMUMS (IFR)-  The minimum visibility prescribed for landing a civil aircraft while using an instrument approach procedure.  The minimum applies with other limitations set forth in FAR Part 91, with respect to the Minimum Descent Altitude (MDA) or Decision Height (DH) prescribed in the instrument approach procedures as follows. 

            (1)  Straight-in Landing Minimums-  A statement of MDA and visibility, or DH and visibility, required for straight-in landing on a specified runway; or 

            (2)  Circling minimums-  A statement of MDA and visibility required for the circle-to-land maneuver.  Descent below the established MDA or DH is not authorized during an approach unless the aircraft is in a position from which a normal approach to the runway of intended landing can be made, and adequate visual reference to required visual cues is maintained. 

MINIMUM DECENT ALTITUDE (MDA) (P/CG)-  The lowest altitude, expressed in feet above mean sea level  to which descent is authorized on final approach or during a circle-to-land maneuver in execution of a standard instrument approach procedure where no electronic glideslope is provided. 

MINIMUM DESCENT ALTITUDE (NATO)-  The lowest altitude to which descent shall be authorized in procedures not using a glideslope, until the required visual reference has been established. 

MINIMUM HOLDING ALTITUDE (MHA)-  The lowest altitude prescribed for a holding pattern  which assures navigational signal coverage, communications, and meets obstacle clearance requirements.   

MINIMUM SAFE ALTITUDE (MSA) (P/CG)-   

            (1)  The minimum altitude specified in FAR Part 91, for various aircraft operations. 

            (2)  Altitudes depicted on approach charts which provide at least 1000 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. 

MINIMUM SECTOR ALTITUDES (P/CG)-  Altitudes depicted on approach charts which provide at least 1000 feet of obstacle clearance within a 25 nautical mile radius of the navigational 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. 

EMERGENCY SAFE ALTITUDES- 

Altitudes depicted on approach charts which provide at least 1000 feet of obstacle clearance in non-mountainous areas and 2000 feet of obstacle clearance in designated mountainous areas within a 100 nautical mile radius of the navigation facility upon which the procedure is predicted, and normally used only in military procedures.  These altitudes are identified on published procedures as “Emergency Safe Altitudes.” 

MINIMUM SECTOR ALTITUDE (ICAO)-  The lowest altitude which may be used under emergency conditions which will provide a minimum clearance of 300 meters (1000 feet) above all obstacles located in an area contained within a sector of a circle of 25 nautical miles radius centered on a radio aid to navigation.

 MINIMUM VECTORING ALTITUDE (MVA)-  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.  (Refer to AIM) 

MISSED APPROACH (P/CG) 

            (1)  A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing.  The route of flight an altitude are shone 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. 

            (2)  A term used by the pilot to inform ATC that he is executing the missed approach. 

            (3)  At locations where ATC radar service provided the pilot should conform to radar vectors, when provided by ATC, in lieu of the published missed approach procedure. 

MISSED APPROACH POINT (MAP)-  A point prescribed in each instrument approach procedure at which a missed approach shall be executed if the required visual reference does not exist. 

MISSED APPROACH PROCEDURE (NATO, ICAO)-  The procedure to be followed if, after an instrument approach, a landing is not effected, and occurring normally: 

            (1)  When the aircraft has descended to the decision height and has not established visual contact, or, 

            (2)  When directed by air traffic control to pull up or to go around. 

MISSED APPROACH WAYPOINT-  A flyover waypoint used to designate the missed approach point (MAP) and used for construction of the final approach area. 

POINT IN SPACE APPROACH (COPTER)-  In such procedures the point in space and missed approach point are identical and upon arrival at this point, helicopters must  proceed under visual flight rules (or Special VFR in control zone as applicable) to a landing area or conduct the specified missed approach procedure.  The published procedure shall be noted to this effect and also should identify available landing areas in the vicinity by noting the course and distance from the MAP to each selected landing area.  The point in space is located more than 2600 feet from the center of the landing area. 

PRECISION APPROACH PROCEDURE-  A standard instrument approach procedure in which an electronic glideslope is provided; e.g., ILS, MLS, and PAR. 

PRECISION APPROACH RADAR (PAR) (P/CG)

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 non-radar 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. 

PROCEDURE TURN (PT) (P/CG)-  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, 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 INBOUND-  The 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. 

REFERENCE FACILITY-  A VOR/DME, VORTAC, TACAN facility used for the identification and establishment of an RNAV route, waypoint, or standard instrument approach  procedure.   

RNAV - RNAV is the acronym for area navigation. RNAV provides enhanced navigation capability to the pilot. RNAV equipment can compute the aircraft position, actual track and ground speed and then provide meaningful information relative to a route of flight selected by the pilot. 

RNAV DECENT ANGLE-  A vertical angle defining a descending flight path from the FAWP to the RWY WP. 

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., if Runway 4 magnetic heading is 044 degrees, fly 044 degrees regardless of wind conditions.   

RUNWAY WAYPOINT-  A waypoint located at the runway threshold and used for construction of the final approach area when the final approach course meets straight-in alignment criteria. 

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 1200 feet to either side of the runway to which the instrument approach was conducted. 

STEP-DOWN 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. 

STRAIGHT-IN APPROACH (IFR)-  A instrument approach wherein final approach is begun without first having to executed a procedure turn.  Not necessarily completed with a straight-in landing or made to straight-in landing minimums.   

SURVEILLANCE APPROACH (ASR) (P/CG)-  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. 

TOUCHDOWN ZONE (P/CG)-  The first 3000 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 ELEVATION (TDZE)-  The highest elevation in the first 3000 feet of the landing surface.  TDZE is indicated on the instrument approach procedure chart when straight-in landing minimums are authorized. 

TRACK (P/CG)-  The actual flight path of an aircraft over the surface of the earth. 

TRANSITION-  The general term that describes the change from one phase of flight or flight condition to another, e.g., transition from instrument flight to visual flight. 

TURN WAYPOINT-  A waypoint which identifies a change from one course to another. 

VNAV - VNAV means vertical navigation. A function of RNAV equipment which calculates, displays, and provides vertical guidance to a profile or path. 

VISIBILITY (P/CG)-  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 at night.  Visibility is reported as statute miles, hundreds of feet or meters. 

            (1)  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 at night. 

            (2)  GROUND VISIBILITY-  Prevailing horizontal visibility near the earth’s surface as reported by the United States National Weather Service or an accredited observer. 

            (3)  PREVAILING VISIBILITY-  The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle which need not necessarily be continuous.  

            (4)  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 fraction of miles) for the runway.  RVV is used in lieu of prevailing visibility in determining minimums for a  particular runway. 

            (5)  RUNWAY VISUAL RANGE (RVR)-  A instrumentally derived value, based on standard calibrations, that represents the horizontal distance the 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 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. 

WAYPOINT (P/CG)-  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.