AC 90-92 2/5/93 Appendix 2 Fix Dimensions - This characteristic defines whether the navigation system provides a onedimensional (linear), 2D, or 3D position fix. The ability of the system to derive a fourth dimension (time) from the navigational signals is also included.
Fix Rate -- The number of independent position fixes or data points available from the system per unit time.
Flight Level (FL) - Flight level refers to the altitude when the aircraft's Kollsman altimeter window is set to 29.92 inches of mercury (or 1,015 millibars). It is also referred to as the "QNE" altimeter setting.
Flight Management System (FMS) - An integrated airborne sensor, receiver, and computer (with both navigation and aircraft performance data bases) which provides optimum performance guidance to a display and automatic flight control system. FMS units may provide 2D, 3D, or 4D RNAV.
Flight Verified/Not Flight Verified -- Refers to Loran-C coverage diagrams, appendix 1.
Flight-verified data involves the correlation of ground-based and airborne Loran-C data for Loran-C stations within the U.S., or correlation of airborne inertial guidance data and Loran-C data from specially configured aircraft operating over the North Atlantic (NAT). The computer-generated coverage model is then adjusted to agree with this empirical data.
Gateway Fix -- See coast-out fix.
Geometric Dilution of Precision (GDOP) -- This numerical parameter expresses the degrading of accuracy relative to a change in lines of position (LOP's) crossing angles. As the relative crossing angle decreases, the GDOP increases and the relative positional accuracy becomes less precise. GDOP can be expressed in either ft/us or as a unitless measurement.
"Great Circle" Route -- The line of shortest distance between two points on the spherical earth. A "great circle" route is plotted as a straight line on aviation plotting charts.
Gross Navigational Error - Pilots are expected to fly their aircraft along the centerline of their assigned route and to stay within the accuracy limits of their installed navigation systems. Navigational errors greater than 20 nm off course are investigated by the various countries that provide oceanic ATC service. If an aircraft is off course, it is usually for one of the following reasons: a communication error between the pilot and the controller, a pilot deviation due to weather without prior ATC approval or without declaring an emergency, an unintentionally entered waypoint not along the assigned route, or a navigational equipment 5
AC 90-92 Appendix 2 2/5/93 NOTE: The accuracy tolerance limits for Loran-C equipment used in IFR oceanic navigation is 5.8 nm.
Ground Wave - Ground wave signals emanate from a Loran-C transmitter and travel parallel to the surface of the earth. Loran-C receivers utilize this portion of the signal. The range of the usable ground wave signal is dependent upon the transmitter power and the surface conductivity of the earth (see also sky wave and figure 10).
Group Repetition Interval (GRI) -- Represents the length of time (in microseconds) between the start of one transmission from the master station in a Loran-C chain and the start of the next.
High Seas - Any body of water outside the 12 nm limit. U.S. airspace within this 12 nm limit is governed by domestic FAA regulations, with some exceptions (see FAR 91.1, "Applicability," for further details).
Hyperbolic Radio Navigation System -- A system such as Loran-C or Omega that derives its position from measurement of differential distances to several stations.
IFR Navigation - Oceanic IFR navigation techniques may include use of ICAO standard NAVAID's supplemented by DR, pilot-operated, electronic, long-range navigation equipment, or use of a flight navigator. Aircraft operating in controlled airspace with appropriate ATC clearance may enter instrument meteorological conditions (IMC).
Independent Fix - A position fix that does not depend on a previous or following measurement.
Independent Receiver Function - The function of any part of a receiver does not depend upon the functioning of any part of another unit. Today's receivers can be single-sensor, multi-sensor, or "embedded" as part of a multi-function flight management (and navigation) system (FMS). A combined communication-navigation system meets the requirement for an independent navigation receiver.
Initial Approach Fix (LAF) - A transitional navigation fix between en route airspace and the initial approach segment of an instrument approach. The initial approach is the segment between the IAF and the intermediate fix or the point where the aircraft is established on the intermediate course or final approach course.
Integrity - A system's ability to provide timely warnings to users when navigation information is unreliable.
AC 90-92 2/5/93 Appendix 2 Lines of Position (LOP'S) - For Loran-C, a hyperbolic line plotted on the surface of the earth representing a set of constant values of navigation information.
Minimum Navigation Performance Specification (MPS) -- A specified set of minimum navigation performance standards which aircraft must meet 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 (MINPS) Airspace -- Designated airspace in which MPS separation standards are applied between MNPS-equipped and certified aircraft. MNPS airspace is located over certain areas of the North Atlantic (NAT) and Northern Canada. NAT MNPS airspace, for example, is defined as the volume of airspace between FL 275 and FL 400 and bounded by certain geographical coordinates (see figure 5).
To obtain MNPS authorization, operators must ensure that:
a. Each aircraft is suitably equipped and capable of meeting MNPS standards.
b. Operating procedures are established to ensure that MPS standards are met.
c. Flightcrews are capable of operating with sufficient precision to consistently meet MNPS requirements and are aware of the emergency procedures specific to MNPS airspace.
Missed Approach Point (MAP) -- That point in a published instrument approach procedure from which a missed approach is initiated if the required visual reference cannot be identified.
The missed approach is that segment between the MAP, or point of arrival at the decision height, and the missed approach fix while simultaneously at the prescribed altitude.
Multiple-Sensor Navigation System -- A navigation system that incorporates at least two different and physically separate navigation sensors, each sending position data to a single navigational display. Each sensor operates independently (not integrated). Such systems do not provide a blended position solution or a position integrity comparison. Each sensor must be manually selected by the flightcrew.
Multi-Sensor Navigation System - A navigation system which uses a single sensor component or "black box" containing two (or more) navigation sensors that are physically integrated into a single unit. This type of system monitors the integrity of information by comparing the difference between the position computed using information from one sensor and the position computed from another approved sensor. The device automatically selects
AC 90-92 Appendix 2 2/5/93 and displays the best possible navigation data. It must also detect when sensors required for en route, terminal, or non-precision approach operations are not of the required accuracy or are not available for a specific phase of flight (such as en route, terminal, or approach).
Under such conditions, a warning device, alerting the flightcrew that the system does not meet IF requirements, is required. The pilot has the option of manually selecting or deselecting data and displaying the output of a specific sensor.
National Airspace System (NAS) -- 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.
Nautical Mile (nm or NM) -- The distance equal to one arc minute of latitude. One nautical mile is equivalent to 6,076.1155 feet and is the fundamental measurement unit used in both sea and air navigation.
Navigation - The means by which an aircraft is given guidance to fly from one known position to another known position. The process involves referencing the aircraft's actual position to its desired course.
Navigation Aid (NAVAID) -- A visual or electronic device which provides point-to-point guidance information or position data. Examples of standard ICAO NAVAID's include VHF omnidirectional range stations (VOR's), with or without distance measuring equipment (DME), and nondirectional, ground-based beacons (NDB's).
Navigation Guidance - The calculation of steering commands to maintain the desired track from the aircraft's present position to desired position.
Navigation Information - Aircraft parameters such as position, velocity vector and related data such as track angle, ground speed, and drift angle used for navigation guidance.
Not Flight Verified - See flight verified Oceanic Airspace - Airspace over the oceans of the world is considered international airspace where aircraft separation and air traffic procedures are standardized by ICAO. The responsibility for air traffic service in oceanic airspace is delegated to the various ICAO member states according to geographic proximity and availability of the required resources.
Specific procedures are defined by ICAO Document 7030.
AC 90-92 2/5/93 Appendix 2 Oceanic Published Route -- A route established in international airspace and charted or described in flight information publications, such as route charts, DOD en route charts, chart supplements, NOTAM's, and track messages.
Oceanic Transition Route (OTR) -- An ATS route established for the purpose of transitioning aircraft to/from an organized track system.
Off Course - An aircraft is off course when it reports a position fix (or is observed on radar) at a point not on the ATC-approved route of flight.
Offshore Airspace -- The airspace between the United States' 12 nm limit and the oceanic CTA/FIR boundary. Offshore airspace is normally within the limits of conventional landbased NAVAID's.
Organized Track System (OTS) - A series of air traffic service routes (ATSR's) which may be fixed and charted or are flexible and are described by NOTAM's. For example, the North Atlantic (NAT) organized track system is a movable system of oceanic tracks that traverses the NAT between Europe and North America, the physical position of which is determined twice daily by taking the best advantage of the winds aloft. In comparison, the NOPAC, or North Pacific route system, is an organized charted route system between the Alaska West Coast and Japan. Likewise, the Central East Pacific (CEP) route system consists of charted routes between the U.S. West Coast and Hawaii.
Over-Water -- FAR 91.511 establishes the kinds of radio equipment required for navigation of large and of turbine-powered, multiengine aircraft operated under FAR Part 91 more than 30 minutes of flying time or 100 nm from the nearest shore. This differs from the extended over-water" definition found in FAR Part 1 (see the definition for extended over-water in this appendix).
Parallel Offset Path - A desired track specified in nm of offset distance parallel to and left or right of the "parent" track.
Pilotage - Aerial navigation by means of visual reference to landmarks.
Pilot's Operating Handbook (POH) -- The POH is the result of a 1976 industry-developed specification for the operation of FAR Part 23 certificated aircraft. Only Sections I and II of the POH are FAA approved. These sections contain operating limitations for the airframe and engine combination. Section IX of the POH contains additional operating instructions and FAA-approved limitations for all supplemental installed equipment, including Loran-C.
AC 90-92 Appendix 2 2/5/93 Some type certificates issued for airplanes manufactured after 1977-1978 require that the POH be carried on the airplane (and therefore accessible to the pilot during flight) as a condition to meeting its type design.
Polar Track Structure (PTS) - A system of organized routes between Iceland and Alaska which overlie Canadian MNPS Airspace.
Position Referenced Navigation -- Navigation referencing the aircraft's position in terms of latitude/longitude coordinates relative to the lat/long coordinates of the destination waypoint.
Primary Navigation System - The active system which is being used for navigation.
P-Static (Precipitation Static) -- Static electricity caused by rain, hail, snow or dust storms in the vicinity of a receiving antenna, and measured at frequencies less than 10 mhz.
Precipitation static is a significant source of interference with the Loran-C signal.
Random Route -- Any route that is not established, charted or published or is not otherwise available to all users.
Reliability - The reliability of a navigation system is a function of the frequency of failures within the system. It is the probability that a system will perform its function within defined performance limits for a specified period of time under given operating conditions.
"Rhumb-Line" Course -- A track connecting the origin and destination points along a path that maintains a constant true course. The course crosses successive lines of longitude at a constant angle. A "rhumb-line" course appears as a straight line only on mercator projection charts which are not readily available to pilots for aviation use.
RNAV Equipment - An airborne sensor, receiver or computer which allows the pilot to define waypoints anywhere desired to provide point-to-point navigation capability.
Route -- A defined path consisting of one or more courses in a horizontal plane, which aircraft traverse over the surface of the earth.
Self-Contained Navigation System - A system which is not dependent on external navigation sources on a continuous basis to determine position or navigation track. Most self-contained navigation systems must be updated periodically with station-referenced or position-referenced fixes to maintain their accuracy.
AC 90-92 2/5/93 Appendix 2 Signal-to-Noise Ratio (SNR) -- SNR is a comparison of signal strength to electronic noise intensity and is stated in "db SNR." A signal of equal intensity and of equal noise is represented by "O db." A positive db number represents a stronger signal than the existing noise, and a negative number indicates stronger noise.
Sky Wave - This is the portion of the Loran-C signal which encounters the electrified layer of the atmosphere called the ionosphere and is reflected back towards the earth's surface.
This sky wave signal is considered to be unusable for aircraft navigating by Loran-C because it is unstable and varies with the height of the ionosphere and other variable atmospheric conditions. Another definition -- "An indirect radio wave that reflects off the ionosphere, rather than taking a direct path from transmitter to receiver (see figure 10).
FIGURE 10
LORAN-C SKY WAVE AND GROUND WAVE SIGNALS lonosphere Skywave Groundwave Receiver Transmitter The Loran-C sky wave signal (—) is reflected earthward from the ionosphere, requiring a longer time to reach the aircraft than the ground wave (- --).
Sole-Means Navigation System -- An approved navigation system that can be used for specific phases of air navigation without the need for any other navigation system.
AC 90-92 Appendix 2 2/5/93 Stand-Alone Navigation System - A navigation system that is physically independent of, and whose output is not combined with, another type of navigation system or sensor.
Examples include VOR, Loran-C, Omega, and the Global Positioning System (GPS).
Standard Service Volume - The reception limits of VOR/DME and NDB ground-based NAVAID's useable for random/unpublished route navigation. Standard service volume limitations do not apply to published IFR routes or procedures. Standard service volume is a standard value that has been flight checked. Coverage limits for restricted VOR/DME and NDB's are first published as NOTAM's, then in the "Airport Facility/Directory" (AF/D).
Station-Referenced Navigation - Position determination referenced to a stationary NAVAID source, such as VOR's/NDB's.
Statistical Measure of Accuracy -- Specifications of radio navigation system accuracy generally refer to one or more of the following definitions:
(1) Predictable accuracy: The accuracy (in nm or feet) of a position with respect to geographic or geodetic coordinates; also known as geodetic or absolute accuracy.
(2) Repeatable accuracy: The accuracy (in feet) with which a user can return to a position whose coordinates have been measured at a previous time with the same navigation system.
(3) Relative accuracy: The accuracy (in feet) with which a user can measure position relative to that of another user of the same navigation system at the same time.
"Strap-Down" Navigation Equipment - Navigation equipment that is temporarily installed in an aircraft, usually for the purpose of a ferry flight (not to be confused with a "strap-down" inertial navigation system). The installation must meet FAA requirements for 'form, fit and function" for its intended use. Depending upon the specific installation, an FAA Form 337 may be required.
Supplemental Air Navigation System - An approved navigation system that can be used in conjunction with a sole-means navigation system. It can be credited as an additional system to establish the required "redundancy" of navigation equipment for use in oceanic operations.
System Capacity - The maximum number of users that a system can accommodate simultaneously.
AC 90-92 2/5/93 Appendix 2 VFR Navigation - Navigation by pilotage, dead reckoning (DR) or electronic means in visual meteorological conditions (VMC) under visual flight rules (VFR). There are no published accuracy standards for either VFR oceanic (en route) navigation or Loran-C navigation equipment.
Visual Meteorological Conditions (VMC) -- Meteorological conditions which are expressed in terms of visibility, distance from clouds, and ceiling equal to or better than specified minimums. VFR differ when operating inside and outside (beyond the 12 nm limit) the NAS (see chapter 4 of ICAO Annex 2).
AC 90-92 2/5/93 Appendix 3 APPENDIX 3. ACRONYMS This is a list of acronyms frequently used in this document.
AC Advisory Circular AFM Airplane Flight Manual ATSR Air Traffic Service Route Control Area/Flight Information Region Distance Measuring Equipment Department of Transportation DR Dead Reckoning Federal Aviation Regulations FL Flight Level (in 100's of feet) Flight Standards District Office Geometric Dilution of Precision Government Printing Office GPS Global Positioning System GRI Group Repetition Interval JAF Initial Approach Fix International Civil Aviation Organization IFR Instrument Flight Rules IMC Instrument Meteorological Conditions LOP Line of Position Loran-C Long-Range Navigation System LRN Long-Range Navigation MAP Missed Approach Point MEL Minimum Equipment List MNPS Minimum Navigation Performance Specifications MSL Mean Sea Level NAS National Airspace System NAT North Atlantic NAVAID Navigation Aid NDB Nondirectional Radio Beacon nm (or NM) Nautical Mile (6,076 feet) NOTAM(S) Notice(s) to Airmen POH Pilot's Operating Handbook RNAV Area Navigation SNR Signal-to-Noise Ratio VER Visual Flight Rules VMC Visual Meteorological Conditions VOR VHF Omnidirectional Range Station * U.S. G.P. 0.: 1993-343-120:85799