Introduction to Navigation and Navigational Aids

Basic Navigation Principles

Fundamental concepts that guide the understanding of navigation.

Navigational Aid (NAVAID)

A device or system that provides information to assist in navigation.

ILS Components

The components of the Instrument Landing System used for guiding aircraft during landing.

Service Volume Limitations

The operational range and constraints within which a navigational aid is effective.

Malfunctioning NAVAID Procedure

The steps taken when a navigational aid is reported to be malfunctioning.

Earth Size and Shape

For navigational purposes, the earth is assumed to be a perfect sphere.

Great Circle

A circle on the surface of a sphere whose center and radius are those of the sphere itself.

Arc of a Great Circle

The shortest distance between two points on a sphere.

Small Circle

A circle on the surface of the earth whose center and/or radius are not that of the sphere.

Latitude

The measurement of distance north or south of the equator.

Equator

An imaginary circle equidistant from the poles of the earth.

Parallels of Latitude

Circles parallel to the equator that measure degrees of latitude.

Angular Distance to the Pole

The distance from the equator to the pole is 90 degrees.

Longitude

The measurement of distance east or west of the Prime Meridian.

Meridians of Longitude

Lines drawn from the North Pole to the South Pole at right angles to the Equator.

Prime Meridian

The zero line of longitude that passes through Greenwich, England.

Time Zones

Regions of the Earth that have the same standard time.

Rotation of the Earth

The Earth makes one complete rotation of 360° in one day.

Rate of Earth Revolution

The Earth revolves at the rate of 15° an hour.

Coordinated Universal Time (UTC)

The standard time system based on the 0° line of longitude.

Zulu Time

Another term for Coordinated Universal Time (UTC).

Conversion to Zulu Time

The method of adjusting local times to UTC.

International Date Line

The line that deviates from the 180th meridian for geographical convenience.

Crossing the International Date Line Eastbound

Subtract a day while keeping the same time.

Crossing the International Date Line Westbound

Add a day while keeping the same time.

Direction

Measured in degrees, in a clockwise direction from true north.

Compass rose

A circle (360 degrees), graduated in degrees.

North

360/000 degrees.

East

090 degrees.

South

180 degrees.

West

270 degrees.

Magnetic Variation

The angle between true north and magnetic north, expressed as east variation or west variation.

Isogonic lines

Broken magenta lines on aeronautical charts that connect points of equal magnetic variation.

Agonic line

The line connecting points at which there is no variation between true north and magnetic north.

Magnetic Course (Heading)

The new course after applying variation along the route of flight.

Magnetic Deviation

The difference between compass heading and magnetic heading due to localized magnetic influences.

Compass Course

The course that takes the aircraft from point A to point B, adjusted for deviation.

Heading Corrections

True heading plus or minus variation equals magnetic heading.

True Bearing

Measured from true north.

Relative Bearing

The clockwise angle in degrees from the nose of the aircraft.

Distance

The spatial separation between two points, measured by the length of a line joining the two points.

Nautical Mile

Equals 6,076 feet, used in conjunction with airspace, separation, and airborne operations.

Statute Mile

Equals 5,280 feet, used to describe visibility.

Airspeed

The speed of an aircraft relative to its surrounding mass.

Indicated airspeed

The speed shown on the aircraft airspeed indicator.

True airspeed

The airspeed of an aircraft relative to undisturbed air.

Ground speed

The speed of an aircraft relative to the surface of the earth.

Tailwind

A tailwind increases ground speed.

Headwind

A headwind decreases ground speed.

Navigational Aids

Various types of air navigational aids in use, owned by the FAA and military services.

FAA

The Federal Aviation Administration has the authority to establish and maintain air navigation facilities.

Radio Navigation

Provides pilots with position information from ground stations.

Radio

The transmission and reception of electronic impulses or signals through space by means of electromagnetic waves.

Frequency

Basic unit is Hertz.

Radio frequencies (RF)

Frequencies falling between 3,000 Hertz (3 kHz) and 300,000,000,000 Hertz (300 GHz).

Kilohertz (kHz)

Thousands of Hertz per second.

Megahertz (MHz)

Millions of Hertz per second.

Gigahertz (GHz)

Billions of Hertz per second.

Usable radio frequency range

Roughly 10 kilohertz to 100 gigahertz.

Low frequency (LF)

30 kHz to 300 kHz.

Medium frequency (MF)

300 kHz to 3 MHz.

High frequency (HF)

3 MHz to 30 MHz.

Very high frequency (VHF)

30 MHz to 300 MHz.

Ultra high frequency (UHF)

300 MHz to 3 GHz.

Military radios

Range from 225 to 399.975 MHz.

Very High Frequency (VHF) Omnidirectional Range (VOR)

Provides magnetic bearing information to and from the station.

VOR frequency band

Operates within the 108.00 to 117.95 MHz frequency band.

VOR accuracy

The accuracy of course alignment of the VOR is excellent, generally plus or minus 1 degree.

VOR roughness

Certain RPM settings can cause the VOR Course Deviation Indicator to fluctuate as much as plus or minus six degrees.

VOR Test Facility (VOT)

Transmits a test signal which provides users a convenient means to determine the operational status and accuracy of a VOR receiver while on the ground.

Airborne use of VOT

Permitted; however, its use is strictly limited to those areas/altitudes specifically authorized in the Airport/Facility Directory (A/FD) or appropriate supplement.

Airborne and ground check points

Consist of certified radials that should be received at specific points on the airport surface or over specific landmarks while airborne in the immediate vicinity of the airport.

Error indication for ground check

Should an error plus or minus 4 degrees be indicated, IFR flight shall not be attempted without first correcting the source of the error.

Error indication for airborne check

Should an error plus or minus 6 degrees be indicated, IFR flight shall not be attempted without first correcting the source of the error.

Tactical Air Navigation (TACAN)

Ultra High Frequency (UHF) Omnidirectional Navigation Aid which provides bearing and slant range distance information.

TACAN channels

Has a total of 126 two-way channels and identifies itself aurally through Morse Code every 35 seconds.

TACAN usable radials

Provides 360 usable radials or courses aligned to magnetic north, labeled outbound from the TACAN.

Bearing information limitation

Cannot be received below the horizon or directly above the navigational aid, an area called the 'Cone of Confusion.'

Range information limitation

Subject to line-of-sight restrictions, with a line-of-sight/slant range of approximately 300 nautical miles.

Bearing/distance unlock

Can occur due to line-of-sight restrictions or if the TACAN signals are obstructed.

VHF Omni-directional Range/Tactical Air Navigation (VORTAC)

A facility at one site consisting of two components, VOR and TACAN, which provide three individual services: VOR azimuth, TACAN azimuth (bearing), and TACAN distance (DME).

VORTAC operation

Considered a unified navigational aid, as both components operate simultaneously and provide three services at all times.

DME operation

Involves paired pulses sent out from the aircraft (interrogation) and received at the ground station, which then transmits paired pulses back on a different frequency.

DME distance measurement

The time required for the round trip is measured in the airborne DME unit and converted into distance (nautical miles).

Global Positioning System (GPS)

Provides global positioning, navigation, and timing via the U.S. satellite constellation.

GPS Standard Positioning System Performance Standard

Defines GPS for civil use.

GPS system description

A space-based radio navigation system used to determine precise position globally, including 24 satellites.

Minimum satellites for GPS

At least 5 satellites must always be visible to a user, with a minimum of four required to determine an accurate three-dimensional position.

Minimum Elevation Angle

The angle above the horizon that a satellite must be at for the receiver to use its data.

Department of Defense (DOD)

The U.S. government department that operates and monitors the GPS satellite system.

Ephemeris Data

Orbital parameters transmitted by each satellite.

World Geodetic System 1984 (WGS-84)

The GPS coordinate system that is Cartesian earth-centered.

Instrument Landing System (ILS)

A system that provides an approach path for exact alignment and descent of an aircraft on final approach to a runway.

Ground Equipment for ILS

Includes directional transmitting systems, marker beacons, localizer, and glide slope transmitters.

Localizer

A component of the ILS that provides course guidance to the runway centerline.

Glide Slope

A component of the ILS that provides vertical guidance for descent.

Marker Beacon

An ILS component that indicates specific points along the approach path.

DME

Distance Measuring Equipment used in ILS for range information.

Precision Radar

A system that may substitute for marker beacons at the outer or middle marker.

Front Course

The approach course towards the runway.