Navigational Aids

QUESTIONS: ANSWERS:

The art of detecting the movements of a craft from one point to another along a desired path.

NAVIGATION

The navigator fixes his position on a map by NAVIGATIONAL BY PILOTAGE

Also called as Astronomical Navigation. It is accomplished by measuring the angular position of the celestial body.

CELESIAL NAVIGATION

The position of craft at any instant of time is calculated fro previously determined position; the speed of its motion with respect to the earth with the direction and time elapsed. It is the most common and widely used method of navigation

NAVIGATION BY DEAD RECKONING

Uses electromagnetic waves to attain a fix.

RADIO NAVIGATION

RADAR

RADAR OR RADIO DETECTING AND RANGING

Basically means gathering information about distant objects or targets by sending electromagnetic waves at them and analyzing the echoes.

RADAR

Determines the maximum distance to the target to be measured.

PULSE REPETITION TIME

Range beyond, which the objects appear as second return echoes.

MAXIMUM UNAMBIGUOUS RANGE

Band Name Frequency Range (GHz) UHF 0.3-1.0 L 1.0-1.5 S 1.5-3.9 C 3.9-8.0 X 8.0-12.5

RADAR FREQUENCY

Ku 12.5-18 K 18.0-26.5 Ka 26.5-40.0 V 40.0-80.0 N 80.0-170.0 A ABOVE 170.0

The radar cross section or effective area of the target depends on the frequency used

TARGET FREQUENCY

The target is small compared to the wavelength, its cross sectional area for radar appears much smaller than its real

RAYLEIGH REGION

QUESTIONS: ANSWERS:

The circumference of a spherical target is between 1 and 10 wavelenghts, the radar cross section oscillates about the real one

RESONANCE REGION

For shorter wavelengths, the radar and true cross sections are equal.

OPTICAL REGION

The RADAR Cross Section of the target depends on

1.Polarization of the incident wave. 2.Degree of surface roughness 3.Use of special coatings on the target 4.Aspect of the target

Flat topped rectangular pulses.

PULSE CHARACTERISTICS

To ensure that the leading edge of the received pulse is also close to vertical for exact measurement of target range

LEADING EDGE MUST BE VERTICAL

Is required for the voltage pulse applied to the magnetron anode. The efficiency of the magnetron or other amplifier drops significantly if the supply voltage is reduced

FLAT TOP

Is needed for the transmitted pulse so that the duplexer can switch the receiver over to the antenna as soon as the body of the pulse has passed.

STEEP TRAILING EDGE

Use dipole or horn fed paraboloid reflectors or at least reflectors of basically paraboloid shape.

RADAR ANTENNAS

Antenna Tracking 1.LOBESWITCHING TECHNIQUE 2.CONICAL SCANNING 3.MONOPLUSE TRACKING

Sequential Lobing The direction of the antenna beam is rapidly switched between 2 positions

LOBE SWITCHING TECHNIQUE

Logical extension of lobe switching

CONICAL SCANNING

A system using 4 horn antennas displaced about the central focus of the reflector

MONOPULSE TRACKING

Disadvantages A.More complex motion of the antenna B.Additional servomechanisms are required C.More than one returned pulse is required

RADAR Display Method 1. A SCOPE 2.PLANPOSITION INDICATOR 3.AUTOMATICTARGET DETECTION

Deflection modulation in the CRT screen.

A SCOPE

QUESTIONS: ANSWERS:

Intensity modulation Sow the map of the target area The brightness at any point on the screen indicates the presence of an object there, with its position corresponding to its actual physical position and its being measured radially out from the center

PLAN POSITION INDICATOR

Direct feeding to the computer. AUTOMATICTARGET DETECTION

General Task of a Radar System

1.Search for targets 2.Track them once when they are acquired

Tracking Radar Systems

1.TRACKING IN ANGLE 2.TRACKING IN RANGE

A system that gives the angular position of a target accurately.

TRACKING IN ANGLE

Range information is continuously obtained.

TRACKING IN RANGE

Transmitting and receiving antenna are located at the same point

MONOSTATIC RADAR

Transmitter and receiver are located separately by quite large distances.

BISTATIC RADAR

The apparent freq. of electromagnetic or sound waves depend on the relative radial motion of the source and the observer. Postulated by Christian Doppler in 1842 Was given a firm mathematical basis by Armand Fizeau

DOPPLER EFFECT

Small radar sets consisting of a receiver a separate transmitter and an antenna, which is often omnidirectional. When another radar transmits a coded set of pulses at the beacon; i.e. interrogates it, the beacon responds by sending back its specific pulse code, thereby earning its name Transponder.

RADAR BEACONS

Application of RADAR Beacons

1.Identification friend or foe.(IFF) 2.Calculation of position like in lighthouse

Uses localizer glide and marker beacon transmitter to provide a slopping glide path for instrument (blind) landing approach of an aircraft.

ILS (INSTRUMENT LANDING SERVICE)

ILS Consists of

a.A VHF radio transmitter and antenna system using the same general range as VOR (very high omnidirectional range) transmitters. (between 108.10 MHz abd 111.95 MHz)

LOCALIZER WHICH PROVIDES LATERAL GUIDANCE

b.Which provides vertical guidance is produced by ground base UHF transmitter and antenna system, operating at the range 329.30 MHz to 335.0 MHz, with a 150 KHz spacing between each channel. The transmitter is located 750 to 1250ft. down the runway from the threshold offset 400 to 600 ft. from the runway centerline.

GLIDE SLOPE EQUIPMENT WHICH PROVIDES VERTICAL GUIDANCE

QUESTIONS: ANSWERS:

c.Provides information on distance from the runway to identifying predetermined point along the approach track. These beacons are low-power transmitters that operates at a frequency of 75 MHz with 3 watts or less rated power output. They radiate an elliptical beam upward from the ground. At altitude of 1,000 ft., wide. At higher altitudes the dimensions increase significantly

ILS MARKER BEACON

Marker Beacon

Code Light

Distance to Threshold

Modulated Frequency

Outer Blue 4 to 7 nm 400Hz

Middle Amber 3,500 ft 1,300Hz

Inner White 1,000Ft 3,000 Hz

MARKER BEACON CHARACTERISTICS

d.Provides guidance to the pilot on an approaching aircraft to the runway.

RUNWAY LIGHTS APPROACH LIGHTS (WHITE)

A part of an approach light it flashes twice in second in sequence. I

SEQUENCE LIGHTS

t distinguishes aeronautical ground lights in an aero dome to the lights in

the area

Provide sufficient guidance to the pilot during landing and take off especially at night or zero visibility.

RUNWAY EDGE LIGHTS (YELLOW)

Provides information on the extremely runway when a landing aircraft is intended to land.

THRESHOLD LIGHTS (GREEN)

Signifies the end of the runway and is placed on a line at right angle to the runway access.

RUNWAY END LIGHTS (RED)

Provides the indicating on the aircraft position relative to the optimal slope during final approach to the runway.

PAPI LIGHTS (PRECISION APPROACH PATH INDICATOR)

-An airplane is talk down to a blind landing by means ground based search precision radars -This is an instrument approach system consisting of extremely high precision microwave radar equipment that gives the position of an aircraft in range, azimuth and elevation. It is primary designed to bring the pilot through low overcast of low horizontal visibility so that he can make a normal landing by visual contact. Skilled operations of this system in the aircraft and on the ground permits emergency landing under conditions of nearly zero visibility. -Basically the ground equipment at the airport consists of two microwave radar sets, which are usually installed in a single trainer placed adjacent to the runway. One of the radar’s know as the search system, locates all aircraft within 30 miles or so of the airport and thus provides a radar map of the miles or so of the airport and thus provides a radar map of the vicinity. It is the initial phase of the GCA and is accomplished with medium range radar called plan position indicator. -The other radar, called the precision system, provides continuous information regarding the position of the incoming aircraft with respect to the runway. The plane may thus be safety talked down along the sloping glide path. -On the final approach leg, the controller, using precision

GROUND CONTROLLED APPROACH (GCA)

scopes, takes control. He also broadcasts verbal instructions, principally concerning attitude and lateral deviation from the desired glide path, and guides the pilot virtually to the end of the runway -On the final approach the GCA operator uses precision approach radar (PAR), short-range precision radar that indicates the proper glide path for descent.

QUESTIONS: ANSWERS:

-Are low frequency transmitters operating into an omni directional vertically polarized antenna. Usually place at the ILS outer and middle marker beacon sites where it is known as compass locator. -Are beacons sending its signal equally well in all directions. It a low-frequency beacon with a frequency range of 200kHz to 415kHz. The reception range of the radio beacon is at least 15 nautical miles and it transmits 2 to 3 letters of identification signal from the Morse code 8 times per minute. NDB provides a radio station for use by aircraft. The equipment in the aircraft consists of an ADF or radio compass, which gives the pilot information in the form of a pointer indicating the bearing of the NDB transmitter. The pilot can thus fly courses to or from the NDB. If dual ADF equipment is provided on an aircraft, it is possible to fix position by combining the information’s provided by two NDB’s

NON – DIRECTIONAL BEACONS (NDB)

An equipment that provides information of the distance between an aircraft and the VOR station. Together with VOR, they provide the information necessary for enroute naviugation.

DME (DISTANCE MEASURING SYSTEM)

DME Components

Sends out signals to ground station.

TRANSCEIVER

Built within the transceiver that measures time interval that elapsed until the response.

INTERNAL COMPUTER

Use for both transmission and reception. It is very small mounted on the underside of the aircraft.

ANTENNA

Incorporate digital readouts of frequency, DME and ground speed information

DME CONTROLS

DME displays information in the form of

-Expressed in nautical miles

DISTANCE TO THE STATION

-Expressed in knots AIRCRAFT’S GROUND SPEED

-Expressed in minutes TIME TO STATION

-A radio facility providing bearing information to and from such facility at all azimuth within its service area. It provides an unlimited number of visual course legs through the phase comparison of a cardiodshaped rotating radiation pattern with a fixed 30-cps reference signal.

VERY HIGH FREQUENCY OMNI RANGE (VOR)

VOR components

1. The VOR signals are received on the antenna normally located on the vertical stabilizer or on top of the fuselage. This antenna resembles a “V” lying in a horizontal plane. The VOR receiver converts signals from the antenna to the readings displayed on the navigation indicator.

VOR RECEIVER

QUESTIONS: ANSWERS:

2. The VOR navigation indicator gives the pilot aircraft position information by means of three components,

NAVIGATION INDICATOR

A. The track selector sometimes called the ‘________________’ or _____. Used to rotate the azimuth ring, which displays the VOR track.

OMNIBEARING SELECTOR (OBS)

B. Indicates whether the track will take the pilot to or from the station

TO-FROM/OFF FLAG

C. Shows the pilot the position relative to the track selected and indicates whether the radial is to the right or left when the aircraft heading agrees generally with the track selector.

TRACK DEVIATION BAR(TB)

3. A needle that you could think of as a line that runs through the station and points in the direction of the selected track that divides the area around the VOR station into halves

TRACK ARROW

4. Is a line perpendicular to the track arrow and intersecting it at the station. It also divides the VOR reception area to additional sectors

REFERENCE LINE

-A microwave pulse system that provides highly accurate bearing and range information from a shipboard or ground radio. -Like the VOR-DME system, the TACAN system provides an aircraft with continuous distance (range) and bearing (azimuth) information from a ground beacon station, located within a line-of-sight range up to 195 nautical miles.

1. TACAN operates completely in the UHF band from 962 to 1213 megacycles

2. The system has a total of 126 channels in the UHF band, each being capable of providing full service for over 100 aircraft.

3. It provides compass direction with less than one degree error and is capable of indicating true distance from the ground station within about 600 feet

4. TACAN can use a very small ground station antenna which permits it’s installation on Air Force Mobile units and Navy carriers

TACTICAL AIR NAVIGATION (TACAN)

TACAN Components

1) The airborne set is a radio set that could be turned to 126 channels and has a special range and azimuth circuit. It is generally provided with two indicators, one for showing the range in nautical miles, the other for indicating the bearing (azimuth) of the aircraft on the station.

AIRBORNE INTERROGATOR-RESPONSOR

2) This is a beacon that could be triggered by distance interrogation pulse coming from an airborne radio set. When trigged, it will respond by sending out synchronized reply pulses and also identifies itself aurally in International Morse Code characters

GROUND OR SHIPBOARD SURFACE BEACON

QUESTIONS: ANSWERS:

-Is a facility consisting of two components or is referred to as VORTAC

a combination of a VOR (VHF Omnidirectional Range) and a TACAN (Tactical Air Navigation) therefore deriving its name VORTAC. This system is an ICAO (International Civil Aviation Organization) Rho-Thela system implemented by co-locating VOR and TACAN stations. VORTAC provides three individual services, VOR azimuth, TACAN azimuth and TACAN distance measuring capability at one sight.

-Range station that provide four aircraft course legs (the overlapping of two figure – 8 pattern) -The low frequency radio range depends on the superposition of two figure-8 directional antenna patterns at right angle with each other. These patterns provide ‘ON-Course’ signals. Which interlock with those of surrounding station to form easily followed airways. When two vertical antenna towers are properly fed with radio frequency energy they produce two figure-8-radiation patterns. This makes production of on course signals simpler and easier. Radio range stations operate on frequency between 200 kHz and 400 kHz -Four sector are does created by this towers, between which are four regions that overlap each other. In these regions, both signals from tower are present. Signal in this overlapping zones are heard as continuous tones called on course signals. This is accomplished by keying, making signal blend rather than be heard individually. As long as an aircraft files over this zone where on course signals are present, pilot would hear continuous signals. -If two pairs of vertical tower are placed in a square patterns at right angles to each other. The fifth center tower is used for transmitting weather reports. With two figure-8 patterns available the production of on course signals become a simpler matter. The code signal A is transmitted over one pair of diagonally opposite towers and the code signal N is transmitted over the pair of tower. In this way four signal zones, called sectors, are produced two of which carry the A signal, while other two carry the N signal. Between the four sectors there are regions of overlapping

LFR (Low Frequency Range)

-Directly above a radio range there exist an area where practically no signal

is heard. This area has the shape of inverted cone, and is known as “the Cone of Silence”. A pilot passing through the cone of silence would

know that he was directly over the range station. Whose signal he had been

receiving

CONE OF SILENCE

Long Distance Navigation System

A. Station Reference

1. Navigational aids installed in therapira.

GROUND REFERENCE

2. Fix determined by measurement of the angle of arrival of the emission from the ground by employing interferometric techniques in the satellite

SATELLITE REFERENCED

B. Self – Contained: CNS; INS

Operates on the principle of hyperbola.

HYPERBOLIC SYSTEM

QUESTIONS: ANSWERS:

Provides hyperbolic lines of position through the measurement on the difference in times of transmission of radio signals from two or more synchronized transmitters at fixed point. When synchronized signals are received from two transmitting stations, the difference in the times of arrival is constant on a hyperbola having the two transmitting stations as foci. The measured time difference locates the receiver on the hyperbolic line of position for that time difference. Another pair of transmitters provides another hyperbolic line of position. The intersection of the lines of position provides a navigational fix

HYPERBOLIC NAVIGATION SYSTEM

-An electronic method of determining ship position by the reception of signals from transmitting stations of known location -Radio signals consisting of short pulses are continually transmitted from a pair of shore-based stations. These signals are received abroad the ship by means of a specially designed receiver. The difference in time of arrival of the two signals is measured by means of an indicator associated with the receiver. The measured by means of an indicator associated with the receiver. The measured time difference is used together with special tables or charts to determine lint of position on the surface on the earth’s surface. Two line of position obtained from two pairs of transmitting stations intersects at a given Loran fix.

LONG RANGE NAVIGATION (LORAN)

The ground waves of a Loran A transmitter with a peak power of 100 kW can be received over sea at a distance of 500 to

LORAN A SYSTEM

700 nautical miles, and at a distance of Up to 1100 nautical miles with ground and sky waves. Over land these distance are considerably shorter

Operates at lower frequencies of 100 kHz. At this frequency, ground waves of a 300 kW transmitter can be received up to 1200 nautical miles.

LORAN C SYSTEM

The advantage of Loran D over Loran A is that ground stations and

transportable and can therefore be quickly deployed. This mobility is gained

atthe expense of the substantially reduced radiated power (30 kW inherent

in the somewhat smaller transmitter and lower antenna lowers (400ft. or

120m) to partially compensate for this reduction in radiated power. Loran D

is configured to use 16-phasecoded pulses 500s part in each group. Loran

D phase code is different but compatible with Loran C. pulse sampling is carried out near the signal peak because sky-wave delays are greater at

short range.

LORAN D

-Continuous wave hyperbolic system operating in the 70 to 130 kHz band. -A hyperbolic navigation system, which establishes a line of position from measurement of the phase difference between two continuous-wave signals

DECCA

-A navigation system developed by US navy in 1957. it is a Hyperbolic system which works in the very low frequency region and has a very long base line of the order of 7,000 km. -A global radio navigation system developed by the U.S. Navy. It provides position information by measuring the phase difference between signals radiated by a network of transmitting stations

OMEGA

Operates from 20 to 85 Mhz GROUND ELECTRONICS ENGINEERING (GEE)

QUESTIONS: ANSWERS:

A system used abroad navy ships for sonic and ultra sonic under water detection, ranging, sounding, and communications.

SOUND NAVIGATION & RANGING (SONAR

Alerts the flight crew of possible conflicts with other airplanes in the same area. TCAS tracks these other airplanes or intruders, if equipped with a Air Traffic Control Radar Beacon System (ATCRBS) or a Mode S ATC transponder

TRAFFIC ALERT & COLLISION AVOIDANCE SYSTEM (TCAS)

TCAS Provides 2 Types of Collision Avoidance Alerts they are

TRAFFIC ADVISORY (TA) RESOLUTION ADVISORY (RA)

Shows the relative position of any intruder airplanes. TA

Shows a vertical maneuver to avoid a possible airplane collision

RA

GLOBAL POSITIONING SYSTEM

Is a worldwide navigation radio aid which uses satellite signals to provide accurate navigation information.

NAVIGATION SYSTEMS TIME & RANGING GLOBAL POSITIONING SYSTEM

The architecture of the system is composed of 3 parts called segments:

SEGMENTS

Composed of 24 satellites, arranged in six orbital planes of four satellites each on a circular orbit.

-55° inclination to the equator -An attitude of approximately 20200km with an orbital period of 12 sideral hours

These satellites give -Provides satellite position -Provides constellation data -Provides atmospheric correction

SPACE SEGMENT

Composed of four monitor stations and one master control station which tracks the satellite, compute the ephemeris, clock corrections and control the navigation parameters and

CONTROL SEGMENT

transmit them to the GPS users.

The four monitor stations are located at -Kwajalein -Hawaii -Ascension Island -Diego Garcia -The master control station is located at Colorado Springs

-GPS is funded by and controlled by the U.S. Department of Defense (DOD). While there are many thousands of civil users of GPS world-wide, the system was designed for and is operated by the U.S. military -GPS provides specially coded satellite signals that can be processed in a GPS receiver, enabling the receiver to compute position, velocity and time. -Four GPS satellite signals are used to compute positions in three dimensions and the time offset in the receiver dock -Navigation in three dimensions is the primary function of GPS

GPS IS A SATELLITE NAVIGATION SYSTEM

QUESTIONS: ANSWERS:

-GPS –Global Positioning System -Instantaneous position -Velocity -Time information -NAVSTAR- Navigation Satellite Timing And Ranging -Nominal altitude of 20,200 Kms -55o inclination -24 satellites with 4 SVs in each plane -6 orbital planes -GPS is based on a system of coordinates -World Geodetic System 1984 (WGS 84)

WHAT IS GPS

-Anytime, anywhere, and in any weather -Highly accurate measurement -GPS has almost endless application

MAIN ADVANTAGE OF GPS

-Measurement becomes less accurate when affected by SA and AS -GPS – A NEW CONSTELLATION -GPS Nominal Orbit Planes -GPS Constellation

DISADVANTAGE OF GPS

-24 satellite with min. of 21 operating 98% of time -6 orbital planes -55° inclination -20,200 km above the earth surface -11 hrs. 58 min. orbital period -Visible approximately 5 hrs. above the Horizon.

-Global Orbiting Navigation Satellite System -Global Navigation Satellite System -21 satellite in 3 orbital plane -3 on orbit system -L-band

GLONASS