Air Craft Surveillance &

Instrumental Landing System

Bikas Chandra Sadashiv ECE – IGNIT

3rd Year

Air Craft SurveillanceThrough RADAR

IntroductionRADAR FrequenciesRADAR ApplicationsTypes of RADAR

Topics To Be Covered

IntroductionRADAR is stand for Radio

Detection And Ranging and was developed prior to World War II.

Today RADAR is extremely important in civil aviation.

It is used by ATC to monitor and control numbers of aircrafts in airspace as well as by pilot for weather warning and navigation.

Radar FrequenciesRadar operates on UHF and SHF -

Super High Frequency (1 GHz - 30 GHz).

RADAR systems are in SHF bands because:

a) These frequencies are free from disturbance.

b) Higher frequency, shorter wavelength, RADAR more effective.(shorter wavelengths are reflected more efficiently.)

RADAR Applications

RADAR has a wide range applications including

1. Ground RADAR : extensively used by Air Traffic Control to separate aircrafts.

2. Airborne Weather RADAR: used by pilots. It provide pilots with information regarding weather ahead.

Types of RADAR

(RSR) En-Route Surveillance Radar

TAR- Terminal Approach

Radar (PSR & SSR)

AWR (Airborne Weather Radar)

SMR (Surface Movement

Radar)

Classifications of RADAR

1) En-Route Surveillance Radar (RSR)En-Route Surveillance Radars

(RSR) are long range radars which the signal goes to 300 NM.

It operates with frequency between 1 to 2 GHZ.

It used for airway surveillance to provide range and bearing of aircraft.

**Surveillance: close observation, especially of a suspected spy or criminal.

2) Terminal Approach Radar (TAR)

TAR is a high definition radio detection device which provides information on identification, air speed, direction and altitude of aircraft to assist air traffic controllers to track the position of aircraft in the air within the vicinity of the airport.

This radar gives the air traffic controller a better or true picture of all aircraft flying in his control zone.

2) Terminal Approach Radar (TAR)

PSR

SSR

Working of PSR : Primary Surveillance Radar (PSR)

transmits a high power signal. When a signal strikes an object or target,

some signal energy is reflected back and is received by the radar receiver.

RADAR receiver will plot the direction and the distance of the target (aircraft) from the radar station.

Thus, the ATC could know the position of aircraft. through the RADAR display.

Primary Surveillance Radar (PSR)

Primary Surveillance Radar (PSR)

Antenna

TransmittedPulse

TargetCross

Section

Propagation

ReflectedPulse

(“echo”)

Radar observable:• Target range• Target angles (azimuth & elevation)• Target size (radar cross section)• Target speed (Doppler)

Secondary Surveillance Radar (SSR)

Working of SSR :Secondary Surveillance Radar (SSR)

transmits an interrogation signal which is received by the target aircraft.

The aircraft transponder sends back a coded reply to the ground radar equipment.

From the coded signal, information of the aircraft’s call sign, altitude, speed and destination.

SSR requires an aircraft to be fitted with transmitter/receiver called as transponder.

How SSR Works?

The ground secondary radar transmits 1030MHz signal.

The aircraft radar receives on 1030MHz and transmits back 0n 1090MHz.

The transponder reply is more powerful than the reflected radar signal allowing for far greater range. (250nm).

3) Surface Movement Radar (SMR)

SMR installed at airport (at top of ATC tower building) to provide a very accurate radar display in all weathers and conditions of visibility. (operate with frequency 18-40Ghz)

SMR radar display can show all of airfield infrastructure including aircraft movements on runway, taxiway and apron.

It is designed to provide clear display of all aircraft on runway or taxiway so that ATC can ensure runway are clear for take-off/landing and also guide aircraft to apron in order.

3) Surface Movement Radar (SMR)

RADARS USED IN ATCAirport Surveillance Radar (ASR)Air Route Surveillance Radar

(ARSR)Airport Surface movement

Detection Equipment (ASDE)/Advanced Surface Movement Guidance & Control System (ASMGCS)

Precision Approach Radar (PAR)Mono-pulse Secondary

Surveillance Radar (MSSR)

INSTRUMENT

LANDING

SYSTEM (ILS)

IntroductionThe Uses of ILSILS ComponentsHow Localizer WorksHow Glide Path WorksMarker Beacons

Topics To Be Covered

INTRODUCTION

Radio beam transmitter that provides a direction for approaching aircraft that tune their receiver to the ILS frequency

The Uses of ILSTo guide the pilot during the approach and landing.◦Very helpful when visibility is limited

To provide an aircraft with a precision final approach.

To provide an aircraft guidance to the runway both in the horizontal and vertical planes.

ILS Components ILS consists of Ground Installations and Airborne

Equipments There are 3 equipments for Ground

Installations, which are: 1. Ground Localizer (LLZ) Antenna – To

provide horizontal navigation2. Ground Glide path (GP) Antenna – To

provide vertical navigation3. Marker Beacons – To enable the pilot cross

check the aircraft’s height. There are 2 equipments for Airborne

Equipments, which are: 1. LLZ and GP antennas located on the

aircraft nose.2. ILS indicator inside the cockpit

Localizer

Localizer is the horizontal antenna array located at the opposite end of the runway.

Localizer operates in VHF band between 108 to 111.975 MHz

Transmit two signals which overlap at the centre. The left side has a 90 Hz & right has a 150 Hz modulation.The overlap area provides the on-track signal.

Right

Left

How Localizer Works

Localizer

Needle indicates direction of runway.

Centered Needle = Correct Alignment

Glide Path Antenna ArrayGlide Path is the vertical antenna

located on one side of the runway about 300 m to the end of runway.

Glide Path operates in UHF band between 329.15 and 335 MHz

How Glide Path Works

Glide path produces two signals in the vertical plane.The upper has a 90 Hz modulation and the bottom has a 150 Hz modulation.

Glide Path

Needle indicates above/below glide

path.

Centered Needle = Correct Glide path

Marker BeaconsMarker beacons operating at a

carrier frequency of 75 MHz are provided.

When the transmission from a marker beacon is received it activates an indicator on the pilot's instrument panel.

The correct height the aircraft should be at when the signal is received in an aircraft.

Runway Approach

Non-Instrument Runway (NI)

Non-Precision Runway (NP)

Precision Runway (P)

Threshold

Touchdown zone

Aiming point

Types of Runway Approach

1.Non-Instrument Runway (NI)◦ A runway intended for the operation of

aircraft using visual approach procedure2. Instrument Runway

◦ A runway intended for the operation of aircraft using instrument approach procedures

a) Non-Precision Runway (NP) • An instrument runway served by visual

aids and a non-visual aid providing at least lateral guidance adequate for a straight-in approach

b) Precision Runway (P) • Allow operations with a decision height

and visibility

How ILS works? Ground localizer antenna transmit VHF signal

in direction opposite of runway to horizontally guide aircraft to the runway centre line.

Ground Glide Path antenna transmit UHF signal in vertical direction to vertically guide aircraft to the touchdown point.

Localizer and Glide Path antenna located at aircraft nose receives both signals and sends it to ILS indicator in the cockpit.

These signals activate the vertical and horizontal needles inside the ILS indicator to tell the pilot either go left/right or go up/down.

By keeping both needles centered, the pilot can guide his aircraft down to end of landing runway aligned with the runway center line and aiming the touch down.