AAI Report on CNS (winter training)

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Tulihal Airport
Imphal, Manipur-795140
Training Report On:
CNS
Communication, navigation and surveillance
Submitted By:-
Students of NIT Manipur,
B.Tech (ECE), 3rd
year
Winter Training (2016).

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Contents
1. Acknowledgement.
2. Training Faculty
3. Functions of AAI
4. CNS (Communication Navigation Surveillance).
5. VHF Communication.
6. DVR
7. VCR
8. DATIS
9. AMSS (Automatic Message Switching System).
10. DME
11. DVR
12. ILS (Instrument Landing System).
13. RADAR.
14. CCTV
15. Security Equipments
16. Conclusion
17. Reference

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Acknowledgement
Acknowledgement is something which really comes from the
bottom of the heart of every writer .We are obliged to staff
members at AAI of TULHAL airport, for the valuable
information provided by them in their respective fields. We
are grateful for their cooperation during the period of our
assignment.

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Training Faculty
1.Ashish Shrivastava
2. S.Nandhulal
3. Kh.Siddhartha
4. Ajay Sangwan
5. T.Mankhothang
6. Shibina
7. Parthasarthi
8. Jhon Singh
9. Smita

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Functions of AAI
The functions of AAI are as follows:
1. Design, Development, Operation and Maintenance of
international and domestic airports and civil enclaves.
2. Control and Management of the Indian airspace
extending beyond the territorial limits of the country, as
accepted by ICAO.
3. Construction, Modification and Management of
passenger terminals.
4. Development and Management of cargo terminals at
international and domestic airports.
5. Provision of passenger facilities and information system
at the passenger terminals at airports.
6. Expansion and strengthening of operation area, viz.
Runways, Aprons, Taxiway etc.
7. Provision of visual aids.
Provision of Communication and Navigation aids, viz. ILS,
DVOR, DME, Radar etc.

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Communication-Navigation-Surveillance
(CNS)
-------------------------------------------------------------------
Communication is the exchange of voice and data
information between the pilot and air traffic
controllers or flight information centres.
Communication Facilities are
1. VHF Air-to-Ground Voice Communication
Facilities
2. Digital Voice Tape Recorder
3. Dedicated Satellite Communication Network
4. Voice Communication System
5. Digital Automatic Terminal Information Service
6. Automatic Message Switching System

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VHF-Communication
The electromagnetic waves having frequency range 30
MHz to 300 MHz are defined as Very High Frequency
(VHF) radio waves. VHF communication is usually
suitable for mobile applications, as these frequencies
are not affected by atmospheric noise.
VHF Range in ATS: (117.975-136.975) MHz
Users: Air Traffic Controllers (ATCO), Airlines/Defence
Pilots
For VHF Communication we require Transmitter,
Receiver here in imphal we are using OTE company
transmitter (DT 100) and receiver (DR 100).
At airport we are using Amplitude Modulation for
communication with aircraft because it has its own
advantages over F.M

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TRANSMITTER:-
1. A transmitter uses an oscillator to produce the desired
radio frequency current.
2.In electronics and telecommunications a transmitter or
radio transmitter is an electronic device which generates
a radio frequency alternating current. When a connected
antenna is excited by this alternating current, the
antenna emits radio waves.
A radio transmitter is an electronic circuit which transforms
electric power from a battery or electrical mains into a radio
frequency alternating current, which reverses direction millions
to billions of times per second. The energy in such a rapidly
reversing current can radiate off a conductor (the antenna) as
electromagnetic waves (radio waves). The transmitter also
impresses information such as an audio or video signal onto
the radio frequency current to be carried by the radio waves.
When they strike the antenna of a radio receiver, the waves
excite similar (but less powerful) radio frequency currents in it.
The radio receiver extracts the information from the received
waves. A practical radio transmitter usually consists of these
parts:
A power supply circuit to transform the input electrical power to
the higher voltages needed to produce the required power
output.
An electronic oscillator circuit to generate the radio frequency
signal. This usually generates a sine wave of constant

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amplitude often called the carrier wave, because it serves to
"carry" the information through space. In most modern
transmitters this is a crystal oscillator in which the frequency is
precisely controlled by the vibrations of a quartz crystal.
A modulator circuit to add the information to be transmitted to
the carrier wave produced by the oscillator. This is done by
varying some aspect of the carrier wave. The information is
provided to the transmitter either in the form of an audio signal,
which represents sound, a video signal, or for data in the form
of a binary digital signal.
In Imphal airport we are using the frequencies like
1. 124.35 MHz (main)
2. 126.65 MHz (Broadcast)
3. 118.55 MHz (stand by)

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RADIO-RECEIVER (VHF)
In radio communications, a radio receiver (commonly also
called a radio) is an electronic device that receives radio
waves and converts the information carried by them to a usable
form. It is used with an antenna. The antenna intercepts radio
waves (electromagnetic waves) and converts them to
tiny alternating currents which are applied to the receiver, and
the receiver extracts the desired information. The receiver
uses electronic filters to separate the desired radio
frequency signal from all the other signals picked up by the
antenna, an electronic amplifier to increase the power of the
signal for further processing, and finally recovers the desired
information through demodulation.
The information produced by the receiver may be in the form of
sound (an audio signal), images (a video signal) or digital
data.[1]
A radio receiver may be a separate piece of electronic
equipment, or an electronic circuit within another device.
Devices that contain radio receivers include television
sets, radar equipment, two-way radios, cell phones, wireless
computer networks, GPS navigation devices, satellite
dishes, radio telescopes, bluetooth enabled devices, garage
door openers, and baby monitors.
In consumer electronics, the terms radio and radio receiver are
often used specifically for receivers designed to reproduce
the audio (sound) signals transmitted by radio
broadcasting stations, historically the first mass-
market commercial radio application.

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Block diagram of receiver :
Super-heterodyne
Here we use PTT
Push-to-talk (PTT), also known as press-to-transmit, is a
method of having conversations or talking on half-
duplex communication lines, including two-way radio, using
a momentary button to switch from voice reception mode to
transmit mode.

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Digital Voice Recorder (DVR)
1. It records all voice communicationsand sounds like siren,
alarms etc
2. These recordings are stored for minimum 30 days
3. We can retrieve the data whenever we want from DVR
4. Thisis connected to a switch so that it can be remotely
monitored by other pc
5. Connectionfrom tower is given to distributionbox and
then to krone ,from here it is given to splitter such that it
splits the channeland given to two servers (dvr), these are
connected to a monitor, keyboard and mouse by kvm switch.
6. Servers are connected to a switch where all remote pc’s
and G.P.S clock are connected.
7. We can use a remote pc as replay station.
8. For redundancy purpose we use two servers and data is
stored in both paralleland U.P.S is used for backup power
supply.
9. Here data is stored digitallyand replayed from replay
station.
10. The block diagram of D.V.R setup at imphalairport is
shown below.

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11. The IP address of devices are shown above, as these are
ip based we can operate from remote desktop and
maintenancebecome easy.
12. It is important to store this data because when there is a
flight accidentsor any problem they can retrieve that data
and can be used for inspection.

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Voice Communications System (VCS)
Voice Communication System is a state-of-art solution
for ATC communication. Based on voice-over-ip
technology, it allows effective interconnection of multiple
communication system including UHF and VHF radios,
telephones, and intercoms.
Key features
 VoIP
 Colour touch-screen Control Panel
 Set of audio accessories and PTTs
 Easiest way to upgrade your current system or add a
failback equipment
 Modularity & scalability & robustness
 Easy to integrate with other equipment
 Multiple GUIs library to select from
 Fail proof & zero maintenance
 Intuitive configurator
 Compatible with common as well as VoIP radios
 Compatible with radios network and remote radios
control
 Compatible with PBX interfaces
 Outputs for recording & replay equipment
 Special support for usage in simulators: GUI replicas
library, communications in the background, library of
VCS configurations.

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Key benefits
 Simple data network infrastructure instead od dedicated
cabling and wiring
 COTS hardware instead of fragile, expensive and
difficult to get electronics
 Fully digital chain from the operator to the transceiver
and vice versa
 Monitoring and data sharing in the country-wide network
 Instantaneous back-up with control transfer to an
adjacent location

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Basic Block Diagram of VCS System
1.Voice CommunicationSystem is a switching system that
connects variousair traffic controllers’ positionsto various
air-to-ground and ground-to-ground communicationsystems.
2.Voice switching and routing between (A-to-G and G-to-G)
communication systems and airtraffic controllers’ working
positionsis done by using advancedmicroprocessor and
DSPs.

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Digital Automatic terminal Information Service
(D-ATIS)
Automatic terminal information service, or ATIS, is a
continuousbroadcast of recorded noncontrol aeronautical
informationin busier terminal (i.e. airport) areas.[1]
ATIS
broadcasts containessential information, such as weather
information,which runways are active, availableapproaches,
and any other informationrequired by the pilots, such as
important NOTAMs. Pilots usually listen to an availableATIS
broadcast before contacting the localcontrol unit, in order to
reduce the controllers' workload and relieve frequency
congestion
Automatic Terminal Information Service system
 Compact device allowing to handle and transmit
continuous broadcast of information in terminal area
 Used as operational equipment as well as in ATC
simulators
 Can work fully automatically
 Consists of a server with one or more working positions
for operator to prepare, check and dispatch messages
for broadcasting based on manual or automated inputs
 Sends a VoIP message to receivers with VoIP interface,
or analog audio to receivers with analog input as well as
to an output for voice recorder
 Weather information is entered manually or
automatically from connected source of data

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 Includes an internal GPS based Time Reference
System or can be synchronised by external NTP
 Linux based, industrial hardware
 Speaker independent, no mike, no recordings required
 Near to zero maintenance
The system is available for remote servicing.
The recording is updated in fixed intervals or when there
is a significant change in the information, e.g. a change
in the active runway. It is given a letter designation
(e.g. bravo) from the ICAO spelling alphabet. The letter
progresses through the alphabet with every update and
starts at alpha after a break in service of 12 hours or
more. When contacting the local control unit, a pilot will
indicate he/she has "information <letter>", where
<letter> is the ATIS identification letter of the ATIS
transmission the pilot received. This allows the ATC
controller to verify whether the pilot has all the current
information.
Example at a General Aviation airport in the UK (Gloucestershire
Airport):-

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Information Section Details
Airfield this ATIS broadcast is for Gloucester (Phonetically GLOSTER)
ICAO spelling alphabet letter Quebec
Time (UTC) 14:20
Runway Use 27 (i.e. 270º)
Circuit Direction (General Aviation) Right Hand Circuit
Wind Speed and Direction 270º @ 2 kts
Visibility 10 Kilometres or more (maximum)
Cloud Cover Few @ 2600 feet and Broken @ 4000 feet
Temperature 19 °C
Dew Point 13 °C
QNH (Pressure @ Sea level) 1020 mBar
QFE (Pressure @ Airfield Elevation) 1017 mBar
Other Information
Request to report altimeter setting in use on first contact.
Noise abatement procedures in effect.
Tower Frequency: 122.900 MHz (Departing Aircraft)
Approach Frequency: 128.550 MHz (Arriving Aircraft)
There is intense gliding activity in the vicinity of the airfield
Instruction to report you have information Quebec

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Block diagram of D-ATIS
1.VAU(Voice AnnouncementUnit)
2.KVM switch
3.Server

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AMSS
(AUTOMATIC MESSAGE SWITCHING SYSTEM)
AFTN IN INDIA
AFTN (Aeronautical Fixed Telecommunication
Network) in India is under the control of Airports
Authority of India. The AAI has established AMSS
centers throughout the country in major stations. India
plays a key role in the international AFTN, bridging the
gap between the eastern and western parts of the
world. Messages originating in the western countries
are routed through India to the eastern countries and
vice-versa.
AFTN SWITCHING SYSTEM
In AFTN, informationis exchanged between many stations.
The simplest form of communicationis point-to-pointtype,
where information is transmitted from a source to sink
through a medium. The source is where information is
generated and includes all functionsnecessary to translate
the informationinto an agreed code, format and procedure.
The medium could be a pair of wires, radio systems etc. is
responsible for transferring the information.The sink is
defined as the recipient of information;it includes all
necessary elements to decode the signals back into
information.

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• CLASSIFICATION OF AFTN SWITCHING SYSTEM
A switching system is an easy solution that can allow
on demand basis the connection of any combination of
source and sink stations. AFTN switching system can be
classified into 3 (three) major categories:
1. Line Switching
2. Message Switching
3. Packet Switching.
Line Switching
When the switching system is used for switching lines
or circuits it is called line-switching system. Telex
switches and telephones exchanges are common
examples of the line switching system.
Message Switching
In the Message Switching system, messages from the
source are collected and stored in the input queue
which are analyzed by the computer system and
transfer the messages to an appropriate output queue
in the order of priority. The messageswitching system
works on store and forward principle. It provides good

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line utilization, multi-addressing, messageand system
accounting, protects against blocking condition, and
compatibility to various line interfaces.
Packet Switching System
This system divides a messageinto small chunks called
packet. These packets are made of a bit stream, each
containing communication control bits and data bits.
The communication control bits are used for the link
and network control procedure and data bits are for
the user.
A packet could be compared to an envelope into which
data are placed. The envelope contains the destination
address and other control information. Long messages
are being cut into small chunks and transmitted as
packets. At the destination the network device stores,
reassembles the incoming packets and decodes the
signals back into information by designated protocol. It
can handle high-density traffic. Messages are
protected until delivered. No direct connection
required between source and sink. Single port handles
multiple circuits access simultaneously and can
communicate with high speed.

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• SIGNIFICANCE OF AMSS
Safe, economic and orderly movement of Air traffic
depends largely on an efficient communication system.
The communication system must be able to provide an
accurate and speedy exchange of aeronautical
information, such as, Air Traffic Service (ATS) messages
consists of Flight Plan, Departure and Estimate
messages etc. between stations to enable them to
control the air space and movement of Air traffic in an
orderly manner. With the advent of high speed
aircrafts, increasing number of flights in the airspace
across the continent and the competitive operation of,
Air Traffic managementhas become a difficult task. In
order to facilitate Air Traffic Control the information
available to the Air traffic service personnel should be
fast and accurate. Delayed information can lead to a
disaster, both in the air and ground .To overcome the
above (AFTN) messages is a must as per the ICAO
standards.

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Networking Concepts Used in AMSS
• NETWORK TOPOLOGY
The topology of a network is the, geometric
representation of all the links and linking devices
(usually called nodes) to one another. There are four
basic topologies possible: mesh, star, bus, and ring.
Mesh
In a mesh topology, every device has a dedicated
point-to-point link to every other device. The term
dedicated means that the link carries traffic only
between the two devices it connects.
Topology
Mesh Star Bus Ring

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Advantages:
1. Eliminating the traffic problems.
2. A mesh topology is robust. If one link becomes
unusable, it does not incapacitate the entire system.
3. Privacy or security. When every message travels
along a dedicated line, only the intended recipient
sees it.
Disadvantages:
1. Installation and reconnection are difficult.
2. The sheer bulk of the wiring can be greater than the
available space (in walls, ceilings, or floors) can
accommodate.
3. The hardware required to connect each link (I/O
ports and cable) can be prohibitively expensive.
Star
In a star topology, each device has a dedicated point-
to-point link only to a center controller, usually called a
hub.
Star topology.

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Advantages:
1. A star topology is less expensive than a mesh
topology. 2. It easy to install and reconfigure.
Disadvantages:
1. If hub fails complete NM/ fails which is a main
disadvantage of star topology.
Bus
A bus topology on the other hand, is multipoint. One
long cable acts as a backbone to link all the devices in a
network.
Nodes are connected to the bus cable by drop lines
and taps. A drop line is a connection running between
the device and the main cable.
Advantages:
1. A bus topology include ease of installation.
2. A bus uses less cabling than mesh or star
topologies.
Disadvantages:
1. Difficult to add new devices.

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2. Signal reflection at the taps can cause degradation in
quality.
3. A fault or break in the bus cable stops all
transmission, even between devices on the same side
of the problem.
Ring
In a ring topology, each device has a dedicated point-
to-point connection only with two devices on either
side of it. A signal is passed along the ring in one
direction, from device to device, until it reaches its
destination.
Advantages:
1. A ring is relatively easy to install and reconfigure. Each device is
linked only to it immediate neighbors (either physically or logically).
2. To add or delete a device require changing only two connections.
3. Fault isolation is simplified.
Disadvantages:
1. In a simple ring, a break in the ring (such as a
disabled station) can disable the entire network.

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NAVIGATION
NAVIGATION is the process of reading, and giving guidance
to aircraft or vehicle from one place to another. It is also
the term of art used for the specialized knowledge used by
navigators to perform navigation tasks.
NAVIGAT IONAL AIDS
➢Navigation element of CNS/ATM system is meant to
provide accurate, reliable and seamless position
determination capability to aircrafts.
➢ Navigation is the 'ART' of determining the position of an
aircraft over earth's surface and guiding its progress from
one place to another.
➢ To accomplish this ART, some sort of 'aids' is required
by the PILOTS.
➢ In the twentieth century, electronics also entered in the
Aviation field. Direction finders and other navigational aids
enabled the navigators to obtain 'Fixes' using electronic aids
only. Hence such aids became more and more popular and
came into extensive use.

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TYPES OF NAVIGATION
• GROUND BASED navigation system
• SATELLITE BASED navigation system
GROUND BASED NAVIGATION SYSTEM
Navigation in civil aviation is accomplished by means of
various equipments called NAVIGATIONAL AIDS (NAV-
AIDS)

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Location of Various NAV-AIDS on The Runway
NAVIGATION FACILITIES
 VHF Omni-directional Range(VOR)
 Non-Directional Beacon(NDB)
 Instrument Landing System (ILS)
 Distance Measuring Equipment (DME)
VHF Omni-directional Range (VOR)
It is very high frequency and directional omni-range
equipment which measures the azimuth angle with
respect to the magnetic north. When an aircraft comes
overhead a VOR it gives the pilot the direction it must
move in order to reach the next VOR on the air route
to its destination.

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It is a type of radio navigation system for aircraft.
VORs broadcast a VHF radio signal encoding both the
identity of the station and the angle to it, informing the
pilot in what direction he/she is from the VOR station,
referred to as the radial.
It operates in the VHF band of 112-118 MHz, used as a
medium to short range radio navigational aid. It works
on the principle of phase comparison of two 30 Hz
signals.
There are two types of VOR:
1) Conventional VOR (C-VOR)
2)Doppler VOR (D-VOR)
VHF OMNI-DIRECTIONAL RANGE

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VOR EQUIPMENT PROVIDE ABSOLUTE BEARING
TO AN AIRCRAFT WITH RESPECT TO MAGNETIC NORTH
IRRESPECTIVE OF AIRCRAFT HEADING.
PURPOSES OF VOR
* The main purpose of the VOR is to provide the
navigational signals for an aircraft receiver, which will allow
the pilot to determine the bearing of the aircraft to a VOR
facility.

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* VOR enables the Air Traffic Controllers in the Area
Control Radar (ARSR) and ASR for identifying the aircraft
in their scopes easily. They can monitor whether aircraft are
following the radials correctly or not.
* VOR located outside the airfield on the extended Centre
line of the runway would be useful for the aircraft for
making a straight VOR approach.
* VOR located enroute would be useful for air traffic 'to
maintain their PDRS (PRE-DETERMINED ROUTES) and are
also used as reporting points.
* VORs located at radial distance of about 40 miles in
different directions around an International Airport can be
used as holding VORs for regulating the aircraft for their
landing in quickest time.
Non-Directional Beacon(NDB)
It provides relative bearing to the aircraft with respect
to the direction of NDB equipment irrespective of
aircraft heading.
➢NDB GIVES THE RELATIVE BEARING.
➢ NDB GIVES THE CLOCKWISE ANGLE BETWEEN THE NOSE
OF AN AIRCRAFT AND THE NDB.

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➢ IF ILS IS NOT WORKING THEN NDB CAN DO THE TASK.
Instrument Landing System(ILS)
It is the instrument landing system which helps the
aircraft to land safely.
The Instrument Landing System provides a means
for safe landing of aircraft at airports under
conditions of low ceiling and limited visibility.
The use of the system materially reduces
interruptions of services at airports resulting from
bad weather by allowing operations to continue at
lower weather minimum.

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The function of an ILS is to provide the PILOT or
AUTOPILOT of a landing aircraft with the
guidance to and along the surface of the runway.
It also increases the traffic handling capacity of
the airport under all weather conditions.
This guidance must be of very high integrity to
ensure that each landing has a very high
probability of success.
The basic philosophy of ILS is that ground
installations, located in the vicinity of the runway,
transmit coded signals in such a manner that pilot
is given information indicating position of the
aircraft with respect to correct approach path.
It consist of :
1. Distance Measuring Equipment(DME) - Gives the
slant distance of the aircraft from the runway.
2. Glide Path - Provides vertical guidance to a
landing aircraft.

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 DME equipment co-lated with GLIDE PATH
which provide slant distance of aircraft from
touch down point
3. Localizer - Provides the central line of the runway
to the aircraft.
Here we use logarray antennas,
 Localizer transmits two signals which overlap
at the centre.
 It operates in the VHF band:108MHz to
117MHz.
 The left side has a 90Hz modulation and
right has a 150Hz modulation.
 The overlap area provides the on-track signal.
 Difference in Depth of modulation will align
the aircraft with the runway center line.
4. Marker - Gives fixed distances from runway
threshold and provide height over markers.

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DME
Distance measuring equipment (DME) is a
transponder-based radio navigation technology
that measures slant range distance by timing
the propagation delay of VHF or UHF radio
signals.
Developed in Australia, it was invented by James
"Gerry" Gerrand under the supervision of Edward
George "Taffy" Bowen while employed as Chief of the
Division of Radio physics of the Commonwealth
Scientific and Industrial Research Organisation (CSIRO).
Another engineered version of the system was
deployed by AmalgamatedWireless AustralasiaLimited
in the early 1950s operating in the 200 MHz VHF band.
This Australian domestic version was referred to by the
Federal Department of Civil Aviation as DME (D) (or
DME Domestic), and the later international version
adopted by ICAO as DME.

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DME is similar to secondary radar, except in reverse.
The system was a post-war development of the IFF
(identification friend or foe) systems of World War II.
To maintain compatibility, DME is functionally identical
to the distance measuring component of TACAN.
Timing
SEARCH MODE: 150 interrogation pulse-pairs per
second.
The aircraft interrogates the ground transponder with
a series of pulse-pairs (interrogations) and, after a
precise time delay (typically 50 microseconds), the
ground station replies with an identical sequence of
pulse-pairs. The DME receiver in the aircraft searches
for reply pulse-pairs (X-mode= 12 microsecond

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spacing) with the correct interval and reply pattern to
its original interrogation pattern. (Pulse-pairs that are
not coincident with the individual aircraft's
interrogation pattern e.g. not synchronous, are
referred to as filler pulse-pairs, or squitter. Also, replies
to other aircraft that are therefore non-synchronous
also appear as squitter).
TRACK MODE: less than 30 interrogation Pulse-pairs
per second, as the average number of pulses in
SEARCH and TRACK is limited to max 30 pulse pairs per
second.
The aircraft interrogator locks on to the DME ground
station once it recognizes a particular reply pulse
sequence has the same spacing as the original
interrogation sequence. Once the receiver is locked on,
it has a narrower window in which to look for the
echoes and can retain lock.
Distance calculation
A radio signal takes approximately 12.36 microseconds
to travel 1 nautical mile (1,852 m) to the target and
back—also referred to as a radar-mile. The time
difference between interrogation and reply, minus the

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50 microsecond ground transponder delay, is
measured by the interrogator's timing circuitry and
converted to a distance measurement (slant range), in
nautical miles, then displayed on the cockpit DME
display.
The distance formula, distance = rate * time, is used by
the DME receiver to calculate its distance from the
DME ground station. The rate in the calculation is the
velocity of the radio pulse, which is the speed of light
(roughly 300,000,000m/s or 186,000 mi/s). The time in
the calculation is (total time – 50µs)/2.
Accuracy
The accuracy of DME ground stations is 185 m
(±0.1 nmi).It's important to understand that DME
provides the physical distance from the aircraft to the
DME transponder. This distance is often referred to as
'slant range' and depends trigonometrically upon both
the altitude above the transponder and the ground
distance from it.
For example, an aircraft directly above the DME station
at 6,076 ft (1 nmi) altitude would still show 1.0 nmi
(1.9 km) on the DME readout. The aircraft is technically

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a mile away, just a mile straight up. Slant range error is
most pronounced at high altitudes when close to the
DME station.
Radio-navigation aids mustkeep a certain degree of
accuracy, given by international standards,
FAA, EASA, ICAO, etc. To assure this is the case, flight
inspection organizations check periodically critical
parameters with properly equipped aircraft to calibrate
and certify DME precision.
ICAO recommends accuracy of less than the sum of
0.25 nmi plus 1.25% of the distance measured.
The Radio Frequency and modulation data :
DME frequencies are paired to VHF omnidirectional
range (VOR) frequencies and a DME interrogator is
designed to automatically tune to the corresponding
DME frequency when the associated VOR frequency is
selected. An airplane’s DME interrogator uses
frequencies from 1025 to 1150 MHz. DME
transponders transmit on a channel in the 962 to
1213 MHz range and receive on a corresponding
channel between 1025 and 1150 MHz. The band is
divided into 126 channels for interrogation and 126

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channels for reply. The interrogation and reply
frequencies always differ by 63 MHz. The spacing of all
channels is 1 MHz with a signal spectrum width of
100 kHz.
Technical references to X and Y channels relate only to
the spacing of the individual pulses in the DME pulse
pair, 12 microsecond spacing for X channels and 30
microsecond spacing for Y channels.
DME facilities identify themselves with a
1,350 Hz Morse code three letter identity. If collocated
with a VOR or ILS, it will have the sameidentity code as
the parent facility. Additionally, the DME will identify
itself between those of the parent facility. The DME
identity is 1,350 Hz to differentiate itself from the
1,020 Hz tone of the VOR or the ILS localizer.
.DME operation will continue and possibly expand as
an alternate navigation source to space-based
navigational systems such as GPS and Galileo

44 | P a g e
SURVEILLANCE
The act of watching or monitoring the behaviour,
activities or other changing information, is said to
be Surveillance.
Surveillance is the monitoring of the behavior,
activities, or other changing information, usually of
people for the purpose of influencing, managing,
directing, or protecting them. This can include
observation from a distance by means of
electronic equipment (such as CCTV cameras), or
interception of electronically transmitted
information (such as Internet traffic or phone
calls); and it can include simple, no- or relatively
low-technology methods such as human
intelligence agents and postal interception. The
word surveillance comes from a French phrase for
"watching over" (sur means "from above"
and veiller means "to watch"), and is in contrast to
more recent developments such as sousveillance.
This mainly includes Radar, CCTV and security
equipments.

45 | P a g e
RADAR
RADAR stands for “Radio Detection And Ranging”.
Radar is an object-detectionsystem that uses radio
waves to determine the range, angle, or velocity of
objects. It can be used to detect aircraft,
ships, spacecraft, guided missiles, motor vehicles, weather
formations, and terrain. A radar system consists of
a transmitter producing electromagnetic waves in the
radio or microwaves domain,a transmitting antenna,a
receiving antenna(often the same antennais used for
transmitting and receiving) and a receiver and processor to
determine properties of the object(s). Radiowaves (pulsed
or continuous) from the transmitter reflect off the object
and return to the receiver, giving informationabout the
object's locationand speed.
Radarwas developedsecretly for militaryuse by several
nationsin the period before and during World War II. The
term RADAR was coinedin 1940 by the United States
Navy as an acronym for RAdioDetection And Ranging.The
term radar has since entered English and other languages
as a common noun, losing all capitalization.

46 | P a g e
The modern uses of radarare highly diverse, includingair
and terrestrial traffic control, radarastronomy, air-defence
systems, antimissilesystems, marine radars to locate
landmarks and other ships, aircraft anti-collision
systems, ocean surveillancesystems, outer space
surveillance
and rendezvous systems, meteorological precipitation
monitoring, altimetry and flight control systems, guided
missile target locatingsystems, ground-penetrating
radar for geologicalobservations, and range-controlled
radar for publichealth surveillance.High tech radar
systems are associated with digitalsignal
processing, machine learning and are capableof extracting
useful informationfrom very high noise levels.
A radar system has a transmitter that emits radio
waves called radar signals in predetermined directions.
When these come into contact with an object they are
usually reflected or scattered in many directions. Radar
signals are reflected especially well by materials of
considerable electrical conductivity—especially by most
metals, by seawater and by wet ground. Some of these
make the use of radar altimeters possible. The radar
signals that are reflected back towards the transmitter
are the desirable ones that make radar work. If the
object is moving either toward or away from the
transmitter, there is a slight equivalent change in
the frequency of the radio waves, caused by the Doppler
effect.

47 | P a g e
Radar receivers are usually, but not always, in the same
location as the transmitter. Although the reflected radar
signals captured by the receiving antenna are usually
very weak, they can be strengthened by electronic
amplifiers. More sophisticated methods of signal
processing are also used in order to recover useful radar
signals.
Radar equation
The power Pr returning to the receiving antenna is given by the
equation:
Where
 Pt = transmitter power
 Gt = gain of the transmitting antenna
 Ar = effective aperture (area) of the receiving antenna; this
can also be expressed as , where
 = transmitted wavelength
 Gr = gain of receiving antenna
 σ = radar cross section, or scattering coefficient, of the
target
 F = pattern propagation factor
 Rt = distance from the transmitter to the target
 Rr = distance from the target to the receiver.
In the common case where the transmitter and the
receiver are at the same location, Rt = Rr and the
term Rt² Rr² can be replaced by R4
, where R is the range.
This yields:

48 | P a g e
This shows that the received power declines as the fourth
power of the range, which means that the received power from
distant targets is relatively very small.
Additional filtering and pulse integration modifies the radar
equation slightly for pulse-Doppler radar performance, which
can be used to increase detection range and reduce transmit
power.
The equation above with F = 1 is a simplification for
transmission in a vacuum without interference. The propagation
factor accounts for the effects of multipath and shadowing and
depends on the details of the environment. In a real-world
situation, pathloss effects should also be considered.
Doppler effect
Frequency shift is caused by motion that changes the
number of wavelengths between the reflector and the
radar. That can degrade or enhance radar performance
depending upon how that affects the detection process.
As an example, Moving Target Indication can interact
with Doppler to produce signal cancellation at certain
radial velocities, which degrades performance.
Sea-based radar systems, semi-active radar
homing, active radar homing, weather radar, military
aircraft, and radar astronomy rely on the Doppler effect
to enhance performance. This produces information
about target velocity during the detection process. This
also allows small objects to be detected in an
environment containing much larger nearby slow moving
objects.

49 | P a g e
Doppler shift depends upon whether the radar
configuration is active or passive. Active radar transmits
a signal that is reflected back to the receiver.
Passive radar depends upon the object sending a signal
to the receiver.
Otherthan primary and secondary radar there aai uses
Surface Movement Radar.
Surface Movement Radar (SMR) is used to detect
aircraft and vehicles on the surface of an airport. It is
used by air traffic controllers to supplement visual
observations. It may also be used at night time and
during low visibility to monitor the movement of aircraft
and vehicles. Surface movement radar is the term
accepted by ICAO, but it has historically been known by
other names such a ground movement radar, airport
surface detection equipment (ASDE) and airfield surface
movement indicator.
Security Equipments used are like
1. Hand Held Metal Detector
2. Door Frame Metal Detector
3. X-RAY Baggage Inspection System
4. Explosive Trace Detector
5. Liquid Explosive Detector

50 | P a g e
CONCLUSION
As an undergraduate of the National Institute of Technology Manipur
We would like to say that this training program was an excellent
opportunity for us to get to the ground level and experience the things
that we would have never gained through going straight into a
job. We are grateful to Airports Authority of India for giving us
this wonderful opportunity.
The main objective of the industrial training is to provide an
opportunity to undergraduates to identify, observe and practice how
engineering is applicable in the real industry. It is not only to get
experience on technical practices but also to observe live equipment
and to interact with the staff of AAI. It is easy to work with people,
but not with sophisticated machines. The only chance that an
undergraduate has to have this experience is the industrial training
period. I feel I got the maximum out of that experience. Also I learnt
the way of work in an organization, the importance of being punctual,
the importance of maximum commitment, and the importance of team
spirit. The training included VHF TRANSMITTER-RECEIVER,
VCS, DVR, DATIS, AMMS, ILS.NDB, DVOR, and
SURVEILLANCE. We learned not only through theory classes but
also by practical on live equipments. In our opinion, we have gained
lot of knowledge and experience needed to be in Aviation
communication engineering. As in my opinion, Engineering is after
all a Challenge, and not a Job.
REFERENCE:-
1.wikipedia.
2.AAI Reference books.
3.Training notes.

AAI Report on CNS (winter training)

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