Final report on CNS

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FINAL REPORT
(JULY 2017)
on CIVIL AVIATION
in the field of
COMMUNICATION NAVIGATION & SURVEILLANCE
SUMMER TRAINING 2017
LOKPRIYA GOPINATH BORDOLOI INTERNATIONAL AIRPORT,
GUWAHATI
Submitted to -
THE AIRPORT DIRECTOR
Directorate/Wing: ANS/CNS
HOD: Shri. B.L. YADAV, DGM(CNS)
Coordinator: Shri. M.JAGAN MOHAN RAO, Mgr(Elex)
Submitted by -
GAURAB DUTTA
4th BATCH
DIBRUGARH UNIVERSITY INSTITUTE OF ENGINEERING & TECHNOLOGY

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ACKNOWLEDGEMENT
I wish to express my sincere gratitude to The Airport Director for providing me an
opportunity to do my summer training at L.G.B.I Airport, Guwahati.
I sincerely thank Mr. M.Jagan Mohan Rao (Coordinator) for his guidance and
encouragement in carrying out this report.
I also wish to express my gratitude to the officials and other faculty members of
AAI, Guwahati who rendered their help during the period of my training.
I am very thankful to my institute for arranging and providing us with all the
necessary information regarding the training.
I also thanks to my fellow batch mates and friends for helping and supporting me
throughout the training period.
GAURAB DUTTA

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ABSTRACT
This report presents the thorough study and summery of the topic covered in this
training, conducted by CNS (Communication Navigation & Surveillance)
department of AAI at L.G.B.I Airport, Guwahati.
During this training period, we got the basic ideas of the airport functioning under
which the most important is the communication, navigation and surveillance part.
We also got a brief idea of security equipments installed in the airport, RADAR
functioning, operational lines etc.
The objective of this training is the academic curriculum requirement for
correlation and learning practical implementation of subjective knowledge in Civil
Aviation in the field of Communication, Navigation and Surveillance.
Hence, this report is a brief description of the entire topic studied theoretically and
practically during this training period.
TABLE OF CONTENT

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ABOUT AAI
Airports Authority of India (AAI) was constituted by an Act of Parliament and came into being
on 1st April 1995 by merging erstwhile National Airports Authority and International Airports
Authority of India. The merger brought into existence a single Organization entrusted with the
responsibility of creating, upgrading, maintaining and managing civil aviation infrastructure both
on the ground and air space in the country. It covers 2.8 million square nautical miles area whivh
includes oceanic area of 1.7 million square nautical miles.
1. Air Navigation Services
In tune with global approach to modernization of Air Navigation infrastructure for seamless
navigation across state and regional boundaries, AAI has been going ahead with its plans for
transition to satellite based Communication, Navigation, Surveillance and Air Traffic
Management. A number of co-operation agreements and memoranda of co-operation have been
signed with US Federal Aviation Administration, US Trade & Development Agency, European
Union, Air Services Australia and the French Government Co-operative Projects and Studies
initiated to gain from their experience. Through these activities more and more executives of
AAI are being exposed to the latest technology, modern practices & procedures being adopted to
improve the overall performance of Airports and Air Navigation Services.
Induction of latest state-of-the-art equipment, both as replacement and old equipments and also
as new facilities to improve standards of safety of airports in the air is a continuous process.
Adoptions of new and improved procedure go hand in hand with induction of new equipment.
Some of the major initiatives in this direction are introduction of Reduced Vertical Separation
Minima (RVSM) in India air space to increase airspace capacity and reduce congestion in the air;
implementation of GPS and Geo Augmented Navigation (GAGAN) jointly with ISRO which
when put to operation would be one of the four such systems in the world.
2. Security
The continuing security environment has brought into focus the need for strengthening security
of vital installations. There was thus an urgent need to revamp the security at airports not only to
thwart any misadventure but also to restore confidence of traveling public in the security of air
travel as a whole, which was shaken after 9/11 tragedy. With this in view, a number of steps
were taken including deployment of CISF for airport security, CCTV surveillance system at
sensitive airports, latest and state-of-the-art X-ray baggage inspection systems, premier security
& surveillance systems. Smart Cards for access control to vital installations at airports are also
being considered to supplement the efforts of security personnel at sensitive airports.

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3. Aerodrome Facilities
In Airports Authority of India, the basic approach to planning of airport facilities has been
adopted to create capacity ahead of demand in our efforts. Towards implementation of this
strategy, a number of projects for extension and strengthening of runway, taxi track and aprons at
different airports has been taken up. Extension of runway to 7500 ft. has been taken up to
support operation for Airbus-320/Boeing 737-800 categories of aircrafts at all airports.
4. Functions of AAI
The functions of AAI are as follows:
 Design, Development, Operation and Maintenance of international and domestic airports
and civil enclaves.
 Control and Management of the Indian airspace extending beyond the territorial limits of
the country, as accepted by ICAO.
 Construction, Modification and Management of passenger terminals.
 Development and Management of cargo terminals at international and domestic airports.
 Provision of passenger facilities and information system at the passenger terminals at
airports.
 Expansion and strengthening of operation area, viz. Runways, Aprons, Taxiway etc.
 Provision of visual aids.
 Provision of Communication and Navigation aids, viz. ILS, DVOR, DME, Radar etc.
5. Airports in India
 Total – 125
 International – 18
 Domestic Airports – 78
 Custom Airports – 08
 Civil Enclaves – 26
 Air Navigation Services - 2.8 Million Square Nautical Miles of Air Space.
 AAI Handles Aircrafts Movements More Than 15,36,60000 During Last Year
[International 335.95 & Domestic 1200.65], Passengers handled 168.91 Million
[International 46.62 & Domestic 122.29] and the cargo handled 2279.14 thousand MT
[International 1443.04 & Domestic 836.10].

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6. AAI Infrastructure
 AIR NAVIGATION SERVICES
 ENGINEERING: CIVIL/ELECTRICAL
 FINANCE
 HUMAN RESOURCE
 OPERATIONS
 PLANING
 VIGILANCE
 FIRE SERVICE
 AVIATION SAFETY
 COMMERCIAL
7. Different Regions of AAI
 NORTHERN REGION - Headquarter at DELHI
 EASTERN REGION – Headquarter at KOLKATA
 WESTERN REGION – Headquarter at MUMBAI
 SOUTHERN REGION – Headquarter at CHENNAI
 NOTH-EASTERN REGION – Headquarter at GUWAHATI
8. Airports under North-Eastern Region
1. GUWAHATI
2. AGARTALA
3. DIBRUGARH
4. LENGPUI
5. LILABARI
6. TEZPUR
7. DIMAPUR
8. IMPHAL
9. SILCHAR
10. TEZU
11. BARAPANI
12. JORHAT

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AIR NAVIGATION SERVICE
An air navigation service provider (ANSP) is a public or a private legal entity providing Air
Navigation Services. It manages air traffic on behalf of a company, region or country. Depending
on the specific mandate an ANSP provides one or more of the following services to airspace
users:
 Air Traffic Management/Control (ATM/ATC)
 Communications, navigation and surveillance systems (CNS)
 Meteorological service for air navigation (MET)
 Search and rescue (SAR)
 Aeronautical information services/aeronautical information management (AIS/AIM).
These services are provided to air traffic during all phases of operations (approach, aerodrome
and en-route).
Air navigation services is the term applied to the bundle of services provided to aircraft to enable
safe and efficient flight from one destination to another.
Air Traffic Control service
Air traffic control service is a service provided by licensed ATCOs for the purpose of:
 preventing collisions:
o between aircraft, and
o on the maneuvering area between aircraft and obstructions; and
 expediting and maintaining an orderly flow of air traffic.
Phases of Flight:
 Departure
 En-Route
 Arrival
Communication, navigation and surveillance service
Communication, navigation and surveillance service is the technical backbone of the Air Traffic
Management system. It is responsible for planning, installing and maintaining the technical
systems used by ATCOs to provide air traffic.
The communication service is responsible for the voice and data communication systems used
for air-ground communication between pilots and ATCOs and communication between ATC
units and other relevant stakeholders.

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The navigation service is responsible for the ground installed navigation equipment which
facilitates the efficient and safe navigation of aircraft in the air. These equipment continuously
transmit radio signals which help aircraft determine their location in space regardless of the
weather conditions. Navigation equipment is critical especially for Instrument Landing Systems
(ILS) which enables aircraft to land based solely on signals transmitted by such equipment.
The surveillance service is responsible for surveillance systems which provide ATCOs with a
visual overview of the aircraft flying in the airspace under their control. The traditional
surveillance systems such as primary and secondary radar systems are still the most widely used
systems by air navigation service providers. However, more recent surveillance systems which
rely on satellite signals, such as ADS-B and MLAT, are increasingly being deployed in European
airports.
Meteorological service
The meteorological service provides aeronautical weather information to airspace users, ATC
units and other relevant stakeholders. They provide both weather observation reports such as
METAR, SPECI, etc., and weather forecast reports such as TAF and SIGMET. The
meteorological service also provides warnings and other significant meteorological information
concerning meteorological conditions that may affect flights on the ground, airport facilities,
airport services, and safe flight services on the runway.
Search & Rescue
Search and rescue (SAR) is the search for and provision of aid to people who are in distress or
imminent danger. The general field of search and rescue includes many specialty sub-fields,
typically determined by the type of terrain the search is conducted over.
Aeronautical information service (AIS)
The aim of the aeronautical information service (AIS) is to ensure the flow of aeronautical
information/data necessary for safety, regularity, economy and efficiency of international air
navigation. AIS is responsible for collating/assembling, editing, formatting, publishing and
distributing aeronautical data to pilots, ATC units and other stakeholders. The aeronautical data,
depending on the nature of the information, is published and distributed via these main
documents:
 Aeronautical Information Publication (AIP)
 Notice to Airmen (NOTAMs)
 Aeronautical Information Circulars (AIC)
 Pre-flight Information Bulletins (PIB)

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COMMUNICATION NAVIGATION AND
SURVEILLANCE (CNS)
Communication, Navigation and Surveillance are three main functions which constitute the
foundation of Air Traffic Management (ATM) infrastructure. Communication, Navigation and
Surveillance system for Air Traffic Management uses various systems including satellite system,
varying levels of automation to achieve a seamless global Air Traffic management system.
Functionality of CNS:
 COMMUNICATION involves exchange of voice and data information between ACFT
and ATS
 NAVIGATION enables the pilot in pinpointing the location of the ACFT
 SURVEILLENCE assists air traffic controller in pinpointing the position of the ACFT at
any time.
Various services provided by CNS:
 Aeronautical mobile service
 Aeronautical radio navigation service
 Aeronautical fixed service
 Aeronautical information service
 Aeronautical broadcast service
CNS WING
COMMUNICATION NAVIGATION SURVEILLANCE

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COMMUNICATION
Communication is the exchange of voice and data information between the pilot and air traffic
controllers or flight information centers.
Need for Communication:
During flight the pilot
 May seek authorization for flight maneuvers
 Requires weather conditions
 Questions the operational status of the navigational aids
 Requires traffic information
To achieve smooth functioning of all services an uninterrupted communication system is
required.
Forms of Communication:
• Voice Communication in the form of RADIO TELEPHONY (VHF R/T, HF R/T etc) for
Air-Ground Connectivity.
• Various forms of Telecommunication for ground-to-ground connectivity.
• Data communication involving computer Networks
• Satellite Communication
Voice Communication using Radio Telephony:
There are mainly two types of Radio telephony used in aviation sector, namely:
 VHF (Very High Frequency).
 HF (High Frequency)
Characteristics of VHF Communication:
 Frequency Range: 30 MHz to 300 MHz
 Suitable for Air to Ground Communication (AMS – Air Mobile Service).
 Follows straight line of sight.
 Modulation technique used is Amplitude Modulation.
Characteristics of HF Communication:
 Frequency Range: 3MHz to 30MHz.
 Suitable for Ground to Ground Communication (AFS – Air Fixed Service).
 Signals get reflected, refracted & deflected through different layers of the atmosphere.

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Frequency Range distribution:
 3KHz to 300GHz – Radio Frequency.
 108MHz to 137MHz - Civil Aviation (ARNS – Aeronautical radio navigation service).
 88MHz to 108MHz - FM Radio.
 108MHz to 112MHz – Instrument Landing System (ILS).
 108MHz to 117.95MHz – Doppler Very High Frequency Range (DVOR).
 118MHz to 137MHz – Voice Communication (AMS – Aeronautical Mobile Service)
 960MHz to 1215MHz – Distance Measuring Equipment (DME).
 190KHz to 1750KHz – Non-Directional Beacon (NDB).
VERY HIGH FREQUENCY (VHF)
The VHF (very high frequency) range of the radio spectrum is the band extending from
30 MHz to 300 MHz. The wavelengths corresponding to these limit frequencies are 10 meters
and 1 meter.
In the VHF band, electromagnetic fields are affected by the earth's ionosphere and troposphere.
Ionospheric propagation occurs regularly in the lower part of the VHF spectrum, mostly at
frequencies below 70 MHz. In this mode, the communication range can sometimes extend over
the entire surface of the earth.
The VHF band is popular for mobile two-way radio communication. A great deal
of satellite communication and broadcasting is done at VHF. Wideband modulation is used by
some services; the most common example is fast-scan television broadcasting. Channels and
subbands within the VHF portion of the radio spectrum are allocated by the International
Telecommunication Union (ITU).
Significance of VHF in AAI:
A network of VHF ground radio stations ensure that aircraft can communicate with ground end
systems in real time, practically from anywhere in the world. VHF communication is line of
sight propagation and provides communication with ground based transceivers (often referred to
as remote ground stations). The typical range depends on altitude, with a 200 miles transmission
range common at high altitudes. Thus VHF communication is only applicable over land masses
which have a VHF ground network installed. A pilot wants to inform his flight operations
department that departure has been delayed by air traffic control. The pilot loads from the
communication management unit a multifunction control display unit screen that allows him to
enter the expected length of and region for the delay. The control display unit generates a digital
message containing the delay information. This message may include such information as
aircraft registration number, the origination and destination airport codes, the current estimated
time of arrival before the delay, and the current expected duration of delay. The communication

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management unit then sends the message to an existing radio (HF, satellite communication or
VHF, with the selection of the radio based on special logic contained within the communication
management unit). For a message to be sent over the VHF network, the radio transmits the VHF
signal containing the delay message, which is then received by a VHF remote ground station. Air
traffic control messages are used to communicate between the aircraft and air traffic control. In a
nutshell, VHF is used in AAI for communication between the pilot and the air traffic controllers
(ATC) as mobile communication is not possible in this stratosphere layer.
VHF Transmitter & Receiver:
VHF AM Transmitter
VHF AM Receiver
Transmitters & Receivers used in AAI are:
 PYE
 ECIL
 OTE
 PAE

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HIGH FREQUENCY (HF)
HFRT communication is the acronym of high frequency radio Tele Communication. When
aircraft crosses 200 NM radius from the aerodrome, one of the ways of communication is HFRT
communication. It is a distant communication. Unlike VHF, it’s not dependent on line of sight
(LOS) & it uses sky wave. Hence distance communication is possible through HFRT. Mainly it
is used in oceanic region where there is no way to make communication through VHF frequency
range.
It is operated in two modes:
 MWARA: Major World Air Route Area (It is used for International Flight)
 RDARA: Regional Domestic Air Route Area (It is used for Domestic Fights)
HFRT is very noisy because transmission is done using ionospheres reflection. The difference in
elevation levels that can be assigned to flight in the same direction is 1000 ft and in opposite
direction it is 2000 ft. Minimum horizontal separation between any two aircrafts is 10 NM.
HF Receiver:

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AMSS (AUTOMATIC MESSAGE SWITCHING SYSTEM)
AMSS - Automatic Message Switching System - is the integrated Vitrociset solution for
switching ATS messages over AMHS, AFTN and CIDIN networks.
The AMSS system operates in accordance with the "store and forward" principle and in
accordance with the ICAO reference recommendations.
The architecture is fault tolerant, in master / hot-stand-by configuration.
Each critical component is redundant and, in case of malfunction, the twin element switch is
automatic. The system is configured on a Linux / Intel platform with Oracle data base.
 AFTN – A worldwide system of aeronautical fixed circuits provided, as part of the
aeronautical fixed service, for the exchange of messages and/or digital data between
aeronautical fixed stations having the same or compatible communication characteristics.
FLIGHTPLAN (FPL)

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The figure above shows the International Flight Plan registration form. The main information
provided in the flight plan is as follows:
• 7 letter Aircraft Identification Code
• Flight Rules - I (IFR), V (VFR) or Y (Both)
• Type of Flight – N (Non Scheduled), S (Scheduled) or M (Military)
• Number – Denotes number of aircraft (1 for normal flights, more for formation flights)
• Type of Aircraft – Boeing (B737), Airbus (A320, A380), ATR flights (AT72), etc.
• Wake/Turbulence Category – L (Light, less than 7000Kg), M(Medium, 7000-136000Kg)
or H(Heavy, greater than 136000Kg)
• Equipment – N (NDB), V (DVOR), I (ILS), etc.
• Departure Aerodrome (4 letter Airport Identification Code)
• Time – Time of departure in GMT
• Cruising Speed (expressed in Nautical Miles per hour)
• Level – Denotes flight level or the altitude
• Route – The full route from source to destination, via all the major airports
• Destination Aerodrome (4 letter Airport Identification Code)
• Estimated time to reach destination aerodrome
• 1st alternate aerodrome
• 2nd alternate aerodrome
NOTAM
NOTAM is quasi-acronym for “Notice to Airmen”. NOTAMs are created & transmitted to all
airport operators under guidelines specified by Annex 15.
Aeronautical Information Services of the Convention on International Civil Aviation (CICA)
specified the term NOTAM for more formal notice to airman following the ratification of CICA,
which came into effect on 4th April, 1947.
Previously NOTAM from a particular airport was published after a specific time. Due to various
developments of AAI now-a-days it is possible to automatically update the information i.e.
NOTAM to pilots.
NOTAM is issued (and reported) for a numbers of reasons following:
• Hazards such as air-shows, parachute jumps, kite flying etc.
• Flights by important people such as heads of state (Terminal Flight Restrictions, TFRs).
• Closed runways.
• Inoperable radio navigational aids.
• Military exercises with resulting airspace restrictions.

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• Inoperable light on tall obstructions.
• Temporary erection of obstacles near airfields.
• Passages of flocks of birds through airspace (a NOTAM in this category is known as
BIRDATM).
• Notifications of runway/taxiway/apron status with respect to snow, ice & standing water
(SNOWTAM).
• Notification of an operationally significant change in volcanic ash or other dust
contamination (an ASHTAM).
• Software code risk announcements with associated patches to reduce specific
vulnerabilities.
• Aviation authorities typically exchange NOTAMs over AFTN circuits.
Priority list of messages:
1. SS – Distress message (maximum priority)
2. DD – Urgency message
3. FF – Flight plans
4. GG – NOTAM
5. KK – Administrative message (minimum priority)
 AFTN – Dedicated Network for Aviation all over the world.
 FIC no. & ADC no. – Specific number provided by military personals to every flight.
List of some Equipment in Equipment Room:
 VHF Transmitter & Receiver. (Range of VHF is up to 200 Nautical Miles)
 DATIS – Data Link Airport Terminal Information System
It broadcasts some necessary information like change in whether, air traffic etc.
repeatedly in a particular interval of time to all the aircrafts in its range.
o Range of DATIS in Guwahati – 126.6 Nautical Miles.
o Frequency used – 126.6 MHz (Domestic) & 126.4 MHz (International).
 VCS – Voice Communication System.
 RCAG – Remote Control Air to Ground system.
It is used to overcome the limitations of VHF, in case of any obstacle in the line
of sight. Also known as extended VHF.
 DDR – Voice Recorder.
 GPS master clock.

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8 important frequencies of Civil Aviation:
The VHF communication in Civil Aviation is a vast field of communication. So it is been
divided into different sectors for the convenience of the air traffic controller and the pilot
according to the range or distance from the airport with each sector provided with a dedicated
frequency. The sectors are listed below:
1. Area Control:
o Frequency – 120.5 MHz,
o Range – 200 NM
2. Approach:
o Frequency – 123.9 MHz
o Range – 70 NM
3. Tower:
o Range – 20 NM
4. SMC (Surface Movement Control):
o Range – Airport (Runway, Taxiway, Apron)
5. Emergency Frequency – 121.5 MHz (Same all over India)
6. Standby Frequency – 127.95 MHz
7. Search and Rescue – 123.1 MHz
8. DATIS (Data Link Airport Terminal Information System):
o Frequency – 126.6 MHz (Domestic)
126.4 MHz (International)
VHF Sectors:

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OPERATIONAL LINES
Operational lines are the medium of transmission of voice and data messages from one station to another
station. It is a point to point ground communication system. In navigation, ATC pass estimate instantly
through telephone because of time factor.
Types of transmission channel:
1. Wired
2. Wireless
WIRED WIRELESS
 Twisted pair
 Co-axial cable
 Optical fiber
 Arm filled jelly wire
Operational Telephone
STD HOTLINE Dial up circuit MLLN MPLS Satellite phone EPABX
NON-STD
FAX ATC IM
WLL
CORDLESS AHCR AT DATA SPEECH
[RCAG]
S&R MN
Emergency LB
KU (Silchar)
Tx CHANNEL Rx

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 STD – It stands for Subscribe Trunk Dialing. STD is used for long distance
communication. NON-STD is for short distance.
 HOTLINE – It is a point to point communication that automatically connects for
emergency services.
Functions of HOTLINE:
i. Call transferring.
ii. Call forwarding.
iii. Conference call.
iv. Automatic redial voice mail.
v. Call back, etc.
 MLLN – It is the Manage Leased Line Network. Leased line is a highly secured
dedicated communication facility that is available all the time.
Applications of MLLN:
i. Speech circuit: Dedicated telecom link for speech say hotline for voice between
two different locations is stabilized by local or long distance telecom site without
dialing facility.
ii. Data circuit: Dedicated long distance point to point or point to multipoint data
circuit at different speed, namely nx64 Kbps upto 2 Mbps bandwidth.
 MPLS – It is the acronym of Multiprotocol Level Switching. It is based on OSI model.
 EPABX – It stands for electronic private automatic branch exchange. It serves as
particular business or office. It is a switching system which has both internal and external
switching functions. It has a powerful microprocessor inbuilt in it.
 Satellite phone – It is a phone that connects to orbiting satellite instead of terrestrial cell
site. Functions of satellite phone are voice mail, SMS, voice call, low bandwidth internet
etc.
 RCAG – Remote Communication Air to Ground is used to extend the range of VHF in
case of any obstacle in the line of sight of VHF. The VHF-RCAG Coverage in India is
shown in the figure below.

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NAVIGATION
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.
Navigational Aids used in AAI:
 ILS – Instrument Landing System
 DVOR – Doppler VHF Omni-directional Radio range
 DME – Distance Measuring Equipment
 NDB – Non-Directional Beacon
ILS (INSTRUMENT LANDING SYSTEM)
It is a standard international Civil Aviation Organization (ICAO) precision landing aid that is
used to provide accurate azimuth and descent guidance signals for guidance to aircraft for
landing on the runway under normal or adverse weather conditions. ILS facility is a highly
accurate and dependable means of navigation to the runway in IFR conditions. The ILS provides
the lateral and vertical guidance necessary to fly a precision approach. When all components of
the ILS systems are available, including the approved approach procedure, the pilot may execute
a precision approach.
The components of ILS are:
1. Localizer
2. Glide path
3. Marker Bacons
4. LPDME (Low Power Distance Measuring Equipment)
ILS Parameter ILS Component
a. Azimuth Approach Guidance Provided by Localizer
b. Elevation Approach Guidance Provided by Glide Path
c. Fixed Distances from Threshold Provided by Marker Beacons
d. Range from touchdown point Provided by DME

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The ILS consists of:
Localizer of ILS:
 Angle of Glide Path - 3° ± 0.5
 GP Antenna – M-array Antenna
 Clearance Zone – 17 NM from Runway
 Course Zone – 25 NM from Runway

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Location of ILS Components:
Localizer: The primary component of the ILS is the localizer, which provides the lateral
guidance. The transmitter and antenna (Shown above) are on the centerline at the opposite end of
the runway from the approach threshold.
Glide Path: The glide path component of ILS provides vertical guidance to the pilot during the
approach. Glide path is located 750 to 1,250 feet (ft) down the runway from the threshold, offset
400 to 600 ft from the runway centre line.
Markers:-
(i) Outer marker; (OM): The outer marker (if installed) is located 3 1/2 to 6 NM from the
threshold within 250 ft of the extended runway centerline to provide the pilot with the ability to
make a positive position fix on the localizer.

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(ii) MIDDLE MARKER (MM): The middle marker ( if installed) is located approximately 0.5
to 0.8 NM from the threshold on the extended runway centerline. The middle marker crosses the
glide slope at approximately 200 to 250 ft above the runway elevation.
DME: Distance Measuring Equipment (DME) is normally collocated with glide path and
provides slant distance to the aircraft with respect to touch down point.
The approach lighting system: Various runway lighting systems serve as integral parts of the
ILS system to aid the pilot in landing. Any or all of the following lighting systems may be
provided at a given facility: approach light system (ALS), sequenced flashing light (SFL),
touchdown zone lights (TDZ) and centerline lights (CLL-required for Category II & III
operations.)
RUNAWAY VISUAL RANGE (RVR): In order to land, the pilot must be able to see
appropriate visual aids not later than the arrival at the decision height (DH) or the missed
approach point (MAP).
DVOR (DOPPLER VHF OMNI-DIRECTIONAL RADIO RANGE)
DVOR is a standard international Civil Aviation Organization (ICAO) ground based radio
navigational aid that provides bearing information to aircraft to define air traffic control routes
for en-route, terminal and instrument approach/departure procedures. DVOR when collocated
with DME provides both the angle and slant distance of aircraft with respect to ground station.
VORs broadcast a VHF radio signal encoding both the identity of the station and the angle to it,
telling the pilot in what direction he lies from the VOR station, referred to as the radial.
Uses of DVOR:
 Homing
 Holding (go-around)
 En-routing
Principle of DVOR:
It works on the principle of phase comparison of two 30Hz signals (AM & FM) i.e. an aircraft
provided with appropriate receiver, can obtain its radial position from the range station by
comparing the phases of the two 30Hz sinusoidal signals obtained from the VOR radiation.
Types of DVOR:
 Terminal DVOR (12000 ft, 25NM) – used for holding
 Low Altitude DVOR (14000 ft, 40 NM)
 High Altitude DVOR (60000 ft, 130NM) – generally used DVOR

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Navigation Fix
 VOR's use as a navigation aid is based on the principles of Rho-Theta Navigation
System.
 The Rho-Theta Navigation System is based on the Polar coordinate system of azimuth
and distance.
 The VHF Omni Range (VOR) and DME constitute the basic components of the Rho-
Theta Navigation System.
 VOR provides azimuth information (Theta) to the pilot; DME provides the distance
information (Rho). Pilot receives a continuous navigational fix relative to a known
ground location.
DVOR Site:
DVOR uses Alford loop Antenna. It consists of 48 sideband antenna and one centre antenna. The
48 sideband antennas are used to achieve the FM signal by Doppler Effect and the centre antenna
gives the AM signal. The phase difference between the AM and FM signal gives the direction of
the DVOR station.

26
 Frequency range of DVOR – 108 MHz to 117.95 MHz
 Bearing Angle – Angle made by the aircraft with the magnetic north.
 High power DME (HPDME) is placed with DVOR.
 Cone of Confusion as shown in the figure below is the region above the DVOR station
where the aircraft doesn’t receive DVOR signal. Another small DVOR is installed at a
distant area to overcome cone of confusion.
DME (DISTANCE MEASURING EQUIPMENT)
DME is a standard international Civil Aviation Organisation (ICAO) ground based radio
navigation aid that provides slant distance information to aircraft with respect to ground station
to define air traffic control routes for en-route, terminal and approach/departure procedures.
DME is normally collocated with DVOR or ILS/Glide Path and sometimes with NDB also.
 Allotted DME frequency – 960 MHz to 1215 MHz
 Critically Used DME frequency – 962 MHz to 1213 MHz
 Total DME Channel – 252 (126 for interrogation & 126 for reply)
Principles of Operation of DME:
The operating principle of DME systems is based on the Secondary Radar principle. The time
required for a radio pulse signal to travel to a given point and return. The only difference in the
operating principle of a RADAR and a DME is that, in case of Secondary RADAR, the
interrogator is placed on ground station and the transponder is in air whereas in case of DME, the
interrogator is in air and the transponder is on ground; i.e., the DME is the transponder and the
aircraft is the interrogator, which is just opposite to RADAR.

27
Block Diagram of DME system:
Range Calculation:
The range, in nautical miles, between the aircraft and the transponder is obtained by the simple
formula:
Total time (μsec) – Time Delayed (μsec)
Range = ----------------------------------------------------------
12.36
The denominator 12.36 μsec is the time taken by the pulse to travel 1 nautical mile to and fro.
This time is also called Radar Mile.
DME Antenna:

28
NDB (NON-DIRECTIONAL BEACON)
NDB is a standard international Civil Aviation (ICAO) ground based radio navigational aid.
NDB are used by aircraft to help obtain a fix of their geographic location on the surface of the
earth. NDBs are also most commonly used as “locators” for an ILS approach and standard
approaches.
 NDB frequency range – 190 KHz to 1750 KHz
 NDB has Amplitude Modulation, Ground wave propagation & vertical polarization.
 NDB gives relative Bearing.
 Unlike VOR & DME, NDB is not a line of sight communication
 Range of NDB beyond line of sight communication is upto 1000 km.
Uses of NDB:
 Holding
 Homing
 Weather Forecast
 Back-up to VHF
Types of NDB:
 Low Power NDB: 10 to 15 watt (used for Landing)
 Medium Power NDB: 500 watt (maximum use)
 High Power NDB: 1000 watt
NDB Antenna:
 Symmetrical T-type antenna
o Advantage – i. More efficient
ii. Can transmit high power
o Disadvantage – Maintenance cost is high
 Tower antenna (self radiating mast)
o Advantage – Maintenance cost is low
o Disadvantage – i. Less efficient
ii. Cannot transmit high power

29
SURVEILLANCE
SURVEILLANCE assists air traffic controller in pinpointing the position of the ACFT at any
time. The surveillance system can be divided into two types: Dependent and independent. In
dependent surveillance system, aircraft position is determined on-board and then transmitted to
ATC. Independent surveillance system is a system which measures aircraft position from ground.
Current surveillance is based on either voice position reporting or based on RADAR (Primary
surveillance radar (PSR) or secondary surveillance radar (SSR)).
RADAR (RAdio Detection And Ranging)
RADAR is an object detection system that uses radio waves to determine the range, angle, or
velocity of objects. RADAR is basically a means for gathering information about distant objects
called “targets” by sending electromagnetic waves at them and analyzing the returns called the
“echoes”. The term RADAR was coined in 1940 by United States Navy as an acronym for
RAdio Detection And Ranging or RAdio Direction And Ranging.
Classification of RADAR:
1. Primary RADAR:
Primary radar (PSR Primary Surveillance Radar) is a conventional radar sensor that
illuminates a large portion of space with an electromagnetic wave and receives back the
reflected waves from targets within that space. The term thus refers to a radar system
used to detect and localize potentially non-cooperative targets.
This type of radar uses low vertical resolution antenna but good horizontal resolution. It
quickly scans 360 degrees around the site on a single elevation angle. It can thus give the
distance and radial speed of the target with good precision but requires often one or more
radars to obtain the vertical position and the actual speed.
The advantages of the primary radar are no on-board equipment in the aircraft is
necessary for detecting the target and can be used to monitor the movement of vehicles
on the ground.
The disadvantages are that the target and altitude cannot be identified directly. In
addition, it requires powerful emissions which limit its scope.

30
2. Secondary RADAR:
Secondary surveillance radar (SSR) is a radar system used in air traffic control (ATC)
that not only detects and measures the position of aircraft i.e. bearing, but also requests
additional information from the aircraft itself such as its identity and altitude.
Unlike primary radar systems that measure the bearing of targets using the detected
reflections of radio signals, SSR relies on targets equipped with a radar transponder that
replies to each interrogation signal by transmitting a response containing encoded data.
SSR is based on the military identification friend or foe (IFF) technology originally
developed during World War II, therefore the two systems are still compatible.
 Up-Link of Secondary RADAR: 1030 MHz
 Down-Link of Secondary RADAR: 1090 MHz
ADS-B (AUTOMATIC DEPENDENTSURVEILLANCE-BROADCAST)
ADS-B is a surveillance technology in which an aircraft determines its position via satellite
navigation and periodically broadcast it, enabling it to be tracked. The information can be
received by air traffic control ground stations as a replacement for secondary radar. It can also be
received by other aircraft to provide situational awareness and allow self separation.
ADS-B is “Automatic” in that it requires no pilot or external input. It is “Dependent” in that it
depends on data from aircraft navigation system.

31
The Airports Authority of India (AAI), first commissioned German company Comsoft to install
ADS-B ground stations at 14 airport sites nationwide in 2012. Comsoft finished installing seven
new ADS-B ground stations under a second phase of deployment which India subsequently
integrated into its ATC system in 2014, thus completing its ground network for automatic
dependent surveillance-broadcast (ADS-B) tracking of aircraft.
Purpose of use:
 Installing ADS-B ground stations to provide surveillance redundancy where Radar
coverage exists.
 Filling surveillance gaps where surveillances coverage is not possible due to high terrain
and remote areas.
Components of ADS-B are:
 LAN
 CTS (Common time server)
 RDCU (Radar data compressor unit)
 FDP (Flight data processor)
 SDP (Surveillance data processor)
 SNET (Safety Network)
 DRF (Data recording facility)
 Neptune server
 CMD (Control and monitoring display)
 CWP (Control word position)
Theory of Operation:
The ADS-B system has three main components: 1) ground infrastructure, 2) airborne component,
and 3) operating procedures.
 A transmitting subsystem that includes message generation and transmission functions at
the source; e.g., aircraft.
 The transport protocol; e.g., VHF (VDL mode 2 or 4), 1090ES, or 978 MHz UAT.
 A receiving subsystem that includes message reception and report assembly functions at
the receiving destination; e.g., other aircraft, vehicle or ground system.
The source of the state vector and other transmitted information as well as user applications are
not considered to be part of the ADS-B system.
Benefits of ADS-B:
 It is cost efficient alternative for secondary surveillance radar (SSR)
 It is more efficient and provides high performance.
 It is compact, requires minimum power, has no RF emissions and can be easily installed.

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SECURITY EQUIPMENTS
Civil aviation security exists to prevent criminal activity on aircraft and in airports. Criminal
activity includes acts such as hijacking, damaging or destroying aircraft and nearby areas with
bombs, and assaulting passengers and aviation employees.
OBJECTIVES OF SECURITY CHECKS:
• Prevent attacks on airports or aircraft.
• Prevent accidents and fatalities due to transport of hazardous materials.
• Ensure safety and security of passengers.
Security Equipments used in Airport:
1. CCTV (Close Circuit Television)
2. HHMD (Hand Held Metal Detector)
3. DFMD (Door Frame Metal Detector)
4. ETD (Explosive Trace Detector)
5. X-ray

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