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FREQUENTLY ASKED QUESIONS

CARGO CNS ENGINEERING

FIRE GAGAN GENERAL

SECURITY VIGILANCE

Communication, Navigation and Surveillance

1. What is CNS?

Communication, Navigation and Surveillance are three main

functions (domains) which constitute the foundation of Air Traffic

Management (ATM) infrastructure.

The following provide further details about relevant domains of CNS:

(a) Communication:- Communication is the exchange of voice and

data information between the pilot and air traffic controllers or flight

information centres.

(b)Navigation:-Navigation Element Of CNS/ATM Systems Is meant

To provide Accurate, Reliable And Seamless Position Determination

Capability to aircrafts.

(c)Surveillance:-The surveillance systems can be divided into two

main types:- Dependent surveillance and Independent surveillance.

In dependent surveillance systems, aircraft position is determined onboard and then transmitted to ATC. The current voice position

reporting is a dependent surveillance systems in which the position of

the aircraft is determined from on-board navigation equipment and

then conveyed by the pilot to ATC. Independent surveillance is a

system which measures aircraft position from the ground. Current

surveillance is either based on voice position reporting or based on

radar (primary surveillance radar (PSR) or secondary surveillance

radar (SSR)) which measures range and azimuth of aircraft from the

ground station.

2. What is CNS/ATM system?

CNS/ATM stands for Communications, Navigation and SurveillanceSystems for Air Traffic Management. The system uses various

systems including satellite systems, and varying levels of automation

to achieve a seamless global Air Traffic Management system.

3. Who is responsible for making regulations, procedures and

issuing directions covering the Aeronautical Telecommunication

facilities (I.e. CNS/ATM Automation facilities) in India?

The DGCA (Web site ?dgca.nic.in?) is the designated agency of

Govt. of India under the Ministry of Civil Aviation for making

regulations, procedures and issuing directions covering the

Aeronautical Telecommunication facilities (I.e. CNS/ATM Automation

facilities) . Their instructions are to be complied with both by the Air

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Navigation Service Provider (ANSPs), airlines and the airports.

4. Where one can find information about regulatory

requirements like Civil Aviation Requirements (CARs) etc. about

Aeronautical Telecommunication facilities (I.e. CNS/ATM

Automation facilities) in India?The information is available on DGCA Web site ?dg ca.nic.in?.

5. Who is responsible for providing Aeronautical

Telecommunication facilities (CNS/ATM facilities/Infrastructure)

in India?

Airports Authority of India (AAI) is responsible for providing CNS/ATM

services in India.

6. Who looks after

the Aeronautical

Telecommunication

facilities (I.e.CNS/ATM

Automation

systems)

infrastructure in

AAI?

The Departments of

CNS acts as the

nodal agency in AAI

to carry out its

designated functions

of looking after

AeronauticalTelecommunication

facilities (I.e.

CNS/ATM

Automation systems)

in AAI.

TOP

7. What are the different CNS Departments in AAI?

CNS Departments in AAI are:-

(a) CNS-Operation and Maintenance ( CNS- O&M)

(b) CNS- Planning (CNS- P)

(c) Flight Inspection Unit & Radio construction and Development

Units ( FIU & RCDU)

8. What are the functions/job profiles of the Dte. of CNS-OM in

AAI?

Directorate of CNS-Operation & Maintenance [CNS-OM] at CHQ is

headed by Executive Director [CNS-OM]. ED [CNS-OM] reports to

Member [ANS].Broad functions/job profile of CNS-OM Department is as given below:

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1. The Communication, Navigation, Surveillance and ATM Data

Processing systems are the backbone for provision of Air Traffic

Services for safe and smooth operation of Aircraft at Airports and in

Indian airspace. CNS-OM Directorate ensures provision of these

facilities for their serviceability, reliability and integrity as per Standard

and Recommended practices of ICAO, Civil Aviation Requirements

(CARs) promulgated by DGCA, to support CNS/ATM system for

continental and Oceanic airspace managed by India as mentioned

above. CNS-OM Dept also have the responsibility for maintenance

and operation of security systems (i.e. CCTV, XBIS, DFMD, HHMD,

ETD etc.)_and passenger facilitation system (i.e Flight Information

Display system, PA system etc.) installed at all the airports which are

managed by AAI. The security systems are maintained as per BCAS

guidelines.

2. CNS-OM Dept by framing maintenance policies and supervision

systems delivers system management, maintenance

standards/instructions and maintenance services to assure and

ensure Serviceability, Availability and Reliability of systems asmentioned above.

3. Provision of Aeronautical Mobile Services, Aeronautical Fixed

Telecommunication Network, VOLMET, Pre Flight Com Briefing and

International Notam Offices

4. Provision of Telecom infrastructure (Datacom, Telephones, Fax &

Mobile etc.) to various AAI Units for operational and administrative

requirements.

5. Other main functions of CNS- OM Dept are :-

5.1 Management of CNS Human Resources including:-

Deployment

Training

Placement

Proficiency

5.2 Coordination with DGCA/ICAO for issue related to CNS and

amendment to ICAO Annex/documents related to CNS.

5.3 Coordination with National Regulator, WPC and ICAO for Civil

Aviation Frequency requirements/Protection.

5.4 CNS Standardization & Procedures

5.5 Preparing replacement and up gradation proposal of CNS andATM Data processing system.

5.6 Implementation of Safety Management System (SMS) related to

CNS and Automation facilities.

5.7 Disposal of obsolete CNS facilities proposal received at CHQ

from filed stations.

6. CNS-OM Dept is further divided into following five sections:

i) A & S (Automation & Surveillance)

ii) N&CMC (Navigation & Central Maintenance Cell)

iii) COM (Communication)

iv) CRSD (Central Radio Stores Depot)

v) FTI (Future Telecommunication Infrastructure)

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I) Automation and Surveillance (A &S)

Regular Monitoring of Availability & Serviceability of Surveillance,

ATM Automation facilities at all airports and Aeronautical

Communication Stations. Human Resource Management, Training

and proficiency of CNS Personnel.Regular Monitoring of Availability &

Serviceability of Surveillance, ATM Automation facilities at all airports

and Aeronautical Communication Stations. Human Resource

Management, Training and proficiency of CNS Personnel.

II) Navigation and Central Maintenance Cell (N&CMC)

Regular Monitoring of Availability & Serviceability of Navigational

Aids. Review of NOC cases from CNS point of view received in CNS-

OM Dept. DGCA & ICAO Matters. CMC manages SMUs (Special

Maintenance Unit) which are established for different CNS equipment

for complex component level repairs of faulty modules received from

different stations. At present SMUs are available at Delhi, Kolkata,

Ahmedabad, Chennai, Hyderabad and Mumbai airports for different

CNS/ATM Automation facilities.

III) Communication (Com)

Regular Monitoring of Availability & Serviceability of Communication

systems at all Airports/ACS. Provision of Aeronautical Mobile

Services, Aeronautical Fixed Telecommunication Network, VOLMET,Pre Flight Com Briefing and International Notam Offices. Provision of

Telephones, Fax & Mobile to various AAI Units for operational and

administrative requirements

IV) Central Radio Stores Depot (CRSD)

The Central Radio Stores Depot procures and stocks Spares / PCBs/

Modules/ Discreet Components of CNS equipment and provides

them to the stations to ensure the availability of CNS facilities. CRSD

also arranges custom clearance, Overseas & In-Land insurance and

Re-Export of faulty systems during guarantee/warranty Of CNS

Equipment being procured by Dte. Of CNS-P and forwarding of same

to the consignees.

V) FTI:

FTI is responsible for creation of Telecom Infrastructure with the help

of Managed Service Provider (MSP) on Build, Own & Operate model.

Augmentation of Ground to Ground/Air to Ground communication

infrastructure, provision of SLA (Service Level Agreement) based

telecom services across PAN-India regions covering Voice, Data &

Video applications. Implementation of Aviation System Block

Upgrade (ASBU) under one sky policy of ICAO.

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TOP

9. How can I join AAI in CNS Department?

AAI induct personnel with technical background at various levels in

CNS discipline. Besides Employment News, the recruitment

advertisements are published in reputed National and Regional

newspapers. For more information, detail requirements and

vacancies please visit AAI website "www.aai.aero" under the head

"carriers" regularly.

10. Who are ATSEP?

The recognized terminology as per ICAO DOC 7192 for personnel

involved in the maintenance and installation of CNS/ATM system is

Air Traffic Safety Electronics Personnel (ATSEP).

11. Where is training for CNS Personnel (ATSEP) conducted in

AAI?

Training for CNS Personnel is held at Civil Aviation Training College

(CATC) Allahabad and 04 Regional Training Canters (RTCs) located

at Delhi, Mumbai, Chennai and Kolkata Airports.

12.What are variousservices provided by CNS for air trafficservices and aircraft operations?

Various services provided are:-

1) Aeronautical Radio Navigation Service

2) Aeronautical Mobile Service

3) Aeronautical Fixed Service

4) Aeronautical Information Service

5)Aeronautical Broadcast Service etc.

13. What are different Radio Navigational Aids.

The different Radio navigational aids are:-

(i) NDB/Locators

(ii) VOR; CVOR or DVOR

(iii) DME

(iv) ILS

(v) Markers

14. What is Non Directional Beacon (NDB)?

NDB is a standard International Civil Aviation Organization (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 instrument

landing system (ILS) approach and standard approaches.

15. What is a DVOR?

DVOR Stands for Doppler Very High Frequency Omni Range. DVOR

is a standard International Civil Aviation Organisation (ICAO) ground

based radio navigational aid that provides bearing information toaircraft to define air traffic control routes for en-route, terminal and

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instrument approach/departure procedures. DVOR when collocated

with DME (Distance Measuring Instrument) provides both the angle

and slant distance of aircraft with respect to ground station.

16. What is DME?

DME stands for Distance Measuring Instrument. DME is a standardInternational Civil Aviation Organisation (ICAO) ground based radio

navigational aid that provides slant distance information to aircraft

with respect to ground station to define air traffic control routes for en-

route, terminal and instrument approach/departure procedures. DME

is normally collocated with DVOR or ILS/Glide Path and sometimes

with NDB also.

17. What is an ILS and its different component?

ILS stands for Instrument Landing System and is a standard

International Civil Aviation Organisation (ICAO) precision landing aid

that is used to provide accurate azimuth and descent guidance

signals for guidance to aircraft for landing on the runway undernormal or adverse weather conditions. Instrument landing system

(ILS) facility is a highly accurate and dependable means of navigating

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 system are available, including the approved

approach procedure, the pilot may execute a precision approach.

The ILS consists of: -

1. Localizer:- The primary component of the ILS is the localizer,

which provides lateral guidance. The transmitter and antenna

(Shown above) are on the centreline at the opposite end of the

runway from the approach threshold.

2. Glide Path:- The glide path component of ILSprovides

vertical guidance to the pilot during the approach. Glide path

is located 750 to 1,250 feet (ft) down the runway from the

threshold (shown above), offset 400 to 600 ft from the runway

centre line.

3. 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 centreline to provide the pilot with the ability to make a

positive position fix on the localizer.

(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 theglide slope at approximately 200 to 250 ft above the runway

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elevation.

4. DME: Distance Measuring Equipment (DME) is normally

collocated with glide path and provides slant distance to the

aircraft with respect to touch down point.

5. 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.)

6. 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).

TOP

18. What are different Facility Performance categories of

operation of ILS?

For suitably equipped aircraft, different ILS Facility Performance

categories are mentioned as below:-

(i) Cat I Operation:A precision instrument approach and landing with

a decision height not lower than 60m (200ft) and with either a visibility

not less than 800m or a runway visual range not less than 550m.

(ii) Cat II Operation:A precision instrument approach and landing

with a decision height lower than 60m (200ft) but not lower than 30 m

(100ft) and a runway visual range not less than 350m.

(iii) Cat III Operation:Different CAT III operation are further

subdivided into:-

(a) CAT IIIA Operation:A precision instrument approach and landing

with :-

a) a decision height t lower than 30m (100ft) , or no decision height;

and

b) a runway visual range not less than 200m.(b) Cat IIIB Operation: A precision instrument approach and landing

with :-

a) decision height t lower than 15m (50ft), or no decision height;

and

b) runway visual range less than 200 m not less than 50m.

(c) Cat IIIC Operation: A precision instrument approach and landing

with no decision height and no runway visual range limitations.

19. What is PBN?

ICAO's Performance Based Navigation (PBN) Concept specifies

system performance requirements for aircraft operating agencies

along an ATS route, or on an instrument approach procedure or in a

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designated airspace.

20. What is AFTN?

A world wide 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 orcompatible communications characteristics.

21. What is ATN?

The Aeronautical Telecommunication Network (ATN) comprises

application entities and communication services which allow ground,

air-to-ground and avionics data sub networks to interoperate. This is

done by adopting common interface services and protocols based on

International Standards. ATN is designed with four major elements.

The first element is the ability to transfer data to an aircraft without

sender knowledge of the aircraft location (network mobility). The

second major element is the ability to simultaneously use the multiple

air/ground links that are installed in an aircraft. This requiresapplications to specify cost, link, or speed preferences, which are

used by the ATN when forwarding data. The third element is the

ability to account for the low bandwidth air/ground data links available

today and in the near future. Low bandwidth air/ground links require

the use of data compression. The fourth element is the

standardization of the services required by ATS applications (i.e.,

transport, session, presentation, and application functions) and the

applications themselves, so that they are the same worldwide.

22. What is ADS/CPDLC?

ADS (Automatic Dependent Surveillance) is a surveillance technique

in which aircraft automatically provide, via a data link, data derivedfrom on- board navigation and position- fixing systems, including

aircraft identification, four-dimensional position and additional data as

appropriate.ADS data is displayed to the controller on a screenthat resembles a radar screen.

CPDLC(Controller Pilot Data Link Communications) is a means of

communication between controller and pilot, using data link for ATC

communications). CPDLC is a two -way data-link system by which

controllers can transmit messages to the pilot without the use of voice

communications. The message is displayed on a flight deck visual

display. CPDLC is an essential element of Automatic Dependent

Surveillance (ADS)

Several different forms of ADS are currently in use or under

development, including:

Automatic Dependent Surveillance-Broadcast (ADS-B) is a

function on an aircraft or surface vehicle that broadcasts position,

altitude, vector and other information for use by other aircraft,

vehicles and by ground facilities. It has become the main application

of the ADS principle.

Automatic Dependent Surveillance-Contract (ADS-C) functions

similarly to ADS-B but the data is transmitted based on a contract

between a ground system and an aircraft: Demand contract, periodic

contract, event contract and emergency contract. This application is

most likely to find application to sparsely trafficked transcontinental or

transoceanic crossings.

23. What is Aeronautical Mobile Service (AMS)?

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A mobile service between aeronautical stations and aircraft stations,

or between aircraft stations, in which survival craft stations may

participate; emergency position- indicating radio beacon stations may

also participate in this service on designated distress and emergency

frequencies.

AMS may be further divided & defined into

1. Aeronaut ical m obi le (R) serviceAn aeronautical mobile

service reserved for communications relating to safety and

regularity of flight, primarily along national or international civil

air routes.

2. Aeronaut ical m obi le (OR) service

An aeronautical mobile service intended for communications,

including those relating to flight coordination, primarily outside

national or international civil air routes.

3. Aeronaut ical mob i le-satel li te serviceA mobile-satellite service in which mobile earth stations are

located on board aircraft; survival craft stations and emergency

position-indicating radiobeacon stations may also participate in

this service.

4. Aeron autical mo bile-satel l i te (R) servic e

An aeronautical mobile- satellite service reserved for

communications relating to safety and regularity of flights,

primarily along national or international civil air routes.

5. Aeron autical mo bile-satel l i te (OR) servic e

An aeronautical mobile- satellite service intended forcommunications, including those relating to flight coordination,

primarily outside national and international civil air routes.

24. What is PSR?

PSR is primary Surveillance Radar. Primary radar is ? classical" radar

which reflects all kind of echoes, including aircraft and clouds. A radio

detection system that transmits short bursts (pulses) of RF energy

and detects their echoes from objects (targets) such as aircraft or

ships. The round - trip propagation time for the echo return may be

used to determine the target's range (distance from the

radar's antenna). This type of radar (now called primary radar) can

detect and report the position of anything that reflects its transmitted

radio signals including, depending on its design, aircraft, birds,

weather and land features.

TOP

25. What is SSR?

A Surveillance radar system which uses transmitters/receivers(interrogators) & transponders, detects and measures the position of

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aircraft but also requests additional information from the aircraft itself

such as its identity and altitude. SSR relies on its targets being

equipped with a radar transponder, which replies to each

interrogation signal by transmitting its own response containing

encoded data. SSR is based on the military identification friend or

foe (IFF) technology originally developed during World War II. The

transponder is a radio receiver and transmitter which receives on one

frequency (1090 MHz) and transmits on another (1030 MHz). The

target aircraft's transponder replies to signals from an interrogator

(usually, but not necessarily, a ground station co- located with a

primary radar) by transmitting a coded reply signal containing the

requested information. An SSR continuously transmits interrogation

pulses (selectively rather than continuously in Mode-4, Mode-5, and

Mode-S) as its antenna rotates, or is electronically scanned in space.

A transponder on an aircraft that is within line-of-sight range 'listens'

for the SSR interrogation signal and sends back a reply that provides

aircraft information.

26. What is MSSR?

Mono-pulse secondary surveillance radar (MSSR) is an improved

version of the classic SSR. Due to the problem of Garblingand

the False Replies Unsynchronized with the Interrogation

Transmissionsor simply FRUIT, MSSR was developed.

27. What is Voice Communication Control System (VCCS)?

VCCS controls and connects together various voice communication

systems used for Air Traffic Management such as VHF Tx/RX,

telephone, and other ATC communications. It also provides an

internetworked chain & backbone for numerous interfaces acting as

an exchange for all the interfaces put together. It works on various IT

protocols customized for each set of facility.

28. what is Digital Voice Tape Recorder (DVTR)?

DVTR is a medium/instrument used to real time record various voice

communications used by Air Traffic controllers and other personnel in

support for Air Traffic Management and provides evidence for

incident or accident investigations. The media has evolved from

analog magnetic tape to digital media, engineers adapted magnetic

tape technology to digital recording, producing digital reel- to-reel

magnetic tape machines. Before large hard disks became economical

enough to make hard disk recorders viable, studio digital recording

meant recording on digital tape.

29. What is a NOTAM?

NOTAMor Notice to Airmenare notices distributed by means of

telecommunication containing information concerning the

establishment, condition or change in any aeronautical facility,

service, procedure or hazard, the timely knowledge of which is

essential to personnel concerned with flight operations.

30. What is the information promulgated by NOTAM?

following information is promulgated by Notam:

1. Establishment, withdrawal and significant changes in operation of

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aeronautical services;

2. Establishment, closure or significant changes in operation of

aerodrome(s) or runways;

3. Establishment or withdrawal of electronic and other aids to air

navigation and aerodromes;

4. Establishment, withdrawal or significant changes made to visual

aids;

5. Interruption of or return to operation of major components of

aerodrome lighting systems;

6. Establishment, withdrawal or significant changes made to

procedures for air navigation services;

7. Occurrence or correction of major defects or impediments in the

maneuvering area;

8. Changes to and limitations on availability of fuel, oil and oxygen;

9. Major changes to search and rescue facilities and servicesavailable;

10. Establishment, withdrawal or return to operation of hazard beacons

marking significant obstacles to air navigation;

11. Changes in regulations requiring immediate action;

12. Presence of hazards which affect air navigation (including obstacles,

military exercises, displays, races, major parachuting events outside

promulgated sites);

13. Erecting, removal of or changes to significant obstacles to air

navigation in the take-off/climb, missed approach, approach areas

and runway strip;14. Establishment or discontinuance (including activation or

deactivation) as applicable, or changes in the status of prohibited,

restricted or danger areas;

15. Establishment or discontinuance of areas or routes or portions

thereof where the possibility of interception exists and where the

maintenance of guard on the VHF emergency frequency 121.5 MHz

is required;

16. changes in hazardous conditions due to snow, slush, ice or water on

the movement area;

17. Outbreaks of epidemics necessitating changes in notifiedrequirements for inoculations and quarantine measures;

18. Forecasts of solar cosmic radiation, where provided;

19. Occurrence of pre- eruption volcanic activity, the location, date and

time of volcanic eruptions and the existence, density and extent of

volcanic ash cloud, including direction of movement, flight levels and

routes or portions of routes which could affected;

20. Release into the atmosphere of radioactive materials or toxic

chemicals following a nuclear or chemical incident, the location, date

and time of the incident, the flight levels and routes or portions

thereof which could be affected and the direction of movement.

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31. What is the classification of NOTAMS?

NOTAM are classified as per :-

(1) According to Distribution

a) NOTAM - Distribution by means of telecommunication or AFTN.

b) AIP Supplement - Distribution by means other than

telecommunication or AFTN, such as messenger or postal services.

(2) According to Series

a) Concern to long or medium range flights, and given selected

international distribution;

b) Full information on all airports, facilities and procedures available

for use in international civil aviation, and given international

distribution to adjacent states only;

c) Information of concern to aircraft other than those engaged in

international civil aviation, and given national distribution only;

s) - Presence of removal of hazardous conditions due to snow, slush,

or ice on aerodrome pavements or standing water associated with

these conditions.

TOP

32. What is Volmet?

VOLMET, or meteorological information for aircraft in flight, is the

term applied to a worldwide network of radio stations that broadcast

TAF (Terminal Area Forecast). TAF is a format for reporting weather

forecast information relating to aviation applying to five statute mileradius from the centre of the airport runway complex), SIGMET

(Significant Meteorological Information, is a weather advisory that

contains meteorological information concerning the safety of all

aircraft) and METAR (format for reporting weather information)

reports on shortwave frequencies. In some countries, VOLMET

stations broadcast on VHF frequencies too.

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Last updated on: 14thAugust 2013

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