|FREQUENTLY ASKED QUESIONS|
|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 on board 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 stands for Communications, Navigation and Surveillance Systems 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)
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 Navigation Service Provider (ANSPs), airlines and the airports.
one can find information about
regulatory requirements like Civil
Aviation Requirements (CARs)
etc. about Aeronautical
Telecommunication facilities (I.e.
CNS/ATM Automation facilities)
The information is available on DGCA Web site ?dg ca.nic.in?.
|5. Who is
responsible for providing
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 Aeronautical Telecommunication facilities (I.e. CNS/ATM Automation systems) in AAI.
|7. What are
the different CNS Departments in
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:
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 as mentioned 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:-
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 and ATM 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) COM (Communication)
ii) N & S (Navigation & Surveillance)
iii) CRSD (Central Radio Stores Depot)
iv) CMC (Central Maintenance Cell)
v) Elex (Electronics)
Each section is headed by GM (CNS) who reports to ED (CNS-OM).
Brief details of functions/tasks performed by sections are as given below:
i) Communication (Com)
|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
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.
What are various services
provided by CNS for air traffic
services 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
The different Radio navigational aids are:-
(ii) VOR; CVOR or DVOR
|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
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 to aircraft to define air traffic control routes for en-route, terminal and 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 stands for Distance Measuring Instrument. DME is a standard International 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
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 under normal 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: -
|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 designated airspace.
|20. What is
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 or compatible communications characteristics.
|21. What is
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 requires applications 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 (Automatic Dependent Surveillance) is a surveillance technique in which aircraft automatically provide, via a data link, data derived from 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 screen that 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
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.
|24. What is
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.
|25. What is
A Surveillance radar system which uses transmitters/receivers (interrogators) & transponders, detects and measures the position of 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
Mono-pulse secondary surveillance radar (MSSR) is an improved version of the classic SSR. Due to the problem of Garbling and the False Replies Unsynchronized with the Interrogation Transmissions or simply FRUIT, MSSR was developed.
|27. What is
Voice Communication Control
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 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
NOTAM or Notice to Airmen are 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
following information is promulgated by Notam:
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.
|32. What is
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 mile radius 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.
Last updated on: 01st March 2011