REPORT ON INDUSTRIAL TRAINING AT AIRPORTS AUTHORITY OF INDIABY ANUBHAV MAHAJAN IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE OF BACHELOR OF TECHNOLOGY Bharati Vidyapeeth’s College Of Engineering Approved by A.I.C.T.E., New Delhi, and Affiliated to GGSIP University, New Delhi 1 CANDIDATE’S DECLARATION I, Anubhav Mahajan, hereby declare that the work presented in the training report submitted to Bharati Vidyapeeth’s College Of Engineering , Affiliated to GGSIP University, New Delhi for the partial fulfilment of the award of degree of “Bachelor of Technology” is an authentic record of my work carried out during the sixth semester at New ATS Complex, IGI Airport, New Delhi. Anubhav Mahajan Bharati Vidyapeeth’s College Of Engineering 2 PREFACE Today the world has become very small. People in one part of world can not only communicate with persons sitting in other part of the world instantaneously but also can reach to them within hours. Air travel has made it so easy. As a student of B.Tech I felt the need to understand the various technologies & equipments involved in the communication, navigation and surveillance services rendered by Air Traffic Control Systems. The Industrial training is intended to give the trainee a better understanding of the concepts taught in class through their application in the form of various equipments and processes being used in New ATC under the control of AAI .This Industrial training was successfully completed at ATS Building, New Delhi under the guidance of Training head & individual head of different units in CNS Wing. The first week was utilized in getting an overview of all the CNS units in Air Traffic services, after which three particular units was allotted to every trainee for the rest of training period. I would like to thank them for their co-operation and guidance. 3 ACKNOWLEDGEMENT It was a great privilege for me to get my training in CNS Wing of Air Traffic Services under the Airports Authority of India(AAI). This report describes the training that I underwent, in the month of July-August 20__ at Air Traffic Control (ATC) under Airport Authority of India (AAI).It was completed, keeping in mind the course curriculum as per the university requirements. I would like to express my sincere gratitude to the all the people who have helped and supported me throughout. I am deeply indebted to Mr. _________, Mr. ________ and other Faculty members from CNS wing for organizing our training programme, efficiently and providing us valuable resources and also for their cooperation and willingness to share their expertise and knowledge and to devote their precious time to discuss related topics. The help and co-operation extended by the staff of AAI is fully acknowledged. I thoroughly enjoyed my entire training programme and would like to thank everyone at ATC for their guidance and support. 4 INDEX Contents Introduction Main Functions Of AAI Overall Functions Of ATC Flight Information Regions Curriculum For Industrial Training CNS Communication Navigation Surveillance VHF ZENITAL RADAR RADAR Systems At ATC RADAR Functions And Applications RADARs Used in ATC Automatic Message Switching System References Page No. 6 9 11 13 15 16 17 19 22 24 31 34 37 38 40 42 53 5 INTRODUCTION INTRODUCTION TO AIR TRAFFIC MANAGEMENT : The INTERNATIONAL CIVIL AVIATION ORGANISATION (ICAO) is a specialised agency of the UN. It codifies the principle and techniques of international air navigation and fosters the planning and development of international air transport to ensure an orderly growth. HEADQUATER- Canada MEMBERS OF ICAO : 191 UN countries are the member of the ICAO. INDIA is one among the members. The non-member states are Dominica, Liechtenstein, Niue, Tuvalu, Vatican City, and the states with limited recognition. 6 ICAO D G C A MINISTRY OF CIVIL AVIATION INDIA AIRPORT DEVELOP -ER AIRPORT AUTHORITY OF INDIA (AAI) PURPOSE OF AAI IN BRIEF : Passenger Handling Air Traffic Management Fire Rescue Services AAI has been assigned the responsibility of AIRSPACE MANAGEMENT of Indian Air Space 7 The AIRPORTS AUTHORITY OF INDIA (AAI) is an organization working under the Ministry of Civil Aviation that manages all the airports in India. AIRPORTS AUTHORITY OF INDIA (AAI) came to existence on 1st April 1995. It was formed under the act of parliament (AIRPORTS AUTHORITY OF INDIA ACT 1994) by merging the INTERNATIONAL AIRPORTS AUTHORITY OF INDIA and NATIONAL AIRPORTS AUTHORITY with a view to accelerate the integrated development, expansion and modernization of the air traffic services, passenger terminals, operational areas and cargo facilities at the airports in the country. The corporate headquarters (CHQ) are at Rajiv Gandhi Bhawan, Safdarjung Airport, New Delhi. Mr. V.P. Aggarwal is the current chairman of the AAI. Presently, it is owned 100% by the Government of India. REVENUE Most of AAI's revenue is generated from landing/parking fees and fees charged for providing Air Traffic Control services to aircraft over the Indian airspace. Only 16 of the 126 airfields operated by the AAI are profitable while the other airports incur heavy losses due to under utilisation and poor management. RNFC is the important source of revenue in AAI i.e. Route Navigation Facility Charges. AAI manages and operates 126 airports and 329 airstrips including 16 INTERNATIONAL AIRPORTS 89 DOMESTIC AIRPORTS 26 CIVIL ENCLAVES 8 MAIN FUNCTIONS OF AAI 1. Control and management of the Indian air space extending beyond the territorial limits of the country. 2. Provision of communication, navigation and surveillance aids. 3. Expansion and strengthening of operational areas and movement control aids for aircrafts and vehicular traffic in operational areas. 4. Design, development, operation and maintenance of passenger terminals. 5. Development and management of cargo terminals at international and domestic airports. 6. Provision of passenger facilities and information system in passenger terminals. SERVICES PROVIDED BY THE AAI AAI provides two main services: 1.) Air traffic services 2.) Construction and development of airports and air routes Air traffic services have two main departments that manage different functions. These are: 1.) Air traffic management 2.) CNS WINGS OF AAI : CNS ATC FINANCE P&A (PERSONNEL & ADMIN) ENGINEERING FIRE & CONTROL VIGILANCE COMMUNICATION NAVIGATION and SURVEILLANCE 9 AIR TRAFFIC SERVICES Provides control over the air traffic. Under this AIR TRAFFIC CONTROL (ATC) department control comes which performs the following functions and services Flight information control Area control (250 NM) Approach position (50 NM) Aerodrome position (25 NM) Surface movement control ATC Tower 10 OVERALL FUNCTION OF ATC Air Traffic Services staff performs functions supporting Air Traffic Control and provide supporting services to Air Navigation Services. Their roles are as follows: Aerodrome Flight Information: Provide advice and information for aircraft on or in the vicinity of the aerodrome. Area Flight Information: Provides weather and other information useful for the safe conduct of flight in uncontrolled airspace. This includes the provision of search and rescue alerting services for aircraft on Flight Plan. It also includes the relaying of clearances on behalf of Air Traffic Control and in predefined areas of uncontrolled airspace the provision of traffic information for pilots to determine their position in relation to each other to prevent collisions. International NOTAM Office: Information is processed and distributed (NOTAM) on changes to air navigation services including aerodrome conditions and navigation aids. VHF/HF/UHF: This includes the radio transmitters and receivers operating on various frequencies used for both long-range and short-range air/ground communications with aircraft. A-SMGCS: The A-SMGCS (for surface movement) employs both the multilateral and Automatic Dependent Surveillance-Broadcast (ADS-B) technologies for enhanced surveillance of aircraft and vehicle movements on the airfield, and provision of conflict and runway incursion alerting functions for added air traffic control safety and efficiency 11 NAV-AIDS: Instrument Landing System, a standard ICAO precision landing aid to provide accurate azimuth and descent guidance signals for use by aircraft for landing on the runway under normal or adverse weather conditions. DVOR/DME, standard ICAO radio navigational aids used to provide bearing and distance information to aircraft and to define air traffic control routes for en-route, terminal and instrument approach/departure procedures. RADAR: Primary surveillance radar (PSR) detects and provides both range and bearing information of an aircraft within its effective coverage by radio wave reflection. Secondary surveillance radar (SSR) provides, after processing, the range, bearing, altitude and identity of an aircraft. The coverage can reach 250NM. A SSR can provide more useful information than PSR but is subject to the proper functioning of the aircraft's transponder. To provide the best accuracy of aircraft targets, the SSR is usually paired with a PSR for air traffic control purpose. AMSS: A standard ICAO ground-to-ground communication system for the exchange of air traffic control messages within the Aeronautical Fixed Telecommunication Network (AFTN). 12 FLIGHT INFORMATION REGION (FIR) The airspace of the world has been divided into homogeneous regions called FIR’s. A Flight Information Region (FIR) is an aviation term used to describe airspace with specific dimensions, in which a Flight Information Service and an alerting service are provided. Any portion of the atmosphere belongs to some specific FIR. Smaller country’s airspace is encompassed by a single FIR, a large country’s airspace is subdivided into a number of regional FIRs. Some FIRs may encompass the territorial airspace of several countries. Oceanic airspace is divided into Oceanic Information Regions and delegated to a controlling authority bordering that region. The division among authorities is done by international agreement through ICAO. There is no standard size for FIRs, it is a matter for administrative convenience of the country concerned. The FIR is responsible for providing air traffic services to all the flights that are: Entering (overhead) Leaving (overhead) Taking off Landing India has been categorised into five FIRs. These are DELHI MUMBAI KOLKATA CHENNAI GUWAHATI 13 The region of airspace over which an FIR is responsible for providing air traffic services is broadly classified as: Area Approach Tower An FIR may include many airports within itself. For example the Delhi FIR includes Jaipur, Varanasi, Nagpur, Amritsar airports etc. The Delhi airport is connected to all these stations through various media links to enable the effective management of air traffic services in the Delhi FIR. tower 25NM approach 60NM area 250NM 14 CURRICULAM FOR INDUSTRIAL TRAINING JULY-AUGUST 2012 CNS AMSS AAI RADAR VHF 15 CNS (Communication, Navigation and Survillance) AIR TRAFFIC MANAGEMENT pillars C O M M U N I C A T I O N A V I G A T I O N S U R V I L L A N C E N Communication, Navigation and Surveillance are the three basic facilities which aid civil aviation. Thus, CNS are the building blocks of Air Traffic Management. 16 COMMUNICATION COMMUNICATION is a process of transferring information from one source to another. Communication is commonly defined as "the imparting or interchange of thoughts, opinions, or information by speech, writing, or signs". Communication can be perceived as a two-way process. But in civil aviation it is one-way process. At any time either the controller can speak or the pilot can speak. It can be further classified as: Ground to Ground: This enables various stations in the AFTN (aeronautical fixed telecommunications network) to communicate via low or high speed links. Various messages containing important information are exchanged. The communication is based on store and forward principle. Ground to Air: This includes all the communication between the controllers and the pilot. It may include voice communication or DATIS or any other form of messages. Ground to Air communication generally uses either VHF of HF frequencies. Communication takes place through transmitters and receivers installed o the ground as well as on board the aircraft. VHF and HF are used for voice communication. VHF transmitters have short range while HF can be used for communicating over long distances. Air to Air: This may include communication between the pilots of two aircrafts in the air. Such type of communication also uses VHF and HF frequencies. VHF Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted high frequency(HF), and the next higher frequencies are known as ultra high frequency(UHF). The frequency allocation is done by ITU. Common uses for VHF are FM radio broadcast, television broadcast, land mobile stations (emergency, business, private use and military), long range data communication with radio modems, amateur radio, marine communications, air traffic control communications and air navigation systems (e.g. VOR, DME & ILS). 17 VHF propagation characteristics are ideal for short-distance terrestrial communication, with a range generally somewhat farther than line-of-sight from the transmitter (see formula below). Unlike high frequencies (HF), the ionosphere does not usually reflect VHF radio and thus transmissions are restricted to the local area (and don't interfere with transmissions thousands of kilometres away). VHF is also less affected by atmospheric noise and interference from electrical equipment than lower frequencies. Whilst it is more easily blocked by land features than HF and lower frequencies, it is less affected by buildings and other less substantial objects than UHF frequencies. HF High frequency (HF) radio frequencies are between 3 and 30 MHz. Frequencies immediately below HF are denoted Medium-frequency (MF), and the next higher frequencies are known as Very high frequency (VHF). The Shortwave range (2.310 25.820 MHz) used by international broadcasters is part of the HF frequency spectrum. In aviation virtually the entire spectrum (2 - 29.999 MHz) is used for HF communications. The ionosphere often refracts HF radio waves quite well. This phenomenon is known as skywave propagation. Because of these characteristics this range is extensively used for medium and long range radio communication. UHF Ultra-high frequency (UHF) designates the ITU radio frequency range of electromagnetic waves between 300 MHz and 3 GHz (3,000 MHz). Radio waves with frequencies above the UHF band fall into the SHF (super-high frequency) and EHF (extremely high frequency) bands, all of which fall into the microwave frequency range. Lower frequency signals fall into the VHF (very high frequency) or lower bands. The main advantage of UHF transmission is the physically short wave that is produced by the high frequency. The size of transmission and reception antennas is related to the size of the radio wave. The UHF antenna is stubby and short. Smaller and less conspicuous antennas can be used with higher frequency bands.The major disadvantage of UHF is its limited broadcast range and reception, often called line-of-sight between the TV station's transmission antenna and customer's reception antenna, as opposed to VHF's very long broadcast range and reception, which is less restricted by line of sight. 18 NAVIGATION NAVIGATION is the process of reading, and controlling the movement of a craft 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. TYPES OF NAVIGATION GROUND BASED navigation system SATELLITE BASED navigation system N A V I Navigational aids G A T I O N Landing aids 19 GROUND BASED NAVIGATION SYSTEM : Navigation in civil aviation is accomplished by means of various equipments called NAVIGATIONAL AIDS ( NAV-AIDS) Location Of Various NAV-AIDS On The Runway Non Directional Beacon (NDB)- It provides relative bearing to the aircraft with respect to the direction of NDB equipment irrespective of aircraft heading. 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. ILS – It is the instrument landing system which helps the aircraft to land safely. It consist of : 1.)Distance Measuring Equipment - Gives the slant distance of the aircraft from the runway. 20 2.)Glide Path – Provides vertical guidance to a landing aircraft. 3.)Localizer – Provides the central line of the runway to the aircraft. 4.)Marker - Gives fixed distances from runway threshold and provide height over markers. ATC (Air Traffic Control ) It is a service provided by air traffic controllers on the ground to all the aircrafts in air and on the ground. The air traffic controllers are able to maintain direct contact with the pilots and guide them to move forward towards their destination. Hence, ATC uses all the facilities provided by CNS. GLOBAL NAVIGATION SATELLITE SYSTEM (GNSS) GNSS is a satellite based navigation system that works on the principle of GPS. A satellite navigation or SAT NAV system is a system of satellites that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few metres using time signals transmitted along a line-of-sight by radio from satellites. Receivers calculate the precise time as well as position, which can be used as a reference for scientific experiments. A satellite navigation system with global coverage may be termed a global navigation satellite system or GNSS. GAGAN - The GPS aided geo augmented navigation or GPS and geoaugmented navigation system (GAGAN) is a planned implementation of satellite-based augmentation system (SBAS) by the Indian government. It is a system to improve the accuracy of a GNSS receiver by providing reference signals. 21 SURVEILLANCE SURVEILLANCE is the monitoring of the behaviour of a person or group of people, often in a surreptitious manner. The word surveillance is commonly used to describe observation from a distance by means of electronic equipment. In civil aviation surveillance, equipment is installed in each airport to monitor the movement of all the aircrafts within its region of operation. Primary Radar In primary radars, the cooperation of the target is not required to find the range, the position, the relative velocity of the target. The target is said to be passive and is limited only to reflect the radar signals back to the radar. Most of the radars used for the air traffic control to the group of primary radars Secondary Radar Here the active cooperation of targets is very much required. Hence the role of the targets is said to be active. Secondary Radar system basically consists of two principal components namely the 'Interrogator' which is ground based and the 'Transponder' which is carried on the targets. Each of these components consists of a set of pulse transmitter and receiver. The Interrogator radiates pulses which when received by a corresponding transponder on a target will initiate a reply from that transponder. These replies are then collected by the interrogator to extract information about the targets. 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. 22 Screen Shot From A Surface Movement Radar L-Band Radar L band radars operate on a wavelength of 15-30 cm and a frequency of 12 GHz. L band radars are mostly used for clear air turbulence studies.They have an detection range of 220 nautical miles and rotation frequency of 5 RPM. S-Band Radar S-Band Radar operates on a wavelength of 8-15 cm and a frequency of 2-4 GHz. Because of the wavelength and frequency, S band radars are not easily attenuated. This makes them useful for near and far range weather observation. The National Weather Service (NWS) uses S band radars on a wavelength of just over 10 cm. The drawback to this band of radar is that it requires a large antenna dish and a large motor to power it to make it rotate at the rate of around 15 RPM. Its detection range is 60-150 nautical miles. 23 VHF The VHF (very high frequency) range of RADIO SPECTRUM is the band which extends from 30 MHz to 300 Mhz. The wavelengths corresponding to these limit frequencies are 10 meters and 1 metres. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra frequency (UHF). The frequency allocation is done by ITU. ITU : INTERNATIONAL TELECOMMUNICATION UNION – ITU is the Geneva- based specialised agency of the United Nations which coordintes and standardises the operation of telecommunication networks and services and advances the development of the communications technology. Band Frequency range 3 to 30 MHz 30 to 300 MHz Origin of name HF band VHF band UHF band L band S band C band High Frequency Very High Frequency 300 to 1000 MHz Ultra High Frequency 1 to 2 GHz 2 to 4 GHz 4 to 8 GHz Long wave Short wave Compromise between S and X Used in WW II for fire control, X for cross (as in crosshair) 24 X band 8 to 12 GHz Ku band K band Ka band V band W band mm band 12 to 18 GHz 18 to 27 GHz 27 to 40 GHz 40 to 75 GHz 75 to 110 GHz 110 to 300 GHz Kurz-under German Kurz (short) Kurz-above COMMON USES OF VHF FM Radio Broadcast Television Broadcast Military use Long Range Data Communication Marine Communication Air Traffic Control (ATC) 25 PROPOGATION CHARACTERISTICS VHF propagation characteristics are ideal for short – distance terrestrial communication, with a range generally somewhat farther than Line Of Sight (LOS) from the transmitter. Ionospheric propogation occurs regularly at lower part of the VHF spectrum, mostly at frequencies below 70 MHz. Less affected by atmospheric noise and interference from electrical equipment than lower frequencies. It is more easily blocked by land features than HF and lower frequencies. It is less affected by buildings and other less substantial objects than UHF frequencies. UNIVERSAL USE Certain subparts of the VHF band have the same use around the world. Some national uses are detailed below . 108-118 MHz: Air Navigation Beacons, VOR and Instrument Landing System Localiser. 118-137 MHz : Air band for ATC, Amplitude Modulation 121.5 MHz : Emergency Frequency for aircrafts 144-146 MHz : Amateur radio (In some countries 144- 148 MHz) Aircraft radio communication systems use the VHF band and are allocated the 118.0 to 136.975 Mhz frequencies. On the aircraft, at least one VHF communications radio must be installed. 26 The physics of two way communication is summed up in signal patterns from a transmitter to a receiver. The transmitter is made of a sound energy input transducer, the transmission circuit and the signal radiation antenna as. The receiver basically has the receiving antenna, coupling circuits, detector stages and the output transducer. Sound energy is conveyed from the human voice onto the microphone. A varying electromotive force (e.m.f.) results at the output terminals of the microphone. This e.m.f. is known as the intelligence i.e. the wanted signal. The signal is amplitude or frequency modulated by the modulator onto a carrier wave that is supplied by the local oscillator (this oscillator can be a piezoelectric crystal e.g. quartz). 27 The intermediate frequency from the modulator is amplified and fed into the antenna. The frequency at which the signal oscillates accelerates electrons within the physical structure of the antenna, which in turn setups a varying electromagnetic (e.m.) field. The continual generation of the e.m. field effectively leads to the antenna radiating the electromagnetic waves in lobes. The e.m. waves are transmitted omni directionally by the antenna into the airspace. Any antenna whose radio is tuned to the frequency of that at which the transmission was made sets up electronic charge acceleration in its structure. The pattern or waveform of this acceleration is the same frequency at which the transmission was made. A coupling stage transmits this signal into the mixer stage where a local oscillator frequency will be superimposed onto it. The intermediate frequency is conducted to the detection stage. At this stage, the intelligence is then extracted from the carrier by detector circuits, usually being made of detector diodes. The signal will be of a weak form as that soon after the input transducer. This thus requires a power amplification stage so that the signal can drive the output transducer, which is normally a headphone (most being some 200Ω) or loudspeaker. A similar VHF comms radio is installed in the every aircraft. When a transmission is made, every receiver tuned to the same frequency receives the signal i.e. the transmissions are broadcast. This process is a description of how voice communication is achieved between or among a group of aircraft. The communications radios are maintained in the radio shop, which is air conditioned and kept dust free. The purpose of air conditioning is temperature regulation. Test equipment that is used in the radio shop operates most accurate at room temperature and pressure (r.t.p.). 28 Amplitude Modulation Amplitude modulation is a form of modulation used for radio transmissions for broadcasting and two way radio communication applications. Modulating Principle The amplitude of the signal is changed in line with the instantaneous intensity of the sound. In this way the radio frequency signal has a representation of the sound wave superimposed in it. In view of the way the basic signal "carries" the sound or modulation, the radio frequency signal is often termed the "carrier". 29 Amplitude Modulation, AM When a carrier is modulated in any way, further signals are created that carry the actual modulation information. It is found that when a carrier is amplitude modulated, further signals are generated above and below the main carrier. The bandwidth occupied by the AM signal is twice the maximum frequency of the signal that is used to modulate the carrier, i.e. it is twice the bandwidth of the audio signal to be carried. Advantages of Amplitude Modulation It is simple to implement. Can be demodulated using a simple circuit. AM receivers are very economical. Disadvantages of amplitude modulation It is not efficient in terms of its power usage. It is not efficient in terms of its use of bandwidth, requiring a bandwidth equal to twice that of the highest audio frequency It is prone to high levels of noise because most noise is amplitude based and obviously AM detectors are sensitive to it. 30 ZENITAL Direct Digital Frequency Synthesizer with Digital Signal Processing. Can transmit upto 5KW power signal. Voice Microphone Signal Digital Frequency Synthesizer 1mW High Power Amplifier 120mW Driver 5.8KW Reflectometer Harmonic Filter Matching Unit Reflectometer Antennae Transmission Basic Zenital Transmitter FlowChart 31 Zenital The Zenital VHF/HF transmitter is a 5 kW radio transmitter, designed for use in domestic, maritime, point-to point and air traffic communication. The Zenital is highly modular and can be fully remote controlled. The equipment covers a frequency range of 1.6 to 150 MHz and offers simplex, duplex and semi-duplex radiocommunication. Zenital Transmitter DFS The Digital Frequency Synthesizer has one audio inputs and one microphone input. The DFS generates a modulated low power signal according to the selections of the user (carrier frequency, LF audio input, class of emission, power output level). The signal generation is fully digital by the use of the DDS (Direct Digital Synthesis) technique. Driver Driver amplifies the 1mW output signal from the DFS into 120mW signal and send the amplified signal for further amplification towards the High Power Amplifier Module. High Power Amplifier Here, amplification is done in following steps: 1.) 2.) 3.) 4.) 5.) Amplify signal with amplifier module. Split signal into 3 signals. Amplify each signal with a power amplifier. Recombine all three amplified signals. This process results into a 5 KW signal that can be rendered fit for transmission. 32 Reflectometer A reflectometer is used to measure: 1.) 2.) Amplitude of forward power. Amplitude of reflected power. Harmonic Filter The Harmonic Filter removes the harmonics in the VHF/HF Power Output of the Zenital. Matching Unit The Matching Unit transforms the external load impedance of the Zenital to a value closest to the 50 Ω system impedance. 33 RADAR RADAR stands for Radio Detection and Ranging System. It is basically a means of gathering information about distant objects called 'targets' by sending electromagnetic waves at them and analyzing the returns called the 'echoes'. BASIC PRINCIPLE OF RADAR: It transmits electromagnetic waves to the atmosphere. These electromagnetic waves are reflected back by the target in the form of echoes. The received echoes are analysed and using this information like speed, height, distance from the radar is calculated. EM wave Transmitted echo C=2d/t Where d is distance from radar to target. Basic block diagram of radar Antenna Transmitter (Tx) Duplexer Reciever (Rx) 34 Classification of Radars Based on Role of Targets : Primary Radar - In primary radars, the cooperation of the target is not required to find the range, the position, the relative velocity of the target. The target is said to be passive and is limited only to reflect the radar signals back to the radar. Most of the radars used for the air traffic control to the group of primary radars. Advantages: a. works independently i.e. the active cooperation of the target is not required b. simple and does not get saturated easily. c. requires only one set of transmitter and receiver. Disadvantages : a. b. c. d. poor efficiency . require transmitter power high. receiver has to be highly sensitive. critical alignment of the transmitter and receiver frequency require e. selective response of targets is not possible f. echoes from fixed targets will cause disturbance in detecting moving targets. Secondary Radar - Here the active cooperation of targets is very much required. Hence the role of the targets is said to be active. Secondary Radar system basically consists of two principal components namely the 'Interrogator' which is ground based and the 'Transponder' which is carried on the targets. Each of these components consists of a set of pulse transmitter and receiver. The Interrogator radiates pulses which when received by a corresponding transponder on a target will initiate a reply from that transponder. These replies are then collected by the interrogator to extract information about the targets. 35 Advantages: a. b. c. d. Considerable range increase is possible It allows low powers to be used to get a given performance. Echo is no longer dependent on the target size, material etc. Since there is a frequency difference between the transponder & the interrogator, received signals are totally free from permanent target echoes. e. By suitable coding, some useful information can be conveyed from the target to ground. Disadvantages: a. It can be used for friendly targets only. b. The system operation depends upon the equipment on the target remaining serviceable. c. All secondary radars are liable to be saturate. Radars Based on Waveform used: CW Radar CW – FM Radar Pulse Wave Radar Some Other Radars : Search Radar Tracking Radar 36 Radar Systems at ATC 1. L-BAND Radar System Operates in the frequency range of about 1 to 2 GHz. Can cover range upto 220 nautical miles. Frequency of rotation is about 5 RPM. Have both Primary as well as Secondary surveillance radars. Due to high range of coverage area, impact of information obtained from L-Band Radar system is much less than that obtained from S-band or SMR/ASMGCS radars. As L-Band radar system operates on lower frequencies i.e wavelength is high, updates arrives at lower rate than S-Band radar and SMR/ASMGCS. 2. S-BAND Radar Systems Operates in the frequency range of about 2 to 4 GHz. Can cover range upto 50-160 nautical miles. Frequency of rotation is about 15 RPM. Have both Primary as well as Secondary surveillance radars. Moderate impact as well as clarity of information received from S-Band radar system. 3. SMR and ASMGCS Surface Movement Radar (SMR) and Advanced Surface Movement Guidance and Control System(ASMGCS). Operates in the frequency range of about 8 to 12 GHz. Can cover range upto 5 nautical miles. Frequency of rotation is about 60 RPM. As it operates at higher frequencies i.e wavelength is low, it provides updates at faster rates and hence provides much better clarity of statistics than L-Band and S-Band radar systems. Impact of information received from SMR/ASMGCS is very high due to very high real time nature of the information. 37 Radar Applications Radar has been employed on the ground, in the air, on the sea and in space. Ground based radar has been used primarily for the detection, location and tracking aircrafts or spacecraft. Ship-board radars are used as navigational aid and safety device to locate Buoys, Shore-lines and other Ships. Air-borne radars are used to detect other aircrafts, ships, for land mapping, for weather indication etc. In space radar has assisted in the guidance of spacecraft and for remote-sensing. The major user of radar has been the military, although there have been increasingly important civil applications chiefly for air and marine navigation. The major areas of radar applications are briefly described below. 1. Air Traffic Control: Radars are employed throughout the world for the purpose of safe controlling of the air traffic enroute and in the vicinity of airports. Aircraft and ground vehicular traffic at large airports are monitored by means of high resolution radar. Radar has been used with GCA (Ground Controlled Approaches) system to guide aircraft to a safer landing in bad weather. 2. Aircraft Navigation: The weather avoidance radar installed on the nose of aircrafts is used to outline the regions of precipitation to the pilot. Radar is also used for terrain avoidance and terrain following. Although it may not always be thought of as radar, radio-altimeter is also a form of radar. 3. Maritime Navigation: Radar is used for enhancing the safety of ship travel by warning of potential collision with other ships and for detecting navigation buoys, especially in poor visibility. Shore-based radars of moderately high resolution are also used or surveillance in navigation. 38 4. Military Applications: Many of the civilian applications of radars are also employed by the military. The traditional uses of radar for military application, however, have been to identify enemy aircraft and to control & guide the anti-aircraft Guns and surface to air missiles. 5. Meteorological Applications: Radar is used by meteorological department to detect approaching storms & issue timely forecast and warning thus saving loss of life & property. There is a network of weather radars operating in our country, especially in the eastern coast. 6. Space Applications: Some of the largest ground-based radars are used for the detection and tracking of satellites. Satellite-borne radars have also been used for remotesensing of earth-resources which include the mapping of sea-conditions, water resources, ice-cover, agricultural & forest conditions, geological formations and environmental pollution. 39 Use of Radar in Air Traffic Control Service Radars are employed throughout the world for the purpose of safely controlling air traffic en-route and in the vicinity of airports. Aircraft as well as vehicular traffic at large airports are monitored by means of high-resolution radar. Radar has also been used to guide aircraft to a safe landing in bad weather. Functions The information presented on a radar display may be used to maintain a watch on the progress of air traffic in order to provide the air traffic control unit concerned with: 1. improved position information regarding aircraft under control, 2. supplementary information regarding other traffic, 3. information regarding any significant deviations, by aircraft, from the terms of their respective air traffic control clearances Radars used in Air Traffic Control The following are some of the radars employed for Air Traffic Control. 1. Aerodrome Surface Control: It is also known as Airport Surface Movement Indicator (ASMI) and Airport Surface Detection Equipment (ASDE). Here the radar scans the airfield only and draws a realistic map of the airfield on the scope on which moving and stationary targets are identified. It is an aid for maintaining separation between the aircrafts taxiing, taking off and landing, when the controller may not be able to actually see an aircraft manoeuvring on the ground due to poor visibility. 40 2. Airport Surveillance Radar: It is also called Terminal Approach Radar. It is a short range radar with a maximum range of about 60 nautical miles. This radar continuously scans the airspace surrounding the radar site and is used for terminal control i.e., for guiding the aircraft from the initial approach to a point on the extended centreline of the runway from where final approach starts. 3. Precision Approach Radar: This radar is used to guide a landing aircraft for a safe landing. It is designed to accurately determine the range from the touchdown point, bearing with reference to the extended centreline of the runway and the elevation with reference to the glide angle of an aircraft on the final approach to land. This radar can also be used to crosscheck the performance of the Instrument Landing System. 4. Air Route Surveillance Radar: This is a long range radar with a maximum range of about 200 nautical miles. The main purpose of this radar is to monitor the air traffic in the area region. 5. Secondary Surveillance Radar: This is a secondary radar. The aircraft carries a transponder which replies to suitably coded interrogations from a ground station. From the transponder replies, it is possible to extract information regarding the aircraft like its call-sign, altitude, originating point, destination point etc. which are all included in the flight plan. 41 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 centres 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 viceversa. AFTN SWITCHING SYSTEM INTRODUCTION In AFTN, information is exchanged between many stations. The simplest form of communication is point-to-point type, where information is transmitted from a source to sink through a medium. The source is where information is generated and includes all functions necessary to translate the information into 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. 42 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. 2. 3. Line Switching Message Switching Packet Switching. Line Switching When the switching system is used for switching lines or circuits it is called lineswitching 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 analysed by the computer system and transfer the messages to an appropriate output queue in the order of priority. The message switching system works on store and forward principle. It provides good line utilization, multi-addressing, message and system accounting, protects against blocking condition, and compatibility to various line interfaces. 43 Packet Switching System This system divides a message into 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. 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 management has 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. 44 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. Fully connected mesh topology 45 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 46 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 N/W 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. Bus topology 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. 47 Disadvantages 1. Difficult to add new devices. 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. Ring topology Advantages 1. A ring is relatively easy to install and reconfigure. Each device is linked only to it immediate neighbours (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. 48 Categories of Networks Today when we speak of networks, we are generally referring to three primary categories: local area networks, metropolitan area networks, and wide area networks. Local Area Network (LAN) A local area network (LAN) is usually privately owned and links the devices in a single office, building, or campus. Depending on the needs of an organization and the type of technology used, a LAN can be as simple as two PCs and a printer in someone's home office. Currently, LAN size is limited to a few kilometres. LANs are designed to allow resources to be shared between personal computers or workstations. The resources to be shared can include hardware (e.g., a printer), software (e.g., an application program), or data. One of the computers may be given a large capacity disk drive and may become a server to the other clients (e.g. Database Server of AMSS). 49 Wide Area Network (WAN) A wide area network (WAN) provides long-distance transmission of data, voice, image, and video information over large geographic areas that may comprise a country, a continent, or even the whole. WAN In contrast to LANs (which depend on their own hardware for transmission), WANs may utilize public, leased, or private communication equipment, usually in combinations, and can therefore span an unlimited number of miles. A WAN that is wholly owned and used by a single company is often referred to as an enterprise network. WANs technology such as X.25 and TCP/IP used in AAI AMSS. 50 PROTOCOL A protocol is a set of rules and conventions. The sender and the receiver, the two key parties in data communication must agree on a common set of rules, i.e. protocols before they can communicate with each other. Two devices that are connected to each other need not necessarily be able to communicate with each other unless they agree on a set of data communications protocols. There are many protocols available, some of which are more popular than others. For enabling data communications, a combination of hardware and software is essential. In any data communications system, three characteristics are desired: Correct delivery: When a sender transmits data for an intended recipient, the data must reach only the intended recipient and not someone else. Accurate delivery: The data sent must be received in the same form as the one in which it was sent. There must not be any sort of alterations to it in transit. Timely delivery: The data must travel from the sender to the receiver in a finite amount of time. The main aspect of data communication system that needs a good amount of understanding is the data communication protocols. 51 Figure: A Data Communication Model. Two devices wishing to communicate with each other cannot just begin data transmission arbitrarily. That is, one device cannot simply start sending bit streams to the other. The two devices must agree on a set of rules before this transmission can begin. Otherwise, the receiver would not be able to know what the sender has sent or conversely, the sender would not be able to know if the receiver has correctly received the data that it had sent. 52 REFERENCES Books Training manuals from Airports Authority Of India. Operating manuals from Airports Authority Of India. Websites http://www.aai.aero http://www.wikipedia.org http://www.google.com 53
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Report "Airports Authority of India Industrial Training Report"