Aircraft Communication Study Notes PDF 2024

BS: Aviation Management STUDY NOTES AIRCRAFT COMUNICATION With special reference to Air Traffic Management, Communication,Navigation,Survellance & Airline Flight Operation...

BS: Aviation Management STUDY NOTES AIRCRAFT COMUNICATION With special reference to Air Traffic Management, Communication,Navigation,Survellance & Airline Flight Operation Compilation By Zia ullah sheikh, FCILT(UK) Rtd. Sr.Joint Director (ATS) CAA Islamabad Airport Visiting Faculty - Aviation Management Foundation University School of Science & Technology Rawalpindi Sept 2024 1  Study Notes AIRCRAFT COMMUNICATION (BS. Aviation Management – 3rd semester – Fall 2024) Based upon Source Book: Communication -ATPL Ground Training Series Published by Oxford Aviation Academy (UK) Limited 2008 International documents: ICAO ANNEX-1 , Licensing ICAO ANNEX -2, Rules of the air ICAO ANNEX-10, Vol-II Aeronautical Telecommunication ICAO ANNEX-11, Air Traffic Services ICAO Doc 9705 - Automatic Message Handling System (AMHS) ICAO Doc 9432- Manual of Radiotelephony ICAO Doc 8259- AFTN Planning ICAO DOC - 4444, Air Traffic management & CNS National documents: Civil Aviation Ordinance, 1982 Pakistan CAA Rules-1994 Pakistan AIP & MATS PCAA Air Navigation Orders - ANO PCAA Civil Aviation Orders - CAAO 2  PART- 1 AIRCRAFT COMMUNICATION  Definitions  Flight operation – Ground based systems  Flight operation – Airborne / Aircraft Systems  Aircraft Communications and Navigation Systems  Aircraft Radio based Communication Systems  Aircraft Radio based Navigation Systems  Radio Communication Basics  Radio Waves  Radio Frequency  Radio Waves spectrum  Radio frequency bands  Elements radio frequency transmission  Requirement of operational Radio Equipment in Aircraft  Regulatory requirement of aircraft radio communicarion  Atmosphere and radio wave propagations  Global communication satellite system PART- 2 AIRCRAFT COMMUNICATION  HF Communication System  VHF Communication System  UHF Communication System  Ground-Based Radio Navigational Aids  Selective Calling System  Aircraft Communications Addressing and Reporting System  Flight Intercommunication system  Radar frequency Bands 3  PART- 3 AIRCRAFT COMMUNICATION  Aeronautical Telecommunication Communication Channels  SITA – Société Internationale de Télécommunications Aéronautiques  Radio telephony  Radio telephony Language  Transmitting techniques  Transmission Priority  Transmission of letters and numbers HF Communication System  Radio Telephony transmissions – (Voice Communication):  Transmission of relative bearing in terms of the 12 hour clock  Transmission of time  Readability scale of the transmission VHF Communication System  Radiotelephony standard phrases / words:  Issue of clearance  Radio telephony test procedure  ICAO location indicator  IATA location indicator  AFTN messages PART- 4 AIRCRAFT COMMUNICATION  Misc  Course module  Course coverage plan  FPL performa  AFTN performa 4  DEFINITIONS Aircraft: It is defined as any machine that can derive support in the atmosphere from the reactions of the air other than reactions of the air against the earth’s surface. Communication: Communication is the sending and receiving of information and can be one-on- one or between groups of people, and can be face-to-face or through communication devices. Aircraft communication: Aircraft communication is the means by which aircraft crews connect with other aircraft and people on the ground to relay information. Aviation communication is a crucial component of information exchange between pilots and air traffic control (ATC), command centers, maintenance centers, or other stakeholders pertaining to the successful functionality of flight operation / aircraft movement both on the ground and in the air. Aerodrom: A defined area on land or water (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure, and movement of aircraft. Airport: A defined area designated by the Contracting State (including any buildings, installations and equipment) intended to be used either wholly or in part for the arrival, departure, and surface movement of aircraft,and where the formalities such as refueling, aircraft maintenance, catering,customs, immigration, public health, quarantine and similar regularity procedures are established as per requirement. Aerodrome traffic: All traffic on the manoeuvring area of an aerodrome and all aircraft flying in the vicinity of an aerodrome. Note: An aircraft is in the vicinity of an aerodrome when it is on, entering or leaving a traffic circuit. Aerodrome traffic circuit: The specified path to be flown by aircraft operating in the vicinity of an aerodrome. Air traffic service: A generic term meaning, variously, air traffic control unit, flight information service, alerting service, air traffic advisory service, air traffic control service, approach control service or aerodrome control service. Air traffic services unit: A generic term meaning variously, air traffic control unit, flight information centre or air traffic services reporting office. Airway: A control area or portion thereof established in the form of a corridor equipped with radio navigational aids. 5 Approach control service: Air traffic control service for arriving and departing controlled flights. Area control centre: A unit established to provide air traffic control service to controlled flights in control under its jurisdiction. ATC clearance: Authorisation for an aircraft to proceed under conditions specified by air traffic control service. Clearance limit: The point to which an aircraft is granted an air traffic control clearance. Controlled airspace: An airspace of defined dimensions within which air traffic control service is provided for controlled flights. Control Zone: A controlled airspace extending upwards from the surface to a specified upper level. Control Area: A controlled airspace extending upwards from a specified limit above the surface of the earth. Apron: A defined area, on a land aerodrome, intended to accommodate aircraft for purposes of loading and unloading passengers, Mail or cargo, fuelling, parking or maintenance. Manoeuvring area: That part of an aerodrome to be used for the take-off, landing and taxiing of an aircraft excluding aprons. Movement area: That part of the aerodrome to be used for the take-off, landing and taxiing of aircraft, on the manoeuvring area and the apron(s). Estimated time of arrival (ETA): The time at which the pilot estimates that the aircraft will be over a specified location. Expected approach time (EAT): The time at which ATC expects that an arriving aircraft, following a delay will arrive at the holding point to complete its approach for a landing. Heading: The direction in which the longitudinal axis of an aircraft is pointed, usually expressed in degrees North (true, magnetic, compass or grid). Holding Point: A specified location, identified by visual or other means, in the vicinity of which the point of an aircraft in flight is maintained in accordance with air traffic control clearances. 6 Holding procedure: A predetermined manoeuvre which keeps an aircraft which a specified airspace whilst awaiting further clearance. Runway visual range: The range over which the pilot of an aircraft on the centre line of a runway can see the runway surface markings or the lights delineating the runway or identifying its centre line. Threshold: The beginning of that portion of the runway useable for landing. Touchdown : The point where the nominal glide path intercepts the runway. Station: A station is simply a equipment or location which is used to transmit or receive aeronautical information. It could be a radio in an aircraft or on the ground, or even a network of teleprinters or computers used by controllers, or operations departments. Aeronautical station: A land station in the aeronautical mobile service. In certain instances, an aeronautical station may be located on board ship or on a platform at sea. Air-ground communication: Two-way communication between aircraft and stations or locations on the surface of the earth. Aeronautical Fixed Telecommunication Network: This is a network of fixed local based stations used to send information such as NOTAMS, WEATHER, FLIGHT PLANS, DEPARTURE & ARRIVAL INFORMATION etc. Formerly this was mostly teleprinter information but now it is increasingly a digital (computer) network AFTN station: A station forming part of the aeronautical fixed telecommunication network (AFTN) and operating as such under the authority or control of a State. Aeronautical Mobile Service: This is the service that you will use whenever you use your radio. It is all stations on the groundor in the air involved in the day-to-day operations of the aircraft. Aeronautical mobile service: A mobile service between aeronautical stations and /or aircraft stations, in which survival craft stations , ELT beacon stations may also participate on designated emergency frequencies. Broadcast: A transmission of information relating to air navigation that is not addressed to a specific station or stations. 7 Automatic terminal information service. (ATIS): The provision of current, routine information to arriving and departing aircraft by means of continuous and repetitive broadcasts throughout the day or a specified portion of the day. Read Back: Some important instructions or information must be readback to confirm or to check accuracy of reception. Blind transmission: A transmission from one station to another station in circumstances wherethe communication cannot be established but where it is believed that the called station is able to receive the transmission. VFR flight: A flight conducted in accordance with visual flight rules. Visual meteorological conditions.(VMC): Visual Meteorological Conditions (VMC) are weather conditions under which pilots have sufficient visibility to fly aircraft relying on visual references. VMC is defined by specific criteria regarding visibility, cloud distance, and ceiling, which must meet or exceed established minimums. IFR flight: A flight conducted in accordance with instrument flight rules. Instrument meteorological conditions.(IMC) : Meteorological conditions expressed in terms of visibility, distance, cloud and ceiling, less than the minima specified for visual meteorological conditions, that require pilots to fly primarily by reference to flight instruments, and therefore under instrument flight rules, as opposed to flying by outside visual references under visual flight rules. Flight plan: Specified information provided to air traffic services units, relative to an intended flight or path of a flight of an aircraft. Missed approach procedure: The procedure to be followed if the approach cannot be continued. Radar identification: The process of correlating a particular radar blip of radar position symbol with a specific aircraft. Radar vectoring: Provision of navigational guidance to aircraft in the form of specific headings,based on the use of radar. 8 Reporting point: A specified geographical location in relation to which the position of the aircraft can be reported. Runway 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) Uncertainty phase (INCERFA): a situation wherein uncertainty exists as to the safety of an aircraft and its occupants. Alert phase (ALERFA): a situation wherein apprehension exists as to the safety of an aircraft and its occupants. (PAN,PAN or PAN, PAN MEDICAL) Distress phase (DETRESFA): a situation wherein there is a reasonable certainty that an aircraft and its occupants are threatened by grave and imminent danger and require immediate assistance(MAYDAY). Flight operation – Ground based systems Radio Telegraphic system:Radiotelegraphy is transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Wireless telegraphy : The term wireless telegraphy was also used for for transmitting signals without wires. Radio Telephony system:Radiotelephony is transmission of voice messages by radio waves with out cable network. The term wireless telegraphy was also used for for transmitting signals without wires. Air Traffic Management system: ATM system is a generic term name variously as Air traffic control,Air traffic advisory, Flignt information ,Alerting ,Serach & rescue services. Air Navigation system: CNS is a generic term may be defined variously as electronic navigation, visual navigation ,signology and marking for the safe and expeditious flow of air traffic. Approach lighting system: Various runway lighting systems serve as integral parts of the ILS system to aid the pilot in landing. Includes approach light system (ALS), sequenced flashing light (SFL), touchdown zone lights (TDZ) and centerline lights (CLL-required for Category II & III operations.) AIR-REPORT: A report from an aircraft in flight prepared in conformity with requirements for position, and operational and/or meteorological reporting. ATS direct speech circuit: An aeronautical fixed service (AFS) telephone circuit, for direct exchange of information between air traffic services (ATS) units. Location indicator: A four-letter code group formulated in accordance with rules prescribed by ICAO and assigned to the location of an aeronautical fixed station. 9 NOTAM: A notice 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. Flight operation – Airborn / Aircraft Systems The following are the main operating systems in any aircraft: Aircraft Engineering Systems Aircraft Communications and Navigation Systems Aircraft Flight Instruments and Guidance Systems Aircraft Electrical and Electronic Systems Aircraft Communications ,Navigation and Survalance Systems Aircraft Communications and Navigation Systems can be:  Visual based  Radio based  RADAR - PSR /SSR Aircraft Radio based Communication Systems The aircraft communication system is used for data communications in the form of voice or text for the safety& regularity of flight operation. The various communication systems in aircraft are used for communication between the crew members and between crew members and ground personnel. It is also used to communicate with the passengers, other aircraft, and ground stations. Aircraft Radio communications systems comprise the following:  HF System – For long-distance voice communications  VHF System – For short-range voice communications  SELCAL System – For selective calling using HF and VHF  SATCOM System – For satellite communication  ACARS – For datalink communication  Flight Interphone System – For internal cockpit communication and also with ground mechanics.  Cabin Interphone System – For cabin crew or cabin crew/pilots communications. 10   Service Interphone System – On ground only, for maintenance personnel only.  Passenger Address System – For passenger announcement from cockpit and cabin crew station. Aircraft Radio based Navigation Systems  NDB  VOR  ILS  DME Aircraft Radio based Survalance Systems: Radio Deduction and Ranging (RADAR) is the basic equipment which is used by the ATM for the survalance of flight operation. It may be any of following two main types:  Primary Survalance Radar(PSR)  Secondary Survalance Radar (SSR) Radio Communication Basics Aviation communication is accomplished through the use of radio waves.  Radio Waves: Radio waves are electromagnetic in nature and part of the electronic spectrum. The atmosphere is filled with these waves.  Radion Frequiency: Each wave occurs at a specific frequency and has a corresponding wavelength. The relationship between frequency and wavelength is inversely proportional. A high-frequency wave has a short wavelength and a low-frequency wave has a long wavelength.  Primary frequency: The radiotelephony frequency assigned to an aircraft as a first choice for air-ground communication in a radiotelephony network.  Secondary frequency:The radiotelephony frequency assigned to an aircraft as a second choice for air-ground communication in a radiotelephony network. Carrier wave - Loading Information onto a Radio Wave Radio waves are electromagnetic wave—a wave that has both electric and magnetic field components and travels at the speed of light.The production and broadcast of radio waves do not convey any significant information. The basic radio wave is known as a carrier wave. To transmit and receive useful information, this wave is altered or modulated by an information signal. The information signal contains the unique voice or data information desired to be conveyed. The modulated carrier wave then carries the information from the transmitting radio to the receiving radio via their respective antennas. Two common methods of modulating carrier waves are amplitude modulation and frequency modulation. 11 The Radio frequency spectrum Radio frequency signals are generally understood to occupy a frequency range that extends from a few tens of kilohertz (kHz) to several hundred gigahertz (GHz) known as radio frequency spectrum is divided into a number of bands. The use of each frequency band and range is depends upon a number of factors, paramount among which is the propagation characteristics within the band concerned. The measureing unit of frequency is Hertz. Broad categorization of radio frequency bands: Band Name Abbreviation Frequency  Very low frequency VLF 3-30 kHz  Low frequency LF 30-300 kHz  Medium frequency MF 300-3000 kHz (3 Mhz)  High frequency HF 3-30 MHz  Very high frequency VHF 30-300 MHz  Ultra high frequency UHF 300-3000 MHz (3 GHz)  Super high frequency SHF 3-30 GHz  Extremely high frequency EHF 30-300 GHz VHF Frequencies and Channel Spacing The bandwidth allocated to VHF frequencies at present, are mostly apppart by 25 KHz that is, the spacing between one channel and another. However, in many busy types of airspace, designated by the authorities, the spacing between channels has been reduced to 8.33 KHz (one third of 25 KHz) thus creating many more channels. Channels which are spaced by 25 KHz require 5 digits, not more than 2 digits after the decimal point, whereas channels spaced by 8.33 KHz require 6 digits, 3 digits after the decimal point. However, ICAO has now set a standard that requires all 6 digits of communications frequencies be passed in RTF instructions. So all VHF channels will include 6 digits irrespective of whether the channel is 25 KHz or 8.33 KHz spaced. The only exception to this is where the final two digits are both zero, in which case only the first four digits need to be transmitted. When using a 5 digit radio, (25 KHz spacing), only the first 5 digits of the given frequency need be set on the radio. 12 Elements of Radio Communication  Transmitters: A transmitter consists of a precise oscillating circuit or oscillator that creates an AC carrier wave frequency. This is combined with amplification circuits or amplifiers. The distance a carrier wave travels is directly related to the amplification of the signal sent to the antenna.  Other circuits are used in a transmitter to accept the input information signal and process it for loading onto the carrier wave. Modulator circuits modify the carrier wave with the processed information signal.Essentially, this is all there is to a radio transmitter.  Receivers: Antennas are simply conductors of lengths proportional to the wavelength of the oscillated frequency put out by the transmitter. An antenna captures the desired carrier wave as well as many other radio waves that are present in the atmosphere. A receiver is needed to isolate the desired carrier wave with its information.  The receiver also has circuitry to separate the information signal from the carrier wave. It prepares it for output to a device, such as speakers or a display screen. The output is the information signal originally introduced into the transmitter.  Transceivers: A transceiver is a communication radio that transmits and receives. The same frequency is used for both. When transmitting, the receiver does not function. The push- to-talk (PTT) switch blocks the receiving circuitry and allows the transmitter circuitry to be active. In a transceiver, some of the circuitry is shared by the transmitting and receiving functions of the device. So is the antenna. This saves space and the number of components used.Transceivers are half-duplex systems where communication can occur in both directions but only one party can speak while the other must listen.  Antennas: Antennas are conductors that are used to transmit and receive radio frequency waves. Basic Radio Working Radio signals are made up of a modulated carrier wave.The radio transmitter generates an oscillation at the frequency of transmission, (in the case of VHF this would be in the band of 118- 135.975 MHz). This is known as the carrier wave because it ‘carries’ the audio information.This carrier wave is superimposed the audio signal from the microphone (speech). This process is called modulation. There are two methods of modulation – Amplitude Modulation (AM) and Frequency Modulation (FM).The modulated Radio Frequency (RF) signal is sent to the antenna for onward transmission. At the receiving end, the antenna picks up the modulated RF signal. It passes this through the coaxial cable to the receiver, where it is amplified then de-modulated, then the audio signal alone is amplified for onward transmission to the speakers or headphones. 13 Requirement of Radio Equipment in Aircraft The regulatory documents specifies the minimum numbers and types of radio equipment to be carried on aircraft. VHF (Very High Frequency) radio gives good short-range radio reception but not gives desired results on long-distance line-of-sight communication. Where ground has effect on radio transmission HF (High Frequency) would be used. Now a days satellite based communication is the normal mode for long-range communication. Regulatory / legislative requirement of aircraft communicarion: The following are the documents to meet the Aircraft communication requirement at and national level.  ICAO Annex-10 (Telecommunication -4 volumes)  ICAO Annex-11 ( Air Traffc Services)  ITU regulations  IATA AHM  CAA Pakistan Air avigation Order  CAA Pakistan CAAO’s The Atmosphere The earth’s atmosphere can be divided into five concentric regions having boundaries as defined. These layers, starting with the layer nearest the earth’s surface, are known as the troposphere, stratosphere, mesosphere, thermosphere and exosphere.The boundary between the troposphere and the stratosphere is known as the tropopause. The thermosphere and the upper parts of the mesosphere are often referred to as the ionosphere and it is this region that has a major role to play in the long distance propagation of radio waves. The lowest part of the earth’s atmosphere is called the troposphere and it extends from the surface up to about 10 km (6 miles). The atmosphere above 10 km is called the stratosphere, followed by the mesosphere. It is in the stratosphere that incoming solar radiation creates the ozone layer. 14 Radio wave propagation Depending on a number of complex factors, radio waves can propagate through the atmosphere in various ways,These include:  Ground waves  Ionospheric waves  Space waves  Tropospheric waves. The wave propagation can have different effects and known as:  Reflection  Refraction  Diffraction  Scattering. Skip distance & Silent Zone: Skip distance is a crucial aspect of ionospheric wave propagation. The minimal distance on the earth's surface between the point at which a signal is transmitted and the point at which a signal reflected from the ionosphere is received is known as the skip distance Satellite Communication – SATCOM System Satellite communications provide a more reliable method of communications using the IRIDUM or International Maritime Satellite Organization (INMARSAT) satellite constellation which was originally developed for maritime use. Now, satellite communications, abbreviated to SATCOM, form a useful component of aerospace communications. Satellite Communications (SATCOM) system uses similar technology to GPS. The INMARSAT satellites are placed in Earth’s geostationary orbit above the equator. The system has the satellite network, the ground earth stations (GES), and the aircraft earth stations (AES). The SATCOM system transmits and receives data and voice messages. The system uses satellites as relay stations for long distances. SATCOM is more reliable than the HF communication system because atmospheric interference does not have an effect on it. The satellite network does a relay of radio signals between the AES and the GES. Each GES is a fixed radio station that has interfaces with communication networks through ground links and the aircraft earth stations through the satellite. The AES is the SATCOM system on the airplane that has interfaces with different airplane communication systems and the ground earth stations. 15 Main global communication satellite system providers: The IRIDIUM SATCOM network: The Iridium is a global satellite communications company, providing access to reliable voice and data services anywhere on Earth. The Iridium network -a system of 66 active communication satellites around the Earth allows voice and data communications using handheld devices. The system operates in L-band. Voice and data messages are relayed from one satellite to another until they reach the receiving terminal, the signal is then relayed back to the gateway. When an Iridium customer places a call from a handset or terminal, it connects to the nearest satellite and is relayed among satellites around the globe through 66 active satellites in near polar orbits at an altitude of 485 miles (780 Km). The satellites fly in a typical formation in the six orbital planes, evenly spaced around the planet, each with 11 satellites equally spaced apart from each other in that orbital plane. A single satellite orbits the earth once every 100 minutes, travelling at a speed of 16,382 miles per hour; the time taken from horizon to horizon being a mere ten minutes. As a satellite moves out of view, the subscriber’s call is seamlessly handed over to the next satellite coming into view. Each Iridium satellite is cross-linked to four other satellites – two in the same orbital plane and two in adjacent planes. These links create an autonomous dynamic network in space with calls being routed directly between satellites without reference to the ground. This improves integrity and reliability and helps make Iridium resistant to natural disasters, such as hurricanes, tsunami and earthquakes that can cause major disruption to ground-based networks. 16 INMARSAT- International Maritime Satellite Organization: Inmarsat-International Maritime Satellite Organization- is a British satellite telecommunications company, a non-profit intergovernmental organisation established in 1979 at the behest of the International Maritime Organization ,offering global telephone and data services to users worldwide, via portable or mobile terminals which communicate with ground stations through fifteen geostationary telecommunications satellites. The Inmarsat satellite constellation consists of 13 satellites in a geosynchronous (GEO) orbit approximately 22,000 miles above the earth. The satellites are positioned to transmit radio beams in two global configurations covering the oceans and major land masses. In coordination with the International Civil Aviation Organization in the 1980s, the convention governing INMARSAT was amended to include improvements to aeronautical communications, notably for public safety. In April 1999, INMARSAT was succeeded by the International Mobile Satellite Organization (IMSO) as an intergovernmental regulatory body for satellite communications,its operational unit become Inmarsat Ltd. On 20 September 2018, Inmarsat announced its strategic collaboration with Panasonic Avionics Corporation for an initial ten-year period, to provide in-flight broadband for commercial airlines. On May 30, 2023, Viasat acquired of Inmarsat, combining the teams, technologies and resources of the two companies to create a new global communications partner. 17  PART- 2 AIRCRAFT COMMUNICATION 18 HF Communication System HF use was at one time essential for long-range communications, but with the advent of Satellite Communications (SATCOM), its use is becoming less common. However, it is still in use. The high-frequency (HF) communication system supplies voice communication over long distances. It gives communication between airplanes or between ground stations and airplanes. The HF system operates in the aeronautical frequency range of 2 MHz to 29.999 MHz. The system uses the surface of the earth and an ionized layer to cause a reflection (skip) of the communication signal. The distance between skips changes due to the time of day, radio frequency, and airplane altitude. The HF communication radio uses frequency select and control signals to transmit and receive voice communication. The HF radio modulates an RF carrier signal with voice audio from the flight interphone system. During the receive mode, the HF radio demodulates the RF carrier signal. This isolates the voice audio from the RF signal. The HF transceiver sends the audio to the flight interphone system. The HF system operates in the frequency range of 2.000 MHz to 29.999 MHz and following main components system:  Radio control panel  HF transceiver  HF antenna coupler  HF antenna Use of HF Communication System: HF communication voice ,text is in use long distance aeronautical mobile voice communication and in AFTN for the text data transmission. HF frequency range is aslo used in the form of NDB,and Markers for Radio navigation VHF Communication System VHF radio transmission is the most common system for short to medium-range communication. It provides good and clear communication that is easy to modulate and demodulate. The very high frequency (VHF) communication system supplies communication over line-of-sight distances. It gives communication between airplanes or between ground stations and airplanes. The VHF communication system supplies the flight crew with voice and data line-of-sight communication. The VHF communication system can be used to communicate between airplanes and between airplanes and ground stations. 19 The VHF communication radio is tunable in the frequency range of 118.000 MHz to 136.990 MHz. The VHF radio is used to transmit and receive voice communication. The VHF communication system operates in the frequency range of 118.000 MHz to 136.990 MHz. The 8.33 kHz spacing is only available for these frequency ranges:  118.000 to 121.400  121.600 to 123.050  123.150 to 136.475 Use of VHF communication: The VHF frequency are used for voice communication in ATC and Pilot controller communication.VHF frequency band is used for aircraft navigation pupose in the form of VOR station. UHF Communication System Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz).UHF radio is a two-way radio communication device that uses ultra-high frequency (UHF) radio frequencies to transmit and receive signals. Radio waves in the UHF band travel almost entirely by line-of-sight propagation (LOS). UHF radio waves are blocked by hills, but can penetrate foliage and buildings for indoor reception. It is a reliable and efficient communication tool that beside aviation is used in various industries such as transportation, construction, security, and emergency services.In aviation Ultra High Frequency (UHF) radio stations mostly are used for Air Traffic Control air-ground voice communications for military aircraft flying. Use of UHF communication: UHF frequencies are higher in frequency than VHF frequencies, which makes them better for short-range communications in aviation. In Air Traffic Control (ATC) Communication UHF is used for communication between pilots and ATC, especially in military aviation. In Radio navigation UHF are used in DME, Glide slop and Tactical Air Navigation (TACAN), Modern aircraft use UHF for various systems, including autopilot and onboard communication systems. 20 Ground-Based Radio Navigational Aids Navigation: The process or activity of accurately ascertaining one's position and planning and following a route.Types of navigation may be classified as Pilotage ,Dead reckoning ,Radio navigation ,Celestial navigation. Air navigation is defined as "the process of determining the geographic position and maintaining the desired direction of an aircraft relative to the surface of the earth."Navigational aid (NAVAID), is a general term known as aid to navigation, it may be any sort of signal, markers or guidance equipment which aids the traveler in navigation, usually nautical or aviation travel. Common types of such aids include lighthouses, buoys, fog signals, and day beacons. Radio Navigation aids includes navigation mainly by reference to indications of bearing and distance indicated based upon Radio transmitter equipment (broadcast stations) located on ground as NDB,VOR, ILS and DME whereas signal receiving equipment is installed on the aircraft. Non-Directional Radio Beacon (NDB) The Non-Directional Radio Beacon (NDB) is a low or medium frequency radio beacon transmits non-directional signals whereby the pilot of an aircraft properly equipped can determine bearings and "home" to the station The pilot, through the use of an Automatic Direction Finder, uses these signals in order to determine relative/magnetic bearing and therefore position The entire system consists of: Ground station ,ADF receiver,Antenna: NDB Frequencies  These facilities normally operate in a frequency band of 190 to 535 kilohertz (kHz)  According to International Civil Aviation Organization (ICAO) Annex 10 the frequency range for NDBs is between 190 and 1750 kHz, and transmit a continuous carrier with either 400 or 1020 hertz (Hz) modulation NDB Function  Transmit a continuous three-letter identification in Morse code ,These signals can be used to either home or intercept and track a course for navigation Very High Frequency Omni-Directional Range (VOR) The Very High Frequency Omni-Directional Range (VOR) is a ground-based electronic system and is a navigation aid (navaid). At the most simple level, a VOR is a type of navigation system for aircraft, using very high frequency radio signals emitted by radio beacons. That provides information for high and low altitude routes and airport approaches. 21 VOR stations broadcast the three letter identifier in Morse code. Because VOR signals have a range of about 200 miles, it is possible for an aircraft to receive multiple VOR signals. Therefore, it is necessary that pilots identify a VOR before navigating to it to ensure the proper navigation aid is selected. Although they’ve been around since the 1930s and widely in use since the 1970s, stations are uncommon enough to be foreign and mysterious to those who are unfamiliar with them. VOR navigation includes a ground-based element (those white cones – called stations) and a receiver component installed in an aircraft. Long before GPS was available for aircraft navigation, VOR stations guided aviators around the world. Although this technology is aging and many VORs are being decommissioned, VORs still play an important role in aviation. The VOR infrastructure itself is currently being repurposed as a backup navigation service that can be used during GPS outages. VOR signals may also suffer interference from thunderstorms and the lower accuracy requires instrument approaches based on VOR signals to have higher weather requirements and minimum descent altitudes. VOR Components and Features VOR components include the ground component and the aircraft component. The ground component transmits signals to the aircraft component. Aircraft equipment includes a VOR antenna, a VOR frequency selector and a cockpit instrument to display the course information. Instrument Landing System (ILS): ILS stands for Instrument Landing System and is a standard International Civil Aviation Organization (ICAO) precision landing aid that is used to provide accurate azimuth and descent guidance signals for guidance to aircraft for landing on the runway under normal or adverse weather conditions. 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: Localizer: The primary component of the ILS is the localizer, which provides lateral guidance. The transmitter and antenna (Shown above) are on the centerline at the opposite end of the runway from the approach threshold. 22 Glide Path:  The glide path component of ILS  Provides vertical guidance to the pilot during the approach.  Glide path Is located 750 to 1,250 feet (ft) down the runway from the threshold (shown above), offset 400 to 600 ft from the runway center line. Markers: Outer marker; (OM): The outer marker is located 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.This is followed by MIDDLE MARKER (MM) and INNER MARKER (IM) DME: Distance Measuring Equipment (DME) is normally collocated with glide path and provides slant distance to the aircraft with respect to touch down point. Selective Calling System (SELCAL): Selective Calling (SELCAL) is used in conjunction with the aircraft‘s VHF and HF systems. The system alerts the flight crew when it receives a ground call.This removes the need for continuous monitoring of the communication radios by the flight crew. The SELCAL decoder receives audio signals from the VHF and HF communication systems. Each airplane has a different four-letter SELCAL code. Each letter in the code equals a different audio tone. The ground stations send the applicable tones to call an airplane. When the airplane receives its SELCAL code, flight compartment indications come on to tell the flight crew. Aircraft Communications Addressing and Reporting System (ACARS): The aircraft communications addressing and reporting system (ACARS) is a datalink communication system. It lets you transmit messages and reports between an aircraft and an airline ground station. A message or report from the aircraft to the airline ground station is called a downlink. A message or report from the airline ground station to the aircraft is called an uplink. ACARS automatically sends reports when necessary and at scheduled times of the flight to reduce crew workload. These are typical ACARS reports  Crew identification  Out, off, on, in (OOOI) times  Engine performance  Flight status 23   Maintenance items Flight Inter communication System The Flight Interphone System is for internal cockpit communication and also with ground staff.The flight crew uses the flight interphone system to speak with each other and the ground crew. It consist of Cabin Interphone System, Service Interphone System. Passenger Address (PA) System Passenger Address System is for passenger announcement from cockpit and cabin crew station. The PA system is used forthe following :  Flight crew announcements  Pre-recorded/stored announcements  Boarding music  Chimes Pre-Recorded Announcement Machine (PRAM): Pre-recorded announcement machine supplies music and announcement audio to the PA system. The PA amplifier receives the audio inputs from the PRAM and sets the priority. A PTT signal goes to the PRAM to stop its operation. The PA system audio priorities:  Priority 1 – announcement from the flight compartment  Priority 2 – announcement from an attendant  Priority 3 – pre-recorded announcement  Priority 4 – boarding music. Radar frequency Bands: 24  PART- 3 AIRCRAFT COMMUNICATION 25 Aeronautical Telecommunication Communication Channels :  Aeronautical Mobile telecommunication service  Aeronutical Fix telecommunication service  ICAO – AFTN  IATA - SITA The Aeronautical Fixed Telecommunications Network The Aeronautical Fixed Telecommunications Network is a worldwide system of aeronautical fixed circuits provided, as part of the Aeronautical Fixed Service, for the exchange of messages and/or digital data between aeronautical fixed stations having the same or compatible communications characteristics. SITA – Société Internationale de Télécommunications Aéronautiques SITA is a multinational information technology company specializing in providing Information Technology (IT) and telecommunications services to the aviation community. SITA was founded in February 1949 by 11 airlines as a cooperative providing communications between airports and airlines. SITA has a strong presence in airlines on IATA platform for data processing and transmission between enterprises,provides solutions pertaining to airline operations, airport operations, baggage and cargo operations, commercial management, communications and infrastructure, passenger operations and transportation security. Based in Geneva,SITA works in coordination with the International Civil Aviation Organization (ICAO), the International Telecommunication Union (ITU), the International Air Transport Association (IATA), and other international and national governmental bodies Radio telephony Radiotelephony (RTF) provides the means by which pilots and ground personnel communicate with each other. The information and instructions transmitted are of vital importance in the safe and expeditious operation of aircraft. Radio telephony Language  The air-ground radiotelephony communications shall be conducted in the language normally used by the station on the ground or in the English language.  The English language shall be available, on request from any aircraft station, at all stations on the ground serving designated airports and routes used by international air services. 26   When proper names, service abbreviations and words of which the spelling is doubtful are spelled out in radiotelephony, use the ICAO alphabet  Incidents and accidents have occurred in which a contributing factor has been the use of non-standard procedures and phraseology. ICAO standardized phraseology shall be used in all situations for which it has been specified. Only when standardized phraseology cannot serve an intended transmission, plain language shall be used. Transmitting techniques  The following transmitting techniques will assist in ensuring that transmitted speech is clear:  Listen out on the frequency some seconds before transmitting to ensure that there will be no interference with a transmission from another station  Press the transmit switch fully before speaking and do not release it until the message is completed. This will ensure that the entire message is transmitted  Use a normal conversational tone, and speak clearly and distinctly and maintain the speaking volume at a constant level with rate of speech not exceeding 100WPM  Make a slight pause before and after numbers will assist in making them easier to understand,Avoid using hesitation sounds such as "er" etc.  The importance of using correct and precise standardized phraseology cannot be overemphasized. When an aeronautical station is called simultaneously by several aircraft stations, the aeronautical station shall decide the order in which aircraft shall communicate. Suspend speech temporarily if it becomes necessary to turn the head away from the microphone  After a call has been made to the aeronautical station, a period of at least 10 seconds should elapse before a second call is made. This should eliminate unnecessary transmissions while the aeronautical station is getting ready to reply to the initial call.  Maintain an even rate of speech not exceeding 100 words per minute. Transmission Priority All communication between pilots and ATM/Flight operation can be categorised into 6 categories of messages depending on the priority of information being transmitted (priority set by order):  Distress messages  Urgency messages  Navigation message  Flight safety messages  Meteorological messages  Flight regularity messages 27 Transmission of letters and numbers: In some circumstances it could be difficult to hear clearly what is said over the radio. Perhaps the aircraft is noisy, or the reception poor, or there may be words that sound similar and could be confused. For example, the letter ‘A’ could be confused with the number ‘8’, or the letter ‘C (see) which sounds like ‘D’(dee) or ‘V’(vee). To help overcome these problems a standard wayof saying letters, spellings, numbers and so on has been devised. Letters The standard alphabet has a phonetic pronunciation for each letter. The sound should be the same whatever the speaker’s natural language. A word should be spelt whenever its meaning is not clear technically or when using proper names, service abbreviations and words of which the spelling is doubtful. The phonetic alphabet are as follow:-  A Alpha Al FAH B Bravo BRAH VOH  C Charlie CHAR LEE D Delta DELL TAH  E Echo ECK OH F Foxtrot FOKS TROT  G Golf GOLF H Hotel HOH TELL  I India IN DEE AH J Juliet JEW LEE ETT  K Kilo KEY LOH L Lima LEE MAH  M Mike MIKE N November NO VEM BER  O Oscar OSS CAR P Papa PAH PAH  Q Quebec KEE BECK R Romeo ROW ME OH  S Sierra SEE AIR RAH T Tango TANG GO  U Uniform YOU NEE FORM V Victor VIK TAH  W Whiskey WISS KEY X X-Ray ECKS RAY  Y Yankee YANG KEY Z Zulu ZOO LOO Numbers Similarly numbers must also be said precisely especially when discussing height, altitudes or flight levels. Pronunciation of numbers is as follow:-  0 - ZERO  1 - WUN  2 - TOO  3 - TREE  4 -FOW-ER  5 -FIFE 28   6 -SIX  7 -SEVEN  8 -AIT  9 -NIN-ER  DECIMAL: DAY-SEE-MAL,  HUNDRED: HUN-DRED,  THOUSAND: TOU-SAND Exceptions: Numbers used to describe Altitude, Height, Visibility, and Runway Visual Range (RVR) which contain whole HUNDREDS or THOUSANDS - use “Hundred” and “Thousand”, otherwise single digits: 10 WUN ZERO 100 WUN HUNDRED 2500 TOOTOUSAND FIFE HUNDRED 11,000 WUN WUN TOUSAND 25,000 TWO FIFE TOUSAND Radio Telephony transmissions – (Voice Communication): Aircraft call signs Transmitted as  PIA238 Pakistan two three eight Heading Transmitted as  100° heading one zero zero  080° heading zero eight zero Wind direction / speed Transmitted as  200° 25kt Wind two zero zero degrees two five knots  160° 18kt Wind one six zero degrees one eight knots Runway Transmitted as  27 Runway two seven  09 Runway zero Niner 29 Transmission of altimeter settings The altimeter setting shall be transmitted by pronouncing each digit separately except for the case of a setting of 1 000 hPa which shall be transmitted as ONE THOUSAND. Altimeter Transmitted as  1010 One zero one zero  1000 One thousand  999 Nine(r) nine(r) nine(r) Transmission by using HUNDRED and THOUSAND All numbers used in the transmission of altitude, cloud height, visibility and runway visual range (RVR) information, which contain whole hundreds and whole thousands, shall be transmitted by pronouncing each digit in the number of hundreds or thousands followed by the word HUNDRED or THOUSAND as appropriate. Altitude Transmitted as  800 ft Eight hundred  3400 ft Three t(h)ousand four hundred  12000 ft One two t(h)ousand Cloud height Transmitted as  2200 ft Two t(h)ousand two hundred (prefix the type of cloud)  4300 ft Four t(h)ousand three hundred (prefix the type of cloud) visibility Transmitted as  1000 m Visibility one t(h)ousand (prefix the sector/place)  700 m Visibility seven hundred (prefix the sector/place) Runway visual range Transmitted as  600 m RVR six hundred (prefix the position/place)  1700 m RVR one t(h)ousand seven hundred (prefix the position/place) 30 Transmission of frequency All six digits of the numerical designator should be used to identify the transmitting channel in VHF radiotelephony communications, except in the case of both the fifth and sixth digits being zeros, in which case only the first four digits should be used: Channel Transmitted as  118.000 One one eight decimal zero  118.005 One one eight decimal zero zero five  118.010 One one eight decimal zero one zero  118.025 One one eight decimal zero two five  118.050 One one eight decimal zero five zero  118.100 One one eight decimal one Flight level Transmitted as  FL 180 Flight level one eight zero  FL 200 Flight level two hundred Transponder code Transmitted as  2600 Two six zero zero  1000 One t(h)ousand  2000 Two t(h)ousand  7001 Seven zero zero one Transmission of relative bearing in terms of the 12 hour clock When providing information regarding relative bearing to an object or to conflicting traffic in terms of the 12-hour clock, the information shall be given pronouncing the double digits as TEN, ELEVEN, or TWELVE (O'CLOCK). Transmission of time Only the minutes of the hour should normally be required to transmit time. Each digit should be pronounced separately. However, the hour should be included when any possibility of confusion is possible. Time Transmitted as  0920 Zero nine(r) two zero  09:20 AM/PM Two zero past the hour  1633 One six Three Three 31 Readability scale of the transmission Level of reception  Unreadable 1  Readable now and then 2  Readable but with difficulty 3  Readable 4  Perfectly readable 5 Radiotelephony standard pharases / words: The following words and phrases shall be used in radiotelephony communications as appropriate and shall have the meaning given below. Words Meaning  ACKNOWLEDGE: Let me know you have received and understood this message  AFFIRM: Yes  APPROVED: Permission for proposed action granted  BREAK: I indicate the separation between portions of the message  CANCEL: Annul the previously transmitted clearance  CHECK: Examine a system or procedure  CLEARED: Authorized to proceed under the conditions specified  CONFIRM: I request verification of: (clearance, instruction, information  CONTACT: Establish communications with...  CORRECT: "True" or "Accurate"  CORRECTION: Error has been made in this transmission,The correct version is …  DISREGARD: Ignore last transmission  HOW DO YOU READ: What is the readability of my transmission?  I SAY AGAIN: I repeat for clarity or emphasis  MAINTAIN: Continue in accordance with the condition given or last  MONITOR: Listen out on (frequency).  NEGATIVE: No or Permission not granted or That is not correct.  OVER: My transmission is ended and I expect a response from you.  REPORT: Pass me the following information...  REQUEST: I should like to know... / I wish to obtain...  ROGER: I have received all of your last transmission.  SAY AGAIN: Repeat all, or the following part, of your last transmission  SPEAK SLOWER: Reduce your rate of speech.  STAND BY: Wait and I will call you. 32   UNABLE: I cannot comply with your request, instruction, or clearance  WILCO: I understand your message and will comply with it  WORDS TWICE : Communication is difficult. Please send every word or group of words twice.  READ BACK: Repeat all, or the specified part, of this message back to me exactly as received.  RECLEARED: A change has been made to your last clearance and this new clearance supersedes your previous clearance or part thereof.  BREAK BREAK: I hereby indicate the separation between messages transmitted to different aircraft in a very busy environment Issue of clearance  A route clearance should be passed to an aircraft before start up. Avoid passing a clearance to a pilot engaged in complicated taxiing maneuvers and when the pilot is engaged in line up or take-off manoeuvres.Controllers should pass a clearance slowly and clearly since the pilot needs to write it down and wasteful repetition will thus be avoided. An air traffic control (ATC) route clearance is not an instruction to take off or enter an active runway. The words "TAKE OFF" are used only when an aircraft is cleared for take-off, or when cancelling a take-off clearance. At other times, the word "DEPARTURE" or "AIRBORNE" is used.  ATC shall begin his message with the concerned pilot call sign to be sure that the right pilot carefully listens. An ATC is not required to transmit his call sign with each call if done it at the first contact.The pilots identify themselves using their unique call signs.  The phrase "GO AHEAD" has been deleted from the manual of radiotelephony. So pilots and ATCs should no longer use it in frequency.  If aircraft’s read-back of a clearance or instruction is incorrect, the controller shall transmit the word "NEGATIVE, I SAY AGAIN" followed by the correct version: Establishing communication: First contact: Departing aircraft , pilot initial call shall contain:  Designation of the station being called (ATS Unit)  Call sign of his aircraft, (with the word wake turbulence category)  Position (on the apron or on route)  Additional elements as required by controllersㅤ 33 Radio telephony test procedure When a communication with an air traffic Example: controller seems to be difficult, a pilot can use a radio communication test procedure.Test Islamabad TOWER, Pk 301, RADIO CHECK, 118.5 transmissions should take the following form PK 301,Islamabad Tower , READING YOU 3 as a pilot:  The identification of the aeronautical station being called followed by calling station identification  The words "RADIO CHECK" followed by the frequency being used Replies to test transmissions should be as follows: Example: Islamabad Tower, PK 301 ,Heavy at stand No.6 request airfield  The identification of data for departure Karachi. the station calling following by the PK 301,Islamabad Tower ,Weather fair ,surface wind 270/10 kts,Temprature 25 C , QNH 1013 , No delay expected,Time 50 past identification of the the hour. station replying  The word “Read you ……..(reability scale)” ATC clearance by network station to an aircraft Station: PAKISTAN THREE TWO FOUR KARACHI Aircraft: KARACHI PAKISTAN THREE TWO FOUR Station: PAKISTAN THREE TWO FOUR KARACHI— ATC CLEARS PAKISTAN THREE TWO FOUR KARACHI TO DESCEND TO NINE THOUSAND FEET Aircraft (acknowledging):CLEARED TO DESCEND TO NINE THOUSAND FEET — PAKISTAN THREE TWO FOUR Station (denoting accuracy of read back):KARACHI 34 Notification of communication failure: The air-ground control radio station shall notify the appropriate air traffic services unit and the aircraft operating agency, as soon as possible, of any failure in air-ground communication. Imposition of silence: The station in distress, or the station in control of distress traffic, shall be permitted to impose silence, either on all stations of the mobile service in the area or on any station which interferes with the distress traffic. It shall address these instructions “to all stations”, or to one station only, according to circumstances. In either case, it shall use:  STOP TRANSMITTING;  the radiotelephony distress signal MAYDAY. 35