B737 NG Communications

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Overview of the B737NG Communication systems.

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B737 NG Communications

  1. 1. B 737 NG Ground School. See the aircraft study guide at www.theorycentre.com The information contained here is for training purposes only. It is of a general nature it is unamended and does not relate to any individual aircraft. The FCOM must be consulted for up to date information on any particular aircraft.
  2. 2. COMMUNICATIONS
  3. 3. GENERAL EXTERNAL ANTENNA LOCATIONS
  4. 4. Introduction The communication system includes: • radio communication system • interphone communication system • cockpit voice recorder system • communication crew alerting system The communication systems are controlled using the: • audio control panels • radio tuning panels • radio communication panels
  5. 5. Radio Tuning Panel Navigation radio Audio Control panel SELCAL panel AFT Electronic panel
  6. 6. Audio Systems and Audio Control Panels An ACP is installed at the Captain, First Officer, and Observer stations. Each panel controls an independent crew station audio system and allows the crewmember to select the desired radios, navigation aids, interphones, and PA systems for monitoring and transmission.
  7. 7. Transmitter selectors on each ACP select one radio or system for transmission by that crewmember. Any microphone at that crew station may then be keyed to transmit on the selected system. Receiver switches select the systems to be monitored. Any combination of systems may be selected. Receiver switches also control the volume for the headset and speaker at the related crew stations. Audio from each ACP is monitored using a headset/headphones or the related pilot’s speaker. Audio warnings for altitude alert, ground proximity warning, collision avoidance, and windshear are also heard through the speakers and headsets at preset volumes. They cannot be controlled or turned off by the crew.
  8. 8. AUDIO CONTROL PANEL (Typical) Transmitter Selector (MIC SELECTOR) Switches Illuminated – related switch is active Push – • selects related communication system for subsequent transmission • only one switch may be selected at a time; pushing a second switch deselects first switch • reception possible over selected system regardless of whether related receiver switch is on.
  9. 9. AUDIO CONTROL PANEL (Typical) Receiver Switches Illuminated (white) – related switch is active Rotate – adjusts volume Push – • allows reception of related communication system or navigation receiver • multiple switches may be selected Push again – deselects related system or receiver. The light may also be integral with the volume control
  10. 10. AUDIO CONTROL PANEL (Typical) Push–to–Talk Switch (spring–loaded to neutral position) RADIO (radio–transmit) – keys oxygen mask or boom microphone for transmission as selected by transmitter selector. INT (Intercom) – keys oxygen mask or boom microphone for direct Transmission over flight interphone and bypasses transmitter selector.
  11. 11. AUDIO CONTROL PANEL (Typical) Filter Switch V (Voice) – receive NAV and ADF voice audio. B (Both) – receive NAV and ADF voice and range audio. R (Range) – receive NAV and ADF station identifier range (code) audio.
  12. 12. AUDIO CONTROL PANEL (Typical) Speaker (SPKR) Switch Illuminated (white) – SPKR switch is active. Push – audio from selected receiver is heard on overhead speaker. Rotate – adjusts overhead speaker volume. Push again – deselects audio from selected receiver to be heard on Overhead speaker.
  13. 13. AUDIO CONTROL PANEL (Typical) Alternate–Normal Switch NORM (Normal) – ACP operates normally. ALT (Alternate) – ACP operates in degraded mode.
  14. 14. AUDIO CONTROL PANEL (Typical) CALL Light Illuminated (white) – Accompanied by a chime, indicates call received by SELCAL, ACARS (if installed), ground crew (INT), SATCOM (if installed), or flight crew (CABIN). Resets when transmitter is selected and microphone is keyed. PA does not have a CALL indication.
  15. 15. Speakers and Headsets Each crew station has a headset or headphone jack. The Captain and First Officer have speakers on the ceiling above their seats. There is no speaker at the observer station. Headset volume is controlled by the receiver switches. Speaker volume is controlled by the receiver switches and also the speaker switch.
  16. 16. Microphones Hand microphones and boom microphones may be plugged into the related jacks at the flight deck crew stations. Each oxygen mask also has an integral microphone. An oxygen mask microphone is enabled and the boom microphone is disabled when the left oxygen mask panel door is open. The oxygen mask microphone is disabled and the boom microphone is enabled when the left oxygen mask panel door is closed and the RESET/TEST Switch is pushed. Each hand microphone has a PTT switch to key the selected audio system. The PTT switches on the control wheel or ACP are used to key the oxygen mask or boom microphone, as selected by the RADIO/INT switch. The RADIO/INT switch does not affect the operation of the hand microphone. A MIC switch may be mounted on the captain’s and first officer’s glareshield panel and is used to key the oxygen mask or boom microphone, as selected by the transmitter switch on that pilot’s ACP. Pushing the glareshield MIC switch is the same as pushing the control wheel MIC switch.
  17. 17. RADIO TUNING PANELS VHF Communications Transfer (TFR) Switch Push – selects standby frequency as active frequency for transceiver. Active frequency becomes standby frequency. Frequency Selector Rotate – selects frequency in standby indicator: • outer selector changes three left digits • inner selector changes two right digits. NOTE: There are a number of different RTP’s in use depending on the aircraft radio fit.
  18. 18. RADIO TUNING PANELS Older style ACP is directly connected to the onside radio. Captain Left F/O right.
  19. 19. RADIO TUNING PANELS With Newer style ACP all communications are passed through a Remote Electronics Unit. This enables connection to any radio from any crew position.
  20. 20. B737 Typical Radio tuning Panel Each VHF radio has an Active and Standby frequency. Radio Tuning Switch light indicates which radio is selected on this panel
  21. 21. B737 Typical Radio tuning Panel Panel OFF light illuminated White. Not connected to any Radio.
  22. 22. B737 Typical Radio tuning Panel HF Sensitivity Knob. Hard wire connected to ON SIDE HF Radio. Captain HF 1 and F/O HF 2 as installed.
  23. 23. B737 Typical Radio tuning Panel AM Switch Push – light on sets the AM (amplitude modulation) or light off USB (upper side band) mode for the selected HF radio.
  24. 24. B737 Typical Radio tuning Panel VHF TEST Switch Push – • removes automatic squelch feature, permitting reception of background noise and thereby testing receiver operation • improves reception of weak signals.
  25. 25. The selected Radio is not available The Panel is not able to communicate with the selected Radio. It does not mean a Radio failure has occurred. Selecting on another panel may work.
  26. 26. This RTP has failed.
  27. 27. The Selected Radio has failed. Option on some aircraft only.
  28. 28. Normal Audio System Operation The Captain, First Officer, and Observer audio systems are located in a common remote electronics unit in the E/E compartment. They function independently and have separate circuit breakers. The audio systems are normally controlled by the related ACPs through digital or computerized control circuits. Degraded Audio System Operation If the remote electronics unit or ACP malfunctions, the ACP cannot control the remote electronics unit. Audio system operation can be switched to a degraded mode by placing the ALT–NORM switch to ALT. In this mode, the ACP at that station is inoperative and the crewmember can only communicate on one radio. The ACP transmitter selectors are not functional. Any transmission from that station must be from the radio shown on the chart below. The transmitter selector for the usable radio illuminates when a station is operating in the degraded mode. The receiver switches are not functional, and only the usable radio is heard at a Preset volume, through the headset. The speaker and speaker switch are not functional at that station. In addition, the flight interphone and service interphone cannot be used. The control wheel PTT switch INT position and the ACP PTT switch INT position are not functional since the flight interphone is not functional. Audio warnings for altitude alert, GPWS, and windshear are not heard on an audio system operating in the degraded mode. An audio system operating in the degraded mode cannot access the passenger address system through the audio control panel. The crewmember can still use the service interphone handset and PA microphone if they are installed on the control stand.
  29. 29. Degraded Audio System Operation If the remote electronics unit or ACP malfunctions . Audio system operation can be switched to a degraded mode . ALT–NORM switch to ALT. ACP is inoperative and the crewmember can only communicate on one radio.
  30. 30. LIMITATIONS Do not use VHF–3 (if installed) for voice communication with ATC VHF- 3 is for ACARS use. Note: The following items are not AFM limitations, but are provided for flight crew information. Use the VHF radio connected to the top of fuselage antenna for primary ATC communications on the ground. Note: VHF antennae located on the lower fuselage are susceptible to multipath interference from nearby structures or vehicles. This may disrupt VHF communications. VHF antennae located on the upper fuselage are not as susceptible to this interference. Note; Be cautious with VHF & UHF transmitting antennas No person should ever be near a transmitting antenna VHF & UHF has the most effect on soft tissue WARNING: MAKE SURE THAT PERSONNEL STAY A MINIMUM OF 10 FT (3 M) AWAY FROM THE VERTICAL STABILIZER WHEN THE HF SYSTEM TRANSMITS. RF ENERGY FROM THE HF ANTENNA CAN CAUSE INJURIES TO PERSONNEL.
  31. 31. Flight Interphone System The flight interphone system is an independent communication network. Its primary purpose is to provide private communication between flight deck crewmembers without intrusion from the service interphone system. The ground crew may also use the flight interphone through a jack at the external power receptacle. The pilots can transmit directly over the flight interphone by using the control wheel PTT switch. Alternately, any crewmember with an ACP can transmit/receive over the flight interphone by using their related ACP and normal PTT switches. Any standard microphone may be used with the flight interphone system. the flight interphone cannot be used when the audio system is operating in the degraded mode. Audio warnings for altitude alert, GPWS, TCAS and windshear are not heard on an audio system operating in the degraded mode as they are relayed via the flight interphone speakers.
  32. 32. FLIGHT INTERPHONE SYSTEM For communication between the flight crew. Can be used from the External power panel by the Ground crew.
  33. 33. Service (Attendant) Interphone System The service interphone system provides intercommunication between the flight deck, Flight Attendants, and ground personnel. Flight deck crewmembers communicate using either a separate handset (if installed) or their related ACP and any standard microphone. The Flight Attendants communicate between flight attendant stations or with the flight deck using any of the attendant handsets. Anyone who picks up a handset/microphone is automatically connected to the system. External jacks for use by maintenance or service personnel can be added to the system by use of the service interphone switch.
  34. 34. SERVICE INTERPHONE Used for communication between Flight and cabin crew. Used Cabin crew to cabin crew. Service Interphone switch (Aft Overhead panel.) Turns ON additional interphone connection at service points around the aircraft. Off does not affect Flight crew and cabin crew operation.
  35. 35. All external jacks turned Off by switch. Jack Locations These locations have service interphone jacks: A. P19 external power panel B. Electronic equipment compartment C. Fueling station, door on the right wing D. Right wheel well, E. Left wheel well, F Aft cabin, on the ceiling above the attendant station G. APU service area.
  36. 36. Flight interphone Service Interphone External Power panel
  37. 37. Passenger Address System The passenger address (PA) system allows flight deck crewmembers and flight attendants to make announcements to the passengers. Announcements are heard through speakers located in the cabin and in the lavatories. The flight deck crewmembers can make announcements using a PA handset or by using any standard microphone and the related ACP. Flight Attendants make announcements using PA handset located at their stations. The attendants use the PA to play recorded music for passenger entertainment. PA system use is prioritized. Flight deck announcements have first priority and override all others. Flight Attendant announcements override the music system. Chimes The chime circuits of the PA system supply these chime signals: * High chime * Low chime * High/low chime. High chimes operate when there is an attendant call signal from a passenger service unit or lavatory. Low chimes operate when the no smoking or fasten seat belts signs come on. High/low chimes operate when there is an attendant call from the flight compartment or another attendant station.
  38. 38. Call System The call system is used as a means for various crewmembers to gain the attention of other crewmembers and to indicate that interphone communication is desired. Attention is gained through the use of lights and aural signals (chimes or horn). The system can be activated from the flight deck, either flight attendant station, or from the external power receptacle. Passengers may also use the system to call an attendant, through the use of individual call switches at each seat. The flight deck may be called from either flight attendant station or by the ground crew. The ground crew may only be called from the flight deck. Flight Attendants may be called from the flight deck, the other attendant station, or from any passenger seat or lavatory. Master call lights in the passenger cabin identify the source of incoming calls to the attendants. Call system chime signals are audible in the passenger cabin through the PA system speakers. The PA speakers also provide an alerting chime signal whenever the NO SMOKING or FASTEN SEAT BELT signs illuminate or extinguish.
  39. 39. Master Call Lights Illuminated – • amber – a lavatory call switch is activated or smoke is detected in a lavatory. • pink – flight deck or other flight attendant station is calling. • blue – a passenger seat call switch is activated.
  40. 40. CALL SYSTEM Ground crew can be called only from the flight deck. Call sounds the ground crew call horn in the nose wheel well The Ground crew can call the flight deck from the External power panel. C light illuminates on ACP INT switch. Tone Aural and CALL light if fitted.
  41. 41. VHF Communications Primary short–range voice communications is provided in the VHF range by two or three independent radios. Each radio provides for selection of an active frequency and an inactive (preselected) frequency. Voice transmission and reception are controlled at the related ACP. HF Communications There are one or two independent HF communication radios, designated HF 1 and HF 2. Each HF radio can be tuned by any radio tuning panel. HF radio sensitivity can only be set on the on-side radio tuning panel. Some aircraft have a separate HF radio tuning panel. When an HF transmitter is keyed after a frequency change, the antenna tunes. A steady or intermittent tone may be heard through the audio system. While tuning, the tone can last as long as 7 seconds. If the system fails to tune, the tone will last more than 7 seconds, to a maximum of 15 seconds. The antenna is located in the vertical stabilizer. Both HF radios use a common antenna. When either HF radio is transmitting, the antenna is disconnected from the other HF radio, and it cannot be used to transmit or receive. However, both HF radios can receive simultaneously if neither is being used for transmitting. Note: Data for the last 100 tuned frequencies is stored in memory. Tuning duration for these stored frequencies will be very short and a tune tone may not be noticeable. (Aircraft fit)
  42. 42. Selective Calling (SELCAL) In international aviation, SELCAL or SelCal is a selective-calling radio system that can alert an aircraft's crew that a ground radio station wishes to communicate with the aircraft. SELCAL uses a ground-based encoder and radio transmitter to broadcast an audio signal that is picked up by a decoder and radio receiver on an aircraft. The use of SELCAL allows an aircraft crew to be notified of incoming communications even when the aircraft's radio has been muted. Thus, crewmembers need not devote their attention to continuous radio listening.
  43. 43. SELCAL operates on the high frequency (HF) or very high frequency (VHF) radio frequency bands used for aircraft communications. HF radio often has extremely high levels of background noise and can be difficult or distracting to listen to for long periods of time. As a result, it is common practice for crews to keep the radio volume low unless the radio is immediately needed. A SELCAL notification activates a signal to the crew that they are about to receive a voice transmission. An individual aircraft has its own assigned SELCAL code. To initiate a SELCAL transmission, a ground station radio operator enters an aircraft's SELCAL code into a SELCAL encoder. The encoder converts the four-letter code into four designated audio tones. The radio operator's transmitter then broadcasts the audio tones on the aircraft's company radio frequency channel in sequence: the first pair of tones are transmitted simultaneously, lasting about one second; a silence of about 0.2 seconds; followed by the second pair of tones, lasting about one second. The code is received by any aircraft receiver monitoring the radio frequency on which the SELCAL code is broadcast. A SELCAL decoder is connected to each aircraft's radio receiver. When a SELCAL decoder on an aircraft receives a signal containing its own assigned SELCAL code, it alerts the aircraft's crew by sounding a chime, activating a light, or both. The crew next turns up the volume on the aircraft radio to hear the incoming voice transmission.
  44. 44. An individual aircraft is given a SELCAL code upon application to the SELCAL code registrar, Aviation Spectrum Resources, Inc. (ASRI). The code is technically assigned to the owner-operator of the aircraft rather than the aircraft itself; if an aircraft is sold, the new owners-operators must apply for a new code. The code is a sequence of four letters, written or transmitted as an ordered two sets of two letters each (e.g., AB-CD). The letters are chosen from a subset of the Latin script comprising A through S, excluding I, N and O. The letters within a given pair are written or transmitted in alphabetical order (e.g., AB-CD is an allowable distinct SELCAL code, as is CD-AB, but CD-BA is not). A given letter can be used only once in a SELCAL code; letters may not be repeated (e.g., AB-CD is allowable, but AA-BC and AB-BC are not). Each letter designates a specific audio tone frequency.
  45. 45. The current rules for SELCAL code assignment, with sixteen available letters/tones, limit the number of possible allowable codes to 10,920. Additionally, SELCAL codes assigned previously use a subset of only twelve letters/tones. Therefore, more than one aircraft may be designated by the same code. To avoid confusion from two or more aircraft using the same SELCAL code, ASRI tries to assign code duplicates to aircraft that do not usually operate in the same region of the world or on the same HF radio frequencies. However, aircraft commonly move between different geographical regions and it is now routine for two aircraft with the same SELCAL code to be found flying in the same region. Therefore, air crew always verify both SELCAL and call sign (i.e., aircraft tail registration, or telephony designator and flight identification) to be sure their aircraft is the intended recipient.
  46. 46. SELECTIVE CALLING Selective calling is automatic. Each aircraft has a four letter SELCAL code. Each letter has a tone. The aircraft listens to the airwaves for its own tone using the VHF & HF radios. An aural tone sounds and a SELCAL light illuminates for the radio receiving the message. HF RADIO VHF RADIO SELCAL DECODER SELCAL AURAL RELAY Remote Electronics Unit
  47. 47. SELCAL PANEL
  48. 48. Cockpit Voice Recorder The cockpit voice recorder uses four independent channels to record flight deck audio for 30 minutes or 120 minutes. Recordings older than 30 or 120 minutes are automatically erased. One channel records flight deck area conversations using the area microphone. The other channels record individual ACP output (headset) audio and transmissions for the pilots and observer. (Aircraft fit dependent) The RIPS (Recorder Independent Power Supply) provides power to the cockpit voice recorder for 10 minutes after aircraft power is interrupted either by normal shutdown or by any other loss of power. Normal power supply 115V transfer bus 2 and 28 V from DC bus 2.
  49. 49. VOICE RECORDER Switch (when fitted) AUTO - powers the cockpit voice recorder from first engine start until 5 minutes after last engine shutdown ON - powers the cockpit voice recorder until first engine start, then trips the switch to AUTO. On aircraft with no switch the voice recorder is active anytime 115V AC is applied to airplane.
  50. 50. Area Microphone Active anytime the voice recorder is active. Records one channel The voice recorder unit collects these audio from the R.E.U.at the same time: * Captain microphone and headphone * First officer (F/O) microphone and headphone * First observer (F/OBS) microphone and headphone * The voice recorder unit also receives time from the Captains clock.
  51. 51. STATUS Light Illuminated (momentary green) – no faults are detected during recorder TEST.
  52. 52. ERASE Switch (red) Push (2 seconds) – • all four channels are erased • operative only when airplane is on ground and parking brake is set.
  53. 53. TEST Switch Push – after a slight delay and no faults are detected: • status light illuminates momentarily • a tone may be heard through a headset plugged into HEADPHONE jack.
  54. 54. HEADPHONE Jack Headphone may be plugged into jack to monitor tone transmission during test, or to monitor playback of voice audio.
  55. 55. Aircraft Communications Addressing and Reporting System (ACARS) The ARINC Communications Addressing and Reporting System (ACARS) is an addressable digital data link system which permits exchange of data and messages between an airplane and a ground-based operation centre utilizing an onboard VHF communications system. The ACARS airborne subsystem provides for the manual entry of routine data such as departure/arrival information. Also possible is manual entry of addresses (telephone codes) of parties on the ground for voice communications. The airborne system consists of a management unit in the E/E compartment, either a interactive display unit or multipurpose control display unit (MCDU), and frequently a printer. Data is entered and transmitted to the ground operations centre. A worldwide ground data network of radio stations provides ACARS service. Over the next 20 years, ACARS will be superseded by the Aeronautical Telecommunications Network (ATN) protocol for Air Traffic Control communications and by the Internet Protocol for airline communications.
  56. 56. One of the applications for ACARS is to automatically detect and report changes to the major flight phases (Out of the gate, Off the ground, On the ground, and Into the gate), referred to in the industry as OOOI. These OOOI events are determined by algorithms that use aircraft sensors (such as doors, parking brake and air ground sensors) as inputs. At the start of each flight phase, a digital message is transmitted to the ground containing the flight phase, the time at which it occurred, and other related information such as the amount of fuel on board or the flight origin and destination. These messages are used to track the status of aircraft and crews. In addition to detecting events on the aircraft and sending messages automatically to the ground, There may be interfaces with other on-board avionics. A data link interface between the ACARS management units and flight management systems. This interface enables flight plans and weather information to be sent from the ground to the ACARS management unit, for forwarding to the flight management system. This feature gives the airline the capability to update flight management systems while in flight, and allows the flight crew to evaluate new weather conditions or alternative flight plans.
  57. 57. The ACARS management unit can be linked to the flight data acquisition and management system and the aircraft condition monitoring system systems which analyze engine, aircraft and operational performance conditions to provide performance data to the airlines on the ground in real time using the ACARS network. This reduces the need for airline personnel to go to the aircraft to off-load the data from these systems. These systems are capable of identifying abnormal flight conditions and automatically sending real-time messages to an airline. Transmission of maintenance-related information in real-time through ACARS. enables airline maintenance personnel to receive real-time data associated with maintenance faults on the aircraft. When coupled with the flight data acquisition and management system data, airline maintenance personnel can start planning repair and maintenance activities while the aircraft is still in flight. Detailed engine reports can also be transmitted to the ground via ACARS. The airlines use these reports to automate engine trending activities.
  58. 58. ACARS Aeronautical Radio, Incorporated (ARINC) Communicating Addressing & Reporting System. VHF based digital data link. Used to pass data from Air to Ground and Ground to Air. Can be used to send automatic reports like Brake release for push back and transition to Air mode for T/O time reporting. OOOI reports
  59. 59. ACARS Reports can be sent from the MCDU. Flight information can be sent to the printer. Can be used for voice communication. ACARS is accessed from the CDU Main Menu. There are many possible reports which are configured by the airline. Includes. Report type Flight number Destination and Origin. Aircraft registration number. Date and time sent.
  60. 60. The ACARS management unit receives flight information including flight number from the FMC
  61. 61. ACARS can be used to send both Manual and automatic reports. The Airline can use the information for future performance and flight planning.
  62. 62. Airlines decide how to use ACARS and the ACARS menu on an aircraft dictates what the crew can use it for.
  63. 63. On the Captains Audio Control Panel the ALT/NORM switch is selected to ALT which radios are available for the Captain?
  64. 64. On the Captains Audio Control Panel the ALT/NORM switch is selected to ALT which radios are available for the Captain? The Captain can transmit and receive only on VHF 1.
  65. 65. How is the volume of an Aural warning adjusted?
  66. 66. How is the volume of an Aural warning adjusted? Audio warnings for altitude alert, ground proximity warning, collision avoidance, and windshear are heard through the speakers and headsets at preset volumes. They cannot be controlled or turned off by the crew.
  67. 67. List the PTT switches that each pilot has;
  68. 68. 1. 2. 3. 4. Audio control panel. Hand Microphone. Glare shield. Control wheel.
  69. 69. INOP is shown in both the ACTIVE and STANDBY windows of the Radio Tuning Panel; a) Both VHF radios have failed b) The selected radio has failed. c) The radio tuning panel has failed. d) The selected radio is not available.
  70. 70. INOP is shown in both the ACTIVE and STANDBY windows of the Radio Tuning Panel; a) Both VHF radios have failed b) The selected radio has failed. c) The radio tuning panel has failed. d) The selected radio is not available.
  71. 71. AIR/GROUND PUBLIC TELEPHONE SYSTEM - GENERAL DESCRIPTION (OPTION)
  72. 72. AIR/GROUND PUBLIC TELEPHONE SYSTEM - GENERAL DESCRIPTION (OPTION) The air/ground public telephone system lets the passengers make telephone calls to persons on the ground. The cabin telecommunication unit is the central processor for the air/ground public telephone system. The CTU receives calls from the telephone handsets and sends them to the ground telephone network via the terrestrial flight telecommunication system. The air traffic control system sends the airplane identification and airplane altitude to the CTU. The air/ground relay tells the CTU when the airplane is in the air. The terrestrial flight telecommunication system (TFTS) is a UHF radio system. The TFTS provides line-of-sight connections for telephone calls from the airplane to ground stations.
  73. 73. Satellite Communications (SATCOM) System (OPTION) The SATCOM system provides both data and voice communications. The satellite data unit is controlled through the control display units (CDUs). Voice transmission is controlled using CDUs and the audio control panels. Calls can be initiated using the CDU. Directories of airline defined numbers are line selectable or manual numbers can be entered. The SATCOM CDU control pages are displayed by selecting SAT on the MENU page. SATCOM menu configuration is defined by the individual airline.
  74. 74. Satellite Communications (SATCOM) System
  75. 75. RADIO THEORY FOR THOSE NOT FAMILIAR WITH HF High Frequency (HF) radio is used for first-line and backup communications over long distances, mainly in remote regions. Whilst VHF is used for short-range line-of sight (LOS) communications, only HF is capable of communicating over distances of 3000 km or more. In HF radio transmission there are two modes of operation. amplitude-modulated wave consists of a carrier and two identical sidebands which are spaced above and below the carrier by an amount equal to the modulating frequency. These are called the upper and lower sidebands. One sideband contains all the elements necessary for voice transmission. carrier wave Radio a wave of fixed amplitude and frequency that is modulated in amplitude, frequency, or phase in order to carry a signal in radio transmission, Upper sideband Unmodulated carrier Lower sideband Modulated carrier
  76. 76. RADIO THEORY FOR THOSE NOT FAMILIAR WITH HF Amplitude modulation, AM is the most straightforward way of modulating a signal. Demodulation, or the process where the radio frequency signal is converted into an audio frequency signal is also very simple. An amplitude modulation signal only requires a simple diode detector circuit. The second mode is single-sideband modulation (SSB) this is a refinement of amplitude modulation that more efficiently uses transmitter power and bandwidth. Amplitude modulation produces an output signal that has twice the bandwidth of the original baseband signal. Single-sideband modulation avoids this bandwidth doubling, and the power wasted on a carrier, at the cost of increased device complexity and more difficult tuning at the receiver. The upper sideband USB is used in this form of transmission. USB SSB AM TRANSMISSION
  77. 77. Radio propagation is the behaviour of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization and scattering. Radio propagation is affected by the daily changes of water vapour in the troposphere and ionization in the upper atmosphere, due to the Sun. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems. Radio propagation is also affected by several other factors determined by its path from point to point. This path can be a direct line of sight path or an over-the-horizon path aided by refraction in the ionosphere, which is a region between approximately 60 and 600 km above the Earth. Factors influencing ionospheric radio signal propagation can include solar flares, geomagnetic storms, ionospheric layer tilts, and solar proton events.
  78. 78. Surface mode (ground wave) Lower frequencies (between 30 and 3,000 kHz) have the property of following the curvature of the earth via ground wave propagation in the majority of occurrences. In this mode the radio wave propagates by interacting with the semi-conductive surface of the earth. The wave "clings" to the surface and thus follows the curvature of the earth. Direct mode (line-of-sight) Line-of-sight is the direct propagation of radio waves between antennas that are visible to each other. This is probably the most common of the radio propagation modes at VHF and higher frequencies. Because radio signals can travel through many non-metallic objects, radio can be picked up through walls. This is still lineof-sight propagation. Examples would include propagation between a satellite and a ground antenna or reception of television signals from a local TV transmitter. Ionospheric mode (skywave) Skywave propagation, also referred to as skip, is any of the modes that rely on refraction of radio waves in the ionosphere, which is made up of one or more ionized layers in the upper atmosphere. F2-layer is the most important ionospheric layer for long-distance, multiple-hop HF propagation. The layers, or more appropriately "regions", are directly affected by the sun on a daily diurnal cycle, a seasonal cycle and the 11-year sunspot cycle and determine the effect of these modes
  79. 79. H.F. RADIO Ionosphere ADVANTAGES. Good for transmitting information over long distances. Relatively simple equipment. DISADVANTAGES. Requires high power to transmit. Suffers from many forms of interference. Sky wave Direct wave Ground wave Dead Zone The size of the dead zone is called the skip distance. Skip distance is dependent on the height of the transmitting antenna and the height of the receiving antenna.
  80. 80. This is Amplitude Modulation. It uses a large band width limiting the number of stations which can transmit at any one time. It uses more power to transmit. It is more prone to interference.
  81. 81. USB SSB AM TRANSMISSION This is USB. All of the information is still carried on the carrier, but only half the band width is used. This allows twice as many transmission without interference.
  82. 82. Radio HF/VHF HF (High frequency) radio frequencies are between 3 and 30 MHz.. Frequencies immediately below HF are denoted Medium-frequency (MF) VHF (Very high frequency) is the radio frequency range from 30 MHz to 300 MHz.. Common uses for VHF are FM radio broadcast, television broadcast, air traffic control communications and air navigation systems (e.g. VOR, DME & ILS). HF radio use The high frequency band is very popular with radio operators, who can take advantage of direct, long-distance (often inter-continental) communications VHF radio use VHF propagation characteristics are ideal for short-distance terrestrial communication, with a range generally somewhat farther than line-of-sight from the transmitter. Unlike high frequencies (HF), the ionosphere does not usually reflect VHF radio and thus transmissions are restricted to the local area. 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, it is less affected by buildings and other less substantial objects Universal use Certain subparts of the VHF band have the same use around the world. 108–118 MHz: Air navigation beacons VOR and Instrument Landing System localiser. 118–137 MHz: Air band for air traffic control, 121.5 MHz is the emergency frequency
  83. 83. VHF FM Transmissions. VHF is line of sight only. The higher the frequency the shorter the range. For VHF we do not add amplitude to the carrier we change or MODULATE the frequency of the carrier. This is FM radio.
  84. 84. Which VHF radio should be used on the Ground? WHY?
  85. 85. Which VHF radio should be used on the Ground? Note: The following items are not AFM limitations, but are provided for flight crew information. Use the VHF radio connected to the top of fuselage antenna for primary ATC communications on the ground. WHY? SAFETY!
  86. 86. Communications. Now take the test at www.theorycentre.com For more information info@theorycentre.com

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