Avionic Systems VHF-HF PDF

Avionic Systems  2 Overview of AVS  Part 1 Avionics (VHF/HF, ILS, VOR, ADF, FMS and GPS)  Part 2 Radar (Primary, Weather and Secondary)  3 Assessment (AVS) 1) Semester Examination: 50% 2) Mid-Se...

Avionic Systems  2 Overview of AVS  Part 1 Avionics (VHF/HF, ILS, VOR, ADF, FMS and GPS)  Part 2 Radar (Primary, Weather and Secondary)  3 Assessment (AVS) 1) Semester Examination: 50% 2) Mid-Semester Test: 20% 3) Lab Test: 10% 4) Lab Quiz: 10% 5) General Performance: 10%  4 How do I apply for a Singapore Aircraft Maintenance Engineer (AME) Licence? If you are a Singaporean or a permanent resident, you must: i) be at least twenty-one years old ii) be able to read, write and converse in English iii) be employed by an organisation which operates or services Singapore registered aircraft iv) have had the practical experience specified in the SAR Section 66, and have passed examinations prescribed for the category of licence, and v) not be suffering from any disability likely to adversely affect your technical skill or judgement  5 Chapter 1 VHF/HF COMMUNICATION SYSTEMS  6 Introduction  Communication in aviation is currently mainly achieved by voice modulation of radio waves  The future seems to lie in data transfer, which can be achieved without using the human voice  Nonetheless, voice communication is still important for safe movement of air traffic, and will remain so in many parts of the world  7 Learning Outcomes  Airborne Very High Frequency (VHF) Communication  Airborne High Frequency (HF) Communication  Concept of Selective Calling System (SELCAL)  Operation of Emergency Locator Transmitter (ELT)  8 VHF Communication  VHF is essentially line of sight by direct wave  Provides short range air-to-air and air-to- ground voice communications  The primary use is for Air Traffic Control (ATC)  118-136 MHz (VHF-Band)  9 VHF VHF ATC Very High Frequency Communications  10 Range Available R is in nautical miles Hr & Ht are receiver and transmitter antenna heights in feet  11 Example 1-1  At what maximum range would a VHF signal transmitted from an aircraft flying at 12000 ft be received by another aircraft flying at 9000 ft? Range 1.25   9000  12000  255 nm  12 The factors affecting the range of VHF transmission are:  Transmission power both at aircraft and ground station  Height of the transmitter  Height of the receiver  Obstacles at the transmission site will block the signals  13 VHF system  Frequency control panel Frequency selection will be provided by control panel Flight interphone system provides Microphone (MIC) audio input for voice transmission  Transceiver Transmitter + receiver  Antenna Received and transmitted radio frequency signals travel between transceiver and antenna on a RF- Coax line  14 ANTENNA RF-COAX AUDIO TO FLIGHT INTERPHONE MIC INPUTS VHF TRANCEIVER AUDIO TO SELCAL FREQUENCY 136.00 FLIGHT RECORDER SYSTEM CONTROL PANEL INPUTS VHF System  15  De-modulated audio is guided to the flight interphone system for voice communications and to Selective Calling (SELCAL) for signalling purpose  Flight recorder system receives analog pulse to signify that the transmission has acknowledged 16  17 HF Communication  HF communication is essentially by sky wave  It provides long range air-to-air and air-to- ground voice communications  Primary use is for Air Traffic Control (ATC)  2-22 MHz (HF-band)  18 IONOSPHERE HF/SKY WAVE HF/GROUND WAVE SKIP ZONE HF/GROUND WAVE ATC ATC High Frequency Communications  19 The factors affecting the range of HF transmission are:  Transmission power both at aircraft and ground station  Time of day  Season of the year  Any disturbance in the ionosphere  Geographical location  Frequency in use  20 HF system  Frequency and Power control panel Frequency selection and power setting will be provided by control panel Flight interphone system provides Microphone (MIC) audio input for voice transmission  Transceiver Transmitter + receiver  Coupler (matching network for antenna) The received and transmitted high frequency signals travel between transceiver and antenna with a proper matching (coupler) to save power  21 ANTENNA RF AUDIO TO FLIGHT COUPLER INTERPHONE MIC INPUTS HF TRANCEIVER AUDIO TO SELCAL POWER & FREQENCY 12.000 FLIGHT RECORDER SYSTEM CONTROL PANEL INPUTS HF System  22  De-modulated audio is guided to the flight interphone system for voice communications and to Selective Calling (SELCAL) for signalling purpose  Flight recorder system receives analog pulse to signify that the transmission has been acknowledged  Why in certain circumstances the aircraft or ATC loss HF voice communication? changes in ionosphere conditions  23 Selective Calling (SELCAL)  Pilots on long haul flights used to have to listen to the radio all the time, waiting for their own call sign to alert them  This was tiring, especially on HF frequencies with a lot of static as well as receiver noise  The SELCAL system allows pilots to mute the receiver until ATC transmits a code allocated to a specific aircraft listening on the frequency  24 IONOSPHERE HF VHF ATC ATC Selective Calling  25 Designation Frequency (Hz) RED “A” 312.6 RED “B” 346.7 RED “C” 384.6 RED “D” 426.6 RED “E” 473.2 RED “F” 524.8 RED “G” 582.1 RED “H” 645.7 RED “J” 716.1 RED “K” 794.3 RED “L” 881.0 RED “M” 977.2 RED “P” 1083.9 RED “Q” 1202.3 RED “R” 1333.5 RED “S” 1479.1 SELCAL Tone Allocation  26 4-letter code Rack mounted Selcal encoder  27 SELCAL system  Decoder Decoder consists of five channels  Tone Selector Each VHF/HF transceiver used for voice communications delivers received audio to the decoder  Selcal Lamps/Switches When the relevant code is received, it activates an alarm in the cockpit, either a light or a bell or both, telling the crew to de-select the mute function and use normal communications  28 ALERT TONE SIGNALS AUDIO INPUTS BURSTS SELCAL LAMP /SWITCHES RESET SELCAL DECODER PILOT CALL PANEL TRANCEIVER KEYING SELCAL FOUR_BIT ASSIGNED LETTER ALERT CODE CODES SIGNAL WARNING SELCAL System  29 Emergency Locator Transmitter (ELT)  Emergency locator transmitters are radio devices which can be carried on to the aircraft  In case of emergency ELT’s are activated, its radio transmission aids in locating crash sites and survivals by rescue people  30 LANYARD CORD TRANSMITTER PART ANTENNA BATTERY PART PLASTIC BAG ELT-RESCU 406 (Source: Honeywell Aerospace)  31 RESCU 406 This Programmable compact transmitter consists of  Battery workable in water  Long erecting Antenna  Lanyard card  Plastic water bag This beacon transmits two kinds of rescue signals  Civil Rescue 121.5 MHz  Military Rescue 243.0 MHz  32 Water Operation  At the top of beacon, unroll lanyard card and tie it to a raft  Put the beacon into water  This beacon automatically operates and starts sending distress frequencies  33 40000 FLIGHTLEVEL IN FEET 5000 20000 243 MHz (Military) DISTANCE IN NM 250 175 100 121.5 MHz (Civil) ELT-Water Operation 34  35 Land Operation  Erect and position the antenna in right direction without any obstacles  Pour liquid into container to activate water activated switch  Liquid in the container can be fresh water or salt water  Battery casing end of the beacon is inserted into liquid container  Beacon is held properly, so that it transmits effectively  Normal emission duration of ELT is 48 hours  36 ANTENNA ELT MAXIMUM LIQUID MINIMUM LIQUID LIQUID CONTAINER ELT-Land Operation  37 Example 1-2  An ELT is operating for 24 hours on Nickel- Cadmium battery of 240 mAh rating, calculate the current consumption to power the transmitter? Current consumption = 240 mAh/24 = 10 mA  38 The End