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History and Radio Age
Avionics : Aviation Electronics Combining two large engineering fields that
reached maturity during 20th century.
Major development in aviation dated back in18th century with experiments in lighter-than-air craft.
Much of the fundamental electromagnetic /electricity theories were developed andexperiments were conducted during 18th and19th centuries.
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1901: Trans-Atlantic radio wave transmissionby Marconi, the most advanced application of
electricity for that time. Mark the beginning ofradio engineering.
Dec. 17, 1903: Wilbur and Orville Wrightperformed taking off, flying and landing in a
manned, powered, heavier-than-air craft.
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Early aircraft were dangerous, mostly suitedfor air shows at county fairs.
WW1: Aircraft enter the service for forwardobservation and dropping munitions.
Requirement for command staff on the ground tohave contact with the pilot were highlighted.
The idea of passengers transportation usingaircraft over water and mountain at greaterspeed than train were later conceived.
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Weather is the most important obstacles inthe early aviation.
Lead to the instrumented flying (Blind Flying) In early 20th century, flying requires consistently
fine weather.
For long distances, consistence fine weather along
the route and at destination is almost impossible. 1925 US Army began investigation into “Blind
Flight”
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To make blind flight possible require: An altimeter of sufficient accuracy
A reference to natural horizonDue to several forces acting on the pilot,
determining which way up is not as easy.
A navigation system to guide pilot to a
destination without seeing landmarks, starsor other features outside the cockpit. Important during landing
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Blind flight panel
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Optical system for guidance were foundnot practical because light cannot
penetrate clouds. Solution: Radio navigation.
In Sept. 24, 1929, Lt. James Doolittle
flew the first “Blind Flying”. Instrument used: Artificial horizon,
directional gyro and radio receiver
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In USA, the first commercial broadcastingcommenced in Aug. 20, 1920.
Although no audience at that time.
The electronics of the period were large andheavy and the cost for every gram of mass inan aircraft is high.
The environment was harsh;- widetemperature variation (-40o C to 45o C),enormous vibration due to propeller engineand shock and low frequency shake whilelanding on rough surfaces (concrete and
grass).
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Providing communication was difficult inthe early aircraft. The problems were
Require to install transmitter with largepower consumption.
Mounting the a long antenna
No practical technology for VHFtransmitters and receivers
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In 1920s, the first light beacons were placedon the mountain tops to cover the greatest
range and warn aviators of obstructions.The first navigation aid was Non-DirectionalBeacon, NDB
It provide a heading to fly
With no crosswind, the flight path is straight line.
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Because the first equipment was fornavigation and one-way radio reception, onlyreceivers, with no transmitter, were needed. It was common for an aircraft to blink a landing
light or wiggle its wings in response to atransmission from controller on the ground.
The ground environment wasn’t much better.
The first navigation aids for night flying werebonfires maintained by farmers paid toperform the task.
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The first navigation system with course
information was A-N range. Also known as the Four Course Radio Range.
Placed along airway routes at an intervals. Used 1,500 watts transmitter to operate between
190 to 565 kHz with wire loop antenna.
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Pilot listen to the Morse code signals (“A” and “N”)from ground transmitter.
If an aircraft was exactly on one of four coursesemanating from the station, the pilot heard a
steady tone as the two signal overlapped.
If deviate, either “A” or “N” would be heard.
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