lecture history and radio age

8/13/2019 Lecture History and Radio Age

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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.



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.



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.



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”



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



Blind flight panel



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



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).



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



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.



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.



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.



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.

lecture history and radio age

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