Airways Traffic Computer - 'Rodoniscope'
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During the War, the widespread installation of radio facilities made it possible to take positive control of flights en route. Aircraft were separated by the most rudimentary rules: northbound aircraft flew at odd thousands of feet and those southbound at even thousands. Also, aircraft flying at the same height along an air route had to be separated by ten minutes flying time. With aircraft of vastly different speeds on the same trunk air routes, a procedure was needed to maintain this longitudinal separation.

The problem was for the Flight Checking Officer (FCO - as Air Traffic Controllers were then known) to quickly determine when a faster aircraft would draw closer than 10 minutes to the aircraft in front, or when aircraft flying in opposite directions would pass.

The solution was presented in 1944 by a Sydney Flight Checking Officer, Mr Norman Rodoni, who invented a form of computer known as the Airways Traffic Computer or 'Rodoniscope'.
Aircraft were plotted on the glass disk in grease pencil. The FCO could rotate the plot to any point along the aircraft's route to check the estimated times of arrival at any reporting point. He could also compare one aircraft's position relative to another aircraft on the same route, either in the same or opposite direction.

Fast aircraft appeared on the outside of the disk, slower ones toward the centre. Thus it was possible to tell when a fast aircraft would overtake a slower one.

The limitation of this system was the speed and accuracy of plotting aircraft position reports, which were relayed to the FCO by Aeradio.

Mr Rodoni's simple invention halved the number of controllers needed, and was more accurate than other, more cumbersome, methods of control. Despite its officially agreed merits, it was not until 1950 that he was finally paid £200 by the Public Service Board and a further £250 by the War Inventions Committee.

(Photo: CAHS collection)


EN ACC c.1946< Click on the image at left to see a photo of the Rodoniscope in use.
Click on the image at right to read more about the life of Norm Rodoni >Norm Rodoni

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