Show new automatic direction finding device determines Is position of airplane in flight by WILLIAM KELLER released by western newspaper union CHICAGO the danger of commercial aircraft becoming lost because of inclement weather or faulty gaviga navigation tion has been practically eliminated by a revolutionary new invention location of a plane in flight is automatically mati cally recorded at ground stations by an automatic direction finding radio receiver developed by radio technicians under J P cunningham united air lines director of communications cat ions four years of study and experimentation peri were conducted under cunningham and head of the companas comp anys radio laboratory before the direction finder reached its present stage of perfection an amazing degree of accuracy has been obtained by the device cunningham reports that tests conducted over a period of more than a year reveal that better than 99 per cent of the bearings made by the new receiver proved to be accurate entirely automatic the receiver operates without any special assistance from the plane in flight it is described as remarkably simple in operation each time that a plane in flight makes its routine half hour position reports the receiver acts on the radio waves large antenna that form the heart of the instrument pick up these waves this antenna is constantly being rotated by a motor electric waves picked up by the antenna are transferred to a standard radio receiver which amplifies it into energy this energy operates a moving pen which draws a line on a scroll chart that constantly unrolls beneath it the pen traces the form of the wave in a vertical zigzag line which reveals the maximum and minimum strength of the signal all bearings are based upon the minimum signal or null as it is called by radio engineers the null is recorded when the revolving antenna is exactly at right angles to the direction from which the signal is coming the null as shown on the chart form can be plotted exactly from a transparent plexiglas plate graduated in degrees which is placed over the chart the radio operator can then read off the bearing of the airplane in degrees it is necessary for at least two stations equipped with the antenna and recorder to work together in triangulating ting a planes position this position is then immediately radioed to the pilot who uses the report to check upon his own navigation if three stations take bearings simultaneously from a plane in flight lines from the stations are projected on a map the exact position of the plane will be shown by the point on the map where the lines intersect in practice cunningham explained pla ined we will use two or more ground stations simultaneously in receiving the reports from any given airplane the bearings obtained by these stations will be electrically transmitted to our key dispatching krists on the transcontinental route there the bearings can be plotted on charts in a few seconds and we thus know the loc altion of every plane within a mile or two for practical purposes with a AIRIA air operation ot of the new airplane location recorder is illustrated by this sketch ground stations equipped with the device automatically receive bearings on a plane every time its radio transmitters transmit teris used by taking simultaneous bearings stations A or B which are on the airway can determine the planes position with the help of lot C or D which are off the airway at the lower left is shown the revolving antenna which makes the high degree of accuracy possible swiftly moving object like an airplane this is per cent accuracy cunningham added that the first station is now being installed at salt lake city united airlines expects to install about 20 to serve its entire system from coast to coast finding directions by radio is not a new science it was known in 1912 when radio was still in its infancy and was used at sea during the tha world war of 1914 1918 pan american airways engineers subsequently developed a long range direction finding receiver this receiver gave fairly satisfactory results over water where radio signals are more effective than land unsatisfactory results were obtained about 1935 when the pan american system was tried out over land since then an antenna system that would operate over land has been sought by a number of radio manufacturers the army and the navy accurate results up to 80 per cent of the time were attained by a number of systems but this was not considered sufficiently safe for use with passenger carrying planes static interference was the fundamental cause of trouble with most of these direction finding receivers receivers it spoils signals and gives inaccurate nulls because Unit eds device produces visual charts it is possible to weed out the bad bearings the army and navy are deeply interested in the receiver it has been offered to other airlines in the united states |