Development of Radio Aids to Air Navigation

The development of aircraft has reached a stage where further progress depends upon the conquest of adverse meteorological conditions. The most promising avenue to such mastery of the elements is through adaptations of radio. Intensive work extending over two years has resulted in the development and practical demonstration of a complete set of radio aids to flying on the civil airways of the United States. This development was carried on by the Bureau of Standards for the Aeronautics Branch of the Department of Commerce. The radio aids, which will now be installed on the principal airways, comprise a radio beacon system and telephone service from ground to aircraft. The required radio equipment on the airplanes is reduced to a short pole antenna and a simple receiving set weighing a few pounds, including a visual indicator which tells the pilot whether he is on the course or how far off. All of the expensive and powerful apparatus necessary for the system is on the ground, maintained by the Government. The radio beacons operate in the frequency band 285 to 315 kc and the telephone stations in the band 315 to 350 kc. These are allocated to air service by the 1927 International Radio Convention. For the present the beacons are adjusted to the frequency of 290 kc and the telephone stations to 333 kc. The directive radio beacon is a special kind of radio station, usually located at an airport, just off the landing field.