Abstract :
The paper presents a survey of radio systems which provide shortdistance navigation and landing aids for aircraft by continuous-wave transmission. Navigation requirements are discussed in relation to the needs of small and large aircraft. ¿Self-help aids¿ are considered to be preferable to ¿ground-supported aids¿, which are subject to saturation in areas of high traffic density. C.W. systems are very suitable for the operation of meter indicator instruments. Short-distance navigation aids are classified into (a) fixed-track guides, (b) omni-directional radial-track guides, (c) rotating beacons, (d) hyperbolic systems, and (e) radio compass. The principal features of each system are stated. Distance measurement by continuous waves is considered. The general problems of radio aids to approach and landing are discussed. The provision of a track in descent (glide path) and the presentation of track data on instruments are considered to be essential to the realization of a fully satisfactory landing system. Radio altimeters have a particular contribution to make to navigation; their principles and applications are mentioned. The paper concludes with a statement of the need to provide navigation aids and landing aids as part of a comprehensive traffic-control plan, giving the maximum degree of safety by providing flexibility of operation of the traffic-control system.
