E.M. Iungaitis – Post-graduate Student, South Ural State University (National Research University)
N.I. Voytovich – Dr.Sc. (Eng.), Professor, Head of Department, South Ural State University (National Research University)
A.V. Ershov – Ph.D. (Eng.), Associate Professor, South Ural State University (National Research University)
B.V. Zhdanov – Ph.D. (Eng.), Associate Professor, South Ural State University (National Research University)
A.V. Zotov – Ph.D. (Eng.), Associate Professor, South Ural State University (National Research University)
The main means of providing instrumental approach of aircraft for landing are beacon landing systems. It forms in space a trajectory (glide path), located, as a rule, at an angle of 3º in respect to the horizontal plane. We showed in the paper the dependence of the glide path angle on the height of the snow cover on the underlying surface when using previously known antenna arrays in the glide slope. We proposed in this work a new class of glide slope antenna arrays. The requirements for the amplitude-phase distribution of currents along the antenna array of the glide slope, at which the glide path angle does not depend on the reflective properties of the underlying surface and the level of snow cover on it, are determined. We propose a procedure for constructing an antenna array with two subarrays, one of which radiate the so-called «Carrier plus sideband» (CSB) signal, and the second emits the «Suppressed carrier sideband only» (SBO) signal. In order to ensure the independence of the glide path parameters from the height of the antenna array (glide path angle and slope of the glide path), five conditions must be met as specified in the article.
A special case of the proposed antenna array is an equidistant antenna array, in which the radiating elements of the subarray of the CSB signal and the subarray of the SBO signal partially combine. We performed experimental studies with a 4-element equidistant antenna array as part of a glide slope prototype. We carried out flight measurements of the glide path angle at the airfield in the foothill with a difficult terrain for about two years: in summer, winter, next summer and next winter. The snow depth at the airport was 35…40 cm in the first winter, and 30…35 cm in the second winter. The experimental results showed that the changes in the glide path angle for the stated period of time do not exceed one angle minute. This value is commensurate with the error of the flight experiment.
In order to simulate the influence of a higher level of snow cover on the position of the glide path, we conducted a special experiment. When snow cover of 18 cm high established on the airfield surface, we lowered all four antennas by one meter and measured the glide path zone. The glide path angle remained the same.
Flight tests of a prototype landing system with the proposed glide path beacon showed that this landing system provides parameters for the III-rd category. It means that approaching the aircraft for landing and landing are possible at zero visibility.
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