This thesis deals with multipath scatter disturbances in the Instrument Landing System (ILS) of the civil aviation, their properties, methods of suppressing them during flight, and calculation methods for their mapping an the basis of the data contained in the flight inspection records. The ILS system has remained basically the same despite many improvements during its five decades as an international standard, so theoretical considerations made decades ago, inter alia by the author, are still valid. Although modern two-frequency narrow-beam localizers are quite free of scatter disturbances, single-frequency Localizers are more sensitive to scatter disturbances and often need reliable location of the objects causing them. Because the approach path of the aeroplane is basically irregular but normally gently oscillating about the wanted straight course, a calculation method that requires only modest computer resources suffices to produce a map of scatterers. A calculation method for correcting a meandering and in the Glide Path case also offset flight path mathematically to a straight one along the centreline, and another for mapping that requires data from such straight approach are explained. The flight path correction program covers spatial bend wavelengths from 48.6 m to 437.4 m and works well for deviations from the centreline up to +/-45 m in the Localizer case and up to +/-26 m in the Glide Path case. The -3 dB contour of the image of a point is an ellipse +/- 180 m long on the geographic map; its width is +/-5 m in the Localizer case and only +/- 3 m in the Glide Path case. For just comparison of flight inspection results a tilted perspective of the map is more lucid because the images of points appear then as round spots. Simulated examples as well as results obtained from inspection flights in Kajaani, Kauhava, Kuusamo and New Delhi are shown, compared and discussed.
Mapping of ILS scatterers and suppression of scatter errors
1998
67 Seiten, 20 Bilder, 23 Quellen
Theses
English
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