(d) The radiation from the localizer antenna system must produce a composite field pattern which is pulse duration modulated, the time average equivalent to amplitude modulation by a 90 Hz and 150 Hz tone. (c) At locations where two separate ISMLS facilities serve opposite ends of of a single runway, an interlock must ensure that only the facility serving the approach direction being used will radiate. If other than a runway centerline localizer is used, the criteria in subpart C of part 97 of this chapter is applicable. (b) On runways where limited terrain prevents the localizer antennae from being positioned on the runway centerline extended, and the cost of the land fill or a tall tower antenna support is prohibitive, the localizer antenna array may be offset, including a collocated ground station, so that the course intercepts the centerline at a point determined by the amount of the angular offset and the glide path angle.
(6) Be installed on frangible mounts or beyond the 1000′ light bar. (5) Not obscure any light of the approach landing system and (4) Be located at a distance from the stop end of the runway that is consistent with safe obstruction clearance practices (3) Have the minimum height necessary to comply with the coverage requirements prescribed in paragraph (j) of this section (2) Be adjusted so that the course line be on a vertical plane containing the centerline of the runway served (1) Be located on the extension of the centerline of the runway at the stop end This section prescribes the performance requirements for localizer equipment components of the ISMLS. Volumes of interference parallel to the runway that are generated by aircraft flying parallel to the runway are primarily limited by the frequency of the interference.§ 171.261 Localizer performance requirements.
Interference volumes are limited in altitude by the RF cross sectional area of the interfering aircraft and the vertical lobe structure of the localizer antenna.
AIRPLANE LOCALIZER PLUS
Interference volumes are limited in azimuth to plus and minus 8 degrees.
Interference volumes will have different geometries and positions depending upon geometry and velocities of the aircraft, cross section of the interfering aircraft, beam structures of the antennas, and criteria used for interference. Here the interfered aircraft is landing at 210 fps, 10,000 ft from the localizer, and the interfering aircraft is a DC-3 traveling in the same direction at 340 fps. A typical volume in which one aircraft would cause interference to a second aircraft that is in a landing configuration near touchdown is presented. Field test data were gathered using a standard directional waveguide localizer. The data were derived from field tests and mathematical analysis, and include both static and dynamic receivers. This report describes the reflection interference effects of overflying aircraft on ILS localizer receivers in the landing area.
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