(k) The minimum peak field strength on the ISMLS glide path and within the localizer course sector from a distance of 10 nautical miles to a height of 100 feet (30 meters) above the horizontal plane containing the threshold, may not be less than + 87 dBW/m (j) Except as provided in paragraph (k) of this section, in all parts of the coverage volume specified in paragraph (i) of this section, the peak field strength may not be less than −87 dBW/mĢ, and must permit satisfactory operational usage of ISMLS localizer facilities. The ISMLS localizer signals must be receivable at the distances specified up from a surface extending outward from the localizer antenna and within a sector in the elevation plane from 0.300 to 1.750 of the established glide path angle (θ). The localizer coverage sector must extend from the center of the localizer antenna system to distances of 18 nautical miles minimum within ☑0 degrees from the front course line, and 10 nautical miles minimum between ☑0 degrees and ☓5 degrees from the front course line. (i) The localizer must provide signals sufficient to allow satisfactory operation of a typical aircraft installation within the localizer and glide path coverage sectors. The horizontally polarized component of the radiation of the course line may not exceed that which corresponds to a DDM error of 0.016 when an aircraft is positioned on the course line and is in a roll attitude of 20 degrees from the horizontal. (h) The emission from the localizer must be vertically polarized. The frequency tolerance may not exceed ☐.0001 percent. (g) The ISMLS localizer must operate in the band 5000 MHz to 5030 MHz. The applicable course sector angle will be established and approved on an individual basis. (f) The ISMLS course sector angle must be adjustable between 3 degrees and 9 degrees. (e) All horizontal angles employed in specifying the localizer field patterns must originate from the center of the localizer antenna system which provides the signals used in the front course sector. When an observer faces the localizer from the approach end of the runway, the depth of modulation of the radio frequency carrier due to the 150 Hz tone must predominate on his right hand and that due to the 90 Hz tone must predominate on his left hand. The radiation field pattern must produce a course sector with one tone predominating on one side of the course and with the other tone predominating on the opposite side. The localizer station must transmit angular guidance information over a C-band microwave carrier on narrow, scanned antenna beams that are encoded to produce a modulation in space which, after averaging over several beam scans, is equivalent to the modulation used for conventional ILS as specified in subpart C of this part. (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. § 171.261 Localizer performance requirements.
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