Shielded localizer array

T-45C TS INav-04; ADV INav-02

Components and Characteristics of the Instrument Landing System (ILS)

b. Point of equal overlap is the center of the extended centerline of

the runway indicating on course

8. Shielded localizer array (antenna) is normally located 1,000 ft

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beyond downwind end of the runway centerline

Shielded Localizer

Array (antenna)

a. Actual signal generated by transmitter from a building that is

offset a minimum of 250 ft from center of antenna array

b. Optimum signal strength and minimum possible signal

9. Primary approach of a localizer is called “Front Course”

NOTE: Localizer front course beam is adjusted at the antenna

array for a 700 ft width at the runway threshold. The beam as

displayed on the a/c instruments has a width of 5 degrees allowing

for 2-1/2 degrees left full deflection and 2-1/2 degrees right full

deflection. A full deflection of the CDI at runway threshold would

place the aircraft 350 ft left or right of the runway centerline while

tracking on the localizer.

a. The localizer provides course guidance for descent path:

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Localizer course guidance

(1) 18 nm from the antenna

(2) 1,000 ft above the highest terrain along course line

(3) 4,500 ft above antenna elevation site

(4) Signal acquisition and off-course indications are provided

through angular areas of the operational service volume:

(a) To 10 degrees either side of the course along a radius

of 18 nm from the antenna

(b) To 35 degrees either side of the course along a radius

of 10 nm from the antenna

NOTE: After the missed approach point, any localizer signal

indication received should be disregarded unless it is

designated part of the published missed approach procedure.

Any signal that is not part of the procedure should be

considered unreliable and disregarded. Some fields will have

functional back course localizers (BAC LOC) and are

designated as such.

NOTE: Loss of the localizer information during the approach

will render the approach procedure unusable. The approach

should be terminated or another type of an approach should be

selected, weather permitting.

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(2-02) Original