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AIM

10/12/17

1

−1−8

Navigation Aids

FIG 1

−1−4

Service Volume Lower Edge Terminal

1000

500

0

0

5

10

15

20

25

DISTANCE TO THE STATION IN NM

ALTITUDE IN FEET

FIG 1

−1−5

Service Volume Lower Edge

Standard High and Low

1000

500

0

0

10

20

30

40

DISTANCE TO THE STATION IN NM

ALTITUDE IN FEET

5

15

25

35

1

−1−9. Instrument Landing System (ILS)

a. General

1.

The ILS is designed to provide an approach

path for exact alignment and descent of an aircraft on
final approach to a runway.

2.

The ground equipment consists of two highly

directional transmitting systems and, along the
approach, three (or fewer) marker beacons. The
directional transmitters are known as the localizer
and glide slope transmitters.

3.

The system may be divided functionally into

three parts:

(a) Guidance information: 

localizer, glide

slope;

(b) Range information:

 marker beacon,

DME; and

(c) Visual information: 

approach lights,

touchdown and centerline lights, runway lights.

4.

Precision radar, or compass locators located

at the Outer Marker (OM) or Middle Marker (MM),
may be substituted for marker beacons. DME, when