Localizer

CHAPTER ONE

INSTRUMENT FLIGHT RULES WORKBOOK

Visual information: approach lights, touchdown and centerline lights, runway lights.

Compass locators located at the outer marker (OM) or middle marker (MM) may be substituted

for marker beacons. DME, when specified in the procedure, may be substituted for the OM

(marker beacon receiver not installed in T-34).

Localizer

The localizer transmitter operates on one of 40 ILS channels within the frequency range of

108.10 to 111.95 MHz. Signals provide the pilot with course guidance to the runway centerline.

The approach course of the localizer is called the front course and is used with other functional

parts, e.g., glideslope, marker beacons, etc. The localizer signal is transmitted at the far end of

the runway. It is adjusted for a course width (full scale fly-left to a full scale fly-right) of 700

feet at the runway threshold.

The course line along the extended centerline of a runway, in the opposite direction to the front

course is called the back course.

CAUTION

Unless the aircraft's ILS equipment includes reverse sensing

capability, when flying inbound on the back course it is necessary

to steer the aircraft in the direction opposite the needle deflection

when making corrections from off-course to on-course. This

"flying away from the needle" is also required when flying

outbound on the front course of the localizer. Do not use back

course signals for approach unless a back course approach

procedure is published for that particular runway and the approach

is authorized by ATC.

Identification is in International Morse Code and consists of a three-letter identifier preceded by

the letter I ( WUDQVPLWWHG RQ WKH ORFDOL]HU IUHTXHQF\

Example:

I-DIA

The localizer provides course guidance throughout the descent path to the runway threshold from

a distance of 18 NM from the antenna between an altitude of 1000 feet above the highest terrain

along the course line and 4500 feet above the elevation of the antenna site. Proper off-course

indications are provided throughout the following angular areas of the operational service

volume:

To 10 either side of the course along a radius of 18 NM from the antenna; and

From 10 to 35 degrees either side of the course along a radius of 10 NM (Figure 1-5).

1-8 INTRODUCTION TO AIRBORNE NAVIGATION AND COMMUNICATIONS

EQUIPMENT AND PRINCIPLES OF OPERATION