Appendix F Instrument Landing - System (ILS) Basics

APPENDIX F

INSTRUMENT LANDING SYSTEM (ILS) BASICS

F100. INTRODUCTION

You will be introduced to the ILS approach in the T-1 Syllabus. The following information is

taken from the Aeronautical Information Manual (AIM) and the T-1A Dash-1 to assist you in

preparation for ILS approaches. The T-1A and most Air Force aircraft have ILS. You will be

expected to know the basics of the ILS/localizer system.

F101. ILS/LOCALIZER/GLIDESCOPE

The ILS is a precision approach similar to the Precision Approach Radar (PAR), with the

exception that instead of a final controller using radar to verbalize azimuth and glideslope

information, this information is displayed on the aircraft flight instruments for you to interpret.

An ILS consists of 2 components, the localizer and the glideslope. The localizer provides the

azimuth (centerline) portion of the ILS. Glideslope must be available, otherwise an approach

must revert to the localizer minimums (higher than an ILS). The glideslope is normally 3 but

can be higher depending on local terrain (refer to minimums section in the front portion of the

approach plates). Corresponding VSI/Vertical Velocity Indicator (VVI) information for a given

glideslope at a given airspeed can be found on the inside back cover of any approach plate.

F102. ILS MINIMUMS

There are three categories of ILS minimums: Category I, II, and III.

Category I - 200-1/2 (2400RVR)

Category II - 100-1/4 (1200RVR)

Category III - 0-0

Air Force Air Education Training Command (AETC) has set the 300-1 for IMC operations (ILS

or PAR). In VMC you may use 200-1/2. The T-1A is prohibited from using Category II and III

minimums. Remember, an ILS uses DH and HAT, where a localizer (no glideslope) uses MDA

and HAT.

F103. ILS /LOCALIZER TRANSMITTER

Your approach plate will specify the ILS frequency (see any ILS approach plate). It will be

contained in a box that has a T preceding the airfield's 3 letter identifier (such as: I-PNS or I-

MOB). If the box has a TACAN channel, the ILS provides DME (see Mobile Regional). It is

not necessary to tune up the TACAN if the ILS frequency is entered and VOR/LOC is selected

on the T-1A DSP. If the ILS does not have DME and a TACAN is collocated on the field (see

VFR JET ARRIVAL PROCEDURES

F-1