chapter  12
Instrument landing system
Pages 4

Navigation aids such as automatic direction finder

(ADF), VHF omnidirectional range (VOR) and

distance measuring equipment (DME) are used to

define airways for en route navigation. They are

also installed at airfields to assist with approaches

to those airfields. These navigation aids cannot,

however, be used for precision approaches and

landings. The standard approach and landing

system installed at airfields around the world is

the instrument landing system (ILS). The ILS

uses a combination of VHF and UHF radio waves

and has been in operation since 1946. In this

chapter we will look at ILS principles and

hardware in detail, concluding with how the ILS

combines with the automatic flight control system

(AFCS) to provide fully automatic approach and

landing.