GROUND EQUIPMENT

GROUND EQUIPMENT:

Localizer:

One of the main components of the ILS system is the localizer which handles the guidance in the horizontal plane. The localizer is an antenna system comprised of a VHF transmitter which uses the same frequency range as a VOR transmitter (108,10 ÷ 111,95 MHz), however the frequencies of the localizer are only placed on odd decimals, with a channel separation of 50 kHz. The trasmitter, or antenna, is in the axis of the runway on it’s other end, opposite to the direction of approach. A backcourse localizer is also used on some ILS systems. The backcourse is intended for landing purposes and it’s secured with a 75 MHz marker beacon or a NDB (Non Directional Beacon) located 3÷5 nm (nautical miles), or 5,556÷9,26 km before the beginning of the runway.
The course is periodically checked to ensure that the aircraft lies in the given tolerance.

UHF descent beacon – glide slope

The transmitted signal:

The glide slope, or angle of the descent plane provides the vertical guidance for the pilot during an approach. It’s created by a ground UHF transmitter containing an antenna system operating in the range of 329,30÷335.00 MHz, with a channel separation of 50 kHz.

The transmitter (Fig. 4) is located 750÷1250 ft (228,6÷381 m) from the beginning of the runway and 400÷600 ft (121,92÷182,88 m) from it’s axis. The observed tolerance is ±0,5°. The UHF glide slope is „paired“ with the corresponding frequency of the VHF localizer.