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This post is the first in a series about airport equipment. If you always wanted to know all what these antennas, lights, signs, markings and other stuff are, you landed in the right place.

These orange antennas located in the extended runway axis are transmitting the “Localizer” signal of the Instrument Landing System (ILS). It is a narrow and precise beam which planes use to line-up with runway axis when landing. They are located at the far end of runway they serve, so the approaching planes don’t have to overfly them.

The beam guiding planes vertically during ILS approach is known as “Glide Path” and is transmitted by three antenna located on a mast beside the runway. On this picture it’s on the left side, but it can be any side of the runway. On a perfect approach, aircrafts cross this mast at the level of the middle antenna.

In front of the mast, you can see white and red lights from the PAPI system. This is a visual vertical guidance system (read more about it here). On ground, the PAPI equipment looks like on this picture.

The simplest tool for radio-navigation is the Non-Directional Beacon (NDB). It’s a simple AM transmitter, sending the same signal in all directions. An on-board direction finder indicates to the pilot where the beacon is relatively to the aircraft. The antenna ground looks like that.

The VHF Omni-Range (VOR) is a more advanced and precise navigation beacon. It sends a direction dependent signal, which the crew can use to determine their position relatively to the beacon. An advanced version of it is the “Doppler VOR”. It is used in sites where terrain can generate reflections. It requires then several antennas organized in a circle.