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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.

Flying light aircrafts in and out of large airports is much easier with some flexibility, on both controller and pilot side. The main problems are the distance needed between an airliner and a light aircraft because of the wake vortex, and runway occupancy time by the light aircraft, which usually taxies slowly.

One way light aircrafts pilots can help controllers is by flying high approaches followed by a long landing - closer to the taxiway. The first picture below has been taken while flying a normal approach to Geneva runway 23, aiming at the touch down zone.

On the left hand side, one can see to white and two red lights - the PAPI. This is an optical vertical guidance system. When flying too high, the four lights are white, slightly high results in three white and one red, on slope (like on the picture) gives two white and two red lights, slightly low is indicated by one white and three red, and way low gives four red lights.

The second picture has been taken (by luck) at the same distance, approaching to the same runway, but on a high-approach. To facilitate our integration in the approach sequence the controller asked me to land long and vacate the runway using the second taxiway to the right.

The goal was to vacate quicker, and allow for an earlier line-up of the airliner wating on the left side. As you can see, the PAPI lights are all white.

Just in case you wonder, the round thing in the axis is not a flying-saucer landing pad, but a radio-navigation beacon known as VOR (more precisely a Doppler VOR).

Flying high-approach, inner circuit with short final, high-speed approach, or other special variants helps to maintain a smooth flow of traffic. But there is a possible pitfall. Don’t accept to fly anything to please a controller. It’s much better to fly a couple more 360’s than crash-landing, and if you start something that later becomes uncomfortable, I’ve two words for you: go around !