flight radar

How does in-flight radar work?

Tim Takeoff
09.10.2018
1 picture
4 minutes

Nowadays, most aviation enthusiasts even have aircraft radar on their smartphones or tablets. But how does it actually work?

It’s extremely practical when a family member is going on holiday or travelling for work. You can tell at a glance exactly where their plane is and see when you need to go to the airport to pick them up. You can also see if there are any delays or if their flight has been rerouted. We live in exciting times.

A Match Made in Heaven:Primary and Secondary Radar

The main piece of technical equipment is what is known as primary radar. This rotates to detect all the objects in the air capable of reflecting back its signal. In addition to the object you are interested in, the commercial plane, it also detects and displays smaller flying objects, such as gliders and flocks of birds. It even shows wind turbines!

In order to improve the results displayed, what is known as secondary radar is used. This provides considerably more detailed information than primary radar, as it is based on bearing and range calculations. Every commercial airliner authorised to operate in Germany is required to carry a transponder. These transponders store the aircraft’s precise identifying data and broadcast information including the aircraft’s identifier, altitude, position and speed, as well as any four-digit codes issued by the pilot. The secondary radar enables these signals to be received and evaluated. It overlays the primary radar screen and generates an extremely precise image.

In-Flight Radar for Everyone – ADS

When it comes to explaining how aircraft radar actually works, ADS-B is the most significant form. The “B” in this case stands for “broadcast”, and describes the type of signal used. The aircraft’s signal is radiated in all directions approximately every two seconds and can be received on frequency 1090 MHz simply by using a small USB receiver. This simplicity is leveraged by companies like Flightradar24 and Flightaware to achieve a particularly precise picture of current air traffic. Receiving ADS-B data from planes was initially only possible within Europe, but this information can now be picked up all over the world, as well as being available online. This makes it possible for anyone to keep an aircraft radar system in their pockets using simple hardware – as a simple smartphone app.

For the sake of completeness, I also want to mention ADS-C. “C” in this case stands for the fixed “contract” involved. This is a kind of agreement between the aircraft and the ground system. What is interesting about this system variant is that the air traffic controller or the pilot of the aircraft can request a connection. This enables the air traffic controller to log into the aircraft’s system and call up all the data he or she needs. Information on all the plane’s potential routes can also be requested. This is very useful, for example, when an aircraft is flying over the Atlantic where there is no radar coverage.

ADS-B as a Collision Warning System

Whereas commercial air traffic uses the TCAS collision warning system, private aviation uses the signal output by the ADS-B in order to generate collision warnings. To do this, the signals from two planes approaching each other are compared in the other’s devices. If there is a potential for collision, both visual and audible warning signals are issued. The direction and distance are displayed in detail to enable both pilots to react in good time.

There is, however, one major drawback of the ADS-B, which is that aircraft without transponders are not detected on ADS-B-only radar images. This is also the reason why not all planes (or helicopters and other types of aircraft) are visible on Flightradar24.

Tracking and controlling air traffic is always an exciting topic. To learn more about modern in-flight navigation, take a look at our article on the subject!

Images – Screenshot Flighradar24 / Pixabay – betexion

by Tim Takeoff

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