How Does A Transponder Work?

Many pilots will want to understand anything and everything to do with flying and what there is to learn before becoming a trained flyer of the skies.

Because planes have so many instruments and features that need learning, there’s no wonder that lots of people are interested in finding out what a transponder is and the purpose it serves aircraft around the world.

Follow our guide to find out all about transponders and how important they are to the daily function of airlines all over the globe. By the end of the article, you should have a better idea of what they are and how they work.

How Does A Transponder Work

What Is A Transponder?

Transponders are incredible features in air travel. A transponder is a device that allows an airplane to be seen by radar systems. It does this by sending back information that identifies the plane by its registration number.

The information sent back has been pre-programmed into the transponder at the factory where it was built.

This means that when the transponder sends back information to a radar system, the operator receives exact details on the characteristics of the plane including its weight, speed, altitude, etc.

In other words, the radar system can tell exactly which plane it is talking about because it knows exactly what kind of data to expect.

Types Of Transponders

There are two basic types of transponders: primary and secondary. Primary transponders are used by commercial aircraft while secondary ones are used by general aviation (private airplanes).

Of course, they work in very similar ways, however, it makes sure that people involved know the difference between commercial and privately owned aircraft in the sky.

How Does A Transponder Work?

The main thing we need to cover here is how they actually work. When an airplane flies through the air, it creates a lot of turbulence. This turbulence causes radio waves to bounce off the surface of the wings, fuselage, tail, engines, and any other parts of the plane.

These bouncing waves then go back towards the ground, but not always straight down.

Most of them follow the curvature of the earth until they reach the bottom of the atmosphere. Once they get there, they take a direct path straight up again.

Only those waves that hit the ground directly from above are able to pick up the signal that comes back from the transponder (see also “Does Bluetooth Work On Airplanes?“).

If you think about it like this, it becomes clear why transponders are so useful for radar operators. They make it easier to track down aircraft that might otherwise be hard to see or hear.

How Do I Know If My Plane Has One?

First things first – if your plane doesn’t have one, you’re probably safe! But don’t forget that the manufacturers of most modern aircraft include transponders as standard equipment.

So even if yours isn’t currently equipped with one, chances are good that you’ll soon get one installed.

However, if you own a private aircraft or something else that hasn’t been manufactured recently, there’s a chance that you won’t have a transponder included in your package. Most likely, it will be available separately or as part of a kit.

Are Transponders A Legal Requirement?

In North America, all commercial passenger planes must have a transponder installed because of the purpose that they serve to keep aircraft safe and the number of passengers present on these flights.

However, it is not required for non-commercial planes. Check out FAA regulations here for more info.

Transponder Failure

Even though transponders are incredibly reliable, sometimes they do fail. This is especially true for older aircraft that were made before transponders became standard equipment.

For instance, if your plane has been sitting around for a few years without having had a transponder installed, there’s no guarantee that it’s going to function correctly.

Luckily, transponder failures usually happen only in extreme cases. Generally speaking, if your airplane has been flying for a long time without a transponder, it should still be working fine.

Older transponders obviously have a larger chance of failing, with new ones having to replace the faulty models.

Emergency Codes Known Around The World

There are many emergency codes that can be transmitted via a transponder. Some of them are meant to alert the authorities that an aircraft is in trouble. Others are simply provided for the benefit of the aircraft operator.

In either case, knowing what codes are being transmitted at any given moment can help save lives.

7500 means that there is a hijacking aboard an aircraft, or more specifically, someone with a knife present. 7600 means that there’s a radio failure, which can prove to be fatal whenever a flight needs to communicate with other people outside the flight.

7700 is an emergency, meaning a lot of the time that the plane is going down or forcing an emergency landing.

Are Transponders Used Outside Of Flying?

Since transponders are used for tracking purposes, they can also be used for locating lost objects. For example, if you leave your phone behind while camping somewhere, you could use a handheld GPS receiver along with a transponder to find it again.

You would need to know the code number of your device to be able to locate it, but once you’ve found it, you can send out the correct code to let others know where you left it.

The Benefits Of Using A Transponder On Your Plane

One of the main reasons why airlines prefer to equip their airplanes with transponders is safety. When your plane is equipped with a transponder, its location will always be known.

If the pilot loses contact with air traffic control, he/she knows exactly how far away from the airport he/she is and therefore can make better decisions about his/her next move.

If a plane goes missing, the authorities will have a much easier time finding it when it uses the same frequency that the plane was transmitting on previously. They may even be able to track it using the signal strength, which helps determine whether the plane has landed or crashed.

Final Thoughts

You should now know a bit more about transponders than when you first clicked on the article. The simple explanation is that they help planes to make themselves known to other people and will be used a lot on commercial flights due to their purpose.

A lot of private planes will also have these devices implemented in them to ensure that they’re there in case of an emergency.

At the end of the day, the main thing about flying is the safety of the people involved. Transponders play a huge role in this and will keep people a lot safer having one on board.

Jacob Stern
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