What is an airline transponder?

A transponder (short for transmitter-responder and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders to assist in identifying them on air traffic control radar.

Do all planes have a transponder?

Transponders exist in essentially all air vehicles (including, for example, not only airplanes, but helicopters, blimps, etc.), and some of those, especially in the military, operate in special modes that “regular,” small airplanes do not have.

Where is the transponder on a plane?

A transponder is a radio transmitter in the cockpit that receives a signal from “secondary” radar and returns a squawk code with the aircraft’s position, its altitude and its call sign. It is constantly being pinged, helping air traffic controllers on the ground determine the airplane’s speed and direction, too.

What are the different transponder modes?

Mode A, C, S and Ident Mode A equipment transmits an identifying code only. Mode C equipment enables the ATCO to see the aircraft altitude or flight level automatically. Mode S equipment has altitude capability and also permits data exchange.

In what airspace is a transponder required?

Required for all aircraft in Class A, B and C airspace.

What is an aircraft transponder and how does it work?

Aircraft Transponders: What They Are and How They Work. An aircraft’s transponder (short for “transmitter-responder”) is an electronic device on aircraft that transmits a four digit code (called a “squawk code”) which allows the aircraft to be identified by Air Traffic Control.

What is the traffic collision avoidance system on a transponder?

On the right of the transponder is the Traffic Collision Avoidance System (TCAS) mode selector. The TCAS system receives the broadcasts from other aircraft and if it predicts aircraft will come too close it will issue avoiding action instructions.

What is the alt setting on an airplane transponder?

There is a special mode which is set by putting the transponder in the ALT setting. This tells the transponder to send not only the four-digit code that the pilot has set, but also information on the altitude of the airplane. This is called Mode C, and it is particularly useful to ATC.

Can transponders improve airspace surveillance at airports?

As with other radar environments, surveillance quality on the airport surface can be improved by the use of transponders. Unfortunately, the resolution of the beacon system used for airspace surveillance is inadequate to distinguish between closely spaced aircraft at airports.