ATC Transponder (ATCRBS) | Aircraft Radar Beacon Transponder

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Radar Beacon Transponder

A radar beacon transponder, often known as a transponder, is a device that allows ATC (Air Traffic Control)  to positively identify and locate an aircraft on its radar displays. The transponder equipped with altitude encoders transmits the aircraft's pressure altitude, which is displayed next to the on-screen blip that represents the each aircraft.

How Radar Beacon Transponder works?

Airports may have different types of radar. Air Traffic Control uses two types of radar in general (ATC). The primary radar sends out directed UHF or SHF radio waves in all directions in a sequential manner. When radio waves collide with an aircraft, some of them bounce back to a ground antenna. A receiver performs calculations to calculate the aircraft's direction and distance from the transmitter. On a ATC radar screen, a blip or target representing the aircraft is displayed, it's often known as a plan position indicator (PPI). Controllers can see the aircraft's azimuth direction and scaled distance from the tower, giving them a two-dimensional fix on the aircraft.

ATC uses secondary surveillance radar (SSR) to confirm the plane's position and add the third dimension of height to its location. The transponder on board the aircraft receives coded pulse trains transmitted by SSD radar.

Mode 3/A pulses, as they're known, help confirm the aircraft's location. A pilot is told to select one of 4,096 distinct codes on the transponder once verbal communication with ATC has been established. These are octal codes in digital form. The ground station sends out an energy pulse at 1030 MHz, and the transponder responds at 1090 MHz with the allocated code. This usually involves changing the target symbol on the radar screen to confirm the aircraft's location. Due to the large number of verified aircraft on the screen, ATC may ask the pilot for identification. By pushing the IDENT button on the transponder, the aircraft's target symbol is highlighted on the PPI, making it easily discernible.

The transponder control must be set to ALT or Mode C to obtain altitude clarification. In response to pulse interrogation, the signal sent back to ATC is updated with a code that displays the aircraft's pressure altitude next to the target symbol on the radar screen. An altitude encoder that is electrically coupled to the transponder provides the pressure altitude of the aircraft to the transponder.

Air Traffic Control Radar Beacon System (ATCRBS) 

The Air Traffic Control Radar Beacon System (ATCRBS) is the name for the ATC/aircraft transponder system. Mode S altitude response was created to improve safety. When the transponder answers to SSR inquiry in Mode S, each aircraft is allocated a unique identity code that appears on ATC radar along with its pressure altitude. Because no other aircraft responds with this code, the possibility of two pilots picking the same transponder response code is nil. The beacon code is assigned by a sophisticated flight data processor computer (FDP), which scans flight plan data for helpful information to be displayed on screen next to the target in a data block for each aircraft.

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ATC Radar in Operation

The term "mode select" is sometimes used to refer to Mode S. It's a data packet protocol that's also utilized in collision avoidance systems onboard aircraft. Mode S interrogates one aircraft at a time when used by ATC. Because transponders do not have to reply to every interrogation in airspace, their workload is decreased. Additionally, with Mode S, location data is more accurate. Monopulse, a single response in which the phase of the transponder response is utilized to compute the position of aircraft, is more enough to locate the aircraft. Mode S also has the possibility for a larger range of information sharing, which has yet to be realized. Simultaneously, older radar and transponder technology has been made compatible.

Transponder Tests and Inspections

All transponders on aircraft flying into controlled airspace must be inspected and tested every 24 calendar months, according to regulatory standards. Installation or maintenance that could result in a transponder error is also subject to examination and testing in compliance with the requirements. Only a properly rated repair station, the aircraft manufacturer (if a transponder was installed), and holders of a continuous airworthiness programme are authorised to perform the procedures. A transponder, like many other radio-electronic systems, can be tested for airworthiness using test equipment.

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Aircraft Flight instruments | Six Basic Flight Instruments

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