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Which of the following options are possible SSR-Transponder modes?

  • A

    B, R, S

  • B

    A, C, R

  • C

    A, C, S

  • D

    B, C, V

A transponder, a crucial component in aircraft avionics, has several modes that allow it to communicate with air traffic control (ATC) radar systems. These modes are designated by different four-digit codes and serve various purposes:

Mode A: This mode is the basic identification mode. When selected, the transponder sends out a four-digit squawk code assigned by ATC. This code allows radar systems to identify the aircraft and associate it with the corresponding flight plan or radar track.

Mode C: Mode C supplements Mode A by transmitting the aircraft's pressure altitude. This altitude information is displayed to ATC controllers on their radar screens, enabling them to maintain vertical separation between aircraft. Mode C altitude is typically derived from the aircraft's altimeter.

Mode S: Mode S is an advanced transponder technology that offers more capabilities than Modes A and C. It allows for selective interrogation and addressing, meaning that ATC radar systems can specifically request information from individual aircraft equipped with Mode S transponders. This mode enhances the efficiency of air traffic control and enables additional functionalities like Traffic Collision Avoidance System (TCAS) surveillance.

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