FAA Ground School Practice Test

What is the primary function of a transponder in controlled airspace?

1. To report altitude only

2. To communicate with flight services

3. To provide aircraft identification and altitude to ATC

4. To track and manage fuel efficiency

The correct answer is: To provide aircraft identification and altitude to ATC

The primary function of a transponder in controlled airspace is to provide aircraft identification and altitude information to Air Traffic Control (ATC). This device enhances situational awareness for controllers, as it allows them to visualize the aircraft's position on radar, along with its assigned altitude and unique identification code. When an aircraft is equipped with a transponder, it actively responds to interrogations from ATC radar by transmitting a signal that includes its identity and altitude. This response is critical in ensuring that ATC can manage air traffic safely and effectively, especially in busy or complex environments where multiple aircraft operate in proximity to one another. While reporting altitude is a function of the transponder, limiting its role to just altitude neglects its essential capability of providing identification information. Additionally, transponders are not designed to communicate with flight services or to assist with fuel efficiency tracking, which makes these options irrelevant in the context of the primary function of a transponder in controlled airspace.