Practice question

When should transponders be operated on the ground while taxiing?

  1. Only when ATC specifically requests your transponder to be activated.
  2. Anytime when the airport is operating under IFR.
  3. All the time when at an airport with ASDE-X.
  4. Only when flying at or above 18,000 feet.

Answer: C — All the time when at an airport with ASDE-X.

The operation of transponders on the ground while taxiing is critical for maintaining safe and efficient air traffic control. In environments where ASDE-X (Airport Surface Detection Equipment, Model X) is operational, transponders should be on at all times. ASDE-X relies on the signals from functioning transponders to enhance situational awareness and provide real-time tracking of aircraft on the ground. This capability helps controllers monitor aircraft movements, preventing runway incursions and ensuring safe separation between aircraft during taxiing operations. While there are specific conditions under which transponders must be activated, such as during IFR operations or upon ATC request, the continuous operation of transponders in areas equipped with ASDE-X significantly contributes to the safety and efficiency of airport operations. Therefore, keeping transponders on while at airports with ASDE-X is essential for both effective air traffic management and enhancing safety protocols on the ground.

Practice more: ATPL Air Traffic Control Practice Test →