How often must a transponder be tested for continued airworthiness?

A transponder must be tested for continued airworthiness every 24 months. This requirement is outlined by the Federal Aviation Administration (FAA) regulations, which stipulate that the transponder undergoes a functional check to ensure it operates correctly and in compliance with established performance standards. This biennial requirement helps maintain safety in the airspace as it ensures that transponders can accurately communicate aircraft information such as altitude and identification to air traffic control.

While other intervals may apply to different equipment or requirements, the 24-month period specifically relates to transponder checks and reflects the necessity for regular inspections to ensure that aircraft continue to function effectively and remain compliant with safety regulations.