In which mode is altitude information transmitted from a radar beacon transponder?

Altitude information is transmitted from a radar beacon transponder in Mode C. This mode is specifically designed to include altitude reporting as part of its data transmission. When an aircraft is equipped with a Mode C transponder, it continuously sends out its altitude information along with its identity to air traffic control (ATC) and other aircraft in the vicinity.

This capability allows for improved traffic separation and situational awareness in controlled airspaces, as ATC can track not only the aircraft's position but also its altitude, thereby facilitating safer and more efficient air traffic management.

Understanding the different modes of transponders is critical for any pilot or aviation professional. Mode A provides only a squawk code without altitude information, while Mode B is less commonly referred to in contemporary practice, primarily associated with older equipment. Mode D is used for specific applications like data link communications but does not focus on altitude reporting. Hence, Mode C is the definitive mode for altitude transmission in radar beacon systems.