What indicates that a Nav radio has failed?

A Nav radio failure is typically indicated by the frequencies being displayed in amber color. When a radio is functioning normally, it usually displays frequencies in green, which signifies that the system is operating correctly. Amber, however, serves as a warning that there is an issue with the radio, indicating a potential malfunction or that the system is not fully operational.

The inclusion of amber as an indicator is a common practice in aviation systems, where color codes help pilots quickly assess the status of their instruments. In the case of a Nav radio, the amber indicator alerts the pilot to the need for attention, as the functionality may be compromised, but not necessarily completely failed.

The other indicators, such as frequencies shown in green representing normal operation and frequencies lost being a more serious situation where the navigation radio is non-functional, do not provide the same information as the amber indication does. Thus, the amber color is key for pilots to recognize and address navigation radio issues promptly.