What is an example of a secondary navigation aid?

A secondary navigation aid refers to tools or systems that support primary navigation methods. The Automatic Direction Finder (ADF) falls into this category as it helps pilots determine their position relative to a radio beacon and follow a course toward it, which assists in navigation alongside more advanced systems.

While GPS and VOR are critical component systems in modern aviation navigation, they are often considered primary aids due to their widespread integration in flight operations. A compass, meanwhile, is a basic navigational tool and is typically categorized as a primary instrument in navigation, as it provides essential directional information. In contrast, the ADF is used in conjunction with these systems, functioning as a supplementary method for navigating when other primary systems might not be available or operational. This support role exemplifies its classification as a secondary navigation aid.