Which type of navigation aid is considered primary?

VOR, or VHF Omnidirectional Range, is considered a primary navigation aid because it is widely used as a standard reference point for pilots in both en route and terminal navigation. VOR provides accurate and reliable signal guidance, allowing pilots to determine their position relative to ground-based stations. Its effectiveness in providing directional information helps ensure safe and efficient flight operations, making it a crucial tool in air traffic management.

The system operates by transmitting a radio signal that can be received by aircraft equipped with a VOR receiver, allowing pilots to navigate along airways and approach procedures. The design of the VOR system supports accurate course tracking and is not affected by changing weather conditions like some other navigation methods might be.

In contrast, while GPS offers high precision and efficiency in navigation, it relies on satellite signals, which can sometimes be susceptible to interference or signal loss. NDB (Non-Directional Beacon) lacks the directional capabilities of VOR and is generally considered a less accurate means of navigation. The Flight Management System (FMS) integrates various navigation aids and supports flight planning, but it too depends on VOR and other input for accurate functioning. Thus, among these options, VOR stands out as the primary navigation aid in traditional aviation practice.