What primary air navigation system allows communication of exact distance and bearing from the station under IFR?

The primary air navigation system that allows for communication of exact distance and bearing from the station under Instrument Flight Rules (IFR) is the VHF Omnidirectional Range (VOR). VOR is a type of short-range radio navigation system that enables aircraft to determine their position and stay on course by receiving radio signals transmitted by ground stations.

When an aircraft tunes into a specific VOR frequency, it receives signals that provide both bearing and distance information relative to the station. This is particularly useful for navigation under IFR, as pilots can use the precise bearings to navigate safely and accurately, facilitating the flight path and aiding in approach procedures.

VOR operates in the VHF band, making it less susceptible to interference compared to lower frequency systems, and it provides a clear and reliable means of navigation. This characteristic makes VOR a cornerstone of air navigation, especially in conjunction with IFR approaches and en-route navigation, ensuring that pilots maintain situational awareness and adhere to airspace requirements.

The other navigation systems, while useful, either do not provide the same type of comprehensive distance and bearing information as VOR or serve different specific functions that may not be aligned with the requirements of IFR navigation.