What is required to be equipped in aircraft using VOR navigational receivers for enhanced navigation?

To enhance navigation using VOR (VHF Omnidirectional Radio Range) navigational receivers, having DME (Distance Measuring Equipment) on board is essential. DME operates in conjunction with VOR systems to provide pilots with accurate distance information from the VOR station, enhancing situational awareness and navigational accuracy. This capability is particularly useful in terminal areas and for approaching or departing from airports within a controlled airspace, where precise navigation is crucial.

While other equipment mentioned in the options plays vital roles in aviation safety and operations, they do not specifically augment the functional capabilities of VOR systems in the same manner as DME. Radar equipment is more related to air traffic control and surveillance rather than navigation accuracy directly associated with VOR. Flight data recorders are crucial for incident investigations and safety analysis but do not impact navigation during flight. Short-range communications, while important for operational communications, do not enhance the navigational capacity of VOR. Therefore, the equipping of DME with VOR greatly enhances the reliability and precision of navigation.