Why is DME equipment required when using VOR navigational receivers?

The requirement for DME (Distance Measuring Equipment) when using VOR (VHF Omnidirectional Range) navigational receivers is primarily linked to the need to determine the distance from the VOR station. VOR provides pilots with bearing information to navigate along their intended flight path, but unlike VOR, which only gives the azimuth or direction to the station, DME provides the necessary range or distance information.

By knowing both the direction (from the VOR) and the distance (from the DME), pilots can more accurately assess their position in relation to the VOR station, effectively enhancing navigation, route planning, and situational awareness. This is particularly important during approaches, holding patterns, and en route navigation.

The other options do not align with the primary function of DME in conjunction with VOR. Increasing flight altitude pertains to altitude management rather than navigational accuracy, improving communication with ground control involves radio communication rather than position tracking, and enhancing engine performance is unrelated to navigation systems entirely.