What radio navigation aid measures the time it takes for a signal to indicate distance from an aircraft to a VORTAC station?

The correct choice is DME, or Distance Measuring Equipment, which accurately measures the time it takes for a radio signal to travel between an aircraft and a VORTAC (VHF Omni-directional Range/Tactical Air Navigation) station. This time measurement is then converted into a distance readout for the pilot. DME operates by sending out a signal from the aircraft to the ground station, which then responds with a return signal. The system calculates the distance based on the time delay between sending and receiving these signals, providing vital information for navigation.

Other options, while related to navigation, serve different functions. An NDB (Non-Directional Beacon) is primarily used for bearing information without providing distance measurements. A VOR (VHF Omni-directional Range) provides pilots with directional information but does not measure distance to the station. An ADF (Automatic Direction Finder) aids in determining the direction to an NDB, but like the NDB, it doesn’t give distance information. Thus, DME is the only option that effectively and specifically measures the distance to a VORTAC station based on the timing of a signal.