What is the primary purpose of DME (Distance Measuring Equipment)?

The primary purpose of Distance Measuring Equipment (DME) is to provide pilots with the slant range distance to a VOR (VHF Omnidirectional Range) or other DME ground station. DME operates by sending a signal to the ground station, which then responds, allowing the aircraft to calculate the distance based on the time it takes for the signal to travel to the station and back. This information is crucial for navigation, helping pilots determine how far they are from a navigation aid, which aids in route planning and situational awareness during flight.

In the context of navigation, knowing the slant range distance is vital because it allows pilots to maintain appropriate separation from terrain and other aircraft. This capability directly supports the navigation and safety of the flight, making it an essential tool in modern aviation.