How does Distance Measuring Equipment (DME) operate?

Distance Measuring Equipment (DME) operates by calculating the distance from an aircraft to a ground station using the time delay of radio signals. When an aircraft transmits a signal to the DME ground station, the station responds with a return signal. The aircraft's onboard equipment measures the time it takes for the signal to travel to the station and back. This total time is then halved to account for the return trip, and using the speed of light, the equipment can accurately compute the distance to the ground station.

This functionality is critical for pilots in navigation, especially during approaches and departures, as it helps them determine their position relative to the navigational aid. It does not calculate groundspeed, provide altitude information, or offer weather updates, which are handled by other systems and equipment. Understanding DME is essential for effective instrument flight operations, as it plays a vital role in enhancing navigation accuracy.