DME refers to Distance Measuring Equipment, a technical device utilized for determining distances between aircraft and ground stations or between two aircraft, primarily in the aviation field.
Distance Measuring Equipment (DME) is a vital tool in aviation, operating within the UHF frequency band (960 to 1215 MHz) to measure the slant range distance between an aircraft and a ground-based DME station.
DME systems are often paired with VOR (VHF Omnidirectional Range) and ILS (Instrument Landing System) navigation systems. VOR stations, operating in the VHF band (108.0 to 117.95 MHz), provide directional guidance, while DME provides distance data from the same ground facility or co-located stations. This combination enhances situational awareness and allows for precise position determination and navigation.
In ILS approaches, DME provides distance information relative to the runway threshold to assist in descent planning, complementing the localizer and glide slope signals of the ILS.
Modern avionics, such as the Garmin GDM 450R and GDM 4500, allow pilots to tune two separate DME frequencies and display accurate slant-range distance readings on integrated flight decks. This capability supports improved route flexibility and precision in IFR flight, facilitating RNAV (Area Navigation) by calculating position from multiple DME stations.
The DME device, as defined by EUROCONTROL, provides a continuous slant range distance-from-station readout. During flight, signals are sent from the aircraft to the DME receiver, processed, and then routed back to the aircraft. The distance information is obtained from the round trip time between the signals.
When a marker cannot be established due to geographical conditions or other reasons, a DME device can be installed together with the Glide Slope device to provide distance information for the runway. In VOR/DME systems, the pilot receives direction and distance information at the same time, allowing for exact location determination.
DME devices operate with a transponder antenna on both the aircraft and the ground station, unlike NDB (Non-Directional Beacon) and VOR. The symbol of the DME device on navigation maps and charts is square.
In summary, DME operates at UHF frequencies around 960-1215 MHz, measures slant-range distance to ground stations, and interfaces with VOR and ILS to provide a combined azimuth and distance navigation solution critical for en route navigation and precision approaches. The pilot reads the distance in nautical miles (nm) on the display in the cockpit.
- The combination of VOR and DME navigation systems typically includes DME systems operating within the aircraft, providing distance data from the same ground facility or co-located stations.
- Modern avionics, such as the Garmin GDM 450R and GDM 4500, enable pilots to use DME technology for precise position determination and navigation during Instrument Flight Rules (IFR) flight.
