Definition
A radio navigation system that gives the pilot the slant-range distance in nautical miles between the aircraft and a selected ground station. The aircraft transmits a pulse pair to the ground station, which responds after a fixed delay; the airborne unit measures the round-trip time and converts it to distance. DME stations are commonly co-located with VOR or ILS facilities, and many instrument procedures specify fixes and altitudes by DME distance from a named station.
Plain English
DME is equipment that tells the pilot exactly how far the aircraft is from a chosen ground station, in nautical miles, by timing how long a radio signal takes to travel there and back.
Context Anchor
Seen on instrument procedure charts, in aircraft navigation equipment, and in operations specifications when a procedure or approval requires distance information.
Derivation
From the plain English words 'distance', 'measuring', and 'equipment'. The name is literal: equipment that measures distance. Knowing this helps anchor that DME is purely about range to a station, not about bearing or direction.
Why Pilots Care
DME provides precise distance information needed for timing, waypoint identification, and safe execution of instrument procedures.
Intuition Check
DME does not point you toward a station. It tells distance from the station; another navigation source is needed for direction.
Example Sentence 1
The chart shows the final approach fix at 6 DME from the VOR, so the pilot began descent when the DME read 6.0.
Example Sentence 2
During the missed approach, the DME indicated the aircraft had reached the published holding fix distance.