Definition
A ground-based radio navigation system that measures the slant-range distance between an aircraft and a fixed DME ground station. The aircraft's DME interrogator transmits a pulse signal to the ground station, which replies on a paired frequency; the equipment calculates distance from the elapsed time between transmission and reply and displays it in nautical miles. 'Conventional' distinguishes this ground-based system from RNAV/GPS-derived distance, which computes range from satellite positioning rather than from a physical DME station.
Plain English
A radio system on the ground that tells the aircraft how far it is from a specific station by timing how long a signal takes to travel there and back. 'Conventional' just means it uses the traditional ground station, not GPS.
Context Anchor
Seen on instrument procedures and navigation charts where distances from a VOR/DME, LOC/DME, or other DME facility are used to identify points along a route or approach.
Derivation
Conventional' comes from the Latin convenire, meaning 'to come together' or 'agreed upon' -- the established, standard method everyone has long used. Here it flags the older, ground-station-based way of measuring distance, as opposed to newer satellite-based methods.
Why Pilots Care
It provides accurate distance information required for many instrument procedures and allows pilots to identify fixes without relying solely on GPS.
Grounding Statement
If the aircraft is high above a DME station, the displayed distance includes the aircraft’s height above the station, because the measurement is a straight-line distance.
Intuition Check
Conventional does not mean casual or approximate here. It means the standard ground-based DME system, as opposed to using another source such as satellite navigation for distance.
Example Sentence 1
The approach required conventional distance measuring equipment, so the crew confirmed the DME was tuned to the correct ground station before beginning the procedure.
Example Sentence 2
When the GPS is unavailable, the crew switches to conventional distance measuring equipment to maintain the required distance to the missed approach point.