Definition
A path and terminator leg type used in RNAV procedure coding in which the aircraft flies a specified magnetic heading until it reaches a defined DME (Distance Measuring Equipment) distance from a referenced navaid, at which point the leg terminates and the next leg begins. The two-letter code VD identifies this leg type in procedure databases.
Plain English
Fly a specific compass heading and keep flying it until you are a set distance from a navigation station. When you reach that distance, this part of the procedure is finished and the next part begins.
Context Anchor
Seen in instrument procedure coding, flight management system leg descriptions, and discussions of path and terminator legs for departures, arrivals, approaches, or missed approaches.
Derivation
DME stands for Distance Measuring Equipment, a ground-based system that tells the aircraft how far it is from a station. The 'V' in VD comes from the heading-leg family used in ARINC 424 procedure coding (the database standard for instrument procedures), and 'D' marks the terminator as a DME distance. So VD literally reads as 'heading-to-DME-distance.'
Why Pilots Care
This leg type gives a precise, equipment-based end point to a heading segment so the aircraft transitions cleanly to the next course without relying on a fix or altitude alone.
Grounding Statement
Picture flying a steady assigned heading while watching the DME mileage count up or down; when it reaches the published number, that leg is complete.
Intuition Check
Do not read “heading” as the exact path the airplane will make over the ground; wind can push the ground path sideways while the aircraft maintains the heading. Do not read “termination” as the end of the flight or procedure; it means the condition that ends this one leg.
Example Sentence 1
After takeoff, the procedure coded a VD leg: fly heading 270 until 8 DME from the airport VOR, then turn on course.
Example Sentence 2
We flew the heading to DME distance termination exactly as published and intercepted the next waypoint without overshooting.