Definition
An ARINC 424 path-terminator leg type that instructs the aircraft to fly a specified heading until the pilot or controller manually terminates the leg, typically by being given a vector, a direct-to clearance, or further routing instructions. The leg has a defined heading but no defined endpoint in the navigation database.
Plain English
A leg on a published procedure that tells you to fly a specific heading and keep flying it until ATC tells you what to do next.
Context Anchor
Seen in instrument procedure database coding, especially where a procedure sends the aircraft on a heading that must be ended by pilot action rather than by reaching a waypoint.
Derivation
In the ARINC 424 path-terminator coding system, two letters describe each leg: the first letter is the path (how you fly it), the second is the terminator (what ends it). 'V' stands for heading (vector), and 'M' stands for manual termination. So VM literally means 'fly a heading until someone manually ends the leg.'
Why Pilots Care
Correct execution keeps the aircraft on the protected path until the pilot is ready to sequence the next leg.
Intuition Check
A VM leg is not a course to a waypoint. It is a heading to fly until the pilot manually ends that leg or receives the next instruction.
Example Sentence 1
After takeoff, the SID ended with a VM leg on heading 270, so we held that heading until departure control gave us a turn on course.
Example Sentence 2
After takeoff the departure uses a VM leg to maintain runway heading until radar vectors are received.