Definition
An ARINC 424 path-and-terminator leg type used in RNAV procedure coding that instructs the aircraft to fly a specified heading until it intercepts the next leg in the procedure. The leg has no fixed distance or altitude termination; it ends when the FMS detects interception of the following course or path.
Plain English
A coded instruction in the flight computer that says: fly this heading, and stop flying it once you cross paths with the next part of the procedure.
Context Anchor
Seen in instrument procedure design and in some flight-management-system leg descriptions, especially when a procedure connects a heading segment to the next course.
Derivation
From the ARINC 424 path-terminator naming system, where each leg type is a two-letter code. The first letter describes the path flown (V = heading/vector), and the second letter describes how the leg ends (I = intercept). So 'VI' literally reads as 'fly a heading until intercept.'
Why Pilots Care
It lets ATC provide vectors while still preserving a defined path that the navigation system can capture and follow after intercept.
Intuition Check
VI does not mean “visual” here, and it is not the Roman numeral six. It is a procedure-code label for flying a heading until joining the next path.
Example Sentence 1
After takeoff, the SID coded a VI leg of heading 080 until intercepting the 045 radial from the VOR.
Example Sentence 2
The autopilot remained in heading mode during the VI leg until the localizer was captured.