Definition
A VA leg is a coded flight path segment in an RNAV or RNP procedure in which the aircraft flies a specified magnetic heading until it reaches a specified altitude, at which point the leg terminates and the next leg begins. The leg has a defined heading and a defined terminating altitude, but no defined ground track or fixed endpoint, so the geographic position where the leg ends varies with wind and aircraft performance.
Plain English
Fly this heading until you climb (or descend) to this altitude. When you reach the altitude, that part of the procedure is done and you move on to the next instruction.
Context Anchor
Seen in instrument procedure design, departure procedures, missed approach procedures, and navigation system coding for instrument flying.
Derivation
In the ARINC 424 navigation database standard, each leg of a procedure is given a two-letter 'path terminator' code. The first letter describes the path (V = heading, vector) and the second letter describes how the leg ends (A = altitude). So VA literally reads as 'heading path, altitude termination.'
Why Pilots Care
Because a VA leg ends at an altitude rather than at a fixed point, the FMS cannot show a fixed waypoint at the end of it. Pilots need to recognize that the aircraft will sequence to the next leg only when the altitude is reached — climb performance and ATC altitude assignments directly affect when and where that happens.
Intuition Check
Do not read “leg” as a body part or a trip in the everyday sense. Here it means one segment of a procedure. Do not read “termination” as cancellation; here it means the condition that ends that segment.
Example Sentence 1
The departure begins with a VA leg: fly runway heading until 1,500 feet, then turn left direct to the first waypoint.
Example Sentence 2
After takeoff the VA leg ensures the aircraft climbs straight ahead to the specified altitude before any turn is made.