Definition
A function of area navigation (RNAV) equipment that calculates, displays, and may guide the aircraft along a vertical flight profile, typically a defined descent path between two altitudes at specified points along a route or instrument approach.
Plain English
VNAV is the part of the navigation system that handles climbing and descending. Just as the lateral side of the system tells the aircraft where to go left and right, VNAV tells it how to climb or descend along a planned vertical path between two points.
Context Anchor
Seen in aircraft navigation systems, flight management systems, instrument procedures, descent planning, and some approach operations.
Derivation
Vertical comes from the Latin vertex, meaning the highest point or top. Navigation comes from the Latin navigare, to sail or steer a ship. Together the term describes steering the aircraft in the vertical dimension — up and down — rather than just left and right.
Why Pilots Care
It supports precise, fuel-efficient descents while meeting altitude requirements at each waypoint.
Intuition Check
Do not assume VNAV means the airplane is cleared to descend or that the system is flying the descent for you. VNAV is guidance for the vertical path; the pilot is still responsible for using it correctly and legally.
Example Sentence 1
The crew armed VNAV before the top of descent so the aircraft would follow the planned profile down to the arrival altitude.
Example Sentence 2
VNAV kept the aircraft at the correct altitude when crossing each waypoint on the arrival.