Definition
A vertical navigation system that uses barometric altitude (pressure altitude corrected by the local altimeter setting) to compute and display a descent path, allowing the aircraft to fly a published vertical profile on certain RNAV approaches such as LNAV/VNAV. The flight management system calculates the required vertical path between defined waypoints and provides guidance to keep the aircraft on that path, with accuracy dependent on a current altimeter setting and on temperatures within the published limits for the procedure.
Plain English
A system in the aircraft that uses the altimeter, plus information from the flight computer, to draw a sloping descent path down to the runway and keep the airplane on it. It works like a built-in glide path, but it relies on air pressure rather than a ground signal.
Context Anchor
Seen in instrument approach procedure discussions, especially LNAV/VNAV minimums and aircraft equipment requirements.
Derivation
Baro' is short for barometric, from the Greek 'baros' meaning weight — referring to the weight of the air, which is what an altimeter measures. 'VNAV' stands for vertical navigation. So baro-VNAV literally means 'vertical navigation based on air-pressure altitude,' which is exactly how the system works.
Why Pilots Care
It provides vertical path guidance on approaches for aircraft without WAAS GPS, improving precision and safety where only lateral guidance would otherwise be available.
Analogy
It is like following a planned downhill line using your pressure-based altimeter as the measuring tool, rather than following a radio beam coming up from the runway area.
Grounding Statement
On a baro-VNAV approach, the system uses changing air pressure to judge whether the airplane is above, below, or on the planned descent path.
Intuition Check
Do not assume “VNAV” always means satellite-based or ground-beam guidance. In baro-VNAV, the vertical path is calculated from barometric altitude.
Example Sentence 1
Before flying the LNAV/VNAV approach, the crew confirmed the outside air temperature was within the baro-VNAV limits published on the chart.
Example Sentence 2
Baro-VNAV guidance kept the aircraft on the required vertical profile until reaching the decision altitude.