In aviation, vertical navigation (VNAV, usually pronounced vee-nav) is glidepath information provided during an instrument approach, independently of ground-based navigation aids in the context of an approach and a form of vertical guidance in the context of climb/descent.
An onboard navigation system displays a constant rate descent path to minimums.
The FMS provides flight control steering and thrust guidance along the VNAV path.
[1]: 3–6 VNAV information on an approach plate includes the Final Approach Fix (FAF), the FAF crossing altitude, a Vertical Descent Angle (VDA), the landing runway threshold as a second fix, the Threshold Crossing Height (TCH), and perhaps a Visual Descent Point (VDP).
A pilot uses the VDA, and ground speed, to compute a rate of descent (from a table found in the U.S. Terminal Procedures Publication), which is flown using the Vertical velocity indicator.
In VNAV Path mode, the aircraft adjusts the pitch to achieve and maintain the desired vertical profile.