What does the term "vertical navigation" (VNAV) refer to in aviation?

The term "vertical navigation" (VNAV) refers specifically to a navigation method that emphasizes altitude management and the vertical profile of a flight path. This involves the calculation and monitoring of vertical flight paths to ensure that an aircraft adheres to predetermined altitudes during ascent and descent, as well as during level flight. VNAV is essential for maintaining safe altitudes and ensuring compliance with air traffic control requirements.

In practice, VNAV systems utilize data from various sources, such as GPS and onboard performance databases, to provide pilots with information about vertical descent rates, altitude constraints, and glide paths, facilitating a smoother and more efficient approach and departure. This aspect of navigation is critical for ensuring both safety and efficiency during flight operations.