Plain English Meaning

How fast the airplane is going up or down, measured in feet per minute. If the number is positive, you're climbing; if it's negative, you're descending.

Full Definition

The rate at which an aircraft is climbing or descending, expressed in feet per minute (fpm). A positive value indicates a climb; a negative value indicates a descent. It is shown on the vertical speed indicator (VSI) on the instrument panel.

Context Anchor

In the developed phase of a spin, the airplane may have a large downward vertical speed, meaning altitude is being lost quickly.

Derivation

“Vertical” comes from a word meaning straight up and down. “Speed” means rate of movement. Together, the term points to movement in the up-and-down direction rather than movement across the .