Definition
The rate at which an aircraft is climbing or descending, expressed in feet per minute (fpm). It is displayed on the vertical speed indicator (VSI) and is used to control and verify climb and descent rates during instrument flight.
Plain English
How fast the aircraft is moving up or down, measured in feet per minute.
Context Anchor
Seen during climbs, descents, and level-offs, especially when the pilot is trying to stop climbing or descending at a selected altitude.
Derivation
Vertical means up-and-down (from Latin vertex, meaning top or highest point). Velocity means speed in a specific direction. Together they describe speed in the up-or-down direction only — separate from how fast the aircraft is moving forward through the air.
Why Pilots Care
Precise control prevents altitude overshoots or undershoots during transitions to level flight.
Intuition Check
Vertical velocity does not mean the airplane is pointed straight up or straight down. It means the airplane’s altitude is changing over time.
Example Sentence 1
Approaching the assigned altitude, the pilot reduced the vertical velocity to begin a smooth level-off.
Example Sentence 2
The instrument showed a vertical velocity of 500 feet per minute during the descent.