Definition
The rate at which an aircraft is climbing or descending, expressed in feet per minute (fpm), as displayed on the vertical speed indicator (VSI).
Plain English
How fast the airplane is going up or down, measured in feet per minute. A reading of +500 means climbing 500 feet every minute; -500 means descending at the same rate.
Context Anchor
You see this when reading the vertical speed indicator during straight-and-level flight, climbs, and descents.
Derivation
“Vertical” means up-and-down. “Speed” and “rate” both point to how much something changes over time. Together, “vertical-speed rate” means how fast the airplane’s height is changing.
Why Pilots Care
Holding a steady vertical-speed rate is essential for smooth climbs, controlled descents, and arriving at assigned altitudes on time. ATC clearances often specify or imply a target rate (for example, 'descend at 500 fpm').
Intuition Check
Do not read “speed” here as forward speed through the air. Vertical-speed rate is only about upward or downward movement.
Example Sentence 1
After leveling off, the pilot trimmed the aircraft until the vertical-speed rate settled on zero.
Example Sentence 2
A zero vertical-speed rate confirmed the airplane was holding altitude in level flight.