Definition
Information presented by an instrument that shows how fast something is changing, rather than its current value. The Vertical Speed Indicator (VSI) is a rate instrument because it shows how quickly altitude is changing, expressed in feet per minute, not the altitude itself.
Plain English
Data about how fast a value is going up or down — a speed of change, not a position. The VSI tells you how fast you are climbing or descending, not how high you are.
Context Anchor
Seen in Vertical Speed Indicator discussions and during climbs, descents, and level-off checks.
Derivation
‘Rate’ comes from the Latin rata, meaning ‘calculated’ or ‘reckoned,’ and in modern use means ‘amount of change per unit of time.’ That is exactly what a rate instrument shows — change per minute or per second.
Why Pilots Care
It lets the pilot maintain a precise climb or descent rate for safe altitude control and efficient flight planning.
Intuition Check
Do not read rate information as just any useful information from the instrument. In this context, it specifically means the settled climb-or-descent speed shown by the Vertical Speed Indicator.
Example Sentence 1
The VSI provides rate information, showing the pilot a 500-foot-per-minute climb.
Example Sentence 2
On final approach the pilot watched the rate information to hold a steady 500-foot-per-minute descent.