Definition
On an altimeter, the speed at which the altimeter needles move in response to a change in altitude. A fast rate of movement indicates a large vertical speed; a slow rate of movement indicates a small vertical speed. Pilots use the rate of movement of the altimeter needles, along with the vertical speed indicator, to judge how quickly the aircraft is climbing or descending.
Plain English
How fast the altimeter needles are moving. The faster they move, the faster the aircraft is climbing or descending.
Context Anchor
Seen when using the altimeter during straight-and-level flight to notice whether the aircraft is holding altitude or starting to climb or descend.
Derivation
Rate comes from an older word meaning a calculated amount. In aviation, it often means an amount measured against time, so rate of movement means how much the indication moves in a given amount of time.
Why Pilots Care
Tells the pilot immediately whether altitude is being held constant or is changing.
Intuition Check
Do not read rate of movement as just “the instrument moved.” In this context, the speed of the movement matters because it shows how quickly the aircraft is changing altitude.
Example Sentence 1
A rapid rate of movement on the altimeter told the pilot the aircraft was descending faster than intended, and a small back-pressure on the yoke was applied to level off.
Example Sentence 2
A slow upward rate of movement on the altimeter confirmed a gentle climb was beginning.