Definition
A flight instrument that shows the direction and rate at which an aircraft's state is changing, rather than the current value itself. The Vertical Speed Indicator (VSI) is the classic example: it indicates whether the aircraft is climbing or descending and how fast, signaling a change before it shows up clearly on other instruments such as the altimeter.
Plain English
An instrument that tells you which way things are heading and how quickly, so you can spot a change early and correct it before it becomes a problem.
Context Anchor
Seen in instrument flying when interpreting the vertical speed indicator during straight-and-level flight, climbs, descents, and level-offs.
Derivation
"Trend" comes from the Old English trendan, meaning to turn or roll. It later came to mean the general direction something is moving in. In aviation, a trend instrument shows the direction the aircraft's state is moving, not just where it is right now.
Why Pilots Care
It lets the pilot detect and correct small altitude or heading drifts before they grow into larger deviations.
Grounding Statement
If the airplane begins to climb, the vertical speed indicator should move upward to show that upward trend.
Intuition Check
Do not read “trend” as a guess or prediction. Here, it means the instrument is showing the actual direction and rate of change that is developing.
Example Sentence 1
He used the VSI as a trend instrument, catching the slight descent and adding a touch of back pressure before the altimeter moved.
Example Sentence 2
A downward trend appeared on the instrument, prompting a small pitch adjustment to level off.