Plain English Meaning
A short line on a glass-cockpit display that shows where your speed, altitude, or heading is heading next if you keep doing what you're doing right now.
Full Definition
A graphical line or arrow displayed on an electronic flight instrument (such as a primary flight display) that predicts where a parameter — typically airspeed, altitude, or heading — will be a set number of seconds in the future if the current rate of change continues.
Context Anchor
Seen on electronic flight displays and moving-map displays, especially when monitoring changes in airspeed, altitude, vertical movement, or aircraft path.
Derivation
‘Trend’ comes from the Old English ‘trendan,’ meaning to turn or roll in a direction. ‘Vector’ comes from the Latin ‘vehere,’ meaning to carry. Together, the term carries the idea of ‘the direction something is being carried toward’ — a useful image for a line that shows where a value is going.
Why Pilots Care
It lets the pilot spot and correct a developing deviation early rather than waiting for the actual value to move outside limits.
Intuition Check
Do not read trend vector as a command to fly somewhere. It is a prediction based on what is happening now, not an instruction and not a guarantee.
Example Sentence 1
As the airspeed trend vector reached the top of the green arc, the pilot reduced power to avoid exceeding maneuvering speed.
Example Sentence 2
Watching the altitude trend vector helped the pilot maintain level flight during the approach.