Definition
Visual cues on an electronic primary flight display (PFD) altitude tape that show the predicted altitude the aircraft will reach within a short look-ahead period (typically the next six seconds) if the current vertical speed is maintained. They are usually shown as a magenta or cyan trend vector or arrow extending up or down the altitude tape from the current altitude.
Plain English
A small marker on the altitude display that shows where you will be in altitude in a few seconds if you keep climbing or descending at the same rate. It helps you stop exactly on your target altitude instead of overshooting it.
Context Anchor
Seen on glass-cockpit altitude displays and in instrument flying discussions about trend indicators.
Derivation
From 'trend' (the direction something is heading) and 'indicator' (something that shows). The word 'trend' here means the projected path based on current rate, not a long-term pattern.
Why Pilots Care
They give an immediate visual sense of altitude change without requiring the pilot to compare successive readings.
Analogy
It is like seeing not only your car’s speed, but also a small cue showing whether the speed is increasing or decreasing. The number tells you where you are now; the trend cue tells you where things are headed.
Intuition Check
Do not read “trend indicator” as a separate altimeter. It does not replace the altitude reading; it adds a quick cue about whether altitude is moving up, down, or holding steady.
Example Sentence 1
Climbing through 4,500 feet toward the assigned 6,000, the pilot watched the altimeter trend indicator extend upward and began reducing pitch as it touched the 6,000-foot mark.
Example Sentence 2
Noticing the altimeter trend indicators slowing, the pilot added power to arrest the descent.