Definition
A magenta-colored line or bar displayed on a glass cockpit primary flight display that extends from the current value of an instrument (such as airspeed, altitude, or heading) to predict where that value will be in six seconds if the present rate of change continues. On the turn rate indicator, the magenta trend line shows the heading the aircraft will reach in six seconds at the current rate of turn.
Plain English
A short pink line on a glass cockpit display that shows where a value — like your heading, airspeed, or altitude — is heading next if you keep doing what you're doing. It's a six-second look into the future.
Context Anchor
Seen on a primary flight display or horizontal situation display when using the turn rate indicator during instrument flight.
Derivation
Magenta is the pinkish-purple color chosen by avionics designers to make the trend line stand out from the white scales and other colored references on the display. 'Trend' simply means the direction something is moving. Together: the pink line that shows where things are trending.
Why Pilots Care
It helps the pilot anticipate and smoothly correct heading without overshooting during turns.
Intuition Check
Do not read “trend” as a command or assigned heading. The magenta trend indicator shows what the airplane is doing now; it does not tell you where you should turn.
Example Sentence 1
As the magenta trend indicator on the heading display reached 270°, the pilot began rolling out of the turn so the aircraft would settle exactly on the assigned heading.
Example Sentence 2
Watching the magenta trend indicator, the pilot reduced bank angle to avoid overshooting the turn.