Definition
Small reference lines on an instrument display that indicate predicted future values of a flight parameter at fixed time intervals, typically used on trend vectors to show where a parameter such as airspeed or altitude will be in a set number of seconds if the current rate of change continues.
Plain English
Short marks on a tape display that show where a value, like your airspeed or altitude, will be in a few seconds if nothing changes about how fast it is rising or falling.
Context Anchor
Seen on instrument displays, especially airspeed, altitude, heading, and vertical scales used with trend indicators.
Derivation
From the everyday meaning of a tick as a small mark or check. The name simply describes what they look like on the display: short, evenly spaced lines.
Why Pilots Care
Tick marks let the pilot see at a glance where the aircraft's speed or altitude is heading, not just where it is right now. This makes it easier to lead level-offs, anticipate airspeed changes during configuration changes, and avoid overshoots.
Analogy
They work like the small lines on a ruler. You do not need every number printed, because the smaller lines show the steps between the larger numbers.
Intuition Check
Do not think of tick marks as checkmarks or warning marks. In this context, they are scale marks that show measured steps on an instrument.
Example Sentence 1
As he reduced power for the descent, the airspeed trend tick marks showed the speed dropping toward the target value within the next several seconds.
Example Sentence 2
During the descent, the vertical speed trend aligned with the second tick mark below zero, confirming 500 feet per minute down.