Plain English Meaning

Keeping the airspeed needle pinned on one number and not letting it move.

Full Definition

An airspeed that is held steady at a chosen value during a maneuver or phase of flight, with pitch and power adjusted as needed to prevent the indicated airspeed from drifting up or down.

Context Anchor

Seen when using the airspeed indicator during straight-and-level instrument flight to confirm that the airplane’s speed is staying steady.

Derivation

Constant comes from a Latin word meaning “to stand firm” or “remain fixed.” In aviation, it helps to the idea of a speed that is being held steady, not one that is wandering up or down.