Definition
Rotation of an aircraft about its longitudinal axis — the imaginary line running from the nose to the tail. Roll is controlled primarily by the ailerons and causes one wing to move down while the other moves up.
Plain English
Roll is when the aircraft tilts to the left or right, dipping one wing down and lifting the other.
Context Anchor
Seen in flight-control, stability, and maneuver discussions when describing how the aircraft tilts its wings left or right.
Derivation
From Old English 'rollen,' meaning to turn over or rotate. The word naturally describes the motion of an object turning around a long axis — like a log rolling — which is exactly what the aircraft does around its nose-to-tail line.
Why Pilots Care
Precise roll control lets pilots establish and hold bank angles for turns, maintain coordinated flight, and correct for adverse yaw.
Intuition Check
Roll does not mean the aircraft is moving along the ground here. In this context, roll means the aircraft is rotating so one wing rises and the other lowers.
Example Sentence 1
The pilot used the ailerons to roll the aircraft into a 30-degree bank before starting the turn.
Example Sentence 2
During the steep turn maneuver the student maintained a constant thirty-degree roll while holding altitude.