Definition
The change in direction of airflow as it passes around an airfoil. As air meets the curved upper and lower surfaces of a wing, it is forced to follow those contours, bending downward behind the trailing edge. This downward turning of the air mass is what produces lift, in accordance with Newton's third law: the wing pushes the air down, and the air pushes the wing up.
Plain English
Air gets bent downward as it flows over and under a wing. That downward push on the air is what holds the airplane up.
Context Anchor
Seen in airfoil behavior and lift discussions, especially when explaining how a wing changes the motion of the air around it.
Derivation
Flow comes from an old word meaning “to move along like a stream.” Turning means changing direction. Together, the phrase points to the main idea: the air is moving, and the wing changes where that moving air goes.
Why Pilots Care
Flow turning is the basic mechanism that generates lift; changes in angle of attack directly alter the amount of turning and therefore the amount of lift produced.
Analogy
Hold your hand flat out a car window at speed and tilt the leading edge up slightly. You feel your hand pushed up because you are deflecting the oncoming air downward. Same idea, much smaller scale.
Grounding Statement
Picture air approaching the wing, curving around it, and leaving angled slightly downward behind the airplane.
Intuition Check
Flow turning does not mean the airplane turns left or right. It means the moving air changes direction as it passes around the wing.
Example Sentence 1
The instructor explained that increasing the angle of attack increases flow turning, which increases lift — up to the point of stall.
Example Sentence 2
On the lower surface the air is turned downward, creating an upward reaction force on the wing.