Definition
A pressure greater than the surrounding (ambient) air pressure. In airfoil discussions, positive pressure refers to the higher-than-ambient pressure acting on a surface of the wing — typically the lower surface — which contributes to the upward force of lift.
Plain English
Air pushing harder than the air around it. On a wing, the air underneath pushes up against the wing because its pressure is higher than the air pressure elsewhere.
Context Anchor
Seen in airfoil and lift discussions, especially in diagrams showing pressure above and below a wing.
Derivation
‘Positive’ comes from the Latin positivus, meaning ‘placed’ or ‘settled’ — used here in the sense of ‘above a reference point.’ In pressure terms, it simply means ‘above ambient,’ not ‘good’ or ‘strong.’
Why Pilots Care
Recognizing positive pressure clarifies how lift results from both upward push below the wing and suction above it, improving understanding of wing performance and stall behavior.
Grounding Statement
Picture air under part of the wing pressing upward more strongly than the normal surrounding air would.
Intuition Check
Positive does not mean “good,” “safe,” or electrically charged here. It means higher than the reference pressure being used for comparison.
Example Sentence 1
Positive pressure on the lower surface of the wing pushes upward and contributes to lift.
Example Sentence 2
As angle of attack increases, the region of positive pressure on the bottom of the airfoil grows until airflow separates at the stall.