Definition
The lift produced on the upper surface of an airfoil by an area of reduced (lower-than-ambient) air pressure. As air accelerates over the curved upper surface of the wing, its pressure drops below the pressure beneath the wing, and the wing is effectively pulled upward into that low-pressure region. This upper-surface suction typically accounts for the majority of the total lift generated by a conventional airfoil.
Plain English
Air moving faster over the top of the wing creates lower pressure up there. The higher pressure under the wing then pushes the wing up into that lower-pressure zone — so the wing is partly sucked upward from above, not just pushed up from below.
Context Anchor
Seen in airfoil design and basic lift discussions, especially when learning how wing shape helps produce lift.
Derivation
Negative' here is used in the engineering sense of 'less than the surrounding reference' — in this case, less than ambient atmospheric pressure. It does not mean pressure below zero. Pairing 'negative pressure' with 'lifting action' simply names the phenomenon: lift caused by a region of reduced pressure above the wing.
Why Pilots Care
Recognizing that lift includes both upward push from below and suction from above helps pilots understand how changes in angle of attack affect total lift and stall behavior.
Grounding Statement
Picture the top of the wing as an area where the air presses less strongly than it does underneath, allowing the stronger pressure below to lift the wing.
Intuition Check
Negative pressure does not mean a true vacuum or pressure below zero. Here it means lower pressure compared with the air around it or the pressure on the other side of the wing.
Example Sentence 1
The instructor explained that most of the wing's lift comes from negative pressure lifting action on the upper surface, not from air striking the underside.
Example Sentence 2
At higher angles of attack the negative pressure lifting action increases until airflow separates and lift drops sharply.