Definition
An airfoil shape in which the lower surface curves inward (cups upward) rather than being flat or convex. This curvature increases lift at low airspeeds but produces high drag, so it is found mainly on early aircraft and on certain high-lift wing sections rather than on modern general aviation airfoils.
Plain English
A wing cross-section whose underside is scooped or hollowed inward, like the inside of a spoon, instead of being flat or bulging outward.
Context Anchor
Seen in airfoil design discussions when comparing different wing shapes and how their surfaces affect airflow and lift.
Derivation
Concave comes from the Latin concavus, meaning 'hollow' or 'arched inward.' It describes a surface that curves inward like the inside of a bowl, which is exactly what the lower surface of this type of airfoil does.
Why Pilots Care
The shape of an airfoil affects how air moves around the wing and how the wing produces lift, especially at different speeds and angles to the airflow.
Analogy
Picture the inside curve of a soup spoon turned upside down. The bottom of a concave airfoil curves inward in the same way, scooping toward the wing rather than bulging away from it.
Intuition Check
Concave does not mean simply “curved.” It means curved inward, like a hollow or scoop.
Example Sentence 1
Many early aircraft used a concave airfoil to generate lift at the low speeds those aircraft could achieve.
Example Sentence 2
During preflight study the student noted how the concave lower surface increased camber and improved slow-flight performance.