Definition
An imaginary line drawn from the leading edge to the trailing edge of an airfoil, positioned exactly halfway between the upper and lower surfaces at every point along the chord. The shape and curvature of this line define the airfoil's camber — the amount and distribution of curve built into the wing.
Plain English
A line that runs through the middle of the wing from front to back, staying equally far from the top and bottom surfaces the whole way. The more this line curves, the more curved the wing is overall.
Context Anchor
Seen in wing and airfoil diagrams when learning how wing shape affects lift.
Derivation
‘Mean’ here comes from the Latin ‘medianus’ meaning ‘middle’ — it’s the same ‘mean’ used in mathematics for an average. ‘Camber’ comes from Old French ‘cambre’ meaning ‘curved’ or ‘arched.’ So a mean camber line is literally the ‘middle curve line’ of the wing.
Why Pilots Care
The curvature and position of the mean camber line directly affect how much lift the wing generates at a given angle of attack and influence stall behavior.
Intuition Check
Mean does not mean unkind here; it means middle or average. Camber does not mean a separate part of the wing; it means the curve built into the wing’s shape.
Example Sentence 1
The greater the curvature of the mean camber line, the more lift the airfoil produces at low speeds.
Example Sentence 2
Changing the mean camber line on a new airfoil design improved the aircraft's low-speed handling qualities.