Definition
The highest value of the lift coefficient that a wing can produce before the airflow separates from the upper surface and the wing stalls. It represents the maximum lifting capability of a wing at a given configuration (clean, flaps extended, etc.) and occurs at the critical angle of attack.
Plain English
The most lift a wing can make before it stops flying. Push the wing past this point and it stalls.
Context Anchor
Seen in discussions of flaps, stall speed, lift, and how wing shape changes affect takeoff and landing performance.
Derivation
‘Coefficient’ comes from Latin roots meaning ‘working together’ — in aerodynamics it’s a number that combines all the factors of a wing’s shape and angle into a single lift-producing value. ‘Max’ simply marks the highest point that value can reach before the wing quits flying.
Why Pilots Care
CL-MAX determines the lowest safe speed at which the aircraft can fly and shows how flaps raise that limit for takeoff and landing.
Grounding Statement
When flaps are extended, the wing shape changes so it can reach a higher lift limit before the airflow can no longer stay attached smoothly.
Intuition Check
Do not read “maximum” as the most lift the airplane can ever make in every situation. CL-MAX means the highest lift coefficient for the wing’s current configuration before stall.
Example Sentence 1
Extending the flaps increases the wing’s CL-MAX, which is why the airplane can fly safely at a slower approach speed.
Example Sentence 2
The aircraft reached CL-MAX at the critical angle of attack, after which further nose-up input produced an immediate stall.