Definition
The highest value of the lift coefficient that a wing can achieve before it stalls. It represents the most lift the wing can produce for a given airspeed and air density, and it occurs at the critical angle of attack — the angle just before airflow over the wing separates and lift drops off.
Plain English
It is the most lift a wing can squeeze out of the air before it stalls. Push the wing past this point and it stops flying, no matter how fast you are going.
Context Anchor
Seen in discussions of flap effectiveness, slow flight, approach, landing, and stall speed.
Derivation
‘Coefficient’ comes from Latin roots meaning ‘working together,’ and in engineering it means a number that scales one quantity against others. The maximum lift coefficient is simply the largest value that scaling number can reach for a given wing before the airflow gives up.
Why Pilots Care
CLmax directly sets the aircraft's minimum safe flying speed in any given configuration and is essential for determining takeoff, landing, and maneuvering speeds.
Grounding Statement
When flaps are extended, the wing can usually make more lift at a slower speed before it reaches its limit.
Intuition Check
Do not read “maximum lift coefficient” as simply “the most pounds of lift the airplane can ever make.” It is a lift-efficiency number for a specific configuration, not the total lift force by itself.
Example Sentence 1
Extending the flaps increases the wing’s maximum lift coefficient, which is why the airplane can fly approach speeds well below its clean stall speed.
Example Sentence 2
Deploying the flaps raised the wing's maximum lift coefficient and allowed a slower, safer approach speed.