Definition
A dimensionless number that expresses how much lift a wing produces for a given angle of attack, airfoil shape, and airflow conditions. It captures everything about how efficiently the wing is generating lift at that moment, separate from airspeed, air density, and wing area, which are accounted for elsewhere in the lift equation.
Plain English
A number that tells you how good the wing is at making lift right now. The higher the number, the more lift the wing is producing for the same speed and air conditions. It mostly depends on the angle of attack and the shape of the wing.
Context Anchor
Seen in aerodynamics and ground effect discussions when explaining how a wing can produce the same lift with a different wing angle near the runway.
Derivation
‘Coefficient’ comes from Latin roots meaning ‘working together with.’ In math and physics, a coefficient is a number that scales another quantity. So the lift coefficient is the number that scales the rest of the lift equation to give the actual lift produced.
Why Pilots Care
Changes in lift coefficient near the ground directly affect takeoff and landing distances and the speed at which the wing stalls.
Analogy
Think of lift coefficient as the wing’s effectiveness setting. With the same wing and the same speed, a higher setting means the wing is making more upward force, up to its safe limit.
Grounding Statement
Close to the runway, the ground changes the airflow around the wing, so the same wing position can act more effectively than it does higher above the ground.
Intuition Check
Lift coefficient is not the actual amount of lift in pounds. It is a unitless number that describes how effectively the wing is producing lift under the current conditions.
Example Sentence 1
As the pilot raised the nose, the angle of attack increased and the lift coefficient climbed toward its maximum value.
Example Sentence 2
The pilot uses the published maximum lift coefficient to calculate the indicated airspeed at which the wing will stall in level flight.