The camber of an airfoil is the curvature of its profile, measured as the distance between its chord line (a straight line from the leading edge to the trailing edge) and its mean camber line (an imaginary curve running halfway between the upper and lower surfaces). Camber is typically expressed as a percentage of the chord length, and it directly determines how much lift an airfoil generates at any given angle. A wing with 4% camber, for example, has a maximum deviation between those two lines equal to 4% of the total chord length.
How Camber Is Defined Geometrically
Two reference lines define camber. The chord line is simply a straight line connecting the front tip of the airfoil to the rear tip. The mean camber line is a curve that traces the midpoint between the upper and lower surfaces at every point along the chord. On a perfectly symmetrical airfoil, these two lines are identical, so the camber is zero. On a cambered airfoil, the mean camber line bows away from the chord line, usually upward.
The mean camber line meets the chord line at both the leading and trailing edges but curves above or below it everywhere in between. The maximum distance between the two lines, divided by the total chord length, gives you the camber value. Where along the chord that maximum distance occurs also matters: an airfoil with peak camber near the front behaves differently from one with peak camber near the middle, even if both have the same percentage.
Positive, Negative, and Zero Camber
A positively cambered airfoil has its mean camber line above the chord line over most of the chord. This is the most common configuration for wings on commercial and general aviation aircraft because it produces lift even when the wing is at a zero-degree angle to the oncoming air. Most airplane wings you see have positive camber.
A negatively cambered airfoil curves the opposite way, with the mean camber line dipping below the chord line. This is rare on main wings but sometimes appears in specialized applications or control surfaces.
A symmetrical airfoil (zero camber) has identical upper and lower surfaces. It generates no lift at zero angle of attack, which makes it useful where neutral behavior is desirable. Helicopter rotor blades, aerobatic aircraft wings, and vertical stabilizers often use symmetrical profiles because they need to perform equally well whether airflow hits them from above or below. Symmetrical airfoils also have a predictable center of pressure that doesn’t shift with changing angles, which simplifies control.
Why Camber Matters for Lift
Camber is one of the primary tools engineers use to control how much lift a wing produces. A cambered airfoil forces air to travel a longer path over its curved upper surface, accelerating the flow and lowering the pressure above the wing. The result is lift, even without tilting the wing into the airflow.
Increasing camber increases the lift coefficient. Research comparing NACA airfoil profiles with different camber values (but the same thickness) confirms that higher-camber airfoils consistently produce greater lift at the same angle of attack. For instance, a NACA 6409 (6% camber) generates noticeably more lift than a NACA 4409 (4% camber) under identical conditions. A NACA 0009 (zero camber, symmetrical) produces no lift at all unless the wing is angled into the airflow.
This extra lift comes with a tradeoff. Cambered airfoils create a nose-down pitching tendency. For positively cambered profiles, this pitching moment is negative, with typical values that require the tail of the aircraft to push downward to keep the nose level. The more camber you add, the stronger this tendency becomes, which means the tail has to work harder and the overall design gets more complex. Symmetrical airfoils don’t have this issue: their center of pressure stays fixed regardless of angle changes.
Reading Camber in NACA Numbers
The NACA numbering system, developed by the National Advisory Committee for Aeronautics, encodes camber directly into an airfoil’s name. In the common four-digit series, the first digit is the maximum camber as a percentage of chord, and the second digit tells you where along the chord (in tenths) that maximum camber occurs. The last two digits give the maximum thickness as a percentage of chord.
Take a NACA 2412: the “2” means 2% maximum camber, the “4” means that peak camber sits at 40% of the chord back from the leading edge, and “12” means the airfoil is 12% as thick as it is long. A NACA 0012 has a “0” for camber, making it symmetrical, with 12% thickness.
The five-digit NACA series works similarly but with a slightly different encoding. The second and third digits, when divided by two, give the position of maximum camber in tenths of chord. Both systems use parabolic equations to define the exact shape of the camber line, which lets engineers calculate precise coordinates for manufacturing.
How Pilots Change Camber in Flight
Wings are designed with a fixed camber, but pilots can effectively change it using movable surfaces. Trailing-edge flaps are the most common example. When you extend flaps during takeoff or landing, you reshape the rear portion of the wing, increasing its effective camber. This lets the wing generate more lift at lower speeds, which is exactly what you need when the aircraft is moving slowly near the ground.
Different flap designs alter camber in different ways. Slotted flaps noticeably increase wing camber while also channeling high-energy air over the flap surface to delay airflow separation. Fowler flaps go further: they slide backward as they drop, simultaneously increasing both the wing’s camber and its total area. This combination produces a dramatic boost in lift, which is why Fowler flaps are standard on large transport aircraft that need to land at manageable speeds despite their weight.
Leading-edge devices like slats work on the same principle but at the front of the wing. Deploying slats effectively increases the camber of the leading-edge region, allowing the wing to operate at steeper angles before it stalls. Together, leading-edge slats and trailing-edge flaps can transform a wing’s camber profile from a high-speed cruise shape into a high-lift, low-speed shape within seconds.
Camber vs. Thickness
Camber and thickness are the two most fundamental shape properties of an airfoil, but they describe different things. Camber is about curvature: how much the airfoil’s midline deviates from a straight line. Thickness is about bulk: the total distance between the upper and lower surfaces at any point.
You can have a thick airfoil with zero camber (like a NACA 0024), or a thin airfoil with high camber (like a NACA 6406). Each combination produces different aerodynamic behavior. Thin, highly cambered airfoils tend to see a continuous increase in lift as they get closer to the ground, which matters for aircraft designed to operate in ground effect. Thick airfoils with low camber can actually experience a reduction in lift at very low altitudes and shallow angles, a counterintuitive result that engineers account for in designs like wing-in-ground-effect vehicles.
In practice, designers choose a camber-thickness combination that balances lift, drag, structural strength, and stability for the aircraft’s intended mission. A high-altitude glider might use a highly cambered, thin profile to maximize lift efficiency. A supersonic fighter jet might use a nearly symmetrical, thin profile to minimize drag at high speeds, accepting that it will need a higher angle of attack or other means to generate adequate lift at lower speeds.