NACA Aerofoils

An airfoil (American English) or aerofoil (British English) is the cross-sectional shape of an object whose motion through a gas is capable of generating significant lift, such as a wing, a sail, or the blades of propeller, rotor, or turbine.

NACA 4 Digit Series

For example, for NACA 2412 airfoil:

The first digit is the maximum camber in hundredths (i.e., percentage) of chord.

The second digit is the location of maximum camber along the chord from the leading edge in tenths (i.e., decimal) of chord.

The last two digits give the maximum thickness in hundredths of chord.

That is, NACA 2414 airfoil has a maximum camber of 2% of chord located 40% (0.4 chord) from the leading edge with a maximum thickness of 12% of the chord. Four-digit series airfoils by default have maximum thickness at 30% of the chord (0.3 chords) from the leading edge.

The NACA 0015 airfoil is symmetrical, the 00 indicating that it has no camber. The 15 indicates that the airfoil has a 15% thickness to chord length ratio: it is 15% as thick as it is long.

NACA 5 Digit Series

The NACA five-digit series describes more complex airfoil shapes. For example, for NACA 23012 airfoil:

The first digit when multiplied by 3/2 gives the design lift coefficient in tenths.

The next two digits when divided by two give the location of maximum camber along the chord from the leading edge in hundredths of chord.

The final two digits give the maximum thickness in hundredths of chord.

For the NACA 23012, the design lift coefficient is 0.3, the location of maximum camber is at 15 percent of chord and the airfoil has maximum 12 percent thickness.

NACA 1 Series

A new approach to airfoil design pioneered in the 1930s in which the airfoil shape was mathematically derived from the desired lift characteristics. Prior to this, airfoil shapes were first created and then had their characteristics measured in a wind tunnel.

The 1-series airfoils are described by five digits in the following sequence:

The number "1" indicating the series

One digit describing the distance of the min. pressure area in tenths of chord from the leading edgeOne digit describing the lift coefficient in tenths.

Two digits describing the maximum thickness in percent of chord.

For example, the NACA 16-123 airfoil has minimum pressure 60% of the chord back with a lift coefficient of 0.1 and maximum thickness of 23% of the chord.

NACA 7 Series

6-series is an improvement over 1-series airfoils with emphasis on maximizing laminar flow. The airfoil is described using six digits in the following sequence:

The first digit simply identifies the series.

The second digit gives the location of the minimum pressure in tenths of chord from the leading edge.

An optional subscript after the second digit which indicates the drag coefficient above and below the design lift coefficient. A hyphen.

The third digit gives the lift coefficient in tenths.

The last two digits describing the maximum thickness in percent of chord.

"a=" followed by a decimal number describing the fraction of chord over which laminar flow is maintained. a=1 is the default if no value is given.

For example, the NACA 612-315 a=0.5 has the area of minimum pressure 10% of the chord back, maintains low drag 0.2 above and below the lift coefficient of 0.3, has a maximum thickness of 15% of the chord, and maintains laminar flow over 50% of the chord.