Public Domain Aeronautical Software (PDAS)  

The 2-digit camber line is designated by a 2-digit number. The first digit denotes the maximum camber in percent of chord. The second digit denotes the chordwise position of the maximum camber, expressed in tenths of chord. A 24 camber line (or mean line) has a maximum camber of 0.02 chord located at 0.4c. The camber line is formed by two parabolic segments that match in value and slope (=0) at the maximum camber position. From these conditions, one may derive that the equation of each line is

y/ymax = 2*x/m -(x/m)2 if x ≤ m

y/ymax = (1-2*m + 2*m*x - x2) / (1-m)2 if x > m

where m is the position of the maximum camber as a fraction of chord and x is the position as a fraction of chord.

The NACA airfoil designation requires that m be an integer multiple of one-one-hundredth chord and ymax be an integer multiple of one-tenth chord, but the program will allow any fraction of chord for either quantity.

You may note that both NASA TM 4741 and Abbott and von Doenhoff use the parameters m and p to express the shape of the camber line, but the meanings of m and p are reversed. If you downloaded the PDF from NASA several years ago, the equation in NASA 4741 is incorrect. The copy on the NASA document server has now been corrected.

Public Domain Aeronautical Software (PDAS)