curve along the chord. The coefficient of lift for a two-dimensional airfoil section with strictly horizontal surfaces can be calculated from the coefficient of pressure distribution by integration, or calculating the area between the lines on the distribution. This expression is not suitable for direct numeric integration using the panel method of lift approximation, as it does not take into account the direction of pressure-induced lift. This equation is true only for zero angle of attack. where: is pressure coefficient on the lower surface is pressure coefficient on the upper surface is the leading edge location is the trailing edge location When the lower surface is higher (more negative) on the distribution it counts as a negative area as this will be producing down force rather than lift. See also Lift coefficient Drag coefficient Pitching moment coefficient References Abbott, I.H. and Von Doenhoff, A.E. (1959) Theory of Wing Sections, Dover Publications, Inc. New York, Standard Book No. 486-60586-8 Anderson, John D (2001) Fundamentals of Aerodynamic 3rd Edition, McGraw-Hill. Aerospace engineering Dimensionless numbers of fluid mechanics Fluid dynamics