Center of Pressure (xcp)

The location at which the resultant aerodynamic moment is zero. If we consider the profile (the wing section) as a free body, this point can be assumed as the center of gravity for the pressure distribution along the surface of the profile.

1.1.3 Aerodynamic Center (xac)

This is the point where the aerodynamic moment acting on the wing is independent of the angle of attack. The aerodynamic center is essential for the stability pur­poses. For a finite wing it is the line connecting the aerodynamic centers of each section along the span.

1.1.4 Steady Aerodynamics

If the flow field around a flying body does not change with respect to time, the aerodynamic forces and moments acting on the body remain the same all the time. This type of aerodynamics is called steady aerodynamics.