Refer to figures.
The sum of all the reactive forces on an airfoil is known as the “Total Reaction”, which acts through a point called "Centre of Pressure" at 90º to the chord line.
When an Angle of Attack of a symmetrical airfoil greater than zero exists, the Total Reaction tilts backwards and is split into two elements:
- Lift, which is defined as the proportion of the Total Reaction perpendicular to the Relative AirFlow (RAF).
- Drag, which is the proportion of the Total Reaction which is parallel to and in the same direction with the RAF.
Centre of Gravity is the point of a body through which the sum of the forces of all masses of the body (weight) is considered to act.
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