Static Pressure (Ps) is the absolute pressure of still air surrounding the aircraft. This is the barometric pressure at the altitude where the aircraft is travelling and is independent of any pressure disturbances caused by the motion of the aircraft. Static Pressure will exert the same force per square metre on all surfaces of an aeroplane. The lower the altitude, the greater the force per square metre. It is called Static Pressure because of the air’s stationary or Static presence. An aircraft always has Static Pressure acting upon it.

Dynamic Pressure: Because air has mass, air in motion must possess kinetic energy, and will exert a force per square metre on any object in its path. It is called Dynamic Pressure because the air is moving in relation to the object being considered, in this case an aeroplane.

Dynamic Pressure is proportional to the density of the air and the square of the speed of the air flowing over the aircraft (P_d = ½ m V²). An aircraft immersed in moving airflow will therefore experience both Static and Dynamic Pressure. The sum of Static and Dynamic pressure is known as ‘Total’ pressure (remember, Static pressure is always present).

The Dynamic pressure depends directly on air density and airflow speed squared.