However, if not done correctly, inaccuracies can result. Next, a stagnation pressure will develop at point 3 as the aircraft move through the air.Īs result the velocity of the aircraft can be determine by the following equation.ĭue to its simplicity, the pitot tube is an inexpensive way of measuring fluid speed. As along the difference in height is negligible the pressure at point 1 and 4 can be considered the same. As the aircraft is flying static pressure will develop at point 1 and 4. This can be seen in the equation below by rearranging the terms used to find the stagnation pressure for image above.īelow is an image of an actual pitot tube on an aircraft, with a basic diagram showing how it would work. Once these values are found the fluid velocity can be found. To obtain the stagnation pressure the opening of the tube has to be perpendicular to the fluid flow.Ī Pitot tube works by measuring both static pressure as well as the stagnation pressure of an air flow. As a result the stagnation pressure is found at point 3. The stagnation pressure on the other hand represents all of the kinetic energy that has been converted into a pressure rise represented by H is the figure below. In the figure below the thermodynamic pressure at point 1 can be determine by the fluid height at point 2 by using the following modification of Bernoulli equation. As a result the first part $p$ and the third part $γh$ are both static pressures. First let’s take a look at Bernoulli equation for forces along a streamline.Ī static pressure is a fluid pressure that is independent of fluid velocity. Static and Stagnation Pressureīriefly let me remind you what static and stagnation pressure are. By measuring both types of pressure the pitot tube can determine speed of a fluid, or the speed of an object, such as a plane, moving through the fluid. A pitot tube is a device that measures static pressure as well as stagnation pressure.
One way it does this is by using Pitot-static tubes, or pitot tube for short. Have you ever wondered how an airplane measures its airspeed.