A pitot tube is an instrument that is mounted on the wing of an airplane. It is used to determine the dynamic pressure of the air flow and subsequently, the airspeed of the plane. The pitot tube was invented by the French hydraulic engineer Henri Pitot in the early 18th century. It was initially used to determine the speed of water in a river.
The pitot tube is used to determine the difference between static, dynamic, and total pressure of a fluid. A fluid is basically a liquid or a gas that flows. For example, the water flowing in a river or the oxygen molecules moving in the wind are considered fluids.
A typical pitot tube consists of a device that is situated in the path of the fluid. As the fluid flows through the tube, a pressure is created which is measured. The tube doesn’t have an outlet so the fluid comes to a rest, and its stagnation pressure, which is also called the total pressure, is determined.
In order to calculate the airspeed of a plane, the static pressure of the fluid must also be determined. Static pressure is the pressure created from the moving fluid. This is obtained through a pitot-static tube, which consists of a second tube with holes on the sides.
Once the static pressure is determined, it is subtracted from the stagnation pressure. This calculation provides the dynamic pressure of the fluid. With this information, the airspeed of the plane can be determined.
The pitot tube was first utilized by Henri Pitot to measure the speed of the Seine River. He studied the flow of water at various depths. His findings seemed to disprove the notion that water flowed faster at deeper depths.
In the 19th century, Henry Darcy modified the pitot tube. Darcy was a French engineer that focused his research on hydraulics. His design of the pitot tube is the current model used in most applications.
Typically, the pitot tube is attached to the wing or the fuselage of the plane. It needs to be checked on a regular basis to ensure it is working properly. Any malfunction can cause an incorrect reading of the airspeed.
One cause of an improperly functioning pitot is ice formation. Icing is a serious problem that can result in damage to the instruments on the plane. Regular deicing procedures are required to ensure that the pitot is correctly measuring the pressures associated with the airflow around the plane.