Where sqrt denotes the square root function. Bernoulli’s equation states that the static pressure plus one half the density times the velocity V squared is equal to the total pressure. On the graphic, the Greek symbol rho is used for the air density. With the difference in pressures measured and knowing the local value of air density from pressure and temperature measurements, we can use Bernoulli’s equation to give us the velocity. measurement = q = pt – ps Solve for Velocity The pressure transducer measures the difference in total and static pressure which is the dynamic pressure q. The pressure in this tube is the total pressure (pt) discussed in Bernoulli’s equation. The pressure in these tubes is the static pressure (ps) discussed in Bernoulli’s equation. The center tube, however, is pointed in the direction of travel and is pressurized by both the random and the ordered air velocity. Since the outside holes are perpendicular to the direction of flow, these tubes are pressurized by the local random component of the air velocity. On some airplanes the pitot-static tube is put on a longer boom sticking out of the nose of the plane or the wing. The pitot-static tube is mounted on the aircraft, or in a wind tunnel, so that the center tube is always pointed in the direction of the flow and the outside holes are perpendicular to the center tube. The transducer measures the difference in pressure in the two groups of tubes by measuring the strain in a thin element using an electronic strain gauge. The center hole in the tube is kept separate from the outside holes and is connected to the other side of the transducer. The outside holes are connected to one side of a device called a pressure transducer. Several small holes are drilled around the outside of the tube and a center hole is drilled down the axis of the tube.
![calculating velocity using a pitot tube calculating velocity using a pitot tube](https://i.ytimg.com/vi/-4K5hU5xJrs/maxresdefault.jpg)
The actual tube on the aircraft is around 10 inches (25 centimeters) long with a 1/2-inch (1 centimeter) diameter.
![calculating velocity using a pitot tube calculating velocity using a pitot tube](https://prod-qna-question-images.s3.amazonaws.com/qna-images/answer/db64cdc8-10db-49ba-87b6-813d0a79639b/f1c85c13-ba1d-457c-81ee-5526c72360b8/35223ce0-8221-11eb-9735-57cef19b8714_cg_6.jpg)
Pitot-Static tubes, which are also called Prandtl tubes, are used on aircraft as speedometers. This page shows a schematic drawing of a pitot-static tube. Home > Beginners Guide to Aeronautics Pitot – Static Tube – Speedometer