# pitot tube

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## pitot tube

[pē′tō ‚tüb]
(engineering)
An instrument that measures the stagnation pressure of a flowing fluid, consisting of an open tube pointing into the fluid and connected to a pressure-indicating device. Also known as impact tube.

## Pitot Tube

an L-shaped tube for measuring the total head of a flowing fluid. The tube is named after the French scientist H. Pitot, who invented it in 1732. The Pitot tube is used as a component of the Pitot-static (Pitot-Prandtl) tube.

## Pitot tube

A device to measure the stagnation pressure due to isentropic deceleration of a flowing fluid. In its original form it was a glass tube bent at 90° and inserted in a stream flow, with its opening pointed upstream. Water rises in the tube a distance, h, above the surface, and if friction losses are negligible, the velocity of the stream, V, is approximately 2gh, where g is the acceleration of gravity. However, there is a significant measurement error if the probe is misaligned at an angle α with respect to the stream. For an open tube, the error is about 5% at α &ap; 10°.

The misalignment error of a pitot tube is greatly reduced if the probe is shielded, as in the Kiel-type probe. The Kiel probe is accurate up to α &ap; 45°.

The modern application is a pitot-static probe, which measures both the stagnation pressure, with a hole in the front, and the static pressure in the moving stream, with holes on the sides. A pressure transducer or manometer records the difference between these two pressures. Pitot-static tubes are generally unshielded and must be carefully aligned with the flow to carry out accurate measurements.

When used with gases, estimate of the stream velocity is only valid for a low-speed or nearly incompressible flow, where the stream velocity is less than about 30% of the speed of sound of the fluid. At higher velocities, estimate of the stream velocity must be replaced with a Bernoulli-type theory, which accounts for gas density and temperature changes. If the gas stream flow is supersonic, or the stream velocity is greater than the speed of sound of the gas, a shock wave forms in front of the probe and the theory must be further corrected by complicated supersonic-flow algebraic relations.

A disadvantage of pitot and pitot-static tubes is that they have substantial dynamic resistance to changing conditions and thus cannot accurately measure unsteady, accelerating, or fluctuating flows. See Flow measurement

## pitot tube

A device, used in conjunction with a suitable manometer or other pressure-reading instrument, for measuring the velocity of air in a duct or water in a pipe.

## pitot tube

An open-end tube that points directly into the air flowing over the aircraft structure, providing pressure for the pitot and, often, the static systems. See pitot pressure.
References in periodicals archive ?
Oddly, he cycled the ice protection switches several times and never noticed the directly adjacent pitot heat switch.
It is suggested that the static pressure ports of Pitot tubes mounted at the centerline of the test duct be employed to measure the pressure loss, provided that other stipulations of ASHRAE Standard 120 are satisfied.
Al dia siguiente, Air France anuncio en un comunicado haber observado desde mayo de 2008 "incidentes de perdidas de informaciones anemometricas en vuelos crucero de A340 y A330" y que se vio obligada a acelerar su programa de reemplazo de los Pitot en esos aparatos a partir del 27 de abril.
Airlines around the world have begun replacing Pitot tubes on their aircraft.
On its website, Alter advised pilots to "refuse any flight on an A330/A340 which have not modified at least two pitot sensors".
A malfunctioning Pitot tube could mislead computers controlling the plane to dangerously accelerate or decelerate.
One theory about the cause of the crash is that the pitot tubes may have iced over, giving incorrect information which then led to the plane flying too fast or slow in rough weather.
I'd never even heard of a pitot, but it turns out it's an open-ended, right-angled tube pointing into the flow of fluid, used for measuring pressure.
Pitot: The total value of component exports in 2007 was 4 billion, and represented an average annual growth rate of 23% since 1995.
Most aircraft are equipped with three metallic pitot tubes whose inside diameters are around 6 millimeters.
It can do draft and differential pressure measurement, measures gas velocity with a Pitot tube, and can measure smoke, as well.
Arriving at the aircraft, we saw the TTU-405 test set was hooked up through the pitot static-drain lines in the port cheek panel (blue caps in picture), instead of directly to the pitot and static probes.

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