Pitot tube

A Pitot tube is a measuring instrument used to measure fluid flow. The Pitot tube is named after its inventor, Henri Pitot, and was modified to its modern form by Henry Darcy.

The basic instrument consists of two coaxial tubes: the interior tube is open to the flow, whilst the exterior tube is open at ninety degrees to the flow. A manometer can be used to measure the difference between these two pressures and using Bernoulli's equation the flow rate of the fluid can be calculated.

Pitot tubes on aircraft

Pitot tubes are used on aircraft to measure the craft's airspeed. The tube is parallel to the aircraft's longitudinal axis, and is typically mounted on the wing of small aircraft and on a pylon on the body of larger aircraft. On aircraft, static pressure is typically measured through a port on the side of the fuselage instead of on the pitot tube itself. On sailplanes Pitot tubes are used to compensate Variometers.

Most pitot tubes have a heating device to prevent freezing and ice build up.

See also

• Airspeed indicator
• ventilation engineering