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Pitot Tube

“Pitot tube” is a phrase featured recently in news stories of the tragic Airbus crash off the coast of Brazil that killed all onboard passengers. The surname Pitot is pronounced in English /pee-toe/ with equal stress on both syllables, as in French. The terminal /t/ is silent, as in French. Here’s a sample headline from the Associated Press:

Posted on Tue, Jun. 9, 2009

“ Brazil flies bodies to mainland; Pitot tubes eyed

MARCO SIBAJA and GREG KELLER

The Associated Press

RECIFE , Brazil - Two Brazilian helicopters took off Tuesday morning from the islands of Fernando de Noronha to pick up 16 bodies of Air France crash victims, as airline chiefs at a conference insisted the Airbus A330 was one of the safest planes in the world to fly…”

The definition of Pitot-Static tube is: “a device that consists of a combination of a pitot tube and a static tube and that measures pressures in such a way that the relative speed of a fluid can be determined (as in an airspeed indicator) - called also pitot tube.”

"pitot-static tube." Webster's Third New International Dictionary, Unabridged. Merriam-Webster, 2002.

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This website has more technical detail about pitot tubes.

http://www.navaidsltd.net/pitot/hpitot.html

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Henri Pitot (1695-1771 CE)

The phrase is an English translation from the French tube de Pitot. Henri Pitot (1695-1771) was a French hydraulic engineer and the inventor of the Pitot tube, which measures flow velocity. Early in his career, Pitot received the professional assignment to measure the flow and velocity of water in the River Seine. For this he devised a primitive version of what today has become the chief means of measuring an aircraft’s airspeed. In a Pitot tube, the height of the fluid column is proportional to the square of the fluid’s velocity. This relationship was discovered intuitively by Henri Pitot in 1732 while gauging the gentle purl of the flowing Seine. Pitot’s model was improved and modified by aeronautic engineer Henry Darcy.

Pitot immediately discovered that some ancient ideas about running water and currents were false. Pitot disproved the idea that the velocity of flowing water increases with depth. It does not. Pitot devised a tube, with an opening facing the flow, that provided the first reasonably accurate measurement of flow velocity. The Pitot tube has been used ever since in many applications, for example, in wind-speed measurements as part of anemometers.

From Wikipedia, the free encyclopedia here is a brief explanation of a pitot-static system: “a system of pressure-sensitive instruments that is most often used in aviation to determine an aircraft's airspeed, Mach number, altitude, and altitude trend. A pitot-static system generally consists of a pitot tube, a static port, and the pitot-static instruments. This equipment is used to measure the forces acting on a vehicle as a function of the temperature, density, pressure and viscosity of the fluid in which it is operating. Other instruments that might be connected are air data computers, flight data recorders, altitude encoders, cabin pressurization controllers, and various airspeed switches. Errors in pitot-static system readings can be extremely dangerous as the information obtained from the pitot static system, such as altitude, is often critical to a successful flight. Several commercial airline disasters have been traced to a failure of the pitot-static system.”

  

Two Canadian Pitots

Pitot has a different meaning in Canada. Un pitot is the Acadian French name for a razor shell, a species of edible mollusc, Cyrtodaria siliqua, found in Canadian maritime provinces, particularly Newfoundland. Un pitot is also called un couteau de Bank. “Pitot banks” are the submarine oceanic areas where these mollusks can be harvested. Mi'kmaq people used the pitot as a scraper in leathermaking and preparing deer skins and seal skins.

Un pitot ou couteau de Bank

Pitot is also an Acadian surname, an alternative of a widely dispersed Northern French surname that began as Piteau literally ‘one who pities, one who is compassionate.’ It took many, many forms as French surnames arose and spread, including Pitouz, Pitat, Pitais, Pitoz and the pejorative Pitaud.

 

© 2012 copyright William Gordon Casselman

 

 

 

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