3 May 1695 – Henri Pitot is born

On 3rd May 1695, French hydraulic engineer Henri Pitot was born in Aramon, France.

For more than four years, our Aviation History Friday section is travelling back in time to bring you interesting facts from the early years of aviation and to introduce profiles of aviation pioneers. However, we had never went so far into the past as the 17th century. And what is more, the person we would like to mention today was actually not an aviation pioneer.

Nevertheless, the name Pitot is well known to literally all aviators, due to his famous invention, the so-called pitot tube.

Henri Pitot was, characteristically for scientists from that era, a person with many interests. He studied mathematics, astronomy and physics, was interested in mechanics and hydraulics, as well as carried out several developments of the country´s infrastructure – roads, bridges, fountains and aqueducts. Pitot´s most famous designs were Aqueduc de Saint-Clément near Montpellier and reconstruction of Pont du Gard, a bridge in Nîmes.

In 1724, Henri Pitot became a member of l’Académie des sciences (the French Academy of Sciences) and in 1740, a member of the Royal Society of London for Improving Natural Knowledge. In 1725, he proved a theorem in geometry, related to tangential quadrilateral. It was later named the Pitot theorem.

Pitot was interested in mechanics of liquids and gases, particularly the flow of water in rivers. His studies resulted in many discoveries and theoretical papers. In 1732, when he was assigned the task of measuring the flow in the river Seine, he invented an instrument that became known as the Pitot tube. The initial Pitot´s tube was working on the principle of relationship between height of the fluid column to the square velocity of the fluid at inlet of the tube.

Henri Pitot died on 27th December 1771 in Aramon, aged 76.

´Estimate of the works necessary to conduct the waters of the Fontaine de St-Clément in the city of Montpellier´, manuscript from 1752, by Henri Pitot (source: gallica.bnf.fr,  ark:/12148/btv1b10555488q)

In the 19th century, the pitot tube was modified by another French scientist, Henry Darcy. In its modern form, the pitot tube is still used to determine speed of aircraft and boats, as well as flow velocity of liquids and gases.

In aviation, the pitot tube is a part of the pitot-static system, an essential instrument to determine airspeed, Mach number, altitude and altitude trend. Malfunction of that system is very dangerous as information it provides is critical for proper flight.

History of aviation recorded many cases when errors of the pitot-static system led to tragic accidents. One of the best known is Air France Flight 447 from June of 2009. During the flight, malfunction of the system caused error in airspeed indications that led to stall of Airbus A330 airliner. The crew failed to recover the aircraft from the stall and the A330 crashed into the Atlantic Ocean. No one of the 228 people on board survived the accident.

Other examples of aviation accidents caused by malfunction of the pitot tube are:

  • Northwest Orient Airlines Flight 6231 in 1974 (Boeing 727), 3 fatal casualties (as there were only crew members onboard), caused by ice formed inside the pitot tube,
  • Aeroflot Chelyabinsk to Moscow flight in 1986 (Tu-154), no casualties, incident caused by not turning on the pitot tube heaters by the crew that led to error in airspeed information; eventually, the crew managed to recover the airliner from the stall but the incident resulted in aircraft structural damage,
  • Continental Air Lines New York-Denver flight in 1994 (MD-82), aborted take-off due to error in airspeed indication, the aircraft ran off the runway, no casualties, caused by ice formed inside the pitot tube,
  • Birgenair Flight 301 in 1996 (Boeing 757), 189 fatal casualties, caused by blocking the intake of the pitot tube by a wasp nest built inside of it,
  • Austral Líneas Aéreas Flight 2553 in 1997 (DC-9), 74 fatal casualties, caused by ice formed inside the pitot tube,
  • Saratov Airlines Flight 703 (An-148) in 2018, 71 fatal casualties, caused by not turning on the pitot tube heaters by the crew, that led to error in airspeed information.
Pitot-static system of the MiG-21MF fighter, with main (equipped also with pitch sensor) and secondary tubes.

Cover photo: portrait of Henri Pitot (source: Wikipedia, Public Domain)