Talk:Pitot tube

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External links from Pitot, which now redirects here:

• Pitot Tube -- This one says it all in one diagram.

• eFunda: Theory of Pitot Static Tubes -- This is more exhaustive. — Preceding unsigned comment added by Mendel (talk • contribs) 00:15, 13 November 2004 (UTC)

This article needs the pronunciation of Pitot adding. — Preceding unsigned comment added by Ianhowlett (talk • contribs) 16:08, 20 May 2005 (UTC)

Airspeed?

I am fairly certain that the general standard for measuring airspeed is knots, and not miles per hour Brophmeister (talk) 06:44, 6 August 2008 (UTC)

Yes, you are right, the unit is knots (= nautical miles per hour). It seems that in countries using kilometers on land, people tend to drop the word "nautical".

Sv1xv (talk) 07:58, 6 August 2008 (UTC)

---

Current description is not exactly for a pitot tube, but strictly for a pitot static tube, isn't it? Some aircraft have separated (pure)pitot tubes + static ports. - Marsian / talk 01:21:18, 2005-09-02 (UTC)

It had both ports when Pitot invented it in 1732. One port or two, it is a Pitot tube either way. Meggar 05:04, 23 May 2006 (UTC)

It is worth noting that for compressible flows, the difference between stagnation and static pressures from a pitot tube leads to Mach number, not airspeed. To obtain airspeed, a measurement of stagnation temperature is needed. {Refer to Liepmann & Puckett , Aerodynamics of a Compressible Fluid, Wiley, 1947. pgs. 26-27} — Preceding unsigned comment added by 173.79.230.192 (talk) 14:38, 9 December 2013 (UTC)

parallel vs Perpendicular

I believe these terms are reversed in the description. WRT the diagram the air is being forced down the ceter tube while the outer tube is only exposed indrectly through the holes just as the description states. However wouldn't this make the center tube parallel and the outter perpendicular? — Preceding unsigned comment added by Mhenwood (talk • contribs) 01:40, 23 November 2005 (UTC)

The face of the openings vs. airflow is what determines whether they are parallel or perpendicular I believe - so the centre tube's opening is perpendicular to the direction of airflow, and the outer tube's opening is parallel to the airflow. Hope that's clear? ZoFreX 23:02, 22 May 2006 (UTC)

I think ZoFreX is right, however the context is somewhat ambiguous. I'm intending to give this article a serious overhaul when I get the time. Chrisd87 17:23, 9 July 2006 (UTC)

Operation

This section needs to discuss the actual operation of a pitot tube. In my opinion the airplane mishaps belong elsewhere. — Preceding unsigned comment added by 2601:0:B800:DA:E919:B093:682A:261A (talk) 02:34, 23 March 2014 (UTC)

rewrite

I've done a fairly major rewrite to this page, in an attempt to tidy it up and make it more accurate. I hope I've succeeded - this is the first time I've made such a large-scale edit to a wikipedia article. I'm intending to continue in due course and talk more about errors due to attitude and the like, and in time maybe translate the German article and incorporate that. Chrisd87 21:36, 9 July 2006 (UTC)

Further to this, the image I have added in place of the previous one is translated from the German Wikipedia article. Work is currently underway to translate the other diagrams from that page for inclusion here. Chrisd87 21:40, 10 July 2006 (UTC)

Pitot vs. pitot

Although the Pitot/pitot tube is named after its inventor, Henri Pitot, predominant common usage is for "pitot tube" to be written in lower case (except at the start of a sentence, of course). This article capitalizes it throughout and recently an editor has gone through the Pitot-static system article to capitalized it throughout there as well. Isn't it Wikipedia policy to use the most common expression? Askari Mark (Talk) 18:38, 11 January 2007 (UTC)

My sources all show the worid pitot tube being in lower case. Including source in FAA documentation. Is that good enough to assume common use? I have other sources I can consult as well but I feel that they will all show lower case usage. -- Chrislk02 (Chris Kreider) 20:17, 11 January 2007 (UTC)

I was just reading an Associated Press article on the Air France 447 disaster and noticed that the author made a good summary of the workings of a pitot tube that appears to have drawn on this article as reference. Why do I think this? Because the author capitalized “Pitot” which is rarely found in most sources. Accordingly, I’m decapitalizing the term here. Since no contrary comment has appeared here in two and a half years, I’m assuming this is consensus. If not, please address the issue here before reverting. Askari Mark (Talk) 20:24, 6 June 2009 (UTC)

Unnecessary capitalization of the word "pitot" has crept in over the past decades, notably in captions for images. I will change these instances to lower case. Dolphin (t) 00:33, 15 November 2018 (UTC)

This is not "unnecessary" capitalization. This is following good grammar. Pitot is a proper noun and should be capitalized. Is the "Joule-Thomson effect" unnecessary capitalization? It is acknowleged that the FAA has made the same error over and over again by dropping the cpaitalzation. However, if you read all text from its Eiuropemna counterpar, EASA, it is corretcly written as Pitot tube, in their standards and other associated publications, therefore official regulatory text. 104.158.159.149 (talk) 14:30, 6 July 2022 (UTC)

That proves nothing except that you agree with EASA's usage and disagree with the FAA's. What matters here is usage across a broad range of English language sources, which seem to favor no capitalization. Remember, the EASA represents mostly non-English speaking countries, so may reflect non-English usage in its publishings. BilCat (talk) 01:42, 7 July 2022 (UTC)

External Sources

I am working on a semi re-write/expansion of this article, as well as work on the article on Henri Pitot. I am using this as kind of a staging area for sources I find related to this/these topics. If you find any good reliable ones, feel free to add them! Thanks -- Chrislk02 (Chris Kreider) 20:22, 11 January 2007 (UTC) a paper on pitot tubes

Marine use

Boats use pitot tubes to measure water speed, but this page makes no mention of that. -- Mikeblas (talk) 02:23, 15 June 2008 (UTC)

Specific Use

Pitot tubes on airplanes are a specific use and should not take over the body of the article. Aircraft should not be mentioned at all in the definition of pitot tube. The use of pitot tubes in aviation can be described in a number of other places. Perhaps in a seperate stub or even as another section in the pitot tube article called something like "common uses" or "in industry".

Understand that saying "A Pitot (pronounced /ˈpiːtoʊ/) tube is a pressure measurement instrument used to measure fluid flow velocity, and more specifically, used to determine the airspeed of an aircraft.", is a lot like saying "A mirror reflects images, and more specifically, used to determine what is behind your car."

When I came across this article I was expecting to see information more like what is contained on the Dwyer website: http://www.dwyer-inst.com/HTDOCS/airvelocity/AirVelocityIntroduction.cfm

Forgive me for not being more constructive; I am just learning to wiki.Steveandaugie (talk) 15:48, 24 June 2008 (UTC)

Air France 447

I have commented out the paragraph on the Air France Flight 447 incident from the end of the lede. First of all, it's speculative as a possible cause. Secondly, it's far too much detail for an article on the pitot tube; if it should be retained (should it become found to be a probable cause), then it probably should just be added to .

Air France 447 mention; it's too specific to that incident and only speculation at this time as to being the incident's cause. If proven, this needs to be simply added to the list in the line above that mentions two cases. If consensus agrees, I’d recommend deleting it altogether. Askari Mark (Talk) 20:39, 6 June 2009 (UTC)

I agree with the removal of the passage on AF 447. Much too speculative at this time. May be appropriate to add a mention later, if there is ever any proof that pitot tube icing was a contributing factor to the loss of AF 447. I see that some AF pilots are now refusing to fly Airbus 330's until the tubes are replaced, but that belongs in an article on the AF 447 crash, not here. Pechmerle (talk) 21:43, 8 June 2009 (UTC)

New information from the AF 447 investigation is pointing to failure due to pitot tubes. see: http://www.spiegel.de/international/world/0,1518,679980,00.html . Therefore, I suggest attributing AF 447 crash to Pitot tube failure. --Arorasal (talk) 01:48, 26 February 2010 (UTC)

• I added the connection between AF447 and pitot failure. The fact can no longer be in dispute.-Lester

To say that the pitot tube problem was a contributory factor to AF447 crash is not wrong, but it is highly misleading, and does not belong in the article. I see that the sentence is back, although it's in a more appropriate location in a paragraph lower down now if it has to be there at all, and says:

The French air safety authority BEA said that pitot tube icing was a contributing factor in the crash of Air France Flight 447...

The cause of the crash was overwhelmingly pilot error. It's true that the pitot tube problem (which cleared itself after a few minutes and was not contributory to loss of altitude) started a chain of events which caused the copilots to become confused and make tragic errors, including holding the stick back far enough to cause the aircraft to stall (means to lose lift over the wings--"stall" has nothing to do with engines) and to lose altitude, and ultimately to fall into the sea. The copilot actually held the stick back continually for several minutes, keeping the plane in a stall all the way to impact. Simply letting go of the stick would've caused the plane to come out of the stall. Many other things other than pitot tube failure might've led to the same confusion (autopilot failure for example), the fact that it happened to be pitot tube failure is almost incidental. The cause of the crash was pilot error.

Among the BEA (and FAA) recommendations are plenty of things concerning pilot training, but nothing about making better pitot tubes (having an AoA or combi pitot/AoA indicator would've prevented the accident entirely as the pilots never realized they were in a stall, but that's a separate issue, as A330s don't have them). The sentence about AF447 should be struck from the article. Mathglot (talk) 06:50, 25 June 2013 (UTC)

The immediate cause of the accident was the handling pilot's failure to take his hands and feet off the controls when the Captain returned to the cockpit, sat down, and said "I have control". — Preceding unsigned comment added by 95.144.50.132 (talk) 09:26, 3 November 2017 (UTC)

Stagnation vs Total Pressure

The author uses stagnation pressure and total pressure interchangably. This is incorrect and misleading. The author should explain that the stagnation pressure is equal to the total pressure only when the velocity of the fluid equals zero and therefore they are not one in the same. Also, Bernoulli's Equation states the total pressure, not the stagnation pressure, is equal to the dynamic plus the static pressure. See Crowe C, Elger D, and Roberson HJ. Engineering Fluid Mechanics. 7th Ed. Wiley. ISBN 0-471-38482-8. 142.176.6.109 (talk) 19:23, 1 October 2010 (UTC)

I heartily agree with you! Unfortunately, Wikipedia has a comprehensive article on Stagnation pressure but no such article on Total pressure. There are articles where the two concepts are treated as synonymous – for example, see the second sentence HERE. I can recall some occasions where I wrote about total pressure but someone came along later and converted it to stagnation pressure so they could make it into a Wikilink to Stagnation pressure. I thought I was the only one here who saw a significant difference between the two, so I am glad to see there is at least one other! Dolphin (t) 04:15, 2 October 2010 (UTC)

Assumptions about responsibility for Flight 447 crash

I guess there should be some correctional work done on this topic.

Please consult the following article for the idea about the reason for corrections (I don't know if it can be used as a valid source): http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877-2

Regards! — Preceding unsigned comment added by Dmilojevic (talk • contribs) 14:23, 9 December 2011 (UTC)

Yeah, that's a good summary article, based on a translation of the cockpit conversation in "Erreurs de Pilotage" by Otelli. The sentence about the connection to AF447 in this article should be removed entirely. See my reply at Air France 447 above. Mathglot (talk) 06:59, 25 June 2013 (UTC)

Tube or Probe?

Pitot tube is the term generally used in English for the airspeed measuring instrument found in aircraft. A rarer form is Pitot probe. Both expressions are translations from the French.

The Pitot tube is named after the French invention by engineer Henri Pitot, called a fr:Tube de Pitot, which translates word-for-word very literally into the English name (not always the case for many inventions). In French, you also occasionally see the term Sonde de Pitot, which literally translates as Pitot probe, but this is 50 times rarer. On English-language sites, the expression Pitot probe version exists but is even rarer than in French.

On the English wiki, Pitot probe redirects to Pitot tube as of this date; on the French wiki, fr:Probe de Pitot does not exist.

The situation may be somewhat muddled by the fact that among several companies offering a combination instrument measuring both airspeed and AoA, at least one (Dynon) calls it a "Pitot probe". (Side note: although AoA meters have been available for 50 years, they are not required and often not included as standard equipment on commercial aircraft, but only as an option. C.B. "Sully" Sullenberger claimed that the lack of an AoA on the Airbus A330 was partially responsible for the confusion of the pilots leading to the crash of Air France 447 in 2009 and The Daily Telegraph reached a similar conclusion.) Mathglot (talk) 07:10, 25 June 2013 (UTC)

At least some occurrences of "Probe" are probably due to imperfect translation from French to English by a non-native speaker. An example of "Pitot probe" in English can be seen in this Air France press release containing both English and Portuguese text concerning the investigations of the AF447 disaster (as quoted in the AF 447 article). The English translation is very good, but not perfect, and a bilingual speaker (en-fr) can detect very minor problems in the English that don't affect understanding, but that do indicate that a non-native speaker, or a non-aeronautics expert (or both) was responsible for the English. In this case, the references to "Pitot probe" (or just "probe") cannot be relied on as authoritative. Mathglot (talk) 23:16, 25 June 2013 (UTC)

Aircraft

Aircraft is possibly the most important application of pitot tubes there is. Since we do have an article specifically describing the systems used on aircraft (pitot-static), we clearly should summarize it here with a main article link. Oiyarbepsy (talk) 13:21, 25 August 2016 (UTC)

I agree Aircraft are possibly the most important application of pitot tubes, and I support a prominent link to Pitot-static system. I've no objection to heading that section "Aircraft" and providing a {{Main}} link to the article. However, I think readers are done a disservice by the wholesale copy-and-pasting of the article lede into this article, some of which is irrelevant to this article. Please note the version you copied from also contained some problematic material which I removed from the main article earlier. Burninthruthesky (talk) 14:17, 25 August 2016 (UTC)

• User:Burninthruthesky, Very well, sounds like we've settled this. Without edit warring, swearing, or visits to WP:ANI. Where am I? Oiyarbepsy (talk) 04:25, 27 August 2016 (UTC)

The lede contains the following information:

The pitot tube is used to measure the local flow velocity at a given point in the flow stream and not the average flow velocity in the pipe or conduit. Errors induced due to the location of the measuring tube on the aircraft, and the effect of localised airflow upon it, are known as "position errors" and need to be factored into resultant calculations.

This information is incorrect on at least three points:

1. A flow velocity cannot be measured using a pitot tube. Velocity measurement requires extra information from a static port; or a combined pitot-static tube.
2. The local flow velocity at a given point is measured by locating a static port at that given point. Bernoulli's principle tells us that pitot pressure is uniform throughout the flow field, so regardless of where a pitot tube is located, it will supply the same pressure (equal to the total pressure; aka stagnation pressure)
3. Pitot pressure is vulnerable to error in the alignment of the pitot tube, but it is not vulnerable to position error. Position error affects the static pressure because the pressure supplied from any static port is highly sensitive to the flow velocity in the immediate vicinity of the port. In contrast, a pitot tube supplies stagnation pressure and so is insensitive to the flow velocity in the immediate vicinity of the pitot tube. Bernoulli's principle can be stated as "stagnation pressure is equal to total pressure which is uniform throughout the flow field".

The source cited for this information is Transport processes and separation process principles by Geankoplis. I don't have access to this book, but either it is incorrect or it has been cited incorrectly. It is not an aviation book, so it is likely that it has been misinterpreted or paraphrased on matters of airspeed measurement and position error.

I will erase these two sentences. Dolphin (t) 01:15, 15 November 2018 (UTC)

The Machine of Henri Pitot had two tubes

Hi all !

The description of his machine by Henri Pitot in front of the Royal Academy is very clear on this point - see DESCRIPTION D'UNE MACHINE POUR MESURER LA VITESSE DES EAUX COURANTES ET LE SILLAGE DES VAISSEAUX, par Henri PITOT, dans Histoire de l'Académie royale des sciences avec les mémoires de mathématique et de physique tirés des registres de cette Académie, pages 363-376, https://gallica.bnf.fr/ark:/12148/bpt6k35294.image.f543.langFR:

The ‘‘ machine ’’ of Henri Pitot

“AB is a wooden Rod cut in the shape of a triangular prism; on the middle of one of the three faces of this Rod we dug a groove capable of receiving two Pipes of white glass; one of these Pipes is bent at a right angle to D and the DE end goes through a hole made with a Rod. "

One can see these two tubes (one of which is bent at a right angle) on the plan accompanying its description (right).

And further Pitot writes: "The first Pipe being bent at right angles, & the second being straight, if we put the Machine in still water, the water will rise to its level in the two Pipes. But in running water, it will rise in the first Pipe to the height relative to the force of the current, while it will remain at its level in the second Pipe."

Still further, he indicates incidentally that his machine can work, in principle, with the only curved pipe: "The idea of this Machine is so simple & so natural, that as soon as it came to me, I ran straight to the River to give it a first try with a simple glass tube, and the effect responded perfectly to my expectation. "

And when he depicts "the application of this idea to know the velocity of the Vessels", he's still talking about two tubes: "We will place in the middle of the Vessel, either under the master beam, or finally the closest to its center of swing, two metal pipes, either copper, tin or lead, 3 or 4 lines in diameter. These pipes must touch each other, their lower ends must penetrate to the water below the Vessel, which can be done without any risk from the holes necessary for the passage of the pipes, because of their smallness. […] The lower end of one of the pipes will be bent at a right angle, & like a funnel, as in our Machine, & its opening will be turned in the direction of the keel, opposite the bow, […] ”

I note that plenty of authors of Fluid Mechanics books think that the machine of Henri Pitot had only one tube...

Friendly, Bernard de Go Mars (talk) 21:01, 24 April 2020 (UTC)

M. Pitot had created a device (a machine) for observing or measuring the speed of water or the speed of a vessel. It must have contained an element for detecting the static pressure of the fluid because the speed is not proportional to the stagnation pressure; it is proportional to the difference between the two pressures. Presumably the name “static port” was already in use, or suggested itself immediately, because M. Pitot’s name has been given only to the tube that detects stagnation pressure.

M. Pitot’s machine must have had two tubes because it was capable of measuring the relative speed of the fluid but his name has been given only to one of the tubes - the one that does not sense the static pressure. Dolphin (t) 22:28, 24 April 2020 (UTC)

Thank you Dolphin for your response. It seems that there are a lot of ambiguities in the name of the different "Pitot tubes". In "Review of the Pitot tube", R. G. Folsom, Michigan, [1] wrote : "The name "Pitot tube" has been applied to two general classifications of instruments, the first being a tube that measures the impact or total pressures only, and the second a combined tube that measures both the impact and the static pressures with a single primary instrument." Later in his text, Folsom proposed two different names for the two classes of instruments. In French, we have the same ambiguous naming problem and we are working on the fr.wikipedia page to resolve this ambiguity. Note that on this page fr.wikipedia, we added a section on industrial pitometers ... Friendly, Bernard de Go Mars (talk) 08:56, 14 May 2020 (UTC)