Talk:Contra-rotating propellers

Tandem rotor helicopters

Question : should this page include examples of and discuss tandem rotor helicopters? To me these are two different but similiar things : propellers give thrust to a fixed wing aircraft ( or whatever ) and tandem rotor are a special type of helicopter. 145.253.108.22 10:11, 11 January 2007 (UTC)

I don't think tandem rotors should be discussed here because they are counter-rotating, not contra-rotating; the article explains the difference. In fact, barring objection in the next few days, I'll remove the reference to the tandem rotor helicopters (unless I forget). Quickfoot 22:39, 23 February 2007 (UTC)

Would it not be appropriate to mention tandem rotor helicopters that have coaxial rotors? This seems to fit the contra-rotating idea to me. See Helicopter and Coaxial rotors. SmokeySteve (talk) 08:18, 15 June 2008 (UTC)

Yes, any instance of coaxial rotors rotating opposite directions should be mentioned here. Binksternet (talk) 14:13, 15 June 2008 (UTC)

Turbulence between props

I'm no expert in contra-rotation but wouldn't there be a small loss of efficiency caused by the second prop biting into the turbulent stream of the first prop? If so, it's worth a brief mention. Binksternet (talk) 17:23, 20 November 2007 (UTC)

F-35B lift fans

Isn't it worth mentioning that the F-35B lift fans use this principle? The current version of the article about the F-35 Lightning II links here. --RenniePet (talk) 13:28, 25 November 2007 (UTC)

No. They are not propellers. The link needs to be changed/removed. - BillCJ (talk) 17:21, 25 November 2007 (UTC)

Hmm. Well, I've looked a bit more into it, and the F-35 page has had a link to "contra-rotating" for at least a year (can't be bothered going back farther). "Contra-rotating" is a redirect page, redirecting to this page, and has been that since it was created in 2004.

There should be something informative on Wikipedia about contra-rotating in general - I must admit I'd never heard of the concept before seeing it on the F-35 article. Are you suggesting that the "contra-rotating" redirect page should be changed to a stub article, or a disambiguation page? --RenniePet (talk) 18:15, 25 November 2007 (UTC)

Changing it to a stub or DAB page is probably the way to go. We could add some of the info on helicopters and marine screws to the stub as a start, along with a brief summary from this page's current content. Good idea! Thanks. - BillCJ (talk) 18:40, 25 November 2007 (UTC)

Well, I've made a first attempt at it. See Contra-rotating. Please edit it as you think applicable. --RenniePet (talk) 17:26, 26 November 2007 (UTC)

The Bristol Siddeley Pegasus engine from the Harrier has had contra-rotating spools ever since it was designed - the feature is to prevent gyroscopic precession when in the hover. — Preceding unsigned comment added by 80.4.57.101 (talk) 20:17, 22 August 2011 (UTC)

Contra-rotating vs. counter-rotating

As a naval architect and as a foreigner I'm a little bit confused: As everybody can verify with Google, in the context of ship propulsion many people call this principle counter-rotating rather than contra-rotating, and I remember that I've never heared or read contra-rotating till now. On the other hand, the counter-rotating property of twin propellers doesn't need its own term in naval architecture, because it's nearly always the case (one right turning and one left turning ship propeller). As a foreigner, I'm not going to teach English to the native speakers, but I didn't want to leave this unmentioned, and I would like to encourage not only engineers of avionics, but also naval architects to confirm that Wikipedia is right and that it's wrong to call two ship propellers concentrically rotating about a common axis "counter-rotating". Henning (talk) 13:00, 28 April 2008 (UTC)

Official ITTC terminology is:

Contra-rotating propeller - Two propellers rotating in opposite directions on coaxial shafts. ITTC – Recommended Procedures and Guidelines, p. 10

Regards, BoH (talk) 16:36, 11 October 2008 (UTC)

To the person above, who presumably flagged that contra-rotating propellers should be merged with counter-rotating propellers: 1.) they should not be merged; they are completely different things. 1a) contra-rotating are on the same motor- as explained very well by people smarter than I in its own page. 1b) counter-rotating props are on separate engines to counteract the aerodynamics (see P-factor and torque). I have a feeling it was based on a language or nomenclature issue. The topics should remain separate. — Preceding unsigned comment added by C5pilot (talk • contribs) 09:21, 6 February 2011 (UTC)

In fact, "counterrotating" is used widely in the aeronautical literature to apply to coaxial propellers and "contrarotating" occasionally to propellers on separate shafts (many examples cited below). The articles may or may not have a reason to remain separate but in the outside world there is no distinction between the terms. BTW the ITTC citation is a good find but for aerospace, see the NASA and AGARD dictionaries cited below. 2601:14F:4502:6E98:223:7DFF:FEC4:2D73 (talk) 18:48, 4 July 2017 (UTC)

simple physics of CR props

somebody should get the citations for this and put it in the main article. minimizing turbulence is not the main advantage...

crucial to producing even supersonic air trust with CR props is the fact that when two CR blades meet, each going at near-supersonic absolute speed (e.g. relative to the ground), *relative to each other* they are actually moving twice as fast. so if the first blade pushes the air up to say 800kmh, the second one can give a ferocious 2nd slap to the already moving air because it actually hits it at +1600kmh. with 20'000hpXengine the TU95, e.g., could go supersonic without its CR blades going supersonic. —Preceding unsigned comment added by 82.154.64.226 (talk) 22:27, 22 July 2008 (UTC)

For anyone interested, Hermann Glauert was involved in investigating the theory of propellers - including contra-rotating propellers, back in the 1920s - "Hermann Glauert FRS, FRAeS (1892 – 1934)" - he said that there is a slight efficiency increase from using a CR propeller. So apart from the anti-torque and blade length advantages, there is also some gain in efficiency over a single airscrew. — Preceding unsigned comment added by 80.4.57.101 (talk) 21:13, 23 February 2012 (UTC)

ultralights

If there were more makers of contra-rotating gearboxes, we could list them too. I doubt the manufacturer knows or cares that their product is listed here. Neither I nor my dorm mates are spammers, nor do we have any interest in the company that appears to be the only one making a contra-rotating gearbox for Rotax engines. It is listed here because it is in use in the ultralight community. The article probably needs additional information about contra-rotating props in the RC community, but if whomever is so kind as to contribute is accused of being a spammer, control of the article will probably be limited to those playing Wikipedia to gain rank and prestige as a Wikipedia club member rather than truly being a collaborative product of people interested in aviation technology. Markoftimes (talk) 18:52, 7 May 2011 (UTC)

Hi - Welcome to Wikipedia! I admit I probably was a bit hasty labelling it as spam. That para would read less like spam if it discussed the use of CR props in microlights etc before referring to a specific company. It also might fit better into the Rotax article. Other things to remember: include citations, check spelling etc, include an edit summary and wikilink. Improving Wikipedia (which is my aim and that of most editors) includes defending against insertion of advertising etc, but we certainly don't want to discourage newcomers - that's a tricky balance sometimes! DexDor (talk) 22:33, 7 May 2011 (UTC)

(1) Thanks for the reply. That company pretty much the only one in the game, as far as I know. Feel free to contribute any information you have about further uses or products in the ultra/microlight sector. If I can find good sources about why ultralight builders sometimes use the CR system, I'll contribute it, and it would be in front of a reference to the maker of this particular product.

(2) Overall, the article strikes me as a bit spammy for the aerospace industry, in particular the military aviation sector of the industry, with a strong focus on nationalism -- since most of the subheads reference current or former nations (including one that says an aircraft was built in the USSR in 1994, five years after that Union dissolved.

(3) I expected an article about contra-rotating propellers to be about that - contra-rotating propellers, including their maritime and aviation applications, and current popular uses, which, based on items in production would likely be some order of R/C hobby, maritime and ultralight aircraft (order depending on whether you count prominence by number of units in use, or cost of units in use).

(4) Otherwise, the article references "usually" single engine, glossing over the two-engines-per-prop Brabazon, which was perhaps the first pressurized jetliner. Though it never became a production aircraft, that technology seems more significant than the unsourced speculative line "One possibility is to enclose the contra-rotating propellers in a shroud". Only source I can imagine referencing shrouded contra-rotating props would come from the R/C hobby niche. And noise? That maybe be true in the military aircraft mentioned (did I miss the source for that tidbit or is it anecdotal?) but in the ultralight application, reports (from a Manufacturer, if said can be forgiven for applying science) indicate the contra-rotating config is quieter than a single. Markoftimes (talk) 04:24, 8 May 2011 (UTC)

Hope you don't mind, but I've numbered your paragraphs above - you can delete this sentence. (1) I've no knowledge of (and to be honest not that much interest in) microlights. It'd be great if you could put some cited info in. (2) Where the article talks about aircraft rather than companies, I don't think it's spammy. This article could be sectioned differently - e.g. military/civil or production/experimental, but I don't see much advantage in doing so. USSR/Russia - fixed. (3) Maritime is covered by another article (see hatnote) - this article would be better named "... in aviation" to avoid such confusion. A section on R/C aircraft would be good - again it should be cited. (4) I see nothing wrong with the Brabazon bit. I've added tags to the uncited bits about noise levels. DexDor (talk) 07:58, 8 May 2011 (UTC)

Kudos for your interest and responsiveness to comments. You might note that Russia is not the same as the Ukraine. "Russia" is actually the Russian Federation, but whatever it is, Ukraine is a separate nation and that's where Antonov is located. Antonov is owned by the state (which state?) according to Wikipedia, but I'm not sure how current that information might be. FWIW the GE36 ultra-high-bypass turbofan used contra-rotating props. There was a paper published about the areocoustical properties of that engine, but it would probably be a stretch to apply the findings there to all contra-rotating props. Several sources refer to the Wright flyers prop plan as contra-rotating. I'm not sure this article fairly surveys authority on whether contra-rotating and counter-rotating are the same or different concepts -- especially in push-pull configs, contra- and counter-rotating concepts (as suggested in this article) come into play with regard to airflow. I am not nearly so interested in learning about or improving Wikipedia as I am interested in learning about and improving narrative about particular topics, so your response to comments might be as much lift as my contributions will receive. Thanks for your concern. Markoftimes (talk) 15:11, 8 May 2011 (UTC)

I've tweaked the article, but your(?) section still needs wikiling, copyediting and (most importantly) citations. DexDor (talk) 19:52, 8 May 2011 (UTC)

Several articles xref contra-rotating marine propellers point here but there is no mention in the article

Can someone please either: Create a section on marine propellers, OR split off another article specifically about contra-rotating marine propellers. — Preceding unsigned comment added by Pmarshal (talk • contribs) 16:41, 9 July 2011 (UTC)

I've fixed the link at USS Albacore (AGSS-569) to refer to what info WP has on marine contra-rotating props, not sure what other page(s) need this change. There is a hatnote on this page, but it would be better titled "... (aircraft)". DexDor (talk) 20:16, 9 July 2011 (UTC)

Terminology

Both "Contra-rotating" and "counterrotating" are used in the literature to describe coaxial propellers and rotors that rotate in opposite directions. See for example, , , and for examples of "counterrotating" applied to coaxial systems. There is no authoritative basis for applying "contra-rotating" to coaxial systems only or "counterrotating" to non-coaxial arrangements only. — Preceding unsigned comment added by 98.204.65.104 (talk) 23:16, 25 March 2016 (UTC)

Thankyou for the three references. Do you have any that actually include the term "contra-rotating"? In those that do, contra-rotating is taken as specifically implying coaxial and excluding the otherwise counter-rotating. Andy Dingley (talk) 23:31, 25 March 2016 (UTC)

Why thank me for the references... you ignored them in undoing my page edits. Yes, "contra-rotating" is sometimes used for coaxial but so is counterrotating. I don't have a reference with "contra-rotating" used for "non-coaxial" so if you want to claim that "contra-rotating" can only mean "coaxial" I won't object ... for one thing, although I'm sure I can find a counterexample (NB "contraexample" is not even a word) I don't have time. But at a minimum the literature clearly shows that "counterrotating" is used for coaxial, and moreover there never was a basis to assert that "contra-rotating" is the only correct term for coaxial systems. I have cited literature written by people who know a little bit about counterrotating coaxial rotors/propellers, and your best counterargument (NB "contraargument" is not even a word either) is "no" ... But enough of this - I don't care! Just trying to help ... that was my big mistake and I learn from it. Good luck & good bye! 98.204.65.104 (talk) 23:49, 25 March 2016 (UTC)

It's a question of adjectives vs. nouns.

You cite three papers that, even within the realm of aeronautics, are pretty stilted and written in a highly formalised manner. They use the term "counter-rotating" to refer to coaxial and non-coaxial systems. They do not use the term contra-rotating at all. They are also (two of them) referring to helicopter rotors and (one) to ship propellers. None of these papers refer to propeller-driven fixed-wing aircraft, the topic at hand.

In an adjectival sense, these are correct. Contra-rotating propellers are implicitly counter-rotating as well. The cited papers are correct, but they also imply little.

In the ordinal sense of nouns and their definitions, the matter is different. We require clear terms to define and describe two very different pieces of equipment. Your edits, not only to add some references but also to remove the distinguishing hatnote suggests strongly that you would like to see these two articles merged as an indistinguishable overlap. That would do our readers a serious disservice. The convention is, attested by innumerable articles on contra-rotating and counter-rotating propellers in articles on fixed-wing aircraft, that contra-rotating are coaxial and only the non-coaxial are described under the broader term. Andy Dingley (talk) 02:19, 27 March 2016 (UTC)

OK my apologies, I brought this up so you deserve a serious answer.

For the record, I have no thoughts about merging articles, or splitting them out into even more. I am merely pointing out that they are incorrect as written.

And if you want to argue for a formal distinction between the two terms, you can't object to references being formal! To the contrary, the formal technical literature is exactly where people put the most care into getting the words right. As for "stilted" ... I disagree but how would that even matter?!

More terminology: "helicopters" are "aircraft"! You can look at FAR Part 1 for an authoritative definition. Maybe you mean "airplane" and fair enough, so I'll provide a few more examples.

First, a few more examples of "counterrotating" applied to coaxial systems. Ginzel, 1943 refers to "a counterrotating propeller" (singular noun, airplane application, coaxial arrangement). Nelson et al, 1990 refers to "a counterrotating propeller system" (singular noun, airplane application, coaxial arrangement). McKann, 1997 writes of "coaxially mounted contrarotating or counter rotating rotors." Helicopter, sorry, but this is good example because the author is clarifying that the terms are interchangeable.

Next, in response to your challenge, some examples of "contrarotating" used in the non-coaxial context. Eney, 1981 describes a 1/10 scale XV-15 tiltrotor model as having "contra-rotating rotors" and it is clear that this is a situation with separate shafts (and XV-15 is an airplane as well as a helicopter.) Weden, 1984 describes the tandem helicopter configuration as having "twin contrarotating rotors" and offers the CH-47 (separate shafts) as an example. Feistel, 1980, describes a wind tunnel model of a twin-engine airplane (airplane) with wing-mounted engines, noting that "The propellers were contrarotating and propeller rotation was down inboard for all of the tests." A more recent example is Ferrier et al, 2014 who state that "in tandem-rotor rotorcraft, the first and second lift rotors are generally contrarotating" and from the figures it is clear that these are separate rotors on separate shafts.

These are all serious technical documents showing actual usage, authored by professionals working in the field and published by reputable organizations. Bottom line: both "counterrotating" and "contrarotating" are established in the literature in both coaxial and non-coaxial contexts, as adjectives and in compound words, and their only consistent meaning is: rotating in opposite directions. You're entitled to your views on what the words should mean but that's "advocacy," not "information." The article is incorrect as written. 98.204.65.104 (talk) 13:19, 27 March 2016 (UTC)

Hmmm, crickets - I gather we're still not convinced? Here are a few more examples. I've thrown in a couple from the popular media since you seem to object to technical references. I've also avoided helicopter and marine engineering references.

"Counterrotating propellers" are coaxial propellers rotating in opposite directions: General Motors P-75A has "counterrotating propellers" ; "counter-rotation" and "counter-rotating propellers" ; Westland Python-Wyvern TF2 has "a counter-rotating propeller" ; "counter-rotating propellers" (coaxial) ; Propfans with "Counter-rotating propellers" ,

"Contrarotating propellers" are on separate shafts: "The use of contrarotating propellers on the P-38..." ; ; "two contrarotating rotors" (on a tiltrotor)

The amusing irony is that the bit about "should not be confused with counterrotating propellers" practically ensures confusion, because the terms are in fact both used for the same thing. I would agree that applying "contrarotating" to the non-coaxial propellers is less common but it is also found in the literature.

One reads that "Wikipedia articles should be based on reliable, published sources." I have provided a long list, and am still waiting to see a single one to support the notion that the terms properly imply different arrangements. So here's a proposed revision:

1. Replace sentence, "Not to be confused with counter-rotating propellers." with "See also counter-rotating propellers."
2. Delete sentence at end of first paragraph, "Contra-rotating propellers should not be confused with counter-rotating propellers..."
3. Add paragraph immediately after that:

   In the literature, "contrarotating propeller(s)" most commonly suggests a pair of propellers rotating in opposite directions on coaxially arranged shafts. However, the term is also applied to non-coaxial arrangements such as found on wing-mounted twin-engine airplanes [cite examples]. "Counterrotating propellers" are most commonly propellers on separate shafts, but the term is also applied to coaxially arranged propellers [cite examples]. Both "contrarotating" and "counterrotating" are used in the literature to describe helicopter rotors, both coaxial and tandem [cite examples].

This is factually correct and a lot clearer.

98.204.65.104 (talk) 15:33, 3 April 2016 (UTC)

See the Ref. Aeronautical Dictionary. The definition entry for "counter-rotating propeller" states, "Same as Contrarotating Propeller." This is a NASA dictionary - can't get more authoritative than that! And as we've seen, this really is reflective of the actual usage in the literature. In addition to the many examples already cited, see Refs. ,

There are just a few examples I've run across. There are countless others, if one only cares to look.

The facts speak for themselves. Does anyone object to a minor correction to the page? If so, please do explain why.

98.204.65.104 (talk) 16:51, 7 August 2016 (UTC)

PS, Just noticed that a few of the references cited in the article itself refer to coaxial props turning in opposite directions as "counter-rotating propeller(s)" These are the article's Ref 3 (here: ) and the article's Ref. 9 (here: ) and the article's Ref. 11 (here: )

Especially interesting is the "External Link" to http://www.luftfahrtmuseum.com/htmi/itk/u5.htm, which is claimed in the article to contain "Further information and pictures of contra rotators for the Fairey Gannet and Shackleton" but what is actually found there is a reference to "Counter-running propellers on one axis" (emphasis mine). Surely this was an honest mistake.

Again, the facts speak for themselves. "Counterrotating" and "Contrarotating" are interchangeable.

98.204.65.104 (talk) 18:50, 7 August 2016 (UTC)

Just stumbled on yet another authoritative aeronautical dictionary that equates "Counter-Rotating Propellers" with "Contra-Rotating Propellers" on concentric shafts - this one from AGARD From the Foreword: "Each translation has been checked to see that the terms and definitions agree with actual usage..." Just curious: how much evidence do you insist on seeing before admitting that the article needs correction? — Preceding unsigned comment added by 73.250.91.192 (talk) 15:13, 25 December 2016 (UTC) 73.250.91.192 (talk) 15:15, 25 December 2016 (UTC)

Hmm, here's yet another source with (coaxial) "counter-rotating propellers" from AIAA's Aerospace America (who one can safely assume are deliberate about their copyediting): .

No doubt about it, "counterrotating" is at least as correct as "contrarotating." Indeed from the sources cited here, it appears to be the only correct choice.

2601:14F:4502:6E98:223:7DFF:FEC4:2D73 (talk) 18:07, 4 July 2017 (UTC)

References

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"Contrarotating" Propellers = "Counterrotating" Propellers

We run across yet another professional publication that uses "counter-rotation" to describe coaxial counterrotating propellers

The article and the related one on "Counterrotating propellers" really need to be fixed if they are to have any credibility. The semantic distinction between "contrarotating" and "counterrotating" is wholly imaginary. We have tried to correct the article ourselves, but the inertia of Supposed Fact (vs. Documented Fact, ample documentation of which we have provided) seems to get in the way. Someone needs to step forward and fix this situation.

2601:14F:4502:6E98:223:7DFF:FEC4:2D73 (talk) 16:44, 10 December 2017 (UTC)

References

Who is "we"? Also, what does the text of the source actually state about this matter? Does it define any terms, etc? - BilCat (talk) 22:34, 10 December 2017 (UTC)

Sorry about that - "we" is me with my journal reviewer voice on. But it doesn't matter who I am - don't take my word for it, rather, consider the many (20+) verifiable citations provided above that show clearly the lack of formal distinction between "counterrotating" and "contrarotating". In the case of the Hanson reference just cited, there is reference to the "Fairey Gannet counter-rotation propeller aircraft" which makes it clear that the author is speaking about a coaxial arrangement. One could quibble about "counterrotating" vs. "counter-rotation" but the relevant part here is "counter". And there are many direct examples of "counterrotating" as well. This is the way the words are actually used.

2601:14F:4502:6E98:223:7DFF:FEC4:2D73 (talk) 23:44, 10 December 2017 (UTC)

"Fairey Gannet counter-rotation propeller aircraft" - both Fairey and Armstrong Siddeley would have used the term "contra-rotating". — Preceding unsigned comment added by 95.149.247.9 (talk) 12:57, 9 February 2018 (UTC)

The Gannet, on one day in 1983, changed from having a contra.. to having a counter... , with nobody touching it. It had experienced one of the effects of bilingualism. Does that really matter? I don't think so. This is a wikipedia article with next to nothing in it. That's not a reason for trying to turn it into a make-work project on definitions.

Lets help the reader who actually wants to learn something from this article. Namely, that it's ok to call the same thing by different names. Only by accepting this will they be able to search the internet on, for example, vibratory stresses in contra-rotating propeller blades. How do they do that? They look under counter... And they will be a better person for it, able to converse more constructively than is typical on some forums where arguments ensue for no good reason. Why is this? They are definition addicts.Pieter1963 (talk) 20:24, 29 March 2018 (UTC)

Absolutely correct - both terms are OK. We can stipulate to "contrarotating," and "counterrotating" as an equivalent is well represented in the literature as well (to include technical dictionaries). The notion that "contra means this and counter means that" is an imaginary convention. I have heard of (but not seen) a single reference that claims this to be so, but as said, and has been shown, there are any number of references that show that it is not the case. Why not document the world as it actually is? 2601:14F:4500:46A0:223:7DFF:FEC4:2D73 (talk) 05:50, 29 January 2020 (UTC)