Editing Contra-rotating propellers (section)

==Use in aircraft==
While several nations experimented with contra-rotating propellers in aircraft, only the United Kingdom and Soviet Union produced them in large numbers. The first aircraft to be fitted with a contra-rotating propeller to fly was in the US when two inventors from Ft Worth, Texas tested the concept on an aircraft.<ref>{{cite magazine |issn=0161-7370 |url=https://books.google.com/books?id=DygDAAAAMBAJ&pg=PA33 |title=Plane's propellers revolve in opposite directions |date=November 1931 |magazine=[[Popular Science Monthly]] |page=33 |volume=119 |number=5}}</ref>

===United Kingdom===
[[File:Supermarine Spitfire XIX vr.jpg|thumb|right|Contra-rotating propellers of a [[Supermarine Spitfire|Spitfire]] Mk XIX]]

A contra-rotating propeller was patented by [[Frederick W. Lanchester|F. W. Lanchester]] in 1907.<ref>{{cite magazine |given=F. W. |surname=Lanchester |volume=40 |number=1720 |url=http://www.flightglobal.com/pdfarchive/view/1941/1941%20-%202944.html |title=Contra-props: Recollections of early considerations by advisory committee for aeronautics: A pioneer's 1907 patent: Suggestions for further research |magazine=Flight |access-date=3 November 2015 |date=December 11, 1941 |pages=418–419}}</ref>

Some of the more successful British aircraft with contra-rotating propellers are the [[Avro Shackleton]], powered by the [[Rolls-Royce Griffon]] engine, and the [[Fairey Gannet]], which used the [[Armstrong Siddeley Double Mamba|Double Mamba Mk.101]] engine. In the Double Mamba two separate power sections drove one propeller each, allowing one power section (engine) to be shut down in flight, increasing endurance.

Another naval aircraft, the [[Westland Wyvern]] had contra-rotating propellers. The [[Martin-Baker MB 5]] test aircraft also used this propeller type.

Later variants of the [[Supermarine Spitfire]] and [[Supermarine Seafire|Seafire]] used the Griffon with contra-rotating props. In the Spitfire/Seafire and Shackleton's case the primary reason for using contra-rotating propellers was to increase the propeller blade-area, and hence absorb greater engine power, within a propeller diameter limited by the height of the aircraft's [[Landing gear|undercarriage]]. The [[Short Sturgeon]] used two Merlin 140s with contra-rotating propellers.

The [[Bristol Brabazon]] prototype airliner used eight [[Bristol Centaurus]] engines driving four pairs of contra-rotating propellers, each engine driving a single propeller.<ref>{{cite encyclopedia |section-url=http://www.aviationarchive.org.uk/stories/getobjectstory.php?rnum=g1526&enum=GE121&pnum=4&maxp=9 |section=Brabazon engine layout |url=http://www.aviationarchive.org.uk/stories/storycontents.php?enum=GE121 |title=The Bristol Brabazon - Engineering masterpiece or Great White Elephant |encyclopedia=Aviation Archive: Aviation Heritage |access-date=3 November 2015 |archive-url=https://web.archive.org/web/20150923180801/http://www.aviationarchive.org.uk/stories/storycontents.php?enum=GE121 |archive-date=23 September 2015 |url-status=dead }}</ref>

The post-war [[Saunders-Roe Princess|SARO Princess]] prototype flying boat airliner also had eight of its ten engines driving contra-rotating propellers.

===USSR, Russia and Ukraine===
[[File:Kuznetsov NK-12M turboprop on Tu-95.jpg|thumb|left|One of the four contra-rotating propellers on a [[Tu-95]] Russian strategic bomber]]

In the 1950s, the Soviet Union's [[Kuznetsov Design Bureau]] developed the [[NK-12]] turboprop. It drives an eight-blade contra-rotating propeller and, at {{convert|15000|hp|kW|adj=pre|shaft|abbr=off}}, it is the most powerful turboprop in service. Four NK-12 engines power the [[Tupolev Tu-95]] ''Bear'', the only turboprop bomber to enter service, as well as one of the [[fastest propeller-driven aircraft]]. The [[Tupolev Tu-114|Tu-114]], an airliner derivative of the Tu-95, holds the world speed record for propeller aircraft.<ref>{{cite web |url=http://records.fai.org/general_aviation/current.asp?id1=21&id2=3 |website=Fédération Aéronautique Internationale (FAI) |title=General aviation world records |archive-url=https://web.archive.org/web/20071007145139/http://records.fai.org/general_aviation/current.asp?id1=21&id2=3 |archive-date=October 7, 2007 |url-status=dead}}</ref> The Tu-95 was also the first Soviet bomber to have intercontinental range. The [[Tupolev Tu-126|Tu-126]] AEW aircraft and [[Tupolev Tu-142|Tu-142]] maritime patrol aircraft are two more NK-12 powered designs derived from the Tu-95.

The NK-12 engine powers another well-known Soviet aircraft, the [[Antonov An-22]] Antheus, a heavy-lift cargo aircraft. At the time of its introduction, the An-22 was the largest aircraft in the world and is still, by far, the world's largest turboprop-powered aircraft. From the 1960s through the 1970s, it set several world records in the categories of maximum payload-to-height ratio and maximum payload lifted to altitude.

Of lesser note is the use of the NK-12 engine in the [[A-90 Orlyonok]], a mid-size Soviet [[ekranoplan]]. The A-90 uses one NK-12 engine mounted at the top of its T-tail, along with two turbofans installed in the nose.

In the 1980s, Kuznetsov continued to develop powerful contra-rotating engines. The NK-110, which was tested in the late 1980s, had a contra-rotating propeller configuration with four blades in front and four in back, like the NK-12. Its {{convert|4.7|m|in|order=flip|abbr=off|adj=mid|propeller diameter}} was smaller than the NK-12's {{cvt|5.6|–|6.2|m|in|order=flip}} diameter, but it produced a power output of {{cvt|15665|kW|hp|order=flip}}, delivering a takeoff thrust of {{convert|177|kN|lbf|order=flip|abbr=off}}.<ref name="NK110Sheet">{{cite web |language=ru |page=48 |title=NK-110 |url=http://www.uvauga-dvig.narod.ru/nk-110.pdf |website=Ulyanovsk Higher Aviation School of Civil Aviation}}</ref> Even more powerful was the NK-62, which was in development throughout most of the decade. The NK-62 had an identical propeller diameter and blade configuration to the NK-110, but it offered a higher takeoff thrust of {{cvt|245|kN|lbf|order=flip}}. The associated NK-62M had a takeoff thrust of {{cvt|285.2|kN|lbf|order=flip}}, and it could deliver {{cvt|314.7|kN|lbf|order=flip}} of emergency thrust.<ref name="NKLargeThrust">{{cite magazine |language=ru |year=2018 |number=1 |volume=115 |pages=20–24 |given=V. A. |surname=Zrelov |title=Development of engines 'NK' large thrust on the basis of a single gas generator |magazine=Dvigatel |url=http://engine.aviaport.ru/issues/115/pics/pg20.pdf}}</ref> Unlike the NK-12, however, these later engines were not adopted by any of the aircraft design bureaus.

In 1994, Antonov produced the [[Antonov An-70|An-70]], a heavy transport aircraft. It is powered by four [[Progress D-27]] [[propfan]] engines driving contra-rotating propellers. The characteristics of the D-27 engine and its propeller make it a propfan, a hybrid between a turbofan engine and a turboprop engine.

===United States===
[[File:YB-35 42-13603 on the ramp.jpg|thumb|[[XB-35]] Flying Wing showing its quartet of pusher contra-rotating propellers. The option was later discarded due to severe vibration in flight and later changed to traditional single rotating propellers.]]
[[File:B-42 Mixmaster.jpg|thumb|[[Douglas XB-42 Mixmaster]] ]][[File:General Motors P-75 Eagle.jpg|thumb|General Motors P-75 Eagle]]

The United States worked with several prototypes, including the [[Northrop XB-35]], [[XB-42 Mixmaster]], the [[Douglas XTB2D Skypirate]], the [[Curtiss XBTC]], the [[A2J Super Savage]], the [[Boeing XF8B]], the [[XP-56 Black Bullet]], the [[Fisher P-75 Eagle]] and the [[tailsitter|tail-sitting]] [[Convair XFY]] "Pogo" and [[Lockheed XFV]] "Salmon" [[vertical takeoff and landing|VTOL]] fighters and the [[Hughes XF-11]] reconnaissance plane. The [[Convair R3Y Tradewind]] flying boat entered service with contra-rotating propellers. However, both piston-engined and [[turboprop]]-powered propeller-driven aircraft were reaching their zenith and new technological developments such as the advent of the pure [[turbojet]] and [[turbofan]] engines, both without propellers, meant that the designs were quickly eclipsed.

The US propeller manufacturer, [[Hamilton Standard]], bought a [[Fairey Gannet]] in 1983 to study the effects of counter rotation on propeller noise and blade vibratory stresses. The Gannet was particularly suitable because the independently-driven propellers provided a comparison between counter and single rotation.<ref>{{cite conference |pages=708–717 |title=Single rotation and counter rotation prop-fan propulsion system technologies |url=http://www.icas.org/ICAS_ARCHIVE/ICAS1984/ICAS-84-5.6.2.pdf |given1=B. S. |surname1=Gatzen |given2=C. N. |surname2=Reynolds |conference=Congress of the International Council of the Aeronautical Sciences |date=September 9–14, 1984 |location=–Toulouse, France |edition=14th |conference-url=http://www.icas.org/ICAS_ARCHIVE/ICAS1984/1984.html}}</ref>

===Ultralight applications===
An Austrian company, [[Sun Flightcraft]], distributes a contra-rotating gearbox for use on [[Rotax 503]] and [[Rotax 582|582]] engines on ultralight and microlight aircraft. The [[Coax-P]] was developed by Hans Neudorfer of [[NeuraJet]] and allows powered hang-gliders and parachutes to develop 15 to 20 percent more power while reducing torque moments. The manufacturer also reports reduced noise levels from dual contra-rotating props using the Coax-P gearbox.<ref>{{cite web |url=http://sunflightcraft.com/en/coaxp.php |title=COAX-P: Counter rotating propeller gearbox |website=Sun Flightcraft |access-date=July 18, 2019}}</ref><ref name="WDLA04">{{cite journal |surname1=Bertrand |given1=Noel |given2=Rene |surname2=Coulon |title=World Directory of Leisure Aviation 2003-04 |journal=World Directory of Light Aviation |pages=70, 87 |publisher=Pagefast Ltd |location=Lancaster, United Kingdom |year=2003 |issn=1368-485X}}</ref><ref>{{cite web|url=http://www.neurajet.at/englisch/home.html|archive-url=https://web.archive.org/web/20051222043916/http://www.neurajet.at/englisch/home.html|title=Willkommen bei Neura Jet|archive-date=22 December 2005|work=neurajet.at|access-date=3 November 2015}}</ref>