Editing Radial engine (section)

==History==
===Aircraft===
[[File:Rotary Piston Engine 8b03632r.jpg|thumb|[[Continental engine|Continental]] radial, 1944]]
[[File:H19 showing engine.jpg|thumb|[[Pratt & Whitney R-1340]] radial mounted in [[Sikorsky H-19]] helicopter]]

[[C. M. Manly]] constructed a water-cooled five-cylinder radial engine in 1901, a conversion of one of [[Stephen Balzer]]'s [[rotary engine]]s, for [[Samuel Pierpont Langley|Langley]]'s ''Aerodrome'' aircraft. [[Manly–Balzer engine|Manly's engine]] produced {{convert|52|hp|kW|abbr=on}} at 950 rpm.<ref name=vivian>{{cite book | last = Vivian | first = E. Charles | title = A History of Aeronautics | publisher = Dayton History Books Online | year = 1920 | url = http://www.daytonhistorybooks.citymax.com/page/page/3259323.htm | access-date = 2008-07-05 | archive-date = 2009-05-23 | archive-url = https://web.archive.org/web/20090523051050/http://www.daytonhistorybooks.citymax.com/page/page/3259323.htm | url-status = dead }}</ref>

In 1903–1904 [[Jacob Ellehammer]] used his experience constructing motorcycles to build the world's first air-cooled radial engine, a three-cylinder engine which he used as the basis for a more powerful five-cylinder model in 1907.  This was installed in his [[triplane]] and made a number of short free-flight hops.<ref>{{cite book | last = Day | first = Lance | author2 = Ian McNeil | title = Biographical Dictionary of the History of Technology | publisher = Taylor & Francis | year = 1996 | page = [https://archive.org/details/isbn_9780415060424/page/239 239] | url = https://archive.org/details/isbn_9780415060424/page/239 | isbn = 0-415-06042-7 }}</ref>

Another early radial engine was the three-cylinder [[Anzani]], originally built as a W3 "fan" configuration, one of which powered [[Louis Blériot]]'s [[Blériot XI]] across the [[English Channel]]. Before 1914, Alessandro Anzani had developed radial engines ranging from 3 cylinders (spaced 120° apart) — early enough to have been used on a few French-built examples of the famous [[Blériot XI]] from the original Blériot factory — to a massive 20-cylinder engine of {{convert|200|hp|kW|abbr=on}}, with its cylinders arranged in four rows of five cylinders apiece.<ref name=vivian/>

Most radial engines are [[air-cooled]], but one of the most successful of the early radial engines (and the earliest "stationary" design produced for World War I combat aircraft) was the [[Salmson water-cooled aero-engines|Salmson 9Z series of nine-cylinder water-cooled radial engines]] that were produced in large numbers. Georges Canton and Pierre Unné patented the original engine design in 1909, offering it to the [[Salmson]] company; the engine was often known as the Canton-Unné.<ref name="Lumsden225">Lumsden 2003, p. 225.</ref>

From 1909 to 1919 the radial engine was overshadowed by its close relative, the [[rotary engine]], which differed from the so-called "stationary" radial in that the crankcase and cylinders revolved with the propeller. It was similar in concept to the later radial, the main difference being that the propeller was bolted to the engine, and the crankshaft to the airframe. The problem of the cooling of the cylinders, a major factor with the early "stationary" radials, was alleviated by the engine generating its own cooling airflow.<ref name="nahum">{{cite book| last = Nahum| first = Andrew| title = The Rotary Aero Engine| year = 1999| publisher = NMSI Trading Ltd| isbn = 1-900747-12-X }}</ref>

In [[World War I]] many French and other Allied aircraft flew with [[Gnome Engine Company|Gnome]], [[Le Rhône]], [[Clerget-Blin|Clerget]], and [[Bentley BR2|Bentley]] rotary engines, the ultimate examples of which reached {{cvt|250|hp}} although none of those over {{convert|160|hp|kW|abbr=on}} were successful. By 1917 rotary engine development was lagging behind new inline and V-type engines, which by 1918 were producing as much as {{convert|400|hp|kW|abbr=on}}, and were powering almost all of the new French and British combat aircraft.

Most German aircraft of the time used water-cooled inline 6-cylinder engines. [[Motorenfabrik Oberursel]] made licensed copies of the Gnome and Le Rhône rotary powerplants, and [[Siemens-Halske]] built their own designs, including the [[Siemens-Halske Sh.III|Siemens-Halske Sh.III eleven-cylinder rotary engine]], which was unusual for the period in being geared through a [[bevel gear]]train in the rear end of the crankcase ''without'' the crankshaft being firmly mounted to the aircraft's airframe, so that the engine's internal working components (fully internal crankshaft "floating" in its crankcase bearings, with its conrods and pistons) were spun in the opposing direction to the crankcase and cylinders, which still rotated as the propeller itself did since it was still firmly fastened to the crankcase's frontside, as with regular ''umlaufmotor'' German rotaries.
  
By the end of the war the rotary engine had reached the limits of the design, particularly in regard to the amount of fuel and air that could be drawn into the cylinders through the hollow crankshaft, while advances in both [[metallurgy]] and cylinder cooling finally allowed stationary radial engines to supersede rotary engines. In the early 1920s Le Rhône converted a number of their rotary engines into stationary radial engines.

By 1918 the potential advantages of air-cooled radials over the water-cooled [[Inline engine (aviation)|inline engine]] and air-cooled [[rotary engine]] that had powered World War I aircraft were appreciated but were unrealized. British designers had produced the [[ABC Dragonfly]] radial in 1917, but were unable to resolve the cooling problems, and it was not until the 1920s that [[Bristol Aeroplane Company|Bristol]] and [[Armstrong Siddeley]] produced reliable air-cooled radials such as the [[Bristol Jupiter]]<ref>{{cite book |last=Gunston |first=Bill |date=1989 |title=World Encyclopedia of Aero Engines |location=Cambridge, UK |publisher=Patrick Stephens Ltd |pages=29, 31 & 44 |isbn=1-85260-163-9 }}</ref> and the [[Armstrong Siddeley Jaguar]].{{Citation needed|date=October 2014}}

In the United States the [[National Advisory Committee for Aeronautics]] (NACA) noted in 1920 that air-cooled radials could offer an increase in [[power-to-weight ratio]] and reliability; by 1921 the U.S. Navy had announced it would only order aircraft fitted with air-cooled radials and other naval air arms followed suit. [[Charles Lawrance]]'s [[Lawrance J-1|J-1 engine]] was developed in 1922 with Navy funding, and using aluminum cylinders with steel liners ran for an unprecedented 300 hours, at a time when 50 hours endurance was normal. At the urging of the Army and Navy the [[Wright Aeronautical Corporation]] bought Lawrance's company, and subsequent engines were built under the Wright name. The radial engines gave confidence to Navy pilots performing long-range overwater flights.<ref>{{cite book |last=Bilstein|first=Roger E.|title=Flight Patterns: Trends of Aeronautical Development in the United States, 1918–1929|publisher=University of Georgia Press|year=2008|page=26|isbn=978-0-8203-3214-7}}</ref>

Wright's {{convert|225|hp|kW|abbr=on}} [[Wright J-5 Whirlwind|J-5 Whirlwind]] radial engine of 1925 was widely claimed as "the first truly reliable aircraft engine".<ref>{{cite book|last=Herrmann|first=Dorothy|title=Anne Morrow Lindbergh: A Gift for Life|publisher=Ticknor & Fields|year=1993|page=[https://archive.org/details/annemorrowlindbe00herr/page/28 28]|isbn=0-395-56114-0|url=https://archive.org/details/annemorrowlindbe00herr/page/28}}</ref> Wright employed [[Giuseppe Mario Bellanca]] to design an aircraft to showcase it, and the result was the [[Wright-Bellanca WB-1]], which first flew later that year. The J-5 was used on many advanced aircraft of the day, including [[Charles Lindbergh]]'s [[Spirit of St. Louis]], in which he made the first solo trans-Atlantic flight.<ref>"[http://www.charleslindbergh.com/plane/ The Spirit of St. Louis]". Charles Lindergh: An American Aviator, Retrieved 21 August 2015.</ref>

In 1925 the American [[Pratt & Whitney]] company was founded, competing with Wright's radial engines. Pratt & Whitney's initial offering, the [[Pratt & Whitney R-1340|R-1340 Wasp]], was test run later that year, beginning a line of engines over the next 25 years that included the 14-cylinder, twin-row [[Pratt & Whitney R-1830 Twin Wasp]]. More Twin Wasps were produced than any other aviation piston engine in the history of aviation; nearly 175,000 were built.<ref>[https://web.archive.org/web/20131111025015/http://www.pw.utc.com/R1830_Twin_Wasp_Engine - Archived (Nov. 11, 2013) manufacturer's product page, R-1830] Retrieved: 7 February 2019</ref>

[[File:RAR2009 - Rare Bear makes emergency landing.jpg|thumb|[[Rare Bear]] ]]
In the United Kingdom the [[Bristol Aeroplane Company]] was concentrating on developing radials such as the Jupiter, [[Bristol Mercury|Mercury]], and [[sleeve valve]] [[Bristol Hercules|Hercules]] radials. Germany, Japan, and the Soviet Union started with building licensed versions of the Armstrong Siddeley, Bristol, Wright, or Pratt & Whitney radials before producing their own improved versions.{{Citation needed|date=October 2014}} France continued its development of various rotary engines but also produced engines derived from Bristol designs, especially the Jupiter.

Although other piston configurations and [[turboprop]]s have taken over in modern [[Powered aircraft#Propeller aircraft|propeller-driven aircraft]], [[Rare Bear]], which is a [[F8F Bearcat|Grumman F8F Bearcat]] equipped with a [[Wright R-3350 Duplex-Cyclone]] radial engine, is still [[Fastest propeller-driven aircraft#Piston engines|the fastest piston-powered aircraft]].<ref>Lewis Vintage Collection (2018), [http://www.lewisairlegends.com/aircraft/rare-bear "'Rare Bear' web site."] {{Webarchive|url=https://web.archive.org/web/20131027142821/http://www.lewisairlegends.com/aircraft/rare-bear |date=2013-10-27 }}. Retrieved: 6 January 2018.</ref><ref>Aerospaceweb, [http://www.aerospaceweb.org/question/performance/q0023.shtml "Aircraft speed records."] ''AeroSpaceWeb.org''. Retrieved: 6 January 2018.</ref>

125,334 of the American twin-row, 18-cylinder [[Pratt & Whitney R-2800 Double Wasp]], with a displacement of 2,800 in<sup>3</sup> (46 L) and between 2,000 and 2,400&nbsp;hp (1,500-1,800&nbsp;kW), powered the American single-engine [[Vought F4U Corsair]], [[Grumman F6F Hellcat]], [[Republic P-47 Thunderbolt]], twin-engine [[Martin B-26 Marauder]], [[Douglas A-26 Invader]], [[Northrop P-61 Black Widow]], etc. The same firm's aforementioned smaller-displacement (at 30 litres), [[Pratt & Whitney R-1830 Twin Wasp|''Twin Wasp'']] 14-cylinder twin-row radial was used as the main engine design for the [[B-24 Liberator]], [[PBY Catalina]], and [[Douglas C-47]], each design being among [[List of most-produced aircraft|the production leaders]] in all-time production numbers for each type of airframe design.

The American [[Wright Cyclone series]] twin-row radials powered American warplanes: the nearly-43 litre displacement, 14-cylinder [[Wright R-2600|''Twin Cyclone'']] powered the single-engine [[Grumman TBF Avenger]], twin-engine [[North American B-25 Mitchell]], and some versions of the [[Douglas A-20 Havoc]], with the massive twin-row, nearly 55-litre displacement, 18-cylinder [[Wright R-3350|''Duplex-Cyclone'']] powering the four-engine [[Boeing B-29 Superfortress]] and others.

The Soviet [[Shvetsov]] [[OKB|''OKB-19'' design bureau]] was the sole source of design for all of the Soviet government factory-produced radial engines used in its World War II aircraft, starting with the [[Shvetsov M-25]] (itself based on the American [[Wright R-1820|Wright ''Cyclone 9'']]'s design) and going on to design the 41-litre displacement [[Shvetsov ASh-82]] fourteen cylinder radial for fighters, and the massive, 58-litre displacement [[Shvetsov ASh-73]] eighteen-cylinder radial in 1946 - the smallest-displacement radial design from the Shvetsov OKB during the war was the indigenously designed, 8.6 litre displacement [[Shvetsov M-11]] five cylinder radial.

Over 28,000 of the German 42-litre displacement, 14-cylinder, two-row [[BMW 801]], with between 1,560 and 2,000 PS (1,540-1,970&nbsp;hp, or 1,150-1,470&nbsp;kW), powered the German single-seat, single-engine [[Focke-Wulf Fw 190]] ''Würger'', and twin-engine [[Junkers Ju 88]].

In Japan, most airplanes were powered by air-cooled radial engines like the 14-cylinder [[Mitsubishi Zuisei]] (11,903 units, e.g. [[Kawasaki Ki-45]]), [[Mitsubishi Kinsei]] (12,228 units, e.g. [[Aichi D3A]]), [[Mitsubishi Kasei]] (16,486 units, e.g. [[Kawanishi H8K]]), [[Nakajima Sakae]] (30,233 units, e.g. [[Mitsubishi A6M]] and [[Nakajima Ki-43]]), and 18-cylinder [[Nakajima Homare]] (9,089 units, e.g. [[Nakajima Ki-84]]). The [[Kawasaki Ki-61]] and [[Yokosuka D4Y]] were rare examples of Japanese liquid-cooled inline engine aircraft at that time but later, they were also redesigned to fit radial engines as the [[Kawasaki Ki-100]] and [[Yokosuka D4Y]]3.

In Britain, Bristol produced both [[sleeve valve]]d and conventional [[poppet valve]]d radials: of the sleeve valved designs, more than 57,400 Hercules engines powered the [[Vickers Wellington]], [[Short Stirling]], [[Handley Page Halifax]], and some versions of the [[Avro Lancaster]],  over 8,000 of the pioneering sleeve-valved [[Bristol Perseus]] were used in various types, and more than 2,500 of the largest-displacement production British radial from the Bristol firm to use sleeve valving, the [[Bristol Centaurus]] were used to power the [[Hawker Tempest|Hawker Tempest II]] and [[Hawker Sea Fury|Sea Fury]]. The same firm's poppet-valved radials included: around 32,000 of [[Bristol Pegasus]] used in the [[Short Sunderland]], [[Handley Page Hampden]], and [[Fairey Swordfish]] and over 20,000 examples of the firm's 1925-origin nine-cylinder Mercury were used to power the [[Westland Lysander]], [[Bristol Blenheim]], and [[Blackburn Skua]].

===Tanks===
In the years leading up to World War II, as the need for armored vehicles was realized, designers were faced with the problem of how to power the vehicles, and turned to using aircraft engines, among them radial types. The radial aircraft engines provided greater power-to-weight ratios and were more reliable than conventional inline vehicle engines available at the time.  This reliance had a downside though: if the engines were mounted vertically, as in the [[M3 Lee]] and [[M4 Sherman]], their comparatively large diameter gave the tank a higher silhouette than designs using inline engines.{{Citation needed|date=October 2014}}

The [[Continental R-670]], a 7-cylinder radial aero engine which first flew in 1931, became a widely used tank powerplant, being installed in the [[M1 Combat Car]], [[M2 Light Tank]], [[M3 Stuart]], [[M3 Lee]], and [[Landing Vehicle Tracked|LVT-2 Water Buffalo]].{{Citation needed|date=October 2014}}

The [[Guiberson T-1020]], a 9-cylinder radial diesel aero engine, was used in the [[M1 Combat Car|M1A1E1]], while the [[Wright R-975|Continental R975]] saw service in the [[M4 Sherman]], [[M7 Priest]], [[M18 Hellcat]] [[tank destroyer]], and the [[M44 self propelled howitzer]].{{Citation needed|date=October 2014}}

===Modern radials===
[[File:Scarlett mini 5.png|thumb|Four-stroke aircraft radial engine Scarlett mini 5]]

A number of companies continue to build radials today. [[Vedeneyev]] produces the M-14P radial of {{convert|360|-|450|hp|kW|abbr=on}} as used on [[Yakovlev]] and [[Sukhoi]] aerobatic aircraft. The M-14P is also used by builders of [[homebuilt aircraft]], such as the [[Culp Special]], and [[Culp Sopwith Pup]],<ref>{{cite web|url=http://culpsspecialties.com/site_files/suppages/specs.html |title=Aircraft |publisher=Culp Specialties |access-date=2013-12-22}}</ref> [[Pitts Special|Pitts]] S12 "Monster" and the [[Murphy Moose|Murphy "Moose"]]. In Poland, WSK PZL Kalisz produces the [[Shvetsov ASh-62]] engine. A version with direct injection has also been developed<ref>https://www.wsk.kalisz.pl/produkty-i-uslugi/silniki-lotnicze/</ref>. [[Rotec R2800|{{convert|110|hp|kW|abbr=on}}]] 7-cylinder and [[Rotec R3600|{{convert|150|hp|kW|abbr=on}}]] 9-cylinder engines are available from Australia's [[Rotec Aerosport]]. HCI Aviation<ref>{{cite web|url=https://aeroenginesaz.com/en/brand_hci |title=HCI (USA) |publisher=Aerospace Engines A to Z |access-date=2023-02-11}}</ref> offers the R180 5-cylinder ({{convert|75|hp|kW|abbr=on}}) and R220 7-cylinder ({{convert|110|hp|kW|abbr=on}}), available "ready to fly" and as a build-it-yourself kit. [[Verner Motor]] of the Czech Republic builds several radial engines ranging in power from {{convert|25|to|150|hp|kW|abbr=on}}.<ref>{{cite web|title=Verner Motor range of engines|url=http://vernermotor.eu/engines/|work=Verner Motor|access-date=23 April 2013|url-status=dead|archive-url=https://web.archive.org/web/20141006154103/http://vernermotor.eu/engines/|archive-date=6 October 2014}}</ref>  Miniature radial engines for [[Radio-controlled aircraft|model airplane]]s are available from [[O. S. Engines]], Saito Seisakusho of Japan, and Shijiazhuang of China, and Evolution (designed by Wolfgang Seidel of Germany, and made in India) and Technopower in the US.{{Citation needed|date=October 2014}}