The Wright R-3350 Duplex-Cyclone is an American twin-row,

supercharge In theoretical physics, a supercharge is a generator of supersymmetry transformations. It is an example of the general notion of a charge (physics), charge in physics. Supercharge, denoted by the symbol Q, is an operator which transforms bosons in ...

d, air-cooled,

radial Radial is a geometric term of location which may refer to: Mathematics and Direction * Vector (geometric), a line * Radius, adjective form of * Radial distance (geometry), a directional coordinate in a polar coordinate system * Radial set * A ...

aircraft engine with 18

cylinders A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infinite ...

displacing nearly . Power ranged from , depending on model. Developed before

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

, the R-3350's design required a long time to mature, and was still experiencing problems with reliability when used to power the

Boeing B-29 Superfortress The Boeing B-29 Superfortress is a retired American four-engined propeller-driven heavy bomber, designed by Boeing and flown primarily by the United States during World War II and the Korean War. Named in allusion to its predecessor, the Bo ...

. After the war, the engine had matured sufficiently to be used in many civilian airliners, notably in its

turbo-compound A turbo-compound engine is a reciprocating engine that employs a turbine to recover energy from the exhaust gases. Instead of using that energy to drive a turbocharger as found in many high-power aircraft engines, the energy is instead sent to ...

forms, and was used in the

Lockheed L-1049 Super Constellation The Lockheed L-1049 Super Constellation is an American aircraft, a member of the Lockheed Constellation aircraft line. The aircraft was colloquially referred to as the Super Connie. The L-1049 was Lockheed's response to the successful Douglas DC ...

airliners into the 1950s. Its main rival was the ,

Pratt & Whitney R-4360 Wasp Major The Pratt & Whitney R-4360 Wasp Major is an American 28-cylinder four-row radial engine, radial reciprocating engine, piston aircraft engine designed and built during World War II. At , it is the largest-displacement aviation piston engine to be ...

, which first ran some seven years after the Duplex-Cyclone. The engine is commonly used on

Hawker Sea Fury The Hawker Sea Fury is a British fighter aircraft designed and manufactured by Hawker Aircraft. It was the last propeller-driven fighter to serve with the Royal Navy. Developed during the Second World War, the Sea Fury entered service two year ...

and

Grumman F8F Bearcat The Grumman F8F Bearcat is an American single-engined, carrier-based fighter aircraft introduced in late World War II. It served during the mid-20th century in the United States Navy, the United States Marine Corps, and the air forces of other na ...

Unlimited Class Racers at the

Reno Air Races The Reno Air Races, or Roswell Air Races, officially known as the National Championship Air Races, are a multi-day event tailored to the aviation community that took place each September at the Reno Stead Airport a few miles north of Reno, ...

Design and development

In 1927,

Wright Aeronautical Wright Aeronautical (1919–1929) was an American aircraft manufacturer headquartered in Paterson, New Jersey. It was the successor corporation to Wright-Martin. It built aircraft and was a supplier of aircraft engines to other builders in the g ...

introduced its "Cyclone" engine, which powered a number of designs in the 1930s. After merging with Curtiss to become

Curtiss-Wright The Curtiss-Wright Corporation is an American manufacturer and services provider headquartered in Davidson, North Carolina, with factories and operations in and outside the United States. Created in 1929 from the consolidation (business), consoli ...

in 1929, an effort was started to design an engine in the class. The new

Wright R-1820 Cyclone 9 The Wright R-1820 Cyclone 9 is an American radial engine developed by Curtiss-Wright, widely used on aircraft in the 1930s through 1950s. It was produced under license in France as the Hispano-Suiza 9V or Hispano-Wright 9V, and in the Soviet Uni ...

first ran in 1935, and became one of the most used aircraft engines in the late 1930s and early 1940's, powering the

Boeing B-17 Flying Fortress The Boeing B-17 Flying Fortress is an American four-engined heavy bomber aircraft developed in the 1930s for the United States Army Air Corps (USAAC). A fast and high-flying bomber, the B-17 dropped more bombs than any other aircraft during ...

heavy bomber,

General Motors FM-2 Wildcat The Grumman F4F Wildcat is an American carrier-based fighter aircraft that entered service in 1940 with the United States Navy, and the British Royal Navy where it was initially known as the Martlet. First used by the British in the North Atla ...

fighter and

Douglas SBD Dauntless The Douglas SBD Dauntless is a World War II American naval scout plane and dive bomber that was manufactured by Douglas Aircraft from 1940 through 1944. The SBD ("Scout Bomber Douglas") was the United States Navy's main Carrier-based aircraft, ...

dive bomber, among many others. By 1931

Pratt & Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of RTX Corporation (formerly Raytheon Technologies). Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially ...

had started a development of their single-row

Wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...

nine-cylinder engine into the larger and much more powerful fourteen-cylinder, twin-row

R-1830 Twin Wasp The Pratt & Whitney R-1830 Twin Wasp is an American air-cooled radial aircraft engine. It has 14 cylinders, arranged in two rings of seven. It displaces and its bore and stroke are both . The design traces its history to 1929 experiments a ...

with a similar displacement that would easily compete with the single-row Cyclone. In 1935 Wright followed P&W's lead, and developed larger engines based on the Cyclone. The result was two designs, a 14-cylinder short stroke design of nearly displacement that would evolve into the

Wright R-2600 Twin Cyclone The Wright R-2600 Cyclone 14 (also called Twin Cyclone) is an American radial engine developed by Curtiss-Wright, and widely used in aircraft in the 1930s and 1940s. History In 1935, Curtiss-Wright began work on a more powerful version of thei ...

, and a much larger 18-cylinder design that became the R-3350. A larger twin-row 22-cylinder version, the

Wright R-4090 Cyclone 22 The Wright R-4090 Cyclone 22 was an American experimental radial piston engine designed and built in prototype form by Wright Aeronautical during the 1940s. Design and development During the 1940s, Wright Aeronautical Corporation was constant ...

, was experimented with as a competitor to the displacement four-row, 28-cylinder

, but was not produced. With Pratt & Whitney starting development of their own displacement 18-cylinder, twin-row radial as the R-2800 Double Wasp in 1937, Wright's first R-3350 prototype engines with a displacement were run in May of the same year. Development was slow, due to the complexity, and the R-2600 receiving development priority. The R-3350 did not fly until 1941, after the

Douglas XB-19 The Douglas XB-19 was a four-engined, piston-driven heavy bomber produced by the Douglas Aircraft Company for the United States Army Air Forces (USAAF) during the early 1940s. The design was originally given the designation XBLR-2 (''XBLR'' deno ...

had been redesigned to use R-3350s instead of

Allison V-3420 The Allison V-3420 was a large experimental piston aircraft engine, designed in 1937 by the American Allison Engine Company. Design and development In 1937, at the behest of the United States Army Air Corps, the Allison Engine Company agreed t ...

inlines. Things changed dramatically in 1940 with the introduction of a new contract by the

USAAC The United States Army Air Corps (USAAC) was the aerial warfare service component of the United States Army between 1926 and 1941. After World War I, as early aviation became an increasingly important part of modern warfare, a philosophical ri ...

to develop a long-range bomber capable of flying from the US to Germany with of bombs. Although smaller than the Bomber D designs that led to the Douglas XB-19, the new designs required just as much power. When four preliminary designs were presented in mid-1940, three of them used the R-3350. Suddenly development was a priority, and serious efforts to get it into production began. In 1942

Chrysler FCA US, LLC, Trade name, doing business as Stellantis North America and known historically as Chrysler ( ), is one of the "Big Three (automobile manufacturers), Big Three" automobile manufacturers in the United States, headquartered in Auburn H ...

started building the Dodge Chicago Plant, which was ready by early 1944. Wright R-3350 Cyclone Engine 1

By 1943 the new Boeing B-29 Superfortress was flying with R-3350s. The engines remained temperamental, and the rear cylinders tended to overheat, partially due to inadequate clearance between the cylinder baffles and the cowl. A number of changes were introduced to improve cooling, and the aircraft was rushed into service in the Pacific in 1944. This proved unwise, as the early B-29s taking off at maximum weights, in the high temperature conditions of the B-29s tropical airfields, caused overheating that was not completely solved, and the engines also had a tendency to swallow valves. Because of a high

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

content in the crankcase, engine fires could burn with a core temperature approaching which could burn through the main spar in seconds, causing a catastrophic failure. Early R-3350s used

carburetor A carburetor (also spelled carburettor or carburetter) is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Ventu ...

s, though the poorly designed elbow entrance to the supercharger led to serious problems with fuel/air mixtures. Near the end of WWII, the system was changed to use

gasoline direct injection Gasoline direct injection (GDI), also known as petrol direct injection (PDI), is a fuel injection system for internal combustion engines that run on gasoline (petrol) which injects fuel directly into the combustion chamber. This is distinct f ...

which improved reliability. After the war the engine was redesigned and became popular for large aircraft, notably the

Lockheed Constellation The Lockheed Constellation ("Connie") is a propeller-driven, four-engined airliner built by Lockheed Corporation starting in 1943. The Constellation series was the first civil airliner family to enter widespread use equipped with a pressurized cab ...

and

Douglas DC-7 The Douglas DC-7 is a retired American transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. A derivative of the DC-6, it was the last major piston engine-powered transport made by Douglas, being developed shortly after ...

. Following the war, the

Turbo-Compound A turbo-compound engine is a reciprocating engine that employs a turbine to recover energy from the exhaust gases. Instead of using that energy to drive a turbocharger as found in many high-power aircraft engines, the energy is instead sent to ...

Gunston 2006, p. 247. system was developed to deliver better

fuel efficiency Fuel efficiency (or fuel economy) is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical energy, chemical potential energy contained in a carrier (fuel) into kinetic energy or Mechanical work, w ...

. In these versions, three power-recovery

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical ...

s (PRT) were inserted into the exhaust of each group of six cylinders, and geared to the crankshaft by

fluid coupling A fluid coupling or hydraulic coupling is a hydrodynamics, hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power.

s to deliver more power. The PRTs recovered about 20% of the exhaust energy (around ) that would have otherwise been lost, but reduced engine reliability. Mechanics nicknamed them Parts Recovery Turbines, since the increased exhaust heat meant a return to the engine destroying exhaust valves. The fuel burn for the PRT-equipped aircraft was nearly the same as the older Pratt and Whitney R-2800, while producing more useful power. Effective 15 October 1957 a DA-3/DA-4 engine cost $88,200. By this point reliability had improved with the mean time between overhauls at 3,500 hours and specific fuel consumption in the order of 0.4 lb/hp/hour (243 g/kWh, giving a 34% fuel efficiency). Engines in use as of the 2020s are limited to

manifold pressure Manifold vacuum, or engine vacuum in a petrol engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere. Manifold vacuum is an effect of a piston's movement on the induction stroke and the airflow thro ...

, giving with 100/130 octane fuel (or 100LL) instead of the and possible with 115/145, a higher octane fuel, which is no longer available. Several racers at the

use R-3350s. Modifications on one, ''

Rare Bear ''Rare Bear'' is a highly modified Grumman F8F Bearcat that saw major success at the Reno Air Races over multiple decades. History The Bearcat that became Rare Bear was a severely damaged wreck when discovered by Lyle Shelton in 1969. It ha ...

'', include a nose case designed for a slow-turning prop, taken from an R-3350 used on the Lockheed L-1649 Starliner, mated to the power section (crankcase, crank, pistons, and cylinders) taken from an R-3350 used on the Douglas DC-7. The supercharger is taken from an R-3350 used on the Lockheed EC-121 and the engine is fitted with

nitrous oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or factitious air, among others, is a chemical compound, an Nitrogen oxide, oxide of nitrogen with the Chemical formula, formula . At room te ...

injection. Normal rated power of the original stock R-3350 was at 2,600 rpm and of manifold pressure. With these modifications, ''Rare Bear''s engine produces at 3,200 rpm and of manifold pressure, and with nitrous oxide injection.

Variants

;R-3350-13: ;R-3350-23: ;R-3350-24W: ;R-3350-26W: ;R-3350-30W: ;R-3350-30WA: ;R-3350-32W: ;R-3350-34: ;R-3350-35A: ;R-3350-41: Fuel injected

Silverplate Silverplate was the code reference for the United States Army Air Forces' participation in the Manhattan Project during World War II. Originally the name for the aircraft modification project which enabled a B-29 Superfortress bomber to drop ...

variantDoyle p 71 ;R-3350-42WA: ;R-3350-53: ;R-3350-57: ;R-3350-85: ;R-3350-89A: ;R-3350-93W: ;972TC18DA1:Commercial equivalent to the -30W without water injection ;956C18CA1:Commercial, similar to the -26W ;975C18CB1:Commercial, similar to the 956C18CA1

Applications

Engines on display

* Wright R-3350-89 is on public display at the

Aerospace Museum of California The Aerospace Museum of California is a private non-profit aviation museum located in McClellan, California, outside of Sacramento, California, on the grounds of the former McClellan Air Force Base. History Founded as the Air Force Logistics Mus ...

* Wright R-3350 is on public display at

Flyhistorisk Museum, Sola Flyhistorisk Museum, Sola (Sola Aviation Museum) is an aviation museum located at Stavanger Airport, Sola, near Stavanger, Norway. The museum was founded in 1984 and is run by local volunteers. Flyhistorisk Museum, Sola went into cooperation w ...

, near

Stavanger Stavanger, officially the Stavanger Municipality, is a city and municipalities of Norway, municipality in Norway. It is the third largest city and third largest metropolitan area in Norway (through conurbation with neighboring Sandnes) and the ...

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

* Wright R-3350-35A is on public display at

Texas Air Museum - Stinson Chapter The Texas Air Museum - Stinson Chapter is located on Stinson Municipal Airport (which is the second oldest continuous operating airport in the United States). The Stinson Municipal Airport (SSF) is located six miles south of downtown San Anton ...

San Antonio San Antonio ( ; Spanish for " Saint Anthony") is a city in the U.S. state of Texas and the most populous city in Greater San Antonio. San Antonio is the third-largest metropolitan area in Texas and the 24th-largest metropolitan area in the ...

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

* Wright R-3350 is on public display in the

Mackenzie Mackenzie, Mckenzie, MacKenzie, or McKenzie may refer to: People * Mackenzie (given name), a given name (including a list of people with the name) * Mackenzie (surname), a surname (including a list of people with the name) * Clan Mackenzie, a Sc ...

Engineering Building at

Carleton University Carleton University is an English-language public university, public research university in Ottawa, Ontario, Canada. Founded in 1942 as Carleton College, the institution originally operated as a private, non-denominational evening college to se ...

Ottawa Ottawa is the capital city of Canada. It is located in the southern Ontario, southern portion of the province of Ontario, at the confluence of the Ottawa River and the Rideau River. Ottawa borders Gatineau, Gatineau, Quebec, and forms the cor ...

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

File:Air Zoo December 2019 148 (Wright R-3350 Turbo-Compound Duplex Cyclone).jpg, R-3350 on display at the

Air Zoo The Air Zoo, founded as the Kalamazoo Aviation History Museum, is an aviation museum and indoor amusement park next to the Kalamazoo-Battle Creek International Airport in Portage, Michigan. The Air Zoo holds many historical and rare aircraft, inc ...

File:20-09-094-R 3350.jpg, R-3350 on display at Museum of Aviation,

Robins AFB Robins Air Force Base is a major United States Air Force installation located in Houston County, Georgia, United States. The base is located just east of the city of Warner Robins, south-southeast of Macon and approximately south-southeast ...

File:Wright R-3350 - Canadian CP-107 Argus patrol aircraft - Carleton University - 2023.jpg, R-3350 on display at

Specifications (R-3350-C18-BA)

References

Notes

Bibliography

*Gunston, Bill. ''World Encyclopedia of Aero Engines: From the Pioneers to the Present Day''. 5th edition, Stroud, UK: Sutton, 2006. *White, Graham. ''Allied Aircraft Piston Engines of World War II: History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States During World War II''. Warrendale, Pennsylvania: SAE International, 1995. * ''Jane's Fighting Aircraft of World War II''. London. Studio Editions, 1998. . *Doyle, David. "B-29 Superfortress Vol. 1" Schiffer Publishing Ltd. 2020

External links

Wright R-3350-57 Cyclone Fact Sheets from the National Museum of the USAF website

1940s film on Chrysler production of Wright's Duplex-Cyclone radials for the Superfortress

150 hour test of Wright 3350-19 with Bendix fuel injection 1943
{{US military piston aeroengines R-3350 1930s aircraft piston engines Aircraft air-cooled radial piston engines Turbo-compound engines