Wright R-3350
Encyclopedia
The Wright R-3350 Duplex-Cyclone was one of the most powerful radial
aircraft engine
s produced in the United States
. It was a twin row, supercharge
d, air-cooled, radial engine with 18 cylinders. Power ranged from 2,200 to over 3,700 hp (1,640 to 2,760 kW), depending on the model. First developed prior to World War II
, the R-3350's design required a long time to mature before finally being used to power the Boeing B-29 Superfortress. After the war, the engine had matured sufficiently to become a major civilian airliner design, notably in its Turbo-Compound
forms. The engine is now commonly used on Hawker Sea Fury
and Grumman F8F Bearcat Unlimited Class Racers at the Reno Air Races
.
introduced its famous "Cyclone" engine, which powered a number of designs in the 1930s. After merging with Curtiss to become Curtiss-Wright
in 1929, an effort was started to redesign the engine to the 1,000 hp (750 kW) class. The new Wright R-1820
Cyclone 9 first ran successfully in 1935, and would become one of the most-used aircraft engines in the 1930s and World War II.
At about the same time Pratt & Whitney
had started a development of their equally famous Wasp
design into a larger and much more powerful two-row design that would easily compete with this larger Cyclone. In 1935 Wright decided to follow P&W's lead, and started to develop much larger engines based on the mechanicals of the Cyclone. The result were two designs with a somewhat shorter stroke, a 14 cylinder design that would evolve into the Wright R-2600
, and a much larger 18 cylinder design that became the R-3350. An even larger 2-row 22 cylinder version, the R-4090, was experimented with as a competitor to the R-4360 but was not produced.
The first R-3350 was run in May 1937. Continued development was slow, both due to the complex nature of the engine, as well as the R-2600 receiving considerably more attention. The R-3350 didn't fly until 1941, after the prototype Douglas XB-19
had been re-designed from the Allison V-3420
to the R-3350.
Things changed dramatically in 1940 with the introduction of a new contract by the USAAC to develop a long-range bomber capable of flying from the US to Germany with a 2,000 lb (900 kg) bomb load. Although smaller than the Bomber D designs that led to the B-19, the new designs required roughly the same amount of power. When preliminary designs were returned in the summer of 1940, three of the four designs were based on the R-3350. Suddenly the engine was seen as the future of Army aviation, and serious efforts to get the design into production started.
By 1943 the ultimate development of the new bomber program, the B-29, was flying. However the engines remained temperamental, and showed an alarming tendency of the rear cylinders to overheat, partially due to minimal clearance between the cylinder baffles and the cowl. A number of changes were introduced into the aircraft production line in order to provide more cooling at low speeds, with the aircraft rushed into operational use in the Pacific in 1944. This proved unwise, as the early B-29 tactics of maximum weights combined with high temperature airfields produced overheating problems that were not completely solved, and the engines had a tendency to swallow their own valves. Because of a high magnesium
content in the crankcase alloy, the resulting engine fires were often so intense the main spar
could burn through in seconds, resulting in catastrophic wing failure.
Early versions of the R-3350 were equipped with carburetors, though the poorly designed elbow entrance to the supercharger led to serious problems with inconsistent fuel/air distribution. Near the end of World War II, the system was changed to use direct injection
where fuel was injected directly into the combustion chamber. This change improved engine reliability. After the war the engine was redesigned, and became a favorite for large aircraft, notably the Lockheed Constellation
and Douglas DC-7
.
Following the war, to better serve the civilian market, the Turbo-Compound
system was developed to deliver better fuel efficiency and thus economy. In these versions, three power recovery turbine
s (PRT) were inserted into the exhaust piping of each group of six cylinders and geared to the engine crankshaft by fluid coupling
s to deliver more power. The PRTs recovered about 20 percent of the exhaust energy (around 500 hp) that would have otherwise been wasted, but reduced engine reliability. Many aircraft mechanics of the day, nicknamed them "Parts Recovery Turbines" (and worse).
By this point, reliability had improved with the mean time between overhaul
s at 3,500 hours and specific fuel consumption in the order of 0.4 lb/hp/hour (243 g/kWh, giving it a 34% fuel efficiency). Engines still in use are now limited to 52 inches of mercury (1,760.9 hPa) manifold pressure, being 2,880 hp with 100/130 octane fuel (or 100LL) instead of the 59.5 inHg (2,014.9 hPa) and 3,400 HP possible with 115/145, or better, octane fuels, which are no longer available.
Several of the air racers at the Reno Air Races
are powered by R-3350s. Modifications on one, Rare Bear
, include a nose case designed for a slow-turning prop, taken from a R-3350 used on the Lockheed L-1649 Starliner
, mated to the power section (crankcase, crank, pistons, and cylinders) taken from a R-3350 used on the Douglas DC-7
. The supercharger is taken from a R-3350 used on the Lockheed EC-121 and the engine is fitted with Nitrous Oxide
injection. Normal rated power of a stock R-3350 is 2,800 horsepower at 2,600 rpm and 45 inches of manifold pressure. With these modifications, Rare Bear's engine produces 4,000 horsepower at 3,200 rpm and 80 inches of manifold pressure and 4,500 horsepower with Nitrous Oxide injection.
Radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...
aircraft engine
Aircraft engine
An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...
s produced in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. It was a twin row, supercharge
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
d, air-cooled, radial engine with 18 cylinders. Power ranged from 2,200 to over 3,700 hp (1,640 to 2,760 kW), depending on the model. First developed prior to World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, the R-3350's design required a long time to mature before finally being used to power the Boeing B-29 Superfortress. After the war, the engine had matured sufficiently to become a major civilian airliner design, notably in its Turbo-Compound
Turbo-compound engine
A turbo-compound engine is a reciprocating engine that employs a blowdown turbine to recover energy from the exhaust gases. The turbine is usually mechanically connected to the crankshaft but electric and hydraulic systems have been investigated as well. The turbine increases the output of the...
forms. The engine is now commonly used on Hawker Sea Fury
Hawker Sea Fury
The Hawker Sea Fury was a British fighter aircraft developed for the Royal Navy by Hawker during the Second World War. The last propeller-driven fighter to serve with the Royal Navy, it was also one of the fastest production single piston-engined aircraft ever built.-Origins:The Hawker Fury was an...
and Grumman F8F Bearcat Unlimited Class Racers at the Reno Air Races
Reno Air Races
The Reno Air Races, also known as the National Championship Air Races, take place each September at the Reno Stead Airport a few miles north of Reno, Nevada, USA...
.
Design and development
In 1927, Wright AeronauticalWright Aeronautical
Wright Aeronautical was an aircraft and aircraft engine manufacturer located in New Jersey.-History:This American company evolved from the 1909-1916 Wright Company, which merged with the Glenn L. Martin Company in 1916 to form the Wright-Martin Aircraft Corporation. Glenn Martin resigned from...
introduced its famous "Cyclone" engine, which powered a number of designs in the 1930s. After merging with Curtiss to become Curtiss-Wright
Curtiss-Wright
The Curtiss-Wright Corporation was the largest aircraft manufacturer in the United States at the end of World War II, but has evolved to largely become a component manufacturer, specializing in actuators, aircraft controls, valves, and metalworking....
in 1929, an effort was started to redesign the engine to the 1,000 hp (750 kW) class. The new Wright R-1820
Wright R-1820
|-See also:-References:* Bridgman, L, Jane's Fighting Aircraft of World War II. Crescent. ISBN 0-517-67964-7* Eden, Paul & Soph Moeng, The Complete Encyclopedia of World Aircraft. Amber Books Ltd. Bradley's Close, 74-77 White Lion Street, London, NI 9PF, 2002, ISBN 0-7607-3432-1), 1152...
Cyclone 9 first ran successfully in 1935, and would become one of the most-used aircraft engines in the 1930s and World War II.
At about the same time Pratt & Whitney
Pratt & Whitney
Pratt & Whitney is a U.S.-based aerospace manufacturer with global service operations. It is a subsidiary of United Technologies Corporation . Pratt & Whitney's aircraft engines are widely used in both civil aviation and military aviation. Its headquarters are in East Hartford, Connecticut, USA...
had started a development of their equally famous Wasp
Pratt & Whitney Wasp
-External links:*...
design into a larger and much more powerful two-row design that would easily compete with this larger Cyclone. In 1935 Wright decided to follow P&W's lead, and started to develop much larger engines based on the mechanicals of the Cyclone. The result were two designs with a somewhat shorter stroke, a 14 cylinder design that would evolve into the Wright R-2600
Wright R-2600
|-See also:-Bibliography:* Jane's Fighting Aircraft of World War II. London. Studio Editions Ltd, 1998. ISBN 0-517-67964-7-External links:...
, and a much larger 18 cylinder design that became the R-3350. An even larger 2-row 22 cylinder version, the R-4090, was experimented with as a competitor to the R-4360 but was not produced.
The first R-3350 was run in May 1937. Continued development was slow, both due to the complex nature of the engine, as well as the R-2600 receiving considerably more attention. The R-3350 didn't fly until 1941, after the prototype Douglas XB-19
Douglas XB-19
|-See also:-External links:* * * * * Popular Mechanics, December 1940* Popular Mechanics, July 1941*...
had been re-designed from the Allison V-3420
Allison V-3420
|-See also:-References:* Bridgman, L, Jane's fighting aircraft of World War II. Crescent. ISBN 978-0-517-67964-7-External links:...
to the R-3350.
Things changed dramatically in 1940 with the introduction of a new contract by the USAAC to develop a long-range bomber capable of flying from the US to Germany with a 2,000 lb (900 kg) bomb load. Although smaller than the Bomber D designs that led to the B-19, the new designs required roughly the same amount of power. When preliminary designs were returned in the summer of 1940, three of the four designs were based on the R-3350. Suddenly the engine was seen as the future of Army aviation, and serious efforts to get the design into production started.
By 1943 the ultimate development of the new bomber program, the B-29, was flying. However the engines remained temperamental, and showed an alarming tendency of the rear cylinders to overheat, partially due to minimal clearance between the cylinder baffles and the cowl. A number of changes were introduced into the aircraft production line in order to provide more cooling at low speeds, with the aircraft rushed into operational use in the Pacific in 1944. This proved unwise, as the early B-29 tactics of maximum weights combined with high temperature airfields produced overheating problems that were not completely solved, and the engines had a tendency to swallow their own valves. Because of a high magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
content in the crankcase alloy, the resulting engine fires were often so intense the main spar
Spar
In sailing, a spar is a pole of wood, metal or lightweight materials such as carbon fiber used on a sailing vessel. Spars of all types In sailing, a spar is a pole of wood, metal or lightweight materials such as carbon fiber used on a sailing vessel. Spars of all types In sailing, a spar is a...
could burn through in seconds, resulting in catastrophic wing failure.
Early versions of the R-3350 were equipped with carburetors, though the poorly designed elbow entrance to the supercharger led to serious problems with inconsistent fuel/air distribution. Near the end of World War II, the system was changed to use direct injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....
where fuel was injected directly into the combustion chamber. This change improved engine reliability. After the war the engine was redesigned, and became a favorite for large aircraft, notably the Lockheed Constellation
Lockheed Constellation
The Lockheed Constellation was a propeller-driven airliner powered by four 18-cylinder radial Wright R-3350 engines. It was built by Lockheed between 1943 and 1958 at its Burbank, California, USA, facility. A total of 856 aircraft were produced in numerous models, all distinguished by a...
and Douglas DC-7
Douglas DC-7
The Douglas DC-7 is an American transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. It was the last major piston engine powered transport made by Douglas, coming just a few years before the advent of jet aircraft such as the Boeing 707 and Douglas DC-8.-Design and...
.
Following the war, to better serve the civilian market, the Turbo-Compound
Turbo-compound engine
A turbo-compound engine is a reciprocating engine that employs a blowdown turbine to recover energy from the exhaust gases. The turbine is usually mechanically connected to the crankshaft but electric and hydraulic systems have been investigated as well. The turbine increases the output of the...
system was developed to deliver better fuel efficiency and thus economy. In these versions, three power recovery turbine
Turbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...
s (PRT) were inserted into the exhaust piping of each group of six cylinders and geared to the engine crankshaft by fluid coupling
Fluid coupling
A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch...
s to deliver more power. The PRTs recovered about 20 percent of the exhaust energy (around 500 hp) that would have otherwise been wasted, but reduced engine reliability. Many aircraft mechanics of the day, nicknamed them "Parts Recovery Turbines" (and worse).
By this point, reliability had improved with the mean time between overhaul
Time between overhaul
One important measure of an aircraft engine's overall economics is how often it has to be overhauled, the so-called time between overhaul, typically seen as TBO or TBOH....
s at 3,500 hours and specific fuel consumption in the order of 0.4 lb/hp/hour (243 g/kWh, giving it a 34% fuel efficiency). Engines still in use are now limited to 52 inches of mercury (1,760.9 hPa) manifold pressure, being 2,880 hp with 100/130 octane fuel (or 100LL) instead of the 59.5 inHg (2,014.9 hPa) and 3,400 HP possible with 115/145, or better, octane fuels, which are no longer available.
Several of the air racers at the Reno Air Races
Reno Air Races
The Reno Air Races, also known as the National Championship Air Races, take place each September at the Reno Stead Airport a few miles north of Reno, Nevada, USA...
are powered by R-3350s. Modifications on one, Rare Bear
Rare Bear
Rare Bear is a highly-modified Grumman F8F Bearcat that dominated the Reno Air Races for decades.-History:The Bearcat that became Rare Bear was a severely damaged wreck when discovered by Lyle Shelton in 1969. It had been abandoned next to a runway in Valparaiso, Indiana after it crashed there,...
, include a nose case designed for a slow-turning prop, taken from a R-3350 used on the Lockheed L-1649 Starliner
Lockheed L-1649 Starliner
The Lockheed L-1649 Starliner was the last model of the Lockheed Constellation line. Powered by four Wright R-3350 TurboCompound engines, it was built at Lockheed's Burbank, California plant from 1956 to 1958.-Design and Development:...
, mated to the power section (crankcase, crank, pistons, and cylinders) taken from a R-3350 used on the Douglas DC-7
Douglas DC-7
The Douglas DC-7 is an American transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. It was the last major piston engine powered transport made by Douglas, coming just a few years before the advent of jet aircraft such as the Boeing 707 and Douglas DC-8.-Design and...
. The supercharger is taken from a R-3350 used on the Lockheed EC-121 and the engine is fitted with Nitrous Oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
injection. Normal rated power of a stock R-3350 is 2,800 horsepower at 2,600 rpm and 45 inches of manifold pressure. With these modifications, Rare Bear's engine produces 4,000 horsepower at 3,200 rpm and 80 inches of manifold pressure and 4,500 horsepower with Nitrous Oxide injection.
Variants
- R-3350-13 : 2,200 hp (1,600 kW)
- R-3350-23 : 2,200 hp (1,600 kW)
- R-3350-24W : 2,500 hp (1,900 kW)
- R-3350-26W : 2,800 hp (2,100 kW)
- R-3350-32W : 3,700 hp (2,800 kW)
- R-3350-42WA : 3,800 hp (2,830 kW)
- R-3350-53 : 2,700 hp (2,000 kW)
- R-3350-57 : 2,200 hp (1,600 kW)
- R-3350-85 : 2,500 hp (1,900 kW)
- R-3350-89A : 3,500 hp (2,600 kW)
- R-3350-93W : 3,500 hp (2,600 kW)
Applications
- Beechcraft XA-38 Grizzly
- Boeing B-29 Superfortress
- Boeing XC-97 Stratofreighter
- Boeing XPBB Sea Ranger
- Canadair CP-107 Argus
- Consolidated B-32 Dominator
- Curtiss XBTC-2
- Curtiss XF14C
- Curtiss XP-62Curtiss XP-62|-See also:-References:* Green, William. War Planes of the Second World War - Fighters, Volume 4. London: Macdonald. 1961.-External links:*...
- Douglas A-1 Skyraider
- Douglas BTD Destroyer
- Douglas DC-7Douglas DC-7The Douglas DC-7 is an American transport aircraft built by the Douglas Aircraft Company from 1953 to 1958. It was the last major piston engine powered transport made by Douglas, coming just a few years before the advent of jet aircraft such as the Boeing 707 and Douglas DC-8.-Design and...
- Douglas XB-31Douglas XB-31|-See also:-References:NotesBibliography* Francillon, René J. McDonnell Douglas Aircraft since 1920. London: Putnam & Company Ltd., 1979. ISBN 0-370-00050-1....
- Fairchild C-119 Flying Boxcar
- Fairchild AC-119Fairchild AC-119|-See also:-References:NotesBibliography* Hobson, Chris. "Vietnam Air Losses, USAF/USN/USMC, Fixed-Wing Aircraft Losses in Southeast Asia, 1961-1973." North Branch, Minnesota: Specialty Press, 2001. ISBN 1-85780-1156....
- Lockheed ConstellationLockheed ConstellationThe Lockheed Constellation was a propeller-driven airliner powered by four 18-cylinder radial Wright R-3350 engines. It was built by Lockheed between 1943 and 1958 at its Burbank, California, USA, facility. A total of 856 aircraft were produced in numerous models, all distinguished by a...
- Lockheed L-049 ConstellationLockheed L-049 ConstellationThe Lockheed L-049 Constellation was the first model of the Lockheed Constellation aircraft line. It entered service as the C-69 military transport aircraft during World War II for the United States Army Air Forces and was the first civilian version after the war...
- Lockheed C-69 ConstellationLockheed C-69 ConstellationThe Lockheed C-69 Constellation was the first military version of the Lockheed Constellation aircraft line. It first flew in 1943, and only 22 were ever constructed for the United States Army Air Forces...
- Lockheed L-649 ConstellationLockheed L-649 Constellation-See also:- Sources :CitationsBibliography* Breffort, Dominique. Lockheed Constellation: from Excalibur to Starliner Civilian and Military Variants. Paris: Histoire and Collecions, 2006. Print. ISBN 2915239622-External links:...
- Lockheed L-749 ConstellationLockheed L-749 Constellation-See also:- References :CitationsBibliography* Breffort, Dominique. Lockheed Constellation: from Excalibur to Starliner Civilian and Military Variants. Paris: Histoire and Collecions, 2006. Print. ISBN 2915239622-External Links:...
- Lockheed L-1049 Super ConstellationLockheed L-1049 Super ConstellationThe Lockheed L-1049 Super Constellation is an aircraft in the Lockheed Constellation aircraft line. The aircraft was Lockheed's response to the successful Douglas DC-6 airliner and first flew in 1950...
- Lockheed C-121 Constellation
- Lockheed R7V-1 Constellation
- Lockheed EC-121 Warning Star
- Lockheed L-1649A Starliner
- Lockheed P-2 Neptune
- Lockheed XB-30Lockheed XB-30-See also:-References:NotesBibliography* Stringfellow, Curtis K., and Peter M. Bowers. Lockheed Constellation. St. Paul, Minnesota: Motorbooks, 1992.-External links:*...
- Martin JRM Mars
- Martin XB-33 Super Marauder
- Martin P5M Marlin
- Stroukoff YC-134Stroukoff YC-134-See also:...