The Wright R-760 Whirlwind was a series of seven-cylinder air-cooled radial

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many ...

s built by the Wright Aeronautical division of Curtiss-Wright. These engines had a

displacement Displacement may refer to: Physical sciences Mathematics and Physics *Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...

of 756 in³ (12.4 L) and power ratings of 225-350 hp (168-261 kW).

Design and development

Wright introduced the J-6 Whirlwind family in 1928 to replace the nine-cylinder R-790 series. The J-6 family included varieties with five, seven, and nine cylinders. The seven-cylinder version was originally known as the J-6 Whirlwind Seven, or J-6-7 for short. The U.S. government designated it as the R-760; Wright later adopted this and dropped the J-6 nomenclature. Like all the members of the J-6 Whirlwind family, the R-760 had larger cylinders than the R-790. The piston

stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...

of 5.5 in (14.0 cm) was unchanged, but the cylinder

bore Bore or Bores often refer to: *Boredom * Drill Relating to holes * Boring (manufacturing), a machining process that enlarges a hole ** Bore (engine), the diameter of a cylinder in a piston engine or a steam locomotive ** Bore (wind instruments), ...

was expanded to 5.0 in (12.7 cm) from the R-790's bore of 4.5 in (11.4 cm). While the R-790 was

naturally aspirated Naturally may refer to: ;Albums * ''Naturally!'', an album by Nat Adderley * ''Naturally'' (Houston Person album) * ''Naturally'' (J. J. Cale album) * ''Naturally'' (John Pizzarelli album) * ''Naturally'' (Sharon Jones album) * ''Naturally'' ...

, the R-760, like the other J-6 engines, had a gear-driven

supercharger In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement. The current categorisation is that a supercharger is a form of forced induct ...

to boost its power output. Over time, Wright refined the R-760, using suffix letters to indicate successive versions. The original R-760 (or J-6-7) was rated for 225 hp (168 kW),Curtiss-Wright (1940), p. 11 while the R-760E of 1931 could do 250 hp (186 kW) thanks to an improved

cylinder head In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber. In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ov ...

design.Curtiss-Wright (1983), p. 1Curtiss-Wright (1940), p. 13FAA Type Certificate Data Sheet ATC 26 Wright later added another suffix to show different power levels. The R-760E-1, introduced the same year as the R-760E, had a takeoff power rating of 300 hp (224 kW) thanks to higher-compression pistons and a greater

RPM Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...

limit.Curtiss-Wright (1940), p. 14FAA Type Certificate Data Sheet TC 94 The even more powerful R-760E-2 of 1935 could reach 350 hp (261 kW) for takeoff due to increased supercharging and an even higher RPM limit.Curtiss-Wright (1940), p. 17FAA Type Certificate Data Sheet TC 155 On the other hand, the R-760E-T, designed for trainer aircraft, had the R-760E-1's high-compression pistons, but the supercharger was removed, thus giving just 235 hp (175 kW).Curtiss-Wright (1940), p. 16FAA Type Certificate Data Sheet TC 126

Operational history

The R-760 was a direct replacement for the R-790, with similar displacement and power. The U.S. Navy used it as the powerplant for several biplane primary trainers, including the

Consolidated NY The Consolidated Model 2 was a PT-1 biplane trainer diverted to the United States Navy for a trainer competition in 1925. It beat out 14 other designs, and was ordered into production as the NY-1."The Complete Encyclopedia of World Aircraftcover ...

, the Curtiss N2C Fledgling, and the

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N3N Canary. The last of these was produced in large numbers, with most of the engines built under license by the Naval Aircraft Factory. Trainers usually had the unsupercharged R-760E-T engine. A variety of civil utility aircraft also used the R-760, including models built by

Beechcraft Beechcraft is an American brand of civil aviation and military aircraft owned by Textron Aviation since 2014, headquartered in Wichita, Kansas. Originally, it was a brand of Beech Aircraft Corporation, an American manufacturer of general aviati ...

Cessna Cessna () is an American brand of general aviation aircraft owned by Textron Aviation since 2014, headquartered in Wichita, Kansas. Originally, it was a brand of the Cessna Aircraft Company, an American general aviation aircraft manufacturing c ...

, Curtiss-Wright, Howard DGA-8,

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, Stinson, and

Waco Waco ( ) is the county seat of McLennan County, Texas, United States. It is situated along the Brazos River and I-35, halfway between Dallas and Austin. The city had a 2020 population of 138,486, making it the 22nd-most populous city in the st ...

. These aircraft generally used the various supercharged versions of the R-760. Production of the R-760 continued until 1945, with about 1400 examples being built by Wright, and more under licence by foreign manufacturers such as Fábrica Nacional de Motores in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

Variants

* J-6-7 (R-760): 225 hp (168 kW) at 2,000 RPM. * R-760E: 250 hp (186 kW) at 2,000 RPM. Higher power from improved cylinder head. * R-760E-1: 285 hp (213 kW) at 2,100 RPM, 300 hp (224 kW) at 2,250 RPM for takeoff. Higher compression ratio. * R-760E-2: 320 hp (239 kW) at 2,200 RPM, 350 hp (261 kW) at 2,400 RPM for takeoff. Increased supercharging, slightly higher compression ratio. * R-760E-T: 235 hp (175 kW) at 2,000 RPM. Naturally aspirated version of R-760E-1 for trainer aircraft. * R-760-2, -4, -8: 235 hp (175 kW) at 2,000 RPM. U.S. Navy versions of R-760E-T.

Applications

* Abrams P-1 Explorer * Beechcraft Staggerwing * Cessna DC-6B Scout * Consolidated NY-3 * Curtiss N2C-2 Fledgling * Curtiss-Wright CW-A-14D Sportsman Deluxe *

Fairchild Model 45 The Fairchild Model 45 was a 1930s American five-seat cabin monoplane aircraft designed and built by Fairchild. Development During 1934 the Fairchild company designed a business or executive aircraft with five seats, designated the Model 45. It ...

* Howard DGA-8 and DGA-15W *

Naval Aircraft Factory N3N Canary The Naval Aircraft Factory N3N was an American tandem-seat, open cockpit, primary training biplane aircraft built by the Naval Aircraft Factory (NAF) in Philadelphia, Pennsylvania, during the 1930s and early 1940s. Development and design Built t ...

St. Louis YPT-15 __NOTOC__ The St. Louis YPT-15 was an American two-seat primary training biplane, built by the St. Louis Aircraft Corporation for use by the United States Army Air Corps. 13 examples of the type were acquired, serving in the late 1930s. Design a ...

* Stearman C3R Business Speedster *

Stinson Junior The Stinson Junior was a high-winged American monoplane of the late 1920s, built for private owners, and was one of the first such designs to feature a fully enclosed cabin. Design and development Stinson Aircraft had introduced their large high-w ...

Stinson Reliant The Stinson Reliant is a popular single-engine four- to five-seat high-wing monoplane manufactured by the Stinson Aircraft Division of the Aviation Manufacturing Corporation of Wayne, Michigan. Design and development The Reliant is a high-win ...

* Waco CSO and CTO * Waco CJC, CJC-S, DJC, DJC-S, and DJS * Waco CUC, DQC-6, EQC-6, DGC-7 & 8, EGC-7 & 8 *

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Engines on display

Wright R-760 engines on display are uncommon, but there is an R-760E-2 exhibited at the

Evergreen Aviation & Space Museum The Evergreen Aviation & Space Museum is an aviation museum in McMinnville, Oregon. Its exhibits include the Hughes H-4 Hercules (''Spruce Goose'') and more than fifty military and civilian aircraft, unmanned aerial vehicles (drones), and spac ...

in McMinnville, Oregon.. This personal collection of museum aircraft engine photos includes a photo of the museum's R-760E-2 under the section for the Evergreen Aviation Museum.

Specifications (R-760E-2)

References

Notes

Bibliography

*Gunston, Bill. ''World Encyclopedia of Aero Engines''. Cambridge, England. Patrick Stephens Limited, 1989. *''Jane's Fighting Aircraft of World War II''. London. Studio Editions Ltd, 1989. *. Available from the Aircraft Engine Historical Society'
reference page
*. Available from the Aircraft Engine Historical Society'

The following

Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...

type certificate A type certificate signifies the airworthiness of a particular category of aircraft, according to its manufacturing design (''type design''). It confirms that the aircraft of a new type intended for serial production, is in compliance with applica ...

data sheets, all available from the FAA'
Regulatory and Guidance Library
*R-760E: . *R-760E-1: . *R-760E-2: . *R-760E-T: . *R-760-2, -4, -8: .

External links

* Engine Data Sheets: US Aero Engines �

{{US military piston aeroengines 1920s aircraft piston engines Aircraft air-cooled radial piston engines R-760