The Wright R-760 Whirlwind was a series of seven-cylinder 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 An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...

s built by the

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 ...

division of

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 ...

. 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 Stroke is a medical condition in which poor cerebral circulation, blood flow to a part of the brain causes cell death. There are two main types of stroke: brain ischemia, ischemic, due to lack of blood flow, and intracranial hemorrhage, hemor ...

of 5.5 in (14.0 cm) was unchanged, but the cylinder bore 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 A naturally aspirated engine, also known as a normally aspirated engine, and abbreviated to N/A or NA, is an internal combustion engine in which air intake depends solely on atmospheric pressure and does not have forced induction through a turboc ...

, 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 (engine), displacement. It is a form of forced induction that is mechanically ...

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 a piston engine, the cylinder head sits above the cylinders, forming the roof of the combustion chamber. In sidevalve engines the head is a simple plate of metal containing the spark plugs and possibly heat dissipation fins. In more modern ...

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 r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...

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 biplane trainer manufactured by the Consolidated Aircraft Corporation and 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 N ...

, the Curtiss N2C Fledgling, and the

Naval Aircraft Factory The Naval Aircraft Factory (NAF) was established by the United States Navy in 1918 in Philadelphia, Pennsylvania. It was created to help solve aircraft supply issues which the United States Department of the Navy, Navy Department faced upon the ...

N3N Canary The Naval Aircraft Factory N3N is 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 ...

. 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 A utility aircraft is a general-purpose light airplane or helicopter, usually used for transporting people, freight, or other supplies, but also used for other duties when more specialized aircraft are not required or available. The term can al ...

also used the R-760, including models built by

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

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 manufactu ...

, Howard DGA-8,

Stearman Stearman is a surname. Notable people with the name include: * Josiah Stearman (born 2003), American chess master * Lloyd Stearman (1898–1975), American aviation pioneer * Richard Stearman (born 1987), English footballer * William Stearman ( ...

, Stinson, and

Waco Waco ( ) is a city in and 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 U.S. census estimated 2024 population of 146,608, making i ...

. 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, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

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

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 in

McMinnville, Oregon McMinnville is the county seat of and the most populous city in Yamhill County, Oregon, Yamhill County, Oregon, United States at the base of the Oregon Coast Range. The city is named after McMinnville, Tennessee. As of the 2020 United States cens ...

.. 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 a Federal government of the United States, U.S. federal government agency within the United States Department of Transportation, U.S. Department of Transportation that regulates civil aviation in t ...

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

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