The Wright R-975 Whirlwind was a series of nine-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 of about and power ratings of . They were the largest members of the Wright Whirlwind engine family to be produced commercially, and they were also the most numerous. During

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, Continental Motors built the R-975 under license as a powerplant for Allied tanks and other armored vehicles. Tens of thousands of engines were built for this purpose, dwarfing the R-975's usage in aircraft, where it was overshadowed by the similar

Pratt & Whitney R-985 The Pratt & Whitney R-985 Wasp Junior is a series of nine-cylinder, air-cooled, radial aircraft engines built by the Pratt & Whitney Aircraft Company from the 1930s to the 1950s. These engines have a displacement of ; initial versions produced , ...

. After the war, Continental continued to produce its own versions of the R-975 into the 1950s. Some of these produced as much as . The R-975 powered the American

M18 Hellcat tank destroyer which was claimed to have been the fastest tracked armored vehicle until the introduction of the turbine powered

M1 Abrams The M1 Abrams is a third-generation American main battle tank designed by Chrysler Defense (now General Dynamics Land Systems) and named for General Creighton Abrams. Conceived for modern armored ground warfare and now one of the heaviest ta ...

in the 1980s.

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 nine-cylinder version was originally known as the J-6 Whirlwind Nine, or J-6-9 for short. The U.S. government designated it as the R-975; Wright later adopted this and dropped the J-6 nomenclature. Like all the members of the J-6 Whirlwind family, the R-975 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-975, 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. Wright gradually developed the R-975, at first using suffix letters to indicate successive versions. The original R-975 (or J-6-9) was rated for 300 hp (224 kW),Curtiss-Wright (1940), p. 11 while the R-975E of 1931 could do 330 hp (246 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. 2Curtiss-Wright (1940), p. 13FAA Type Certificate Data Sheet ATC 21 Wright later added numeric suffixes to show different power levels. The R-975E-1, introduced the same year as the R-975E, was rated at 365 hp (272 kW) thanks to higher-compression pistons and a slightly 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 87 An even more powerful version, the R-975E-3, was also introduced that year, with greater supercharging and a still higher RPM limit, and was progressively refined until the final model of 1935 could reach 450 hp (336 kW) for takeoff.Curtiss-Wright (1940), pp. 14, 16, 18FAA Type Certificate Data Sheet TC 125

Operational history

As the most powerful Whirlwind to be produced commercially was also the most successful. It powered a wide variety of civil utility aircraft, such as the Beechcraft Staggerwing, and various airliners, such as the Ford 4-AT-E Trimotor and the Lockheed 10B Electra. In addition, it powered U.S. military training aircraft including the

North American BT-9 The North American BT-9 was the United States Army Air Corps (USAAC) designation for a low-wing single engine monoplane primary trainer aircraft that served before and during World War II. It was a contemporary of the Boeing-Stearman PT-13 Kay ...

and

Vultee BT-15 Valiant The Vultee BT-13 Valiant is an American World War II-era basic (a category between primary and advanced) trainer aircraft built by Vultee Aircraft for the United States Army Air Corps, and later US Army Air Forces. A subsequent variant of the ...

for the Army and the Curtiss-Wright SNC Falcon for the Navy. The

Curtiss F9C Sparrowhawk The Curtiss F9C Sparrowhawk is a light 1930s biplane fighter aircraft that was carried by the United States Navy airships and . It is an example of a parasite fighter, a small airplane designed to be deployed from a larger aircraft such as an ...

parasite fighter A parasite aircraft is a component of a composite aircraft which is carried aloft and air launched by a larger carrier aircraft or mother ship to support the primary mission of the carrier. The carrier craft may or may not be able to later recov ...

operated from U.S. Navy airships was also powered by the R-975. One notable record set by a Wright J-6 Whirlwind-powered aircraft occurred during July 28–30, 1931, when

Russell Norton Boardman Russell Boardman (1898–July 1, 1933) was an early American aviation pioneer who, along with John Polando, flew from Floyd Bennett Field to Istanbul, Turkey in 1931 to set an aviation record for the longest continuous distance flown without refue ...

and

John Louis Polando John Polando (1901–1985) was an early American aviation pioneer who, along with Russell Boardman, flew from Floyd Bennett Field to Istanbul in 1931 to set an aviation record for the longest continuous distance flown without refueling. Following t ...

flew non-stop from Floyd Bennett Field, on

Long Island Long Island is a densely populated island in the southeastern region of the U.S. state of New York (state), New York, part of the New York metropolitan area. With over 8 million people, Long Island is the most populous island in the United Sta ...

to Istanbul, Turkey in the ''Cape Cod'', a Bellanca Special J-300 high-wing

monoplane A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple planes. A monoplane has inherently the highest efficiency and lowest drag of any wing confi ...

in 49:20 hours, establishing a distance record of , the first nonstop record flight to surpasse . However, the R-975 faced heavy competition from

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

's R-985 Wasp Junior and from their larger R-1340 Wasp. Pratt & Whitney R-985 outsold the Wright R-975 by a wide margin. Wright's production of the R-975 ceased in 1945, with over 7,000 engines being produced by the company.

Production by Continental Motors

In 1939 the U.S. Army, which had been using Continental R-670 radial engines in its

light tank A light tank is a tank variant initially designed for rapid movements in and out of combat, to outmaneuver heavier tanks. It is smaller in size with thinner armor and a less powerful main gun, tailored for better tactical mobility and ease of ...

s, chose Continental Motors to build the R-975 under license as the engine for its M2

medium tank A medium tank is a classification of tanks, particularly prevalent during World War II which represented a compromise between the mobility oriented light tanks and the armour and armament oriented heavy tanks. A medium tank's classification is ...

s. Subsequently, the same engine was selected for the

M3 Lee The M3 Lee, officially Medium Tank, M3, was an American medium tank used during World War II. The turret was produced in two forms, one for US needs and one modified to British requirements to place the radio next to the commander. In British Co ...

medium tank, the

M4 Sherman } The M4 Sherman, officially Medium Tank, M4, was the most widely used medium tank by the Military history of the United States during World War II, United States and Allies of World War II, Western Allies in World War II. The M4 Sherman prove ...

medium tank, the Canadian

Ram tank The Tank, Cruiser, Ram was a cruiser tank designed and built by Canada in the Second World War, based on the U.S. M3 Medium tank chassis. Due to standardization on the American Sherman tank for frontline units, it was used exclusively for train ...

(which used the M3 chassis), the M7 Priest

self-propelled gun Self-propelled artillery (also called locomotive artillery) is artillery equipped with its own propulsion system to move toward its firing position. Within the terminology are the self-propelled gun, self-propelled howitzer, self-propelled mo ...

, the M18 Hellcat

tank destroyer A tank destroyer, tank hunter, tank killer, or self-propelled anti-tank gun is a type of armoured fighting vehicle, armed with a direct fire artillery gun or missile launcher, designed specifically to engage and destroy enemy tanks, often wi ...

, and other Allied armored vehicles based on these. Continental versions of the R-975 for armored vehicles included the R-975E-C2, the R-975-C1, and the R-975-C4. In contrast to the 7,000 built by Wright, Continental built over 53,000 R-975 engines. When installed in a tank, the R-975 did not have the benefit of being cooled by air slipstream or propeller blast, so a cooling fan was attached to the power shaft and surrounded by a shroud to provide the same effect. After the war, Continental introduced its own R-975 version for aircraft, the R9-A. Though it was basically similar to other R-975 engines, and its compression ratio and supercharger gear ratio were unchanged from the R-975E-3, other improvements in the R9-A allowed it to achieve for takeoff,FAA Type Certificate Data Sheet E-245 surpassing any Wright version. A military version, the R-975-46, could reach , and was used in Piasecki's HUP Retriever and H-25 Army Mule helicopters. Continental's production of R-975 engines continued into the 1950s.

Other license-built R-975s

The engine was built in

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...

as the Hispano-Suiza 9Q or Hispano-Wright 9Q without modification apart from the use of Hispano's patented nitriding finishing process and, on one version only, the 9Qdr, an epicyclic output speed reducer. The R-975 was also produced under licence by 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-6-9 (R-975) : at 2,000 RPM. ;R-975-20 : for airship use ;R-975E : at 2,000 RPM. Higher power from improved cylinder head. ;R-975E-1 : at 2,100 RPM. Higher compression ratio. ;R-975E-3 : at 2,200 RPM up to , at 2,250 RPM for takeoff. Increased supercharging, slightly higher compression ratio. ;R-975E-C2 : at 2,400 RPM. Built by Continental Motors under license for use in armored vehicles.Curtiss-Wright (1940), p. 19 ;Continental R9-A : at 2,300 RPM at , at 2,300 RPM for takeoff. Continental's improved post-war version. ;Hispano-Suiza 9Q :Licence built R-975 J-6 Whirlwind ;Hispano-Suiza 9Qa :variant of the Licence built R-975 J-6 Whirlwind ;Hispano-Suiza 9Qb :variant of the Licence built R-975 J-6 Whirlwind ;Hispano-Suiza 9Qc :variant of the Licence built R-975 J-6 Whirlwind ;Hispano-Suiza 9Qd :variant of the Licence built R-975 J-6 Whirlwind ;Hispano-Suiza 9Qdr :variant of the Licence built R-975 J-6 Whirlwind

Applications

Wright J-6-9 and R-975

ASJA L2 __NOTOC__ The ASJA L2 was a Swedish biplane trainer aircraft built for the Swedish Air Force in the early 1930s. It was designated Ö 9 in that service. The fuselage was of fabric-covered, welded steel tube construction and accommodated the pilot ...

* Avro Anson Mk IV * Beechcraft Staggerwing B17R, C17R, and D17R *

Bellanca CH-300 Pacemaker The Bellanca CH-300 Pacemaker was a six-seat utility aircraft, built primarily in the United States in the 1920s and 1930s. It was a development of the Bellanca CH-200, fitted with a more powerful engine and, like the CH-200, soon became renowne ...

* Berliner-Joyce OJ-2 * Caribbean Traders Husky III * Cessna DC-6A Chief * Curtiss Kingbird * Curtiss-Wright CW-14 Travel Air/Speedwing/Sportsman Deluxe/Osprey *

Curtiss-Wright CW-22 The Curtiss-Wright CW-22 was a 1940s American general-purpose advanced training monoplane aircraft built by the Curtiss-Wright Corporation. It was operated by the United States Navy as a scout trainer with the designation SNC-1 Falcon. Design a ...

* Curtiss-Wright SNC-1 Falcon * de Havilland DH.75B Hawk Moth *

Dewoitine D.31 Constructions Aéronautiques Émile Dewoitine was a French aircraft manufacturer established by Émile Dewoitine at Toulouse in October 1920. The company's initial products were a range of metal parasol-wing fighters which were largely ignored by th ...

Dewoitine D.35 The Dewoitine D.35 was a small, single-engine passenger transport aircraft built and flown by Dewoitine in France for their own use in the early 1930s. Only one was produced. Design and development The D.35 was built solely as a company taxi t ...

* Douglas RD-1 & C-21/OA-3 Dolphin * Emsco B-5 Challenger * Goodyear K-1 *

Fokker Universal The Fokker Universal was the first aircraft built in the United States that was based on the designs of Dutch-born Anthony Fokker, who had designed aircraft for the Germans during World War I. About half of the 44 Universals that were built betwe ...

Fokker C-5 The Fokker F.VII, also known as the Fokker Trimotor, was an airliner produced in the 1920s by the Dutch aircraft manufacturer Fokker, Fokker's American subsidiary Atlantic Aircraft Corporation, and other companies under licence. Design and dev ...

* Fokker C-7 *

Fokker C.XIV The Fokker CXIV-W was a reconnaissance seaplane produced in the Netherlands in the 1930s. It was a conventional, single-bay A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aer ...

Fokker T.VIII The Fokker T.VIII is a twin-engined torpedo bomber and aerial reconnaissance floatplane designed and manufactured by the Dutch aviation company Fokker. It was developed in the late 1930s as a successor to the Fokker T.IV. While the Dutch Nava ...

* Ford 4-AT-E Trimotor *

Interstate XTD3R The Interstate TDR was an early unmanned combat aerial vehicle — referred to at the time as an " assault drone" — developed by the Interstate Aircraft and Engineering Corporation during the Second World War for use by the United States Navy ...

Ireland N-2B Neptune The Ireland Neptune was a four or five place pusher configuration biplane sold in flying boat and amphibian versions. Designed in the U.S. and first flown in 1927, well over 50 were built. Design and development The Neptune was a biplane w ...

Keystone XOK The Keystone XOK was an American biplane observation floatplane developed for the United States Navy during the early 1930s. Design and development In 1929, the Navy issued requirements calling for an observation floatplane intended for service a ...

* Keystone-Loening K-84 Commuter *

Koolhoven F.K.56 The Koolhoven F.K.56 was a 1930s Netherlands, Dutch basic training monoplane designed and built by Koolhoven (aircraft manufacturer), Koolhoven. Development The F.K.56 was a low-wing monoplane powered by a 450 hp (336 kW) Wright Whirlw ...

* Lockheed Model 12B Electra Junior * McDonnell XV-1 * Messerschmitt M 18 * Noorduyn Norseman Mk.1 *

North American NA-57 The North American Aviation NA-16 was the first trainer aircraft built by North American Aviation, and was the beginning of a line of closely related North American trainer aircraft that would eventually number more than 17,000 examples, notabl ...

North American NA-64 Yale The North American NA-64 (NA-64 P-2 or NAA-64 P-2 in French service, Yale in Canadian service) is a low-wing single piston engine monoplane advanced trainer aircraft that was built for the French Air Force and French Navy, served with the Royal ...

Pitcairn PA-19 __NOTOC__ The Pitcairn PA-19 was a four-seat autogyro developed in the United States in the early 1930s.Taylor 1989, p.735 While most of Pitcairn's autogyro designs featured open cockpits in tandem, the PA-19 had a fully enclosed cabin.''The Ill ...

* Pitcairn-Cierva PCA-2/OP-1 * Pitcairn PA-33 & 34/OP-2 *

Ryan B-5 Brougham The Ryan Brougham was a small single-engine airliner produced in the United States in the late 1920s and early 1930s.Taylor 1989, p. 772. Its design was reminiscent of the M-1 mailplane first produced by Ryan in 1926, and like it, was a high-wi ...

* Spartan C4-300 * Stearman Model 6C Cloudboy * Stinson SM-1F Detroiter * Timm T-840 *

Townsend Thunderbird The Townsend Thunderbird is a homebuilt design created by the experienced cropduster Gid Townsend and built in 1956 with assistance of Curtis Pitts. Design The Thunderbird is powered by a Jacobs radial engine with a constant speed propeller. ...

(as rebuilt) * Travel Air B9-4000 *

Travel Air 6000B The Travel Air 6000 (later known as the Curtiss-Wright 6B when Travel Air was purchased by Curtiss-Wright) was a six-seat utility aircraft manufactured in the United States in the late 1920s. Design and development It was developed as a luxury ve ...

Travel Air Type R Mystery Ship The Type R "Mystery Ships" were a series of wire-braced, low-wing racing airplanes built by the Travel Air company in the late 1920s and early 1930s. They were so called, because the first three aircraft of the series (R614K, R613K, B11D) were bui ...

* VL Pyry *

Waco JTO The Waco 10/GXE/Waco O series was a range of three-seat open-cockpit biplanes built by the Advance Aircraft Company, later the Waco Aircraft Company. Design and development The Waco 10 was a larger span development of the Waco 9, both single-eng ...

* Waco JYO * Waco JWM and JYM Mailplanes *

Continental R-975

The British Army in North Africa 1942 E13233

* Beech D-18C *

Grizzly I cruiser The Grizzly I was a Canadian-built M4A1 Sherman tank with relatively minor modifications, primarily to stowage and pioneer tool location and adding accommodations for a number 19 radio set. They used the same General Steel hull castings as late ...

- Canadian production of M4A1 Sherman tank *

Kangaroo Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern gre ...

armoured personnel carrier An armoured personnel carrier (APC) is a broad type of armoured military vehicle designed to transport personnel and equipment in combat zones. Since World War I, APCs have become a very common piece of military equipment around the world. Acc ...

modification of M7 Priest and other vehicles *

Kellett XR-10 The Kellett XR-10 was a military transport helicopter developed in the United States in the 1940s that only flew in prototype form. It was designed in response to a USAAF Technical Instruction issued for the development of a helicopter to transpo ...

* M7 Priest * M18 Hellcat *

M12 Gun Motor Carriage The 155 mm Gun Motor Carriage M12 was a U.S. self-propelled gun developed during the Second World War. It mounted a 155 mm gun derived from the French Canon de 155mm GPF field gun. Development The idea for the M12 was first proposed i ...

M40 Gun Motor Carriage The 155 mm Gun Motor Carriage M40 was an American self-propelled artillery vehicle built on a widened and lengthened Medium Tank M4A3 chassis, but with a Continental engine and with HVSS (Horizontal Volute Spring Suspension), which was intro ...

* McDonnell XV-1 * Piasecki HUP Retriever *

* Sexton self-propelled gun *

Sikorsky XHJS-1 The Sikorsky XHJS-1 (manufacturer designation S-53), was developed by Sikorsky Aircraft Sikorsky Aircraft is an American aircraft manufacturer based in Stratford, Connecticut. It was established by aviation pioneer Igor Sikorsky in 1923 and ...

(S-53) - prototype helicopter *

Skink anti-aircraft tank Tank AA, 20 mm Quad, Skink was a Canadian self-propelled anti-aircraft gun, developed in 1943–44, in response to a requirement from the First Canadian Army. Due to a lack of threat from the German , the Skink was cancelled in 1944 after ...

- anti-aircraft vehicle based on Grizzly I

Engines on display

Some museums which have R-975 engines on display: * Pima Air & Space Museum in Tucson,

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

has a Wright R-975. *

Hiller Aviation Museum The Hiller Aviation Museum is an aircraft history museum located at the San Carlos Airport in San Carlos, California. The museum was founded by Stanley Hiller in June 1998. and is endowed by members of the Hiller family. It specializes in North ...

in San Carlos,

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

has a Wright R-975. *

National Museum of Naval Aviation The National Naval Aviation Museum, formerly known as the National Museum of Naval Aviation and the Naval Aviation Museum, is a military and aerospace museum located at Naval Air Station Pensacola, Florida. Founded in 1962 and moved to its curr ...

near Pensacola,

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

has a Continental R-975. *

Southern Museum of Flight The Southern Museum of Flight is a civilian aviation museum Birmingham, Alabama. The facility features nearly 100 aircraft, as well as engines, models, artifacts, photographs, and paintings. In addition, the Southern Museum of Flight is home to ...

Birmingham Birmingham ( ) is a city and metropolitan borough in the metropolitan county of West Midlands in England. It is the second-largest city in the United Kingdom with a population of 1.145 million in the city proper, 2.92 million in the West ...

Alabama (We dare defend our rights) , anthem = "Alabama (state song), Alabama" , image_map = Alabama in United States.svg , seat = Montgomery, Alabama, Montgomery , LargestCity = Huntsville, Alabama, Huntsville , LargestCounty = Baldwin County, Al ...

has a Continental R-975. * Queensland Air Museum in Caloundra,

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

has a Continental R-975.. This page has
photo of a Continental R-975
* Lake Boga Catalina Museum (Lake Boga, Victoria, Australia) has a Continental Wright R-975.

Specifications (Whirlwind R-975E-3)

References

Notes

Bibliography

*. Available from the Aircraft Engine Historical Society'

* *. 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-975E: . *R-975E-1: . *R-975E-3: . *Continental R9-A: .

External links

* Engine Data Sheets: US Aero Engines �

{{US military piston aeroengines Aircraft air-cooled radial piston engines R-975 1920s aircraft piston engines Tank engines