The Wright R-975 Whirlwind was a series of nine-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 of about and power ratings of . They were the largest members of the

Wright Whirlwind The Wright Whirlwind was a family of air-cooled radial aircraft engines built by Wright Aeronautical (originally an independent company, later a division of Curtiss-Wright). The family began with nine-cylinder engines, and later expanded to in ...

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 (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 ...

, 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 engine, radial aircraft engines built by the Pratt & Whitney Aircraft Company from the 1930s to the 1950s. These engines have a Engine displacement, displace ...

. 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 The M18 Hellcat (officially designated the 76 mm Gun Motor Carriage M18 or M18 GMC) is a tank destroyer used by the United States Army in World War II and the Korean War. Despite being equipped with the same main gun as some variants of th ...

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, it is one of the heavies ...

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

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 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. 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 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 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 it was also the most successful. It powered a wide variety of civil utility aircraft, such as the

Beechcraft Staggerwing The Beechcraft Model 17 Staggerwing is an American biplane with an atypical negative wing Stagger (aviation), stagger (the lower wing is farther forward than the upper wing). It first flew in 1932, and was sold on the civilian market, being ...

, 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 K ...

and Vultee BT-15 Valiant for the Army and the

Curtiss-Wright SNC Falcon 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 of Curtiss, Wrigh ...

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 recove ...

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 and John Louis Polando flew non-stop from

Floyd Bennett Field Floyd Bennett Field is an airfield in the Marine Park, Brooklyn, Marine Park neighborhood of southeast Brooklyn in New York City, along the shore of Jamaica Bay. The airport originally hosted commercial and general aviation traffic before bein ...

, on

Long Island Long Island is a densely populated continental island in southeastern New York (state), New York state, extending into the Atlantic Ocean. It constitutes a significant share of the New York metropolitan area in both population and land are ...

Istanbul, Turkey Istanbul is the largest city in Turkey, constituting the country's economic, cultural, and historical heart. With a population over , it is home to 18% of the population of Turkey. Istanbul is among the largest cities in Europe and in th ...

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 wings. A monoplane has inherently the highest efficiency and lowest drag of any wing con ...

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 RTX Corporation (formerly Raytheon Technologies). Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially ...

'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 The Continental R-670 (factory designation W670) was a seven-cylinder four-stroke radial aircraft engine produced by Teledyne Continental Motors, Continental displacing 668 cubic inches (11 litres) and a dry weight of . Horsepower varied from 21 ...

radial engines in its

light tank A light tank is a Tank classification, tank variant initially designed for rapid movements in and out of combat, to outmaneuver heavier tanks. It is smaller with thinner vehicle armour, armor and a less powerful tank gun, main gun, tailored for ...

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 ...

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 different forms, one for US needs and one modified to British requirements to place the radio next to the commander. ...

medium tank, the

M4 Sherman The M4 Sherman, officially medium tank, M4, was the medium tank most widely used by the United States and Western Allies in World War II. The M4 Sherman proved to be reliable, relatively cheap to produce, and available in great numbers. I ...

medium tank, the Canadian

Ram tank The 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 training purposes a ...

(which used the M3 chassis), the

M7 Priest The 105 mm howitzer motor carriage M7 was an American self-propelled artillery vehicle produced during World War II. It was given the service name 105 mm self propelled, Priest by the British Army, due to the pulpit-like machine gun r ...

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

tank destroyer A tank destroyer, tank hunter or tank killer is a type of armoured fighting vehicle, predominantly intended for anti-tank duties. They are typically armed with a direct fire anti-tank gun, artillery gun, also known as a self-propelled anti-ta ...

, 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 Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

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 The Fábrica Nacional de Motores (FNM) was a Brazilian manufacturer of engines and motor vehicles based in the Xerém district of Duque de Caxias near Rio de Janeiro that operated between 1942 and 1988. In 2018, the manufacturer was refounded, c ...

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-6-9 (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 * Avro Anson Mk IV *

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 renowned ...

* Berliner-Joyce OJ-2 * Caribbean Traders Husky III * Cessna DC-6A Chief *

Curtiss Kingbird __NOTOC__ The Curtiss Model 55 Kingbird was an airliner built in small numbers in the United States in the early 1930s. It was a twin-engine aircraft with a fuselage derived from the single-engine Curtiss Thrush. The Kingbird had two engine nacel ...

* Curtiss-Wright CW-14 Travel Air/Speedwing/Sportsman Deluxe/Osprey *

Curtiss-Wright CW-22 The Curtiss-Wright CW-22 is a 1940s American general-purpose advanced Trainer (aircraft), training monoplane aircraft built by the Curtiss-WCurtiss-Wright Corporation. It was operated by the United States Navy as a Scout plane, scout trainer with ...

* Curtiss-Wright SNC-1 Falcon * de Havilland DH.75B Hawk Moth * Dewoitine D.31 *

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 Germany during World War I. About half of the 44 Universals that were built between 1 ...

* Fokker C-5 * 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 biplane with staggered wings of unequal span braced by N-struts. The pilot and observer sat in tandem, open cockpits, and ...

* Fokker T.VIII * Ford 4-AT-E Trimotor * Interstate XTD3R * Ireland N-2B Neptune * Keystone XOK * Keystone-Loening K-84 Commuter * Koolhoven F.K.56 * Lockheed Model 12B Electra Junior *

McDonnell XV-1 The McDonnell XV-1 is an experimental Convertiplane developed by McDonnell Aircraft for a joint research program between the United States Air Force and the United States Army to explore technologies to develop an aircraft that could take off a ...

Messerschmitt M 18 The Bayerische Flugzeugwerke M 18 (BFW M 18), (later known as Messerschmitt M 18) was an airliner, produced in Germany in the late 1920s. Design and development Designed at the request of Theodor Croneiss to supply his new airline venture which ...

* Noorduyn Norseman Mk.1 *

* North American NA-57 *

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 Ca ...

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 Illu ...

* Pitcairn-Cierva PCA-2/OP-1 * Pitcairn PA-33 & 34/OP-2 * Ryan B-5 Brougham * Spartan C4-300 * Stearman Model 6C Cloudboy * Stinson SM-1F Detroiter * Timm T-840 * Townsend Thunderbird (as rebuilt) * Travel Air B9-4000 * Travel Air 6000B *

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 two aircraft of the series (''R614K'', ''R613K'', together ...

VL Pyry VL Pyry (Finnish language for ''blizzard'') was a Finnish low-winged, two-seated fighter trainer aircraft, built by the State Aircraft Factory (''Valtion lentokonetehdas'') for use with the Finnish Air Force. The Pyry was in use from 1939 to 196 ...

* Vultee BT-15 Valiant * Waco JTO * 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 la ...

– Canadian production of M4A1 Sherman tank *

Kangaroo Kangaroos are 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 ...

M12 gun motor carriage The 155 mm gun motor carriage M12 was a U.S. self-propelled gun developed during World War II. It mounted a 155 mm gun derived from the French Canon de 155 mm GPF field gun. Development The idea for the M12 was first proposed in 1941 and t ...

* M40 gun motor carriage *

Piasecki HUP Retriever The Piasecki HUP Retriever or H-25 Army Mule, later UH-25, is a compact single radial engine, twin overlapping Tandem rotors, tandem rotor utility helicopter developed by the Piasecki Helicopter, Piasecki Helicopter Corporation of Morton, Pennsyl ...

* Sexton self-propelled gun * Sikorsky XHJS-1 (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 afte ...

– anti-aircraft vehicle based on Grizzly I

Engines on display

Some museums which have R-975 engines on display: *

Pima Air & Space Museum The Pima Air & Space Museum is an aerospace museum in Tucson, Arizona, US. It features a display of nearly 400 aircraft spread out over on a campus occupying . It has also been the home to the Arizona Aviation Hall of Fame since 1991. Overv ...

Tucson Tucson (; ; ) is a city in Pima County, Arizona, United States, and its county seat. It is the second-most populous city in Arizona, behind Phoenix, Arizona, Phoenix, with a population of 542,630 in the 2020 United States census. The Tucson ...

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

has a Wright R-975. *

Hiller Aviation Museum The Hiller Aviation Museum is an aviation museum located at the San Carlos Airport in San Carlos, California, focused on Northern California aviation history, Hiller Aircraft and helicopter history. History Background As early as the late 1960 ...

in San Carlos,

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

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 Pensacola ( ) is a city in the Florida panhandle in the United States. It is the county seat and only city in Escambia County. The population was 54,312 at the 2020 census. It is the principal city of the Pensacola metropolitan area, which ha ...

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

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 ...

Birmingham Birmingham ( ) is a City status in the United Kingdom, city and metropolitan borough in the metropolitan county of West Midlands (county), West Midlands, within the wider West Midlands (region), West Midlands region, in England. It is the Lis ...

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

has a Continental R-975. *

Queensland Air Museum The Queensland Air Museum is a not-for-profit all-volunteer aviation museum located near the Caloundra Airport in Queensland, Australia. Its mission is to collect and preserve all aspects of aviation heritage with an emphasis on Australia and Qu ...

Caloundra Caloundra ( ) is a coastal town in the Sunshine Coast Region, Queensland, Australia. In the , the town of Caloundra had a population of 96,305 people. Geography Caloundra is north of the Brisbane central business district. Caloundra is acce ...

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

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 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-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