The Pratt & Whitney R-985 Wasp Junior is 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, a directional coordinate in a polar coordinate system * Radial set * A bearing f ...

aircraft engines built by the Pratt & Whitney Aircraft Company from the 1930s to the 1950s. These engines have 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 ; initial versions produced , while the most widely used versions produce . Wasp Juniors have powered numerous smaller civil and military aircraft, including small transports, utility aircraft, trainers, agricultural aircraft, and helicopters. Over 39,000 engines were built, and many are still in service today.

Design and development

Pratt & Whitney developed the R-985 Wasp Junior as a smaller version of the R-1340 Wasp to compete in the market for medium-sized aircraft engines. Like its larger brother, the Wasp Junior was an air-cooled, nine-cylinder radial, with its power boosted by a gear-driven single-speed centrifugal type supercharger. Its cylinders were smaller, however, with a bore and stroke of , giving a 27% lesser total displacement. The Wasp Junior used many parts from the Wasp and even had the same mounting dimensions, allowing an aircraft to easily use either the smaller or the larger engine. The first run of the Wasp Junior was in 1929, and sales began in 1930. The initial version, the Wasp Junior A, produced .Pratt & Whitney (1956), p. A2FAA Type Certificate Data Sheet ATC 39 The U.S. military designated the Wasp Junior as the R-985, with various suffixes denoting different military engine models. However, Pratt & Whitney never adopted the R-985 designation scheme for its civilian Wasp Juniors, identifying them simply by name and model (e.g. "Wasp Junior A"). Pratt & Whitney followed the Wasp Junior A with more powerful models in the "A series". These had higher compression ratios, greater RPM limits, and more effective supercharging, and they led to the "B series". The first B series model was the Wasp Junior TB, which could maintain at sea level and could reach for takeoff.FAA Type Certificate Data Sheet TC 85 The TB was tuned for best performance at sea level; it was soon joined by the Wasp Junior SB, which was tuned for best performance at altitude and could sustain at altitudes up to , with available for takeoff.FAA Type Certificate Data Sheet E-123 A still later model, the Wasp Junior T1B2, had improved performance at low level, being able to sustain up to while still matching the SB's power at high altitudes.FAA Type Certificate Data Sheet TC 5E-1, see notes 5 and 6. The SB and T1B2, and later versions of these with similar performance, were the most popular Wasp Junior models. One later development of the T1B2, the Wasp Junior B4, was especially designed for vertical mounting in helicopters.Pratt & Whitney (1956), p. A3 During the mid-1930s, Pratt & Whitney developed a still greater improvement of the Wasp Junior, the "C series", with an even higher compression ratio and RPM limit. The only type produced in this series, the Wasp Junior SC-G, could sustain at an altitude of and could produce for takeoff. It also included reduction gearing to allow the high-revving engine to drive a propeller at suitable speeds, hence the "-G" suffix. Aviator

Jacqueline Cochran Jacqueline Cochran (May 11, 1906 – August 9, 1980) was an American pilot and business executive. She pioneered women's aviation as one of the most prominent racing pilots of her generation. She set numerous records and was the first woman to br ...

flew a special Model D-17W

Beechcraft Staggerwing The Beechcraft Model 17 Staggerwing is an American biplane with an atypical negative wing stagger (the lower wing is farther forward than the upper wing). It first flew in 1932. Development At the height of the Great Depression, aircraft ...

with this engine in 1937, setting a speed and altitude record and placing third in the Bendix transcontinental race. However, the SC-G never got past the experimental stage.

Operational history

Early versions of the Wasp Junior were used in various small civilian and military utility aircraft, but only in limited numbers. The type became more popular later in the 1930s. It was selected for the Lockheed Model 10A Electra twin-engined airliner, as well as for other small twin-engined civil transports like the Lockheed Model 12A Electra Junior, the

Beechcraft Model 18 The Beechcraft Model 18 (or "Twin Beech", as it is also known) is a 6- to 11-seat, twin-engined, low-wing, tailwheel light aircraft manufactured by the Beech Aircraft Corporation of Wichita, Kansas. Continuously produced from 1937 to Novem ...

, and the

Grumman Goose The Grumman G-21 Goose is an amphibious flying boat designed by Grumman to serve as an eight-seat "commuter" aircraft for businessmen in the Long Island area. The Goose was Grumman's first monoplane to fly, its first twin-engined aircraft, and i ...

amphibious aircraft. It was also used in single-engined civilian utility aircraft like the

, the

Howard DGA-15 The Howard DGA-15 was a single-engine civil aircraft produced in the United States by the Howard Aircraft Corporation from 1939 to 1944. After the United States' entry into World War II, it was built in large numbers for the United States Navy a ...

, and the

Spartan Executive The Spartan 7W Executive is a cabin monoplane aircraft that was produced by the Spartan Aircraft Company during the late 1930s and early 1940s. The 7W features an all-metal fuselage, as well as a retractable undercarriage. The 7W Executive was ...

. As World War II arrived, the U.S. military chose the Wasp Junior for the

Vultee BT-13 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 ...

and North American BT-14 basic training aircraft and for the

Vought OS2U Kingfisher The Vought OS2U Kingfisher is an American catapult-launched observation floatplane. It was a compact mid-wing monoplane, with a large central float and small stabilizing floats. Performance was modest because of its low-powered engine. The OS2U ...

observation floatplane. Military versions of existing Wasp Junior-powered civilian aircraft were also produced, such as the military derivatives of the Beech 18, Beech Staggerwing, Grumman Goose, and Howard DGA-15. The Wasp Junior also powered some versions of the British

Avro Anson The Avro Anson is a British twin-engined, multi-role aircraft built by the aircraft manufacturer Avro. Large numbers of the type served in a variety of roles for the Royal Air Force (RAF), Fleet Air Arm (FAA), Royal Canadian Air Force (RCA ...

and

Airspeed Oxford The Airspeed AS.10 Oxford is a twin-engine monoplane aircraft developed and manufactured by Airspeed. It saw widespread use for training British Commonwealth aircrews in navigation, radio-operating, bombing and gunnery roles throughout the Seco ...

twin-engined trainers. The demands of World War II led to the production of many thousands of Wasp Juniors. Until the end of the war, the Wasp Junior's closest competitor was

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 ...

's R-975 Whirlwind. However, during the war, the Wasp Junior was far more widely used in aircraft than the R-975, and Wright ceased production of the R-975 in 1945. After World War II, many military-surplus aircraft with Wasp Junior engines entered the civilian market. New designs based on the Wasp Junior were also introduced, such as the

Sikorsky H-5 The Sikorsky H-5 (initially designated R-5 and also known as S-48, S-51 and by company designation VS-327Fitzsimons, Bernard, (general editor). ''Illustrated Encyclopedia of 20th Century Weapons and Warfare'' (London: Phoebus, 1978), Volume 20, ...

helicopter, the

de Havilland Canada DHC-2 Beaver The de Havilland Canada DHC-2 Beaver is a single-engined high-wing propeller-driven short takeoff and landing (STOL) aircraft developed and manufactured by de Havilland Canada. It has been primarily operated as a bush plane and has been use ...

, and

Max Holste Broussard The Max Holste MH.1521 Broussard is a 1950s French six-seat utility monoplane designed by Max Holste to meet a French Army requirement. Design and development Following the end of the Second World War, Avions Max Holste designed and built a n ...

bush airplane A bush airplane is a general aviation aircraft used to provide both scheduled and unscheduled passenger and flight services to remote, undeveloped areas, such as the Canadian north or bush, Alaskan tundra, the African bush, or savanna, Amazon ra ...

s, and

agricultural aircraft An agricultural aircraft is an aircraft that has been built or converted for agricultural use – usually aerial application of pesticides (crop dusting) or fertilizer (aerial topdressing); in these roles they are referred to as "crop duster ...

such as the Snow S-2B and S-2C,

Grumman Ag Cat The Grumman G-164 Ag Cat is a single-engined biplane agricultural aircraft, developed by Grumman in the 1950s. Development In 1955, Grumman preliminary design engineers Joe Lippert and Arthur Koch proposed the design for a "purpose-built" cr ...

, and Weatherley 201. Pratt & Whitney ceased production of the Wasp Junior in 1953, having built 39,037 engines. Many Wasp Junior engines are still in use today in older bush planes and agricultural planes, as well as in antique aircraft. Some antique aircraft, such as the

Boeing-Stearman Model 75 The Stearman (Boeing) Model 75 is a biplane formerly used as a military trainer aircraft, of which at least 10,626 were built in the United States during the 1930s and 1940s. Stearman Aircraft became a subsidiary of Boeing in 1934. Widely known ...

, which originally used other engines, have had them replaced with the Wasp Junior to provide more power or for easier maintenance, since parts for the Wasp Junior are readily available. Pratt & Whitney R-985

Variants

;Wasp Junior A :U.S. military version: R-985-1Pratt & Whitney (1956), p. A1 : at 2,000 RPM at sea level and for takeoff. First production version. ;Wasp Junior S2A ;Wasp Junior TB, TB2 :U.S. military versions: R-985-9, -11, -11A, -21, -46 : at 2,200 RPM at sea level, at 2,300 RPM for takeoff. Early B-series versions rated for sea-level performance. ;Wasp Junior SB, SB2, SB3 :U.S. military versions: R-985-13, -17, -23, -33, -48, -50; R-985-AN-2, -4, -6, -6B, -8, -10, -12, -12B, -14BFAA Type Certificate Data Sheet TC 5E-1 : at 2,200 RPM up to , at 2,300 RPM for takeoff.Pratt & Whitney (1956), pp. A2-A3 Common B-series versions were rated for performance at altitude. ;Wasp Junior T1B2, T1B3 :U.S. military versions: R-985-25, -27, -39, -39A; R-985-AN-1, -1A, -3, -3A : at 2,300 RPM up to and for takeoff. Common B-series versions with improved sea-level performance ;Wasp Junior B4 :U.S. military versions: R-985-AN-5, -7. : at 2,300 RPM up to and for takeoff Vertically mounted development of T1B3, for helicopters ;Wasp Junior SC-G : at 2,700 RPM up to , at 2,850 RPM for takeoff Experimental high-powered version with propeller reduction gearing.

Applications

(AS.46 Oxford V) *

Air Tractor AT-300 The Air Tractor AT-300 is a family of agricultural aircraft that first flew in the United States on September 1973. Type certification was awarded to Air Tractor in November the same year, and serial production commenced in 1976. Of low-wing mono ...

(Mk V) *

Barkley-Grow T8P-1 The Barkley-Grow T8P-1 was an airliner developed in the United States shortly before the Second World War. Although it saw limited production, the type was well-received as a bush plane in Canada. Design and development Typical for the era, the B ...

and military derivatives *

D17S, D17W, G17S *

Bell XV-3 The Bell XV-3 (Bell 200) is an American tiltrotor aircraft developed by Bell Helicopter for a joint research program between the United States Air Force and the United States Army in order to explore convertiplane technologies. The XV-3 featured ...

* Bellanca 300-W * Berliner-Joyce OJ *

(in aftermarket conversions) * Bratukhin G-3 *

CAC Winjeel The CAC CA-25 Winjeel is an Australian-designed and manufactured three-seat training aircraft. Entering service with the Royal Australian Air Force (RAAF) in 1955 as a basic to advanced trainer, it served in this role until 1975. Later, it was u ...

and L-20/U-6 military versions * Douglas C-26 Dolphin * Fleetwings BT-12 *

Gee Bee Model Z The Granville Gee Bee Model Z was an American racing aircraft of the 1930s, the first of the Super Sportster aircraft built by Granville Brothers Aircraft of Springfield, Massachusetts, with the sole intent of winning the Thompson Trophy, whic ...

* Grumman G-164 Ag Cat (some models) *

Grumman G-21 Goose The Grumman G-21 Goose is an amphibious flying boat designed by Grumman to serve as an eight-seat "commuter" aircraft for businessmen in the Long Island area. The Goose was Grumman's first monoplane to fly, its first twin-engined aircraft, a ...

* Howard DGA-11 * Howard DGA-15P *

Junkers F13 The Junkers F 13 was the world's first all-metal transport aircraft, developed in Germany at the end of World War I. It was an advanced cantilever-wing monoplane, with enclosed accommodation for four passengers. 322 planes of the type were manufa ...

(Rimowa F13 replica) *

Koolhoven F.K.51 The Koolhoven F.K.51 was a 1930s Dutch two-seat basic training biplane built by the Koolhoven Company. Design and development The Koolhoven F.K.51 was the winning design in a 1935 Dutch government contest for a new trainer. Designed by Frederic ...

(some models) * Laird Solution (LC-DW Solution, LC-DW300 Super Solution) * Lockheed Model 10-A Electra * Lockheed Model 12-A Electra Junior * Max Holste MH.1521 Broussard * McDonnell XHJH Whirlaway *

Naval Aircraft Factory N3N 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 ...

(in aftermarket conversions) * North American BT-14 *

PWS-24 The PWS-24 was a Polish single-engine passenger aircraft for 4 passengers, built in PWS factory, used from 1933 to 1936 by LOT Polish Airlines. In spite of its limited capacity, it was the only series-built airliner of domestic design ever used ...

bis * Seversky BT-8 *

helicopter (and S-51 civil version) *

Sikorsky S-39 The Sikorsky S-39 is an American light amphibious aircraft produced by Sikorsky Aircraft during the early 1930s. The S-39 was a smaller, single-engine version of the S-38. Operational history Spirit of Africa Filmmakers Martin and Osa Johnson ...

amphibian * Snow S-2B and S-2C * SIAI-Marchetti SM.102 * Spartan Executive 7W * Stinson Reliant SR-9F and SR-10F *

* Waco S3HD * Waco SRE Aristocrat * Weatherly 201 series * Weatherly 620 *

Wedell-Williams Model 44 The Wedell-Williams Model 44 is a racing aircraft, four examples of which were built in the United States in the early 1930s by the Wedell-Williams Air Service Corporation. It began as a rebuilding of the partnership's successful ''We-Will'' 1929 ...

Engines on display

Some museums which have Wasp Junior engines on display: * The National Air and Space Museum's

Steven F. Udvar-Hazy Center The Steven F. Udvar-Hazy Center, also called the Udvar-Hazy Center, is the Smithsonian National Air and Space Museum (NASM)'s annex at Washington Dulles International Airport in the Chantilly area of Fairfax County, Virginia. It holds numerous ...

near

Washington Dulles International Airport Washington Dulles International Airport , typically referred to as Dulles International Airport, Dulles Airport, Washington Dulles, or simply Dulles ( ), is an international airport in the Eastern United States, located in Loudoun County and Fa ...

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

: This engine has been sectioned and motorized for display. *

EAA AirVenture Museum The EAA Aviation Museum, formerly the EAA AirVenture Museum (or Air Adventure Museum), is a museum dedicated to the preservation and display of historic and experimental aircraft as well as antiques, classics, and warbirds. The museum is lo ...

in Oshkosh, Wisconsin *

Hill Aerospace Museum Hill Aerospace Museum is a military aviation museum located at Hill Air Force Base in Roy, Utah. It is dedicated to the history of the base and aviation in Utah. History Preparations for a museum began in 1984, when ground was broken on an "Ae ...

near Ogden, Utah. *

Museum of Flight The Museum of Flight is a private non-profit air and space museum in the Seattle metropolitan area. It is located at the southern end of King County International Airport (Boeing Field) in the city of Tukwila, immediately south of Seattle. ...

Seattle, Washington Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest region ...

. This personal collection of museum aircraft engine photos has R-985 photos under the sections titled "From Canada's National Aviation Museum in Ottawa, ON", "From the SAC Museum in Ashland, NE", and "From the Museum of Flight new galleries in Seattle, WA". *

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 *

National Museum of the United States Air Force The National Museum of the United States Air Force (formerly the United States Air Force Museum) is the official museum of the United States Air Force located at Wright-Patterson Air Force Base, northeast of Dayton, Ohio. The NMUSAF is the ...

near

Dayton, Ohio Dayton () is the sixth-largest city in the U.S. state of Ohio and the county seat of Montgomery County. A small part of the city extends into Greene County. The 2020 U.S. census estimate put the city population at 137,644, while Greater D ...

New England Air Museum The New England Air Museum (NEAM) is an American aerospace museum located adjacent to Bradley International Airport in Windsor Locks, Connecticut. The museum consists of three display hangars with additional storage and restoration hangars. Its co ...

Windsor Locks, Connecticut Windsor Locks is a town in Hartford County, Connecticut, United States. As of the 2020 census, its population was 12,613. It is the site of Bradley International Airport, which serves the Greater Hartford-Springfield region and occupies approxi ...

Pima Air & Space Museum The Pima Air & Space Museum, located in Tucson, Arizona, is one of the world's largest non-government funded aerospace museums. The museum features a display of nearly 300 aircraft spread out over 80 acres (320,000 m²) on a campus oc ...

Tucson, Arizona , "(at the) base of the black ill , nicknames = "The Old Pueblo", "Optics Valley", "America's biggest small town" , image_map = , mapsize = 260px , map_caption = Interactive map ...

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, Alabama Birmingham ( ) is a city in the north central region of the U.S. state of Alabama. Birmingham is the seat of Jefferson County, Alabama's most populous county. As of the 2021 census estimates, Birmingham had a population of 197,575, down 1% fr ...

. *

Strategic Air and Space Museum The Strategic Air Command & Aerospace Museum is a museum focusing on aircraft and nuclear missiles of the United States Air Force during the Cold War. It is located near Ashland, Nebraska, along Interstate 80 southwest of Omaha. The objective of t ...

(formerly the Strategic Air Command Museum) near

Ashland, Nebraska Ashland is a city in Saunders County, Nebraska, United States. The population was 2,453 at the 2010 census. History Ashland is located at the site of a low-water limestone ledge along the bottom of Salt Creek, an otherwise mud-bottomed stream ...

* Canada Aviation and Space Museum in

Ottawa, Ontario Ottawa (, ; Canadian French: ) is the capital city of Canada. It is located at the confluence of the Ottawa River and the Rideau River in the southern portion of the province of Ontario. Ottawa borders Gatineau, Quebec, and forms the core ...

Royal Air Force Museum Cosford The Royal Air Force Museum Cosford, located in Cosford in Shropshire, is a free (currently, 2022) museum dedicated to the history of aviation and the Royal Air Force in particular. The museum is part of the Royal Air Force Museum, a non-departme ...

, near

Wolverhampton Wolverhampton () is a city, metropolitan borough and administrative centre in the West Midlands, England. The population size has increased by 5.7%, from around 249,500 in 2011 to 263,700 in 2021. People from the city are called "Wulfrunians ...

, United Kingdom *

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

Caloundra Caloundra ( ) is a coastal town and the southernmost town in the Sunshine Coast Region in South East Queensland, Australia. Geography Caloundra is north of the Brisbane central business district. Caloundra is accessible from Landsborough ...

, Queensland..

Specifications (R-985 Wasp Junior SB)

References

Notes

Bibliography

*Gunston, Bill. ''World Encyclopedia of Aero Engines: From the Pioneers to the Present Day''. 5th edition, Stroud, UK: Sutton, 2006. *White, Graham. ''Allied Aircraft Piston Engines of World War II: History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States During World War II''. Warrendale, Pennsylvania: SAE International, 1995. * . Available from the Aircraft Engine Historical Society'
reference page
* 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 ...

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
*Wasp Jr. A: . *Wasp Jr. SB, T1B2, B4: . *Wasp Jr. TB: . *Wasp Jr. military models: .

External links

* {{DEFAULTSORT:Pratt and Whitney R-985 Wasp Junior 1920s aircraft piston engines Aircraft air-cooled radial piston engines R-985