The Pratt & Whitney R-4360 Wasp Major is an American 28-cylinder four-row radial

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...

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 ...

designed and built during World War II. First run in 1944, at , it is the largest-displacement aviation piston engine to be mass-produced in the United States, and at the most powerful. It was the last of the

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 ...

Wasp family, and the culmination of its maker's

engine technology. The war was over before it could power airplanes into combat. It powered many of the last generation of large piston-engined aircraft before turbojets, but was supplanted by equivalent (and superior) powered turboprops (such as the Allison T56). Its main rival was the twin-row, 18-cylinder, nearly displacement, up to Wright R-3350 Duplex-Cyclone, first run some seven years earlier (May 1937).

Design and development

The R-4360 was a 28- cylinder four-row air-cooled radial engine. Each row of seven air-cooled cylinders possessed a slight angular offset from the previous, forming a semi-helical arrangement to facilitate effective airflow cooling of the cylinder rows behind them, inspiring the engine's "corncob" nickname. A mechanical

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 ...

geared at 6.374:1 ratio to engine speed provided forced induction, while the

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

was geared at 0.375:1 so that the tips did not reach inefficient

supersonic Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...

speeds. The engine was a technological challenge and the first product from Pratt and Whitney's new plant near

Kansas City, Missouri Kansas City (abbreviated KC or KCMO) is the largest city in Missouri by population and area. As of the 2020 census, the city had a population of 508,090 in 2020, making it the 36th most-populous city in the United States. It is the central ...

. The four-row configuration had severe thermal problems that decreased reliability, with an intensive maintenance regime involving frequent replacement of cylinders required. Large cooling flaps were required, which decreased aerodynamic efficiency, putting extra demands on engine power when cooling needs were greatest. Owing in large part to the maintenance requirements of the R-4360, all airplanes equipped with it were costly to operate and suffered decreased availability. Its commercial application in the Boeing Stratocruiser was unprofitable without government subsidy. Abandonment of the Stratocruiser was almost immediate when jet aircraft became available, while aircraft with smaller powerplants such as the Lockheed Constellation and Douglas DC-6 remained in service well into the jet era. Engine displacement was , hence the model designation. Initial models developed , and later models . One model that used two large turbochargers in addition to the supercharger delivered . Engines weighed , giving a

power-to-weight ratio Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measuremen ...

of . Wasp Majors were produced between 1944 and 1955; 18,697 were built. A derivative engine, the

Pratt & Whitney R-2180-E Twin Wasp E The Pratt & Whitney R-2180-E Twin Wasp E was a radial aircraft engine developed in the United States by Pratt & Whitney. It had two rows of seven cylinders each. Its only production application was on the post-World War II Saab 90 Scandia airli ...

, was essentially the R-4360 "cut in half". It had two rows of seven cylinders each, and was used on the postwar

Saab 90 Scandia The Saab 90 Scandia was a civil passenger aeroplane, manufactured by the Svenska Aeroplan Aktiebolaget (SAAB), in Linköping, Sweden. In 1944, as it was becoming clear that hostilities in Europe (the Second World War) would soon be at an end, SA ...

airliner.

Variants

* R-4360-4 - * R-4360-17 - XB-35 and YB-35 outboard engines with 8-bladed contra-rotating propellers * R-4360-20 - * R-4360-21 - XB-35 and YB-35 inboard engines with 8-bladed contra-rotating propellers * R-4360-25 - * R-4360-41 - * R-4360-45 - YB-35 outboard engines with 4-bladed propellers * R-4360-47 - YB-35 inboard engines with 4-bladed propellers * R-4360-51 VDT - "Variable Discharge Turbine" 4,300 hp (3,210 kW). Intended for B-36C. Used on Boeing YB-50C Superfortress. 2- Power recovery turbines. * R-4360-53 - * R-4360-B3 - * R-4360-B6 -

Applications

Engines on display

Pratt & Whitney Wasp Major R-4360 Engine

* An R-4360 is on display at the

Texas Air Museum - Stinson Chapter Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by bo ...

, San Antonio, Texas * An R-4360 is on display at the Mid America Museum of Aviation and Transportation in Sioux City, Iowa. * An R-4360 is on display at the Museum of Flight in Seattle, Washington. * An R-4360 is on display at the Heritage Flight Museum in

Burlington, Washington Burlington is a city in Skagit County, Washington, United States. Its population was recorded as 9,152 in the 2020 census. Burlington is located approximately halfway between Seattle and Vancouver, B.C. The city is included in the Mount Vernon&n ...

. * An R-4360 is on display at the New England Air Museum, in Windsor Locks, Connecticut. * An R-4360 is on display at the Museum of Alaska Transportation and Industry in Wasilla, Alaska. * An R-4360 is on display at the Pioneer Air Museum in Fairbanks, Alaska. * An R-4360 is on display at the

CAF Airpower Museum The Henry B. Tippie National Aviation Education Center (NAEC) is an aviation museum operated by the American Airpower Heritage Museum (AAHM), an affiliate organization of the Commemorative Air Force (CAF), headquartered at Dallas Executive Airpo ...

in Dallas, Texas. * An R-4360 is on display at the

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Kalamazoo, Michigan Kalamazoo ( ) is a city in the southwest region of the U.S. state of Michigan. It is the county seat of Kalamazoo County. At the 2010 census, Kalamazoo had a population of 74,262. Kalamazoo is the major city of the Kalamazoo-Portage Metropolit ...

. * An R-4360-4W is on display at the

Yankee Air Museum The Yankee Air Museum is an aviation museum located at Willow Run Airport in Van Buren Township, Michigan. The museum has a small fleet of flying aircraft and a collection of static display aircraft outdoors. History The Yankee Air Force Inc. w ...

in Belleville, Michigan * An R-4360-20WA is on display at the Teaneck Ignition Service in Teaneck, New Jersey. * An R-4360-20WD is on display at the Combat Air Museum in Topeka, Kansas. * An R-4360-59B is on display at the Combat Air Museum in Topeka, Kansas. * An R-4360-69 is on display at the Castle Air Museum in Atwater, California. * An R-4360 cutaway is on display at the Hill Aerospace Museum at

Hill Air Force Base Hill Air Force Base is a major U.S. Air Force (USAF) base located in northern Utah, just south of the city of Ogden, and bordering the Cities of Layton, Clearfield, Riverdale, Roy, and Sunset with its largest border immediately adjacent to ...

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. * An R-4360 cutaway is on display at the Air Victory Museum in Lumberton, New Jersey. * An R-4360 cutaway is on display at the

. * An R-4360 cutaway is on display at the Museum of Aviation in Warner Robins, Georgia. * An R-4360 cutaway is on display at the Evergreen Aviation and Space Museum in McMinnville, Oregon. * An R-4360 cutaway is on display at the

in Dallas, Texas. * An R-4360 cutaway is on display at the Pima Air and Space Museum in Tucson, Arizona. * An R-4360 cutaway is on display at the Air Force Armament Museum at

Eglin Air Force Base Eglin Air Force Base is a United States Air Force (USAF) base in the western Florida Panhandle, located about southwest of Valparaiso in Okaloosa County. The host unit at Eglin is the 96th Test Wing (formerly the 96th Air Base Wing). The ...

in Valparaiso, Florida. * An R-4360 cutaway is on display at the

Strategic Air Command & Aerospace 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 o ...

in Ashland, Nebraska. * An R-4360-4 cutaway is on display at the National Museum of Naval Aviation in

Pensacola, Florida Pensacola () is the westernmost city in the Florida Panhandle, and the county seat and only incorporated city of Escambia County, Florida, United States. As of the 2020 United States census, the population was 54,312. Pensacola is the principal ...

. * An R-4360-59B cutaway is on display at the Steven F. Udvar-Hazy Center of the

National Air and Space Museum The National Air and Space Museum of the Smithsonian Institution, also called the Air and Space Museum, is a museum in Washington, D.C., in the United States. Established in 1946 as the National Air Museum, it opened its main building on the Nat ...

in Chantilly, Virginia. * An R-4360-59B cutaway is on display at the

Florida Air Museum The Florida Air Museum, formerly known as the International Sport Aviation Museum and the SUN 'n FUN Air Museum, is designated as Florida's "Official Aviation Museum and Education Center." It features a display of aircraft including one-of-a-kind ...

in Lakeland, Florida. * An R-4360 cutaway is on display at the

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* Wreckage of an R-4360 is on display as a memorial in the Ben Shemen Forest in Israel. * An R-4360 is on display at the presidential gallery at the National Museum of the United States Air Force in Dayton, Ohio. * An operational R-4360 is on display at the Penngrove Power and Implement Museum in Penngrove, California. * Two R-4360s are on public display at the Aerospace Museum of California. One is complete, the other is a cutaway. * An operational R-4360 is on display at Nieman's Harley Rentals in

St Helena, California St. Helena ( ; Wappo: ''Anakotanoma'') is a city in Napa County, in the Wine Country of California. Located in the North Bay region of the San Francisco Bay Area, the population was 5,814 at the 2010 census. St. Helena is a popular tourist d ...

Specifications (R-4360-51VDT)

References

Notes

Bibliography

* * * *

External links

Pratt & Whitney R-4360 page

Pratt Whitney

National Museum of the USAFR-4360 fact sheet
a 1947 ''Flight'' article on the Wasp Major {{DEFAULTSORT:Pratt and Whitney R-4360 Wasp Major 1940s aircraft piston engines Aircraft air-cooled radial piston engines

R-4360 The Pratt & Whitney R-4360 Wasp Major is an American 28-cylinder four-row radial engine, radial reciprocating engine, piston aircraft engine designed and built during World War II. First run in 1944, at , it is the largest-displacement aviation ...