Pratt & Whitney R-4360 Wasp Major
Template:Short description Template:Infobox aero engine
The Pratt & Whitney R-4360 Wasp Major is an American 28-cylinder four-row radial piston aircraft engine designed and built during World War II. At Template:Cvt, it is the largest-displacement aviation piston engine to be mass-produced in the United States, and at Template:Convert the most powerful. The prototype first ran on 28 April 1941,<ref name="White p.35"/> with production-standard engines running in 1944. It was the last of the Pratt & Whitney Wasp family, and the culmination of its maker's piston 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 Template:Cvt displacement, up to Template:Convert 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.Template:Sfn A mechanical supercharger geared at 6.374:1 ratio to engine speed provided forced induction, while the propeller was geared at 0.375:1 so that the tips did not reach inefficient supersonic speeds.
The first prototype R-4360 was assembled using a modified H-3130 nose case and reduction gear, a supercharger and Bendix PT-13 carburetor from the R-2800 “B” series, and connecting rods from the R-2180. It was successfully test-run on 28 April 1941.<ref name="White p.35"/> The first airborne tests followed shortly thereafter. A modified Vultee Vengeance, designated V-85, served as the testbed, and the R-4360 made its maiden flight on 25 April 1942.<ref name="White p.37">Template:Cite book</ref>
The engine was a technological challenge and the first product from Pratt and Whitney's new plant near Kansas City, Missouri.Template:Sfn The four-row configuration had severe thermal problems that decreased reliability, with an intensive maintenance regime involving frequent replacement of cylinders required.Template:Citation needed 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.<ref name=gann>Template:Cite web</ref> 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 Template:Cvt, hence the model designation. Initial models developed Template:Cvt, and later models Template:Cvt. One model that used two large turbochargers in addition to the supercharger delivered Template:Convert. Engines weighed Template:Cvt, giving a power-to-weight ratio of Template:Cvt.
Wasp Majors were produced between 1944 and 1955; 18,697 were built.
A derivative engine, the Pratt & Whitney R-2180-E Twin Wasp E, 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 airliner.Template:Sfn
Variants
- R-4360-4 - Template:Cvt
- R-4360-17 - Template:Cvt XB-35 and YB-35 outboard engines with 8-bladed contra-rotating propellers<ref name="Pape">Template:Cite book</ref>
- R-4360-20 - Template:Cvt
- R-4360-21 - Template:Cvt XB-35 and YB-35 inboard engines with 8-bladed contra-rotating propellers<ref name="Pape"/>
- R-4360-25 - Template:Cvt
- R-4360-41 - Template:Cvt
- R-4360-45 - Template:Cvt YB-35 outboard engines with 4-bladed propellers<ref name="Pape"/>
- R-4360-47 - Template:Cvt YB-35 inboard engines with 4-bladed propellers<ref name="Pape"/>
- R-4360-51 VDT - "Variable Discharge Turbine" 4,300 hp (3,210 kW). Intended for B-36C. Used on Boeing YB-50C Superfortress. <ref>Template:Cite web</ref>
- R-4360-53 - Template:Cvt
- R-4360-B3 - Template:Cvt
- R-4360-B6 - Template:Cvt
Applications
Engines on display
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- An R-4360 is on display at the Mid America Museum of Aviation and Transportation in Sioux City, Iowa.<ref>Template:Cite web</ref>
- An R-4360 is on display at the Museum of Flight in Seattle, Washington.<ref>Template:Cite web</ref><ref name="AEHSNAM">Template:Cite web</ref>
- An R-4360 is on display at the Heritage Flight Museum in Burlington, Washington.<ref>Template:Cite web</ref>
- An R-4360 is on display at the New England Air Museum, in Windsor Locks, Connecticut.<ref name="AEHSNAM" />
- An R-4360 is on display at the Museum of Alaska Transportation and Industry in Wasilla, Alaska.<ref name="AEHSNAM" />
- An R-4360 is on display at the CAF Airpower Museum in Dallas, Texas.<ref name="AEHSNAM" />
- An R-4360 is on display at the Air Zoo in Kalamazoo, Michigan.<ref name="AEHSNAM" />
- An R-4360-20WA is on display at the Teaneck Ignition Service in Teaneck, New Jersey.<ref name="AEHSNAM" />
- An R-4360-20WD is on display at the Combat Air Museum in Topeka, Kansas.<ref name="CAM">Template:Cite web</ref>
- An R-4360-59B is on display at the Combat Air Museum in Topeka, Kansas.<ref name="CAM" />
- An R-4360-69 is on display at the Castle Air Museum in Atwater, California.<ref name="AEHSNAM" />
- An R-4360 cutaway is on display at the Hill Aerospace Museum at Hill Air Force Base in Roy, Utah.<ref>Template:Cite web</ref>
- An R-4360 cutaway is on display at the Air Victory Museum in Lumberton, New Jersey.<ref>Template:Cite web</ref>
- An R-4360 cutaway is on display at the Air Zoo in Kalamazoo, Michigan.<ref name="AEHSNAM" />
- An R-4360 cutaway is on display at the Museum of Aviation in Warner Robins, Georgia.<ref name="AEHSNAM" />
- An R-4360 cutaway is on display at the Evergreen Aviation and Space Museum in McMinnville, Oregon.<ref name="AEHSNAM" />
- An R-4360 cutaway is on display at the CAF Airpower Museum in Dallas, Texas.<ref name="AEHSNAM" />
- An R-4360 cutaway is on display at the Pima Air and Space Museum in Tucson, Arizona.<ref name="AEHSNAM" />
- An R-4360 cutaway is on display at the Air Force Armament Museum at Eglin Air Force Base in Valparaiso, Florida.<ref name="AEHSNAM" />
- An R-4360 cutaway is on display at the Strategic Air Command & Aerospace Museum in Ashland, Nebraska.<ref name="AEHSNAM" />
- An R-4360-4 cutaway is on display at the National Museum of Naval Aviation in Pensacola, Florida.<ref name="AEHSNAM" />
- An R-4360-59B cutaway is on display at the Steven F. Udvar-Hazy Center of the National Air and Space Museum in Chantilly, Virginia.<ref>Template:Cite web</ref>
- An R-4360-59B cutaway is on display at the Florida Air Museum in Lakeland, Florida.<ref>Template:Cite web</ref><ref name="AEHSNAM" />
- An R-4360 cutaway is on display at the Mid-Atlantic Air Museum, Reading, Pennsylvania<ref>Template:Cite web</ref>
- Two R-4360s are on display at the National Museum of the United States Air Force in Dayton, Ohio.<ref>Template:Cite news</ref>
- An operational R-4360 is on display at the Penngrove Power and Implement Museum in Penngrove, California.<ref>Template:Cite web</ref>
- An operational R-4360 is on display at Nieman's Harley Rentals in St Helena, California<ref>Template:Cite news</ref>
Specifications (R-4360-51VDT)
See also
References
Notes
Bibliography
External links
- Pratt & Whitney R-4360 page
- Pratt Whitney
- National Museum of the USAFTemplate:Spaced ndashR-4360 fact sheet
- "3,500 h.p. Radial" a 1947 Flight article on the Wasp Major
Template:P&W aeroengines Template:US military piston aeroengines