Pratt & Whitney R-4360 Wasp Major
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. First run 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 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.Script error: No such module "Unsubst". 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.[1] 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[2]
- R-4360-20 - Template:Cvt
- R-4360-21 - Template:Cvt XB-35 and YB-35 inboard engines with 8-bladed contra-rotating propellers[2]
- R-4360-25 - Template:Cvt
- R-4360-41 - Template:Cvt
- R-4360-45 - Template:Cvt YB-35 outboard engines with 4-bladed propellers[2]
- R-4360-47 - Template:Cvt YB-35 inboard engines with 4-bladed propellers[2]
- R-4360-51 VDT - "Variable Discharge Turbine" 4,300 hp (3,210 kW). Intended for B-36C. Used on Boeing YB-50C Superfortress. [3]
- 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.[4]
- An R-4360 is on display at the Museum of Flight in Seattle, Washington.[5][6]
- An R-4360 is on display at the Heritage Flight Museum in Burlington, Washington.[7]
- An R-4360 is on display at the New England Air Museum, in Windsor Locks, Connecticut.[6]
- An R-4360 is on display at the Museum of Alaska Transportation and Industry in Wasilla, Alaska.[6]
- An R-4360 is on display at the CAF Airpower Museum in Dallas, Texas.[6]
- An R-4360 is on display at the Air Zoo in Kalamazoo, Michigan.[6]
- An R-4360-20WA is on display at the Teaneck Ignition Service in Teaneck, New Jersey.[6]
- An R-4360-20WD is on display at the Combat Air Museum in Topeka, Kansas.[8]
- An R-4360-59B is on display at the Combat Air Museum in Topeka, Kansas.[8]
- An R-4360-69 is on display at the Castle Air Museum in Atwater, California.[6]
- An R-4360 cutaway is on display at the Hill Aerospace Museum at Hill Air Force Base in Roy, Utah.[9]
- An R-4360 cutaway is on display at the Air Victory Museum in Lumberton, New Jersey.[10]
- An R-4360 cutaway is on display at the Air Zoo in Kalamazoo, Michigan.[6]
- An R-4360 cutaway is on display at the Museum of Aviation in Warner Robins, Georgia.[6]
- An R-4360 cutaway is on display at the Evergreen Aviation and Space Museum in McMinnville, Oregon.[6]
- An R-4360 cutaway is on display at the CAF Airpower Museum in Dallas, Texas.[6]
- An R-4360 cutaway is on display at the Pima Air and Space Museum in Tucson, Arizona.[6]
- An R-4360 cutaway is on display at the Air Force Armament Museum at Eglin Air Force Base in Valparaiso, Florida.[6]
- An R-4360 cutaway is on display at the Strategic Air Command & Aerospace Museum in Ashland, Nebraska.[6]
- An R-4360-4 cutaway is on display at the National Museum of Naval Aviation in Pensacola, Florida.[6]
- 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.[11]
- An R-4360-59B cutaway is on display at the Florida Air Museum in Lakeland, Florida.[12][6]
- An R-4360 cutaway is on display at the Mid-Atlantic Air Museum, Reading, Pennsylvania[13]
- Two R-4360s are on display at the National Museum of the United States Air Force in Dayton, Ohio.[14]
- An operational R-4360 is on display at the Penngrove Power and Implement Museum in Penngrove, California.[15]
- An operational R-4360 is on display at Nieman's Harley Rentals in St Helena, California[16]
Specifications (R-4360-51VDT)
Data from White, 1995Template:Sfn
General characteristics
- Type: 28-cylinder supercharged air-cooled four-row radial engine
- Bore: Template:Cvt
- Stroke: Template:Cvt.
- Displacement: Template:Cvt
- Length: Template:Cvt
- Diameter: Template:Cvt
- Dry weight: Template:Cvt
Components
- Valvetrain: Poppet, two valves per cylinder
- Supercharger: Gear-driven single stage variable speed centrifugal type supercharger
- Turbocharger: General Electric CHM-2 (optional)
- Fuel system: Bendix-Stromberg PR-100E2 pressure carburetor
- Fuel type: 115/145 Aviation gasoline
- Oil system: Dry sump
- Cooling system: Air-cooled
Performance
- Power output: Template:Convert at 2800 rpm
- Specific power: Template:Cvt
- Compression ratio: 7:1
- Power-to-weight ratio: Template:Cvt
See also
Related development
- Pratt & Whitney Wasp series
- Pratt & Whitney R-1830 Twin Wasp
- R-1535 Twin Wasp Junior
- Pratt & Whitney R-2180-A Twin Hornet
- Pratt & Whitney R-2180-E Twin Wasp E
- Pratt & Whitney R-2800 Double Wasp
Comparable engines
- BMW 803
- Shvetsov ASh-2
- Bristol Centaurus
- Lycoming XR-7755
- Wright R-3350 Duplex-Cyclone
- Wright R-4090 Cyclone 22
Related lists
References
Notes
Bibliography
- Bridgman, Leonard, ed. Jane's All The World's Aircraft 1951–1952. London: Samson Low, Marston & Company, Ltd 1951.
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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
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