Pratt & Whitney R-4360
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The Pratt & Whitney R-4360 Wasp Major was a large radial piston aircraft engine designed and built during World War II. It was the last of the Pratt & Whitney Wasp family and the culmination of its maker's piston engine technology, but the war was over before it could power airplanes into combat. It did, however, power the last generation of large piston-engined planes before the jet engine and turboprop took over.
It was a 28 cylinder four-row radial engine with each row slightly offset from the previous, forming a semi-helical arrangement (as can be seen in the photograph), to facilitate cooling of the successive rows of cylinders. 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.
Although reliable in flight, the Wasp Major was maintenance intensive. Improper starting technique could foul all 56 spark plugs, which would require hours to clean or replace. As with most piston aircraft engines of the era, the time between overhauls of the Wasp Major was about 600 hours when used in commercial service.
Engine displacement was 4,362.50 in³ (71.5 L), hence the model designation. Initial models developed 3,000 hp (2240 kW), but the final models delivered 4,300 hp (3200 kW) using two large turbochargers in addition to the supercharger. Engines weighed 3,482 to 3,870 lb (1,579 to 1,755 kg), heavy but giving a power to weight ratio of 1.11 hp/lb (1.83 kW/kg), matched by very few engines.
Wasp Majors were produced between 1944 and 1955; 18,697 were built.
A derivative engine, the R-2180, 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.
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[edit] Aircraft usage
The Pratt & Whitney R-4360 was intended as a new powerplant for the Boeing B-29 Superfortress; Wasp Major-powered Superfortresses were eventually designated B-50. They also powered the Convair B-36 as well as a broad assortment of other aircraft:
- Aero Spacelines, Inc. Pregnant Guppy and Mini Guppy
- Boeing 377 Stratocruiser
- Boeing B-50 Superfortress
- Boeing C-97 Stratofreighter
- Boeing XF8B
- Boeing XB-44 Superfortress
- Convair B-36
- Convair XC-99
- Curtiss XBTC
- Douglas C-74 Globemaster
- Douglas C-124 Globemaster II
- Douglas TB2D Skypirate
- Fairchild C-119 Flying Boxcar
- Fairchild C-120 Packplane
- Goodyear F2G Corsair
- Hughes H-4 Hercules ("Spruce Goose")
- Hughes XF-11
- Lockheed R6V Constitution
- Martin AM Mauler
- Martin P4M Mercator
- Northrop B-35
- Republic XP-72
- Republic XF-12 Rainbow
- Vultee A-41
[edit] Specifications (R-4360-51VDT)
General characteristics
- Type: 28-cylinder supercharged air-cooled four-row radial engine
- Bore: 5.75 in. (146 mm)
- Stroke: 6.00 in. (152 mm)
- Displacement: 4,362.5 in³ (71.49 L)
- Length: 96.5 in. (2 451 mm)
- Diameter: 55 in (1397 mm)
- Dry weight: 3,870 lb (1,755 kg)
Components
- Valvetrain: Poppet, two valves per cylinder
- Supercharger: Gear-driven single stage variable speed centrifugal type supercharger
- Turbocharger: General Electric CHM-2
- Fuel system: Stromberg four-barrel pressure carburetor
- Fuel type: 108/135 octane gasoline
- Cooling system: Air-cooled
Performance
- Power output: 4,300 hp (3,210 kW)
- Specific power: 0.99 hp/in³ (45.0 kW/L)
- Compression ratio: 6.7 : 1
- Power-to-weight ratio: 1.11 hp/lb (1.83 kW/kg)
[edit] Related contents
Related development
- Pratt & Whitney Wasp series
- R-1340 Wasp
- R-985 Wasp Junior
- R-1830 Twin Wasp
- R-1535 Twin Wasp Junior
- R-2800 Double Wasp
Comparable engines
[edit] References
- Pratt & Whitney page on the R-4360
- More info
- Information about the 4360 from the Aircraft Engine Historical Society includes photos of the VDT engine.
- Bridgman, Leonard, ed. Jane's All The World's Aircraft 1951-1952. London: Samson Low, Marston & Company, Ltd 1951.
[edit] Further reading
- White, Graham (2006). R-4360: Pratt & Whitney's Major Miracle. North Branch, Minn.: Specialty Press. ISBN 1-58007-097-3.
[edit] External links
- National Museum of the USAF – R-4360 fact sheet
- Aircraft Engine Historical Society – P&W Museum – includes photos of R-4360
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