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First run in 1937, the R-2800 was America's first 18-cylinder radial engine design. The Double Wasp was more powerful than the world's only other modern eighteen, the Gnome-Rhône 18L of 3,442 cubic inches (56.4 L), but it was much smaller and heat dissipation was a greater problem. To enable more efficient cooling, the usual practice of casting or forging the cylinder head cooling fins that had been effective enough for other engine designs was discarded, and instead, much thinner and closer-pitched cooling fins were machined from the solid metal of the head forging. The fins were all cut at the same time by a gang of milling saws, automatically guided as it fed across the head in such a way that the bottom of the grooves rose and fell to make the roots of the fins follow the contour of the head. Cylinder cooling was effected by aluminium cooling muffs that were shrunk onto the steel alloy forged barrels. In addition to requiring a new cylinder head design, the Double Wasp was probably the most difficult to effectively direct a flow of cooling air around.
In 1939, when the R-2800 was introduced it was capable of producing 2,000 hp (1,500 kW), for a specific power value of 0.71 hp/in³ (32.6 kW/L). No other air-cooled engine came close to this figure, and even liquid-cooled ones barely matched it. The designing of conventional air-cooled radial engines had become so scientific and systematic by then that the Double Wasp was introduced at a power rating that was not amenable to anything like the developmental power increases that had been common with earlier engines. Nevertheless, in 1941 the power output of production models increased to 2,100 hp (1,600 kW), and to 2,400 hp (1,800 kW) late in the war. However, even more was coaxed from experimental models, with fan-cooled subtypes producing 2,800 hp (2,100 kW), but in general the R-2800 was a rather highly developed powerplant right from the beginning.
The R-2800 was used to power several types of fighters and medium bombers during the war, notably the US Navy's F4U Corsair and F6F Hellcat, the US Army Air Forces' P-47 Thunderbolt, and the twin-engined B-26 Marauder and A-26 Invader. When the US entered the war in December 1941 there were very quickly some major changes in philosophy, and such long-established engines as the Wright Cyclone and Double Wasp were re-rated on fuel of much higher anti-knock value to give considerably more power, and by 1944 versions of the R-2800 powering late-model P-47s (and other aircraft) had a rating (experimental) of 2,800 hp on 115-grade fuel with water injection.
After World War II, the engine was used in the Korean War, and surplus World War II aircraft powered by the Double Wasp served with other countries well past the Korean War, some being retired as late as the latter part of the 1960s when the aircraft were replaced.
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STATISTICS - R-2800-65W
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Manufacturer:
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Pratt & Whitney
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Model:
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R-2800
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Engine Type:
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Air-Cooled Twin-Row Radial Engine with Water Injection
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Cylinders:
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18
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Bore:
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5.75 in. (146.0 mm)
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Stroke:
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6 in. (152.4 mm)
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Displacement:
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2,804 cubic in. (45.96 L)
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Diameter:
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52.8 in. (1.342 m)
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Dry Weight:
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2,360 lbs. (1,073 kg)
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COMPONENTS
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Valvetrain:
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Poppet, Two Valves per Cylinder
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Fuel System:
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One Stromberg Injection Carburetor
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Supercharger:
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Single Stage Single Speed Centrifugal Type Supercharger
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Fuel Type:
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100/130 Octane Gasoline
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Oil System:
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Cooling System:
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Air-Cooled
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PERFORMANCE
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Power Output:
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2,250 hp @ 2,700 rpm
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Compression:
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PRODUCTION MODELS
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Variant
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Horsepower Rating
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Airframe Application
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R-2800-6
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2,000 hp
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Consolidated TBY Sea Wolf
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R-2800-8W
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2,250 hp
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Vought F4U-1A Corsair
Vought F4U-1D
Goodyear FG-1A Corsair
Goodyear FG-1D Corsair
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R-2800-10
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2,000 hp
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Curtiss XP-60E
Grumman F6F-3 Hellcat
Grumman F6F-3E Hellcat
Grumman F6F-3N Hellcat
Northrop P-61A-1 Black Widow
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R-2800-10W
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2,200 hp
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Grumman F6F-5 Hellcat
Grumman F6F-5N Hellcat
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R-2800-CB-15
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Fairchild XC-123 Provider
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R-2800-CB-16
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Douglas DC-6
Douglas C-118 Liftmaster
Martin 4-0-4
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R-2800-CB-17
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Doublas R6D
Howard 500
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R-2800-18W
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2,450 hp
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Douglas DC-6B
Vought F4U-4 Corsair
Grumman XF6F-6 Hellcat
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R-2800-22W
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2,400 hp
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Grumman F7F-1 Tigercat
Grumman F7F-1N Tigercat
Grumman F7F-2N Tigercat
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R-2800-23
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2,200 hp
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Fairchild XC-123 Provider
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R-2800-27
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2,000 hp
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Douglas A-26B Invader
Grumman XF6F-4 Hellcat
North American XB-28A Dragon
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R-2800-29
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2,000 hp
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Northrop XP-56 Black Bullet
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R-2800-30W
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2,250 hp
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Grumman F8F-2 Bearcat
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R-2800-31
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2,000 hp
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Lockheed Ventura II
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R-2800-32(E)
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2,450 hp
2,850 with water-methanol injection
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Vought F4U-5 Corsair
Vought F4U-5N Corsair
Vought AU-1 Corsair
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R-2800-34
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2,100 hp
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Convair CV-240 Airliner
Convair C-131 Samaritan
Convair T-29 Samaritan
Convair R4Y Samaritan
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R-2800-34W
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2,400 hp
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Curtiss XF-15C
Grumman F7F-3 Tigercat
Grumman F7F-3N Tigercat
Grumman F7F-4N Tigercat
Grumman F8F-1 Bearcat
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R-2800-39
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2,000 hp
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Martin 2-0-2
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R-2800-41
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2,000 hp
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Martin B-26B-2 Marauder
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R-2800-43
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2,000 hp
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Martin B-26B-3 Marauder
Martin B-26C Marauder
Martin B-26E Marauder
Martin B-26F Marauder
Martin B-26G Marauder
Curtiss C-46 Commando
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R-2800-44W
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2,400 hp
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North American AJ-1 Savage
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R-2800-46
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2,300 hp
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Grumman XTB3F-1 Guardian
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R-2800-48
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2,500 hp
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North American AJ-2 Savage
North American AJ-2P Savage
Grumman AF-2S Guardian
Grumman AF-2W Guardian
Grumman AF-3S Guardian
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R-2800-51
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2,000 hp
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Curtiss C-46A Commando
Curtiss C-46D Commando
Curtiss C-46E Commando
Curtiss C-46F Commando
Curtiss C-46G Commando
Curtiss R5C-1 Commando
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R-2800-52W
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2,500 hp
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Douglas B-26K Counter Invader
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R-2800-53
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2,000 hp
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Curtiss XP-60C
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R-2800-54
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2,100 hp
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Sikorsky CH-37A Mojave
Sikorsky CH-37B Mojave
Sikorsky HR2S-1
Sikorsky HR2S-1W
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R-2800-57C
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2,800 hp
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Republic P-47M Thunderbolt
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R-2800-59
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2,300 hp
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Republic P-47B Thunderbolt
Republic P-47D Thunderbolt
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R-2800-59W
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2,500 hp
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Republic P-47C Thunderbolt
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R-2800-65
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2,000 hp
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Northrop P-61A-5 Black Widow
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R-2800-65W
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2,250 hp
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Northrop P-61B Black Widow
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R-2800-73
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2,800 hp
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Northrop P-61C Black Widow
Northrop F-15A Reporter
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R-2800-77(C)
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Republic P-47N Thunderbolt
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R-2800-83
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2,100 hp
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Canadair CL-215
Douglas XA-26D Invader
Douglas XA-26E Invader
Douglas XA-26F Invader
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R-2800-85
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2,100 hp
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Fairchild C-82A Packet
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R-2800-99W
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2,300 hp
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Fairchild C-123B Provider
Fairchild C-123K Provider
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The Northrop P-61 Black Widow was the first operational U.S. military aircraft designed specifically to use radar. The "Black Widow" was an all-metal, twin-engine, twin-boom, aircraft flown as a night-fighter by United States Army Air Forces squadrons in the European Theater, the Pacific Theater, the CBI Theater, and the Mediterranean Theater during World War II. It replaced earlier British-designed night-fighter aircraft that had been updated to incorporate radar when it became available. On the night of 14 August 1945, a P-61B-2 of the 548th NFS named "Lady in the Dark" was unofficially credited with the last allied air victory before VJ Day. The P-61 was also modified to create the F-15 Reporter, the last piston-powered photo-reconnaissance aircraft designed and produced for the U.S. Air Force.
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STATISTICS - Northrop P-61 Black Widow
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Manufa cturer
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Northrop
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Powerpl ant
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Two Pratt & Whitney R-2800-65W Double Wasp Radial Engines
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Crew
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Two to Three (Pilot, Radar Operator, Optional Gunner)
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DIMENSIONS
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Length
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49 ft. 7 in.
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Wing Span
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66 ft. 0 in.
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Height
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14 ft. 8 in.
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Empty Weight
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23,450 lbs.
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Loaded Weight
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29,700 lbs.
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Gross Weight
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36,200 lbs.
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PERFORMANCE
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Max Speed
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366 mph
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Cruise Speed
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Combat Radius
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610 miles
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Ferry Range
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1,900 miles
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Service Ceiling
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33,100 ft.
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Max Climb Rate
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2,540 ft/min
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Thrust/Weight
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ARMAMENT
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Four 20 mm Hispano M2 Cannon in ventral fuselage, 200 rounds per gun
Four .50 caliber Browning M2 Machine Guns in remotely operated turret, 560 rounds per gun
For ground attack, four bombs of up to 1,600 lbs. each or six 5 inch HVAR unguided rockets could be carried under the wings. Some aircraft could also carry one 1,000 bomb under the fuselage.
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