Pratt & Whitney R-2800 Double Wasp

Pratt & Whitney R-2800 Double Wasp
Name	R-2800 Double Wasp
Type	Radial engine
National origin	United States
Manufacturer	Pratt & Whitney
First run	1937
Major applications	Vought F4U Corsair, Republic P-47 Thunderbolt, Grumman F6F Hellcat, Northrop P-61 Black Widow, Douglas A-26 Invader
Number built	125,334
Developed into	Pratt & Whitney R-2800 Double Wasp (C series)

Pratt & Whitney R-2800 Double Wasp was an American 18-cylinder, air-cooled radial engine that became one of the most important piston aircraft engines of World War II. Renowned for its exceptional power, reliability, and compact design, it powered a legendary array of United States Army Air Forces and United States Navy aircraft. Its performance was critical to Allied air superiority in multiple theaters of the war, and its production continued long after the conflict ended.

Design and development

The Pratt & Whitney team, led by engineers like Luke Hobbs, began work on the R-2800 in the late 1930s to meet the demand for higher power from both military and commercial aviation. Its innovative design featured two rows of nine cylinders, which gave it the "Double Wasp" name and allowed for a relatively compact diameter despite its large displacement. A key advancement was its use of fuel injection rather than carburetors, which improved performance at high altitudes and during aggressive maneuvers. The engine also incorporated a robust crankshaft and an efficient supercharger system, developed with expertise from the National Advisory Committee for Aeronautics.

Operational history

The R-2800 entered service in 1941 and quickly proved its worth in combat. It was the powerhouse behind the Republic P-47 Thunderbolt, a formidable fighter aircraft that dominated the skies over Europe and provided crucial close air support. In the Pacific War, it propelled the Grumman F6F Hellcat and the Vought F4U Corsair, which achieved outstanding kill ratios against Japanese aircraft like the Mitsubishi A6M Zero. The engine also saw extensive use in important night fighters like the Northrop P-61 Black Widow and medium bombers such as the Douglas A-26 Invader. Its reliability under extreme conditions made it a favorite among pilots and maintenance crews across the United States Army Air Forces, United States Navy, and United States Marine Corps.

Variants

Numerous variants were produced to suit different airframes and performance requirements. The -8 series, used in early P-47B and P-47C models, featured a single-stage supercharger. The more powerful -21 series, with an improved two-stage supercharger, was pivotal for the P-47D and the F4U-1 Corsair. The -10 series powered the F6F-3 Hellcat, while the -65 and -73 variants were developed for the P-61 Black Widow and A-26 Invader, respectively. Post-war, the "C series" engines incorporated water injection and other refinements for commercial use in airliners like the Douglas DC-6.

Specifications (R-2800-59)

* Type: 18-cylinder, two-row, air-cooled radial engine * Bore: 5.75 in (146 mm) * Stroke: 6.00 in (152 mm) * Displacement: 2,804 cu in (45.96 L) * Length: 76.5 in (1,943 mm) * Diameter: 52.8 in (1,341 mm) * Dry weight: 2,360 lb (1,070 kg) * Valvetrain: Two valves per cylinder * Supercharger: Two-speed, two-stage centrifugal supercharger * Power output: 2,300 hp (1,715 kW) at 2,800 rpm for takeoff * Specific power: 0.82 hp/cu in (37.3 kW/L)

Applications

The R-2800's primary applications were in World War II combat aircraft, but its use extended far beyond. Notable military users included the Curtiss P-60, Martin B-26 Marauder, and the B-17-based Boeing XB-40 Gunship. Post-war, it was adapted for commercial aviation, powering the Convair 240, Lockheed L-749 Constellation, and the Douglas DC-6. It also saw service in Royal Air Force aircraft supplied through Lend-Lease and was utilized in racing planes like the Thompson Trophy-winning Rare Bear.

Survivors and displays

Many R-2800 engines are preserved in museums and on restored aircraft around the world. Examples can be seen at the National Museum of the United States Air Force in Dayton, Ohio, mounted on its P-47 Thunderbolt and P-61 Black Widow. The National Naval Aviation Museum in Pensacola, Florida displays them on F4U Corsair and F6F Hellcat aircraft. The Flying Heritage & Combat Armor Museum and the Planes of Fame Air Museum also have operational aircraft powered by original R-2800 engines. Additionally, numerous engines are held in private collections and by organizations like the Commemorative Air Force.

Category:Aircraft piston engines Category:Pratt & Whitney aircraft engines Category:Radial engines