The Pratt & Whitney R-2800 Double Wasp is an American twin-row, 18-cylinder,

air-cooled Air-cooled engines rely on the circulation of air directly over heat dissipation fins or hot areas of the engine to cool them in order to keep the engine within operating temperatures. Air-cooled designs are far simpler than their liquid-cooled ...

radial

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbin ...

with a

displacement Displacement may refer to: Physical sciences Mathematics and physics *Displacement (geometry), is the difference between the final and initial position of a point trajectory (for instance, the center of mass of a moving object). The actual path ...

of , and is part of the long-lived Wasp family of engines. The R-2800 saw widespread use in many important American aircraft during and after

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. During the war years,

Pratt & Whitney Pratt & Whitney is an American aerospace manufacturer with global service operations. It is a subsidiary of RTX Corporation (formerly Raytheon Technologies). Pratt & Whitney's aircraft engines are widely used in both civil aviation (especially ...

continued to develop new ideas to upgrade the engine, including water injection for takeoff in cargo and passenger planes and to give emergency power in combat.

Design and development

First run in 1937, near the time that the larger competing 18-cylinder Wright Duplex-Cyclone's development had been started in May of that year, the displacement R-2800 was first flown by 1940, one year before the Duplex-Cyclone. The Double Wasp was more powerful than the world's only other modern 18-cylinder engine, the

Gnome-Rhône 18L The Gnome et Rhône 18L was a French-designed twin-row 18-cylinder air-cooled radial engine. The 18L was a large step up in terms of displacement, power and number of cylinders. The majority of Gnome-Rhone engines were either 7, 9 or 14 cylinde ...

of . The Double Wasp was much smaller in displacement than either of the other 18-cylinder designs, 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 cylinder-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, with the elaborate process substantially increasing the surface area of the fins. Cross Section of a Pratt and Whitney R2800 Double Wasp

Cross Section of a Pratt and Whitney R2800 Double Wasp

The

twin Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of Twin Last Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two ...

distributor A distributor is an electric and mechanical device used in the ignition system of older spark-ignition engines. The distributor's main function is to route electricity from the ignition coil to each spark plug at the correct time. Design ...

s on the Double Wasp were prominently mounted on the upper surface of the forward gear reduction housing - with one of the pair of magnetos mounted between them on most models - and almost always prominently visible within a cowling, with the conduits for the spark plug wires emerging from the distributors' cases either directly forward or directly behind them, or on the later C-series R-2800s with the two-piece gear reduction housings, on the "outboard" sides of the distributor casings. When the R-2800 was introduced in 1939, it was capable of producing , for a

specific power Power-to-weight ratio (PWR, also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement ...

value of . The design of conventional air-cooled radial engines had become so scientific and systematic by then that the Double Wasp was introduced with a smaller incremental power increase than was typical of earlier engines. Nevertheless, in 1941 the power output of production models increased to , and to late in the war. Even more was coaxed from experimental models, with fan-cooled subtypes like the R-2800-57 producing , but in general the R-2800 was a rather highly developed powerplant right from the beginning.

WWII

The R-2800 powered several types of fighters and medium bombers during the war, including the US Navy's

Vought F4U Corsair The Vought F4U Corsair is an American fighter aircraft that saw service primarily in World War II and the Korean War. Designed and initially manufactured by Vought, Chance Vought, the Corsair was soon in great demand; additional production con ...

, with the XF4U-1 first prototype Corsair becoming the first airframe to fly (as originally designed) with the Double Wasp in its XR-2800-4 prototype version on May 29, 1940, and the first single-engine American fighter plane to exceed in level flight during October 1940. The R-2800 also powered the Corsair's naval rival, the

Grumman F6F Hellcat The Grumman F6F Hellcat is an American Carrier-based aircraft, carrier-based fighter aircraft of World War II. Designed to replace the earlier Grumman F4F Wildcat, F4F Wildcat and to counter the Japanese Mitsubishi A6M Zero, it was the United St ...

, the US Army Air Forces'

Republic P-47 Thunderbolt The Republic P-47 Thunderbolt is a World War II-era fighter aircraft produced by the American company Republic Aviation from 1941 through 1945. It was a successful high-altitude fighter, and it also served as the foremost American fighter-bombe ...

(which unusually, for single-engined aircraft, used a General Electric

turbocharger In an internal combustion engine, a turbocharger (also known as a turbo or a turbosupercharger) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into th ...

), the twin-engine

Martin B-26 Marauder The Martin B-26 Marauder is an American twin-engined medium bomber that saw extensive service during World War II. The B-26 was built at two locations: Baltimore, Maryland, and Omaha, Nebraska, by the Glenn L. Martin Company. First used in ...

and

Douglas A-26 Invader The Douglas A-26 Invader (designated B-26 between 1948 and 1965) is an American twin-engined light bomber and attack aircraft, ground attack aircraft. Built by Douglas Aircraft Company during World War II, the Invader also saw service during ...

, as well as the first purpose-built twin-engine radar-equipped night fighter, the

Northrop P-61 Black Widow The Northrop P-61 Black Widow is a twin-engine United States Army Air Forces fighter aircraft of World War II. It was the first operational U.S. warplane designed specifically as a night fighter. Named for the North American spider '' Latrodec ...

. When the US entered the war in December 1941, designs advanced rapidly, and long-established engines such as the Wright Cyclone and Double Wasp were re-rated on fuel of much higher

octane rating An octane rating, or octane number, is a standard measure of a liquid fuel, fuel's ability to withstand Compression ratio, compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compres ...

( anti-knock value) to give considerably more power. By 1944, versions of the R-2800 powering late-model P-47s (and other aircraft) had a rating (experimental) of on 115-grade fuel with water injection. After World War II, the engine was used in the

Korean War The Korean War (25 June 1950 – 27 July 1953) was an armed conflict on the Korean Peninsula fought between North Korea (Democratic People's Republic of Korea; DPRK) and South Korea (Republic of Korea; ROK) and their allies. North Korea was s ...

, 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.

Peacetime

Engines grow in power with development, but a major war demands the utmost performance from engines fitted to aircraft whose life in front-line service was unlikely to exceed 50 hours flying, over a period of only a month or two. In peacetime however, the call was for reliability over a period of perhaps a dozen years, and the R-2800's reliability commended its use for long-range patrol aircraft and for the

Douglas DC-6 The Douglas DC-6 is a piston-powered airliner and cargo aircraft built by the Douglas Aircraft Company from 1946 to 1958. Originally intended as a military transport near the end of World War II, Douglas reworked it after the war to compete ...

Martin 4-0-4 The Martin 4-0-4 is an American pressurized passenger airliner built by the Glenn L. Martin Company. In addition to airline use initially in the United States, it was used by the United States Coast Guard and United States Navy as the RM-1G (la ...

, and

Convair 240 The Convair CV-240 is an American airliner that Convair manufactured from 1947 to 1954, initially as a possible replacement for the ubiquitous Douglas DC-3. Featuring a more modern design with cabin pressurization, the 240 series made some inroa ...

transports. The last two were twin-engine aircraft of size, passenger capacity, and high wing loading comparable to the

DC-4 The Douglas DC-4 is an American four-engined (piston), propeller-driven airliner developed by the Douglas Aircraft Company. Military versions of the plane, the C-54 and R5D, served during World War II, in the Berlin Airlift and into the 1960 ...

- itself usually powered by the R-2000 bored-out version of the Twin Wasp - and the first

Constellations A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellations were likely defin ...

, which mostly used Wright Aeronautical's large Duplex-Cyclones. The Double Wasp still flies in restored vintage

warbird A warbird is any vintage military aircraft now operated by civilian organizations and individuals, or in some instances, by historic arms of military forces, such as the Battle of Britain Memorial Flight, the Royal Australian Air Force's No. 100 ...

aircraft displayed at

air show An air show (or airshow, air fair, air tattoo) is a public event where aircraft are trade fair, exhibited. They often include aerobatics demonstrations, without which they are called "static air shows" with aircraft parked on the ground. The ...

s, and sees service worldwide on aircraft such as the

Canadair CL-215 The Canadair CL-215 (Scooper) is the first model in a series of amphibious aircraft, amphibious flying boats designed and built by Canada, Canadian aircraft manufacturer Canadair, and later produced by Bombardier Aerospace, Bombardier. It is o ...

water-bomber. In addition, R-2800s continue to power

cargo and fuel-carrying aircraft in locations such as

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

. A total of 125,334 R-2800 engines were produced between 1939 and 1960.

Variants

This is a list of representative R-2800 variants, describing some of the mechanical changes made during development of the Double Wasp. Power ratings quoted are usually maximum "military" power that the engine could generate on takeoff and at altitude; 100 Octane fuel was used, unless otherwise noted. The R-2800 was developed and modified into a basic sequence of subtypes, "A" through "E" series, each of which indicated major internal and external modifications and improvements, such that the "E" series engines had very few parts in common with the "A".. Pratt & Whitney's internal variant identification incorporated the series letter as part of the designation, for example Double Wasp S1A4-G ("A" series) and Double Wasp CB17 ("C" series). ;Note:Suffixes such as -S14A-G denote engines developed for export to other countries. ''Data from White (Airlife) unless otherwise noted:''

Military

The dash number for each military type (e.g.: -21) was allocated to identify the complete engine model in accordance with the specification under which the engine was manufactured. Thus dash numbers did not necessarily indicate the sequence in which the engines were manufactured. For example: the -18W was a "C" series engine, built from 1945, whereas the -21 was a "B" series engine, built from 1943. Until 1940 the armed forces adhered strictly to the convention that engines built for the Army Air Forces used engine model numbers with odd numeric suffixes (e.g.: -5), while those built for the US Navy used even (e.g.: -8). After 1940, however, in the interests of standardization, engines were sometimes built to a joint Army-Navy contract, in which case the engines used a common numeric suffix (e.g. the -10 was used by both Army and Navy aircraft.) The suffix W e.g.: -10W denotes a sub-series modified to use water injection. The "Anti-Detonant Injection" (ADI) system injected a mixture of water and

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

into the carburetor to increase power for short periods. Several models of the R-2800s were fitted with ADI as standard equipment and were not given the W suffix. Few commercial aircraft used water injection. ''"A" Series:'' * R-2800-1 : at 2,400 rpm at . Production prototype of "A" series engines with the first flight test July 29, 1939. Single-speed two-stage supercharger. Production = 2 (P&W). Tested in Vultee YA-19B. * R-2800-5 : at 2,600 rpm at . Main production "A" series engine used in Martin B-26A, early B series and XB-26D and Curtiss C-55/XC-46. Production = 1,429 (P&W 475, Ford 954.) * R-2800-39 - * Double Wasp S1A4-G - ''"B" Series:'' * R-2800-8 : at 2,700 rpm at ; at 2,700 rpm at . First series production "B" Series engine using a two-stage, two-speed supercharger and with internal engineering changes resulting in increased power and reliability. Updraft Bendix-Stromberg PT-13D-4 pressure carburetor. First production engines delivered to USN November 11, 1941. Used in Brewster F3A-1, Goodyear FG-1, Vought F4U-1 and F4U-2. Production = 3,903 (P&W 2,194; Nash 1,709.) * R-2800-8W : WEP with water injection. First production engine using ADI equipment, major production version of -8 and used in some versions of F4U Corsair. Production = 8,668 (P&W 5,574; Nash 3,094.) * R-2800-10 and R-2800-10W : at 2,700 rpm at ; at 2,700 rpm at ; up to WEP with water injection. Similar to -8 series apart from downdraft PT-13G2-10 and PT-13G6-10 (-10W) carburetor. Used in Curtiss XP-60E, Grumman F6F-3 (-10; late production -10W) and F6F-5 (-10W) series and Northrop XP-61, YP-61, and P-61A-1. Production = 4,621 -10 (P&W 2,931; Nash 1,690) and 12,940 -10W (P&W 3,040; Nash 9,900); Total = 17,561. * R-2800-21 : at 2,700 rpm at ; at 2,700 rpm at . First production variant fed by a

General Electric General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston. Over the year ...

C-1

turbosupercharger In an internal combustion engine, a turbocharger (also known as a turbo or a turbosupercharger) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into th ...

. Designed for use in the Republic P-47B, C, D, G and XP-47F and K. Production = 5,720 (P&W 1,049; Ford 4,671.) * R-2800-25 - — for

* R-2800-27 - * R-2800-31 - * R-2800-41 - * R-2800-43 - * R-2800-51 - * R-2800-59 : at 2,700 rpm at ; at 2,500 rpm at ; WEP with water injection. Main production variant used in P-47 series, fed by an improved C-23 turbosupercharger. Differed from -21 in being fitted with ADI and a General Electric ignition system with a simplified tubular ignition harness developed by the Scintilla company in partnership with Bendix. Used in P-47C and D, XP-47L. Production = 11,391 (P&W 592; Ford 10,799). * R-2800-59W - * R-2800-65 - * R-2800-65W - * R-2800-71 - * R-2800-75 - * R-2800-79 - * Double Wasp 2SB-G - ''"C" Series'' * R-2800-18W : at 2,800 rpm at ; at 2,800 rpm at . First series production variant of the "C" Series, which was a complete redesign of the R-2800. Some of the main changes were:

forged Forging is a manufacturing process involving the shaping of metal using localized compression (physics), compressive forces. The blows are delivered with a hammer (often a power hammer) or a die (manufacturing), die. Forging is often classif ...

rather than

cast Cast may refer to: Music * Cast (band), an English alternative rock band * Cast (Mexican band), a progressive Mexican rock band * The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis * ''Cast'', a 2012 album by Trespassers William ...

cylinders, allowing an increased compression ratio (from 6.65:1 to 6.75:1); a redesigned crankshaft; a single piece (rather than split) crankcase center section; a two section nose casing, incorporating hydraulically operated torque-monitoring equipment and an automatic vacuum-operated spark-advance unit. The supercharger used

fluid coupling A fluid coupling or hydraulic coupling is a hydrodynamics, hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power.

for the second stage. Updraft Bendix-Stromberg PT-13G2-10 carburetor. Used in Vought F4U-4 and variants of the -4. Production = 3,257 (P&W). * R-2800-22W - * R-2800-34 - * R-2800-34W - , with water-methanol injection * R-2800-44 - * R-2800-44W - * R-2800-48 - * R-2800-48W - * R-2800-52W - * R-2800-54 - * R-2800-57 - * R-2800-57C - * R-2800-73 - — with General Electric CH-5-A3 turbocharger for P-61C Black Widow * R-2800-77 - * R-2800-83 - * R-2800-83AM - * R-2800-99W - * R-2800-103W - * Double Wasp CB16 - , * Double Wasp CB17 - * Double Wasp S1C3-G - ''"D" Series:'' * R-2800-23 - * R-2800-29 - ''"E" Series:'' * R-2800-30W - , with water-methanol injection — with variable speed single-stage supercharger for Grumman F8F-2 Bearcat * R-2800-32W - , with water-methanol injection — with variable speed two-stage supercharger for Vought F4U-5 Corsair

Applications

The following is a partial list of aircraft that were powered by the R-2800 (and a few prototypes that utilized it at one point):

Engines on display

* There is an R-2800-39 on display at the

New England Air Museum The New England Air Museum (NEAM) is an American aerospace museum located adjacent to Bradley International Airport in Windsor Locks, Connecticut. The museum consists of three display hangars with additional storage and restoration hangars. Its ...

Bradley International Airport Bradley International Airport – historically known as Bradley Field – is a public international airport in Windsor Locks, Connecticut, Windsor Locks, Connecticut, United States. Owned and operated by the Connecticut Airport Authority, Con ...

, Windsor Locks, CT. * An R-2800 used on

Finnair Finnair Plc (, ) is the flag carrier and largest full-service legacy airline of Finland, with headquarters in Vantaa on the grounds of Helsinki Airport, its airline hub, hub. Finnair and its subsidiaries dominate both domestic and international ...

Convair Metropolitan is on public display at

Helsinki Airport Helsinki-Vantaa Airport (, ) , or simply Helsinki Airport, is the main international airport serving Helsinki, the capital of Finland, as well as its surrounding Helsinki metropolitan area, metropolitan area, and the Uusimaa region in Finland. ...

. * An R-2800 Double Wasp is on display at the Aerospace Discovery at the

Florida Air Museum The Florida Air Museum, formerly known as the International Sport Aviation Museum and the SUN 'n FUN Air Museum, is designated as Florida's "Official Aviation Museum and Education Center." It features a display of aircraft including one-of-a-k ...

. * An R-2800 Double Wasp Cutout is on display at Texas State Technical College in Waco Texas. * An R-2800 Double Wasp manufactured by Ford Motor Company is on display at the

Yankee Air Museum The Michigan Flight Museum, formerly known as the Yankee Air Museum, is an aviation museum located at Willow Run Airport, and in Ypsilanti Township, Michigan. The museum has a small fleet of flying aircraft and a collection of static display air ...

Belleville, Michigan Belleville is a city in Wayne County in the U.S. state of Michigan. A western suburb of Detroit, Belleville is located roughly southwest of downtown Detroit, and southeast of Ann Arbor, and is completely surrounded by Van Buren Township. A ...

* An R-2800-8W Double Wasp is on display at the

Flying Leatherneck Aviation Museum The Flying Leatherneck Aviation Museum is a United States Marine Corps aviation museum currently located at the Orange County Great Park in Irvine, California. The museum contains exhibits and artifacts relating to the history and legacy of Unit ...

MCAS Miramar Marine Corps Air Station Miramar (MCAS Miramar) is a United States Marine Corps installation that is home to the 3rd Marine Aircraft Wing, which is the aviation element of the I Marine Expeditionary Force. It is located in Miramar, San Diego, ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

. * An R-2800 Double Wasp moving cut-away is on display at the

USS Midway Museum The USS ''Midway'' Museum is a historical naval aircraft carrier museum in San Diego, California, United States, located at Navy Pier. The museum consists of the aircraft carrier . The ship houses an extensive collection of aircraft, many of ...

San Diego San Diego ( , ) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. With a population of over 1.4 million, it is the List of United States cities by population, eighth-most populous city in t ...

. * An R-2800 Double Wasp is on display at (The National Museum of WWII Aviation) located in (Colorado Springs, Colorado). * An R-2800-34 Double Wasp is on public at the

Aerospace Museum of California The Aerospace Museum of California is a private non-profit aviation museum located in McClellan, California, outside of Sacramento, California, on the grounds of the former McClellan Air Force Base. History Founded as the Air Force Logistics Mus ...

. * Two R-2800 Double Wasps are displayed alongside a B-25 at the Girua Airport,

Popondetta Popondetta (sometimes spelled Popondota) is the capital of Oro (Northern) Province in Papua New Guinea. In 1951 the city became the focus of relief efforts after nearby Mount Lamington erupted and killed 4,000 people. Popondetta is near to ...

Oro Province Oro Province, formerly (and officially still) Northern Province, is a coastal Provinces of Papua New Guinea, province in the Southern Region, Papua New Guinea, Southern Region of Papua New Guinea. The provincial capital is Popondetta. The provinc ...

Papua New Guinea Papua New Guinea, officially the Independent State of Papua New Guinea, is an island country in Oceania that comprises the eastern half of the island of New Guinea and offshore islands in Melanesia, a region of the southwestern Pacific Ocean n ...

Specifications (R-2800-54)

References

Footnotes

Citations

Bibliography

* * * * *

External links

Pratt & Whitney's R-2800 page
{{DEFAULTSORT:Pratt and Whitney R-2800 Double Wasp 1930s aircraft piston engines Aircraft air-cooled radial piston engines R-2800