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. In all combustion engines, a great percentage of the heat ge ...

radial

aircraft engine An aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many ...

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, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

. During the war years,

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

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. The

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

distributor A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...

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. Cross Section of a Pratt and Whitney R2800 Double Wasp

Cross Section of a Pratt and Whitney R2800 Double Wasp

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 measuremen ...

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. XF4U-1 NACA 1940

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 which saw service primarily in World War II and the Korean War. Designed and initially manufactured by Chance Vought, the Corsair was soon in great demand; additional production contracts ...

, 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 uniquely, for single-engined aircraft, used a General Electric

turbocharger In an internal combustion engine, a turbocharger (often called a turbo) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake gas, forcing more air into the engine in order to pro ...

), 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 t ...

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 ground attack aircraft. Built by Douglas Aircraft Company during World War II, the Invader also saw service during several major Col ...

, 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 as a night fighter, and the first aircraft designed specifically as a night fight ...

. 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 fuel's ability to withstand compression in an internal combustion engine without detonating. The higher the octane number, the more compression the fuel can withstand before detonating ...

(

anti-knock An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs. The mixture known as gasoline or petrol, when used in high comp ...

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 , date = {{Ubl, 25 June 1950 – 27 July 1953 (''de facto'')({{Age in years, months, weeks and days, month1=6, day1=25, year1=1950, month2=7, day2=27, year2=1953), 25 June 1950 – present (''de jure'')({{Age in years, months, weeks a ...

, 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, it was reworked after the war to compete with th ...

Martin 4-0-4 The Martin 4-0-4 was 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 (l ...

, 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 1960s ...

- 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 origins of the earliest constellation ...

, 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 RAAF Museum Historic Flight, or the ...

aircraft displayed at

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

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 flying boat amphibious aircraft designed and built by Canadian aircraft manufacturer Canadair, and later produced by Bombardier. It is one of only a handful of large amphibious a ...

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

cargo and fuel-carrying aircraft in locations such as

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

. 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". ;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 and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

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 - ''"B" Series:'' Pratt & Whitney R-2800-21 USAF

* 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 The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage of ...

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) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...

C-1

turbosupercharger In an internal combustion engine, a turbocharger (often called a turbo) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake gas, forcing more air into the engine in order to pro ...

. 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 - ''"C" Series'' HARP Pratt & Whitney R-2800 Double Wasp

* 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 compressive forces. The blows are delivered with a hammer (often a power hammer) or a die. Forging is often classified according to the temperature at which it ...

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 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 -4 variants. 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 - * R-2800-2SB-G - * R-2800-CB16 - , * R-2800-CB17 - * R-2800-S1A4-G - * R-2800-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 c ...

Bradley International Airport Bradley International Airport is a public international airport in Windsor Locks, Connecticut, United States. Owned and operated by the Connecticut Airport Authority, it is the second-largest airport in New England. The airport is about halfw ...

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

Finnair Finnair ( fi, Finnair Oyj, sv, Finnair Abp) is the flag carrier and largest airline of Finland, with its headquarters in Vantaa on the grounds of Helsinki Airport, its hub. Finnair and its subsidiaries dominate both domestic and internationa ...

Convair Metropolitan 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 inr ...

is on public display at

Helsinki Airport Helsinki-Vantaa Airport (; fi, Helsinki-Vantaan lentoasema, sv, Helsingfors-Vanda flygplats), or simply Helsinki Airport, is the main international airport of the city of Helsinki, its surrounding Greater Helsinki, metropolitan area, and the ...

. * 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-kind ...

. * An R-2800 Double Wasp manufactured by Ford Motor Company is on display at the

Yankee Air Museum The Yankee Air Museum is an aviation museum located at Willow Run Airport in Van Buren Township, Michigan. The museum has a small fleet of flying aircraft and a collection of static display aircraft outdoors. History The Yankee Air Force Inc. w ...

Belleville, Michigan Belleville is a city in Wayne County, Michigan, Wayne County in the U.S. state Michigan. The population was 3,991 at the 2010 United States Census, 2010 census. As a western suburb of Metro Detroit, Belleville is southeast of Ann Arbor, Michig ...

* 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 Marine Corps Air Station Miramar, San Diego, California. The museum contains exhibits and artifacts relating to the history and legacy of ...

MCAS Miramar Marine Corps Air Station Miramar (MCAS Miramar) , formerly Naval Auxiliary Air Station (NAAS) Miramar and Naval Air Station (NAS) Miramar, is a United States Marine Corps installation that is home to the 3rd Marine Aircraft Wing, which is the av ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. * 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 located in downtown San Diego, California at Navy Pier. The museum consists of the aircraft carrier . The ship houses an extensive collection of aircraft, many of which we ...

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the List of United States cities by population, eigh ...

. * 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 North Highlands, California, outside of Sacramento, California, on the grounds of the former McClellan Air Force Base. The museum has a 4.5-acre outdoor Air Park ...

. * 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. Popondetta is a city. In 1951 the city became the focus of relief efforts after nearby Mount Lamington erupted and killed 4,000 people. P ...

Oro Province Oro Province, formerly (and officially still) Northern Province, is a coastal province of Papua New Guinea. The provincial capital is Popondetta. The province covers 22,800 km2, and has 176,206 inhabitants (2011 census). The province shares la ...

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

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 The Pratt & Whitney R-2800 Double Wasp is an American twin-row, 18-cylinder, air-cooled radial aircraft engine with a displacement of , and is part of the long-lived Wasp family of engines. The R-2800 saw widespread use in many important ...