Wright R-2600 Twin Cyclone

Template:Short description Template:Use American English

The Wright R-2600 Cyclone 14 (also called Twin Cyclone) is an American radial engine developed by Curtiss-Wright, and widely used in aircraft in the 1930s and 1940s.

HistoryEdit

In 1935, Curtiss-Wright began work on a more powerful version of their successful R-1820 Cyclone 9. The result was the R-2600 Twin Cyclone, with 14 cylinders arranged in two rows. The Template:Convert R-2600-3 was originally intended for the C-46 Commando (being fitted to the prototype CW-20A). It was also the original engine choice for the F6F Hellcat; a running change (one which would not stop production) for the CW-20A, and one in late April 1942 for the second XF6F-1, led to the adoption of the Template:Convert Pratt & Whitney R-2800 Double Wasp in the R-2600's place for both designs.

The Twin Cyclone went on to power several important American World War II aircraft, including the A-20 Havoc, B-25 Mitchell, TBF Avenger, SB2C Helldiver, and the PBM Mariner.

Over 50,000 R-2600s were built at plants in Paterson, New Jersey, and Cincinnati, Ohio.

VariantsEdit

The following is a list of known R-2600 models. Engines would receive a three-part designation from Curtiss-Wright. For example, "R-2600-1;" the "R" indicating a "radial engine," "2600" indicating an engine displacement of Template:Cvt, and "1" indicating the internal model number, usually assigned chronologically. Engines accepted by the U.S. government were assigned a separate, three-part governmental designation. For example, the "R-2600-13" was accepted into service as the "GR-2600-B655;" the "GR" indicating a "(geared) radial engine," the "2600" indicating an engine displacement of Template:Cvt, and "B655" indicating the governmental model number. The Curtiss-Wright designation is usually utilized more often than the governmental designation, and the U.S. government utilized both designations interchangeably and often together.

The Curtiss-Wright designation will be listed first, followed by the — when known — governmental designation in parentheses (the lack of a governmental designation does not indicate that the model was not accepted into governmental service). Engines known only by their governmental designation will be listed at the bottom.

R-2600-1 - 1,600 hp (1,194 kW)
R-2600-2 - 1,500 hp (1,118 kW); Prototype variant; Few were made.<ref name="Friedman 1">Template:Cite book</ref>
R-2600-3 - 1,600 hp (1,194 kW)
R-2600-4 - 1,650 hp (1,230 kW)<ref>Template:Cite press release</ref>
R-2600-6 - 1,600 hp (1,194 kW)
R-2600-8<ref name="USAF_Parts">Template:Cite report</ref> - 1,700 hp (1,268 kW); Utilized, among other uses, by the National Advisory Committee for Aeronautics (NACA) to test water injection generally and in-regards to the R-2600 series, specifically. Without water injection, the R-2600-8 was capable of producing 1,700 hp (1,268 kW) at 2400 rpm for limited periods at take-off power. With water injection, testing was able to achieve 1,943 hp (1,449 kW) (maintaining the standard 2400 rpm), a 14.3% increase in power, with a fuel efficiency increase of 5%. By increasing to 2600 rpm, testing was able to achieve 2,060 hp (1,536 kW), a 21% increase in power, while providing a 4% boost in fuel efficiency. Water injection would feature heavily in mid- to late-WWII U.S. engines, including some early jet engines<ref>Template:Cite report</ref>
R-2600-8A<ref name="USAF_Parts"></ref> - 1,700 hp (1,268 kW); Powered the Brewster SB2A-4 Buccaneer, 162 SB2As built for the Kingdom of the Netherlands for service in the Dutch East Indies by the Royal Netherlands East Indies Army Air Force. The Dutch East Indies were overrun by Imperial Japan in early 1942 before a single Buccaneer was delivered. The Dutch SB2As were requisitioned by the U.S. Navy (USN). The USN provided them to the U.S. Marine Corps (USMC), complete with Dutch markings. The USN and USMC would designate these 162 models as the SB2A-4. The USMC utilized these models to establish their first night fighter squadron, VMF(N)-531<ref>Template:Cite book</ref>
R-2600-9 - 1,700 hp (1,268 kW); Powered the initial production run of the B-25 Mitchell, the B-25 (24 built), B-25A (40 built), and the B-25B (designated the "Mitchell Mk.I" by the Royal Air Force; 23 built). The B-25C (1,625 built) would see the -9 replaced with the R-2600-13<ref>Template:Cite book</ref>
R-2600-10 (GR-2600-B676) - 1,700 hp (1,268 kW); Experimental high-altitude R-2600 variant with an "advanced" two-stage mechanical supercharger, vice the usual single-stage supercharger. The 2600-10 also served as a testbed for turbo-supercharging the 2600 series (which would come to fruition with the R-2600-16). Very few were produced.<ref name="Francillon 2021-04-03">Template:Cite book</ref><ref name="Grossnick 2021-04-03">Template:Cite encyclopedia</ref> The R-2600-10 powered Grumman's prototype F6F Hellcat, the XF6F-1. The XF6F-2 would be powered by the developmentally similar R-2600-16. Grumman and the U.S. Navy were not happy with the R-2600's performance, which led to the 2,000 hp (1,491 kW) Pratt & Whitney R-2800 engine replacing the R-2600 on the XF6F-3 and F6F production models.<ref name="Cleaver 1">Template:Cite book</ref>
XR-2600-10 - 1,900 hp (1,420 kW); Experimental version of the R-2600-10 uprated to 1,900 hp (1,420 kW), a 12% increase over the 1,700 hp (1,268 kW) R-2600-10. The XR-2600-10 powered two examples of the Grumman TBF Avenger, the XTBF-2 (1 built) and the TBM-2 (1 built). Neither the XTBF-2, TBM-2, nor the XR-2600-10 would enter serial production
R-2600-11 - 1,600 hp (1,194 kW);<ref name="USCAA 2021-04-03">Template:Cite book</ref>
R-2600-12<ref name="USAF_Parts"></ref> (GR-2800-B766) - 1,700 hp (1,268 kW)
R-2600-13<ref name="USAF_Parts"></ref> (GR-2600-B655),<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> 1,700 hp (1,268 kW);<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite book</ref> Powered the Brewster SB2A-4; Curtiss P-37; Douglas A-24A/B/C; Martin A-30A/B; North American XB-25E/F/G, B-25C/D/G/H/J, CB-25J, TB-25J, and F-10; Lockheed O-56/RB-34B/B-37/RB-37; Short Brothers Stirling; and the Vultee A-35A & A-35B.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The -13 would also power a maritime patrol-bomber variant of the B-25, the PBJ-1D.<ref>Template:Cite book</ref> 13,494 R-2600-13s were built between April 1941 and January 1944<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

R-2600-14 - 1,700 hp (1,268 kW); Powered at least one of the prototypes of the Grumman F7F Tigercat (a twin-engined heavy fighter-interceptor), the XF7F-1. The R-2600-14 was a development of the R-2600-10 and featured "advanced supercharging" for high-altitude performance. The R-2600-14 was developed specifically for the Tigercat project. The engines were replaced in initial production versions by the 2,100 hp (1,566 kW) R-2800-22, ultimately trading superior high-altitude performance for the R-2800-22's significantly improved low- and medium-altitude performance.<ref>Template:Cite journal</ref>
R-2600-15 - 1,800 hp (1,342 kW); Planned to power the XB-33A, a prototype model of the B-33 Super Marauder (itself a high-altitude version of the B-26 Marauder). The project was cancelled, and neither the prototype XB-33A or production B-33A were ever built.<ref name="Andrade 1979, p 51">Andrade 1979, p 51</ref>
R-2600-16 - 1,700 hp (1,268 kW); Similar to the R-2600-10 & -14, the -16 was tuned for high-altitude performance; The -16 was designed to be mounted alongside a turbo-supercharger system. The -16 would power the second Grumman F6F, the initial XF6F-2.<ref name="Thruelsen 1976, p 193">Thruelsen 1976, p 193</ref> The XF6F-1 and XF6F-2 was found to be lacking in performance; The XF6F-2 designation was re-used on a third prototype, an R-2800-powered XF6F-2. The R-2800 would carry-over into the final prototype, the XF6F-3, as well as production models.<ref>Template:Cite book</ref>
R-2600-17 - 1,700 hp (1,268 kW); May have powered a Vultee A-31 Vengeance (or A-35) variant. May have also powered one of the C-55 prototypes, a derivative of the C-46 Commando<ref>Template:Cite book</ref>
R-2600-17A - 1,750 hp (1,305 kW); Uprated R-2600-17
R-2600-19 (GR-2600-A5B) - 1,600 hp (1,194 kW), 1,660 hp (1,237 kW)
R-2600-20<ref name="USAF_Parts"></ref> - 1,700 hp (1,268 kW), 1,900 hp (1,420 kW)<ref name="Grossnick 2025-03-22">Template:Cite encyclopedia</ref>
R-2600-21 (GR-2600-A5B) - 1,500 hp (1,118 kW), 1,600 hp (1,194 kW), 1,700 hp (1,268 kW); Experimental R-2600-19 engines modified with new carburetors and cylinder baffles. -21s were "converted" back into -19s and retained their governmental GR-2600-A5B designation
R-2600-22<ref name="USAF_Parts"></ref> - 2,100 hp (1,566 kW); Powerplant of the experimental XSB2C-6 Helldiver<ref>Template:Cite book</ref> as well as the PBM-3D Mariner.<ref>Template:Cite report</ref> Power is referenced as low as 1,900 hp (1,418 kW)<ref>Template:Cite book</ref><ref>Template:Cite journal</ref> and as high as 2,100 hp (1,566 kW)<ref>Template:Cite book</ref><ref>Template:Cite book</ref>
R-2600-23 (GR-2600-A5B-0) - 1,600 hp (1,194 kW), 1,675 hp (1,250 kW); The R-2600-23 required 91 octane fuel (other R-2600 models accepted higher-octane fuel).<ref>Template:Cite report</ref> The -23 was normally rated at 1,600 hp (1,194 kW) at sea level while at take-off power, but could be "uprated" to 1,675 hp (1,250 kW). These "uprated" -23s were utilized in the Douglas A-20G Havoc, the most-produced (2,850 built) A-20 model<ref>Template:Cite book</ref>
R-2600-25 - 1,350 hp (1,007 kW)<ref>Template:Cite book</ref>
R-2600-27 - 2,000 hp (1,491 kW)<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

R-2600-28 - No known information; Occasionally the 2,100 hp (1,566 kW) R-2600-22 is referred to as the R-2600-28
R-2600-29<ref name="USAF_Parts"></ref> - 1,700 hp (1,268 kW),<ref>Template:Cite report</ref><ref>Template:Cite book</ref> 1,850 hp (1,380 kW);<ref>Template:Cite book</ref><ref>Template:Cite book</ref> Likely the most-produced R-2600 variant, with at least 17,848 produced. The R-2600-29 powered the B-25C and -25D (including the PB1-1J, a maritime patrol bomber variant of the B-25)<ref>Template:Cite book</ref> as well as the A-20G and -H. An R-2600-29A is also referenced in various manuals and reports as the powerplant of the twin-engine TB-25N medium bomber trainer aircraft. The R-2600-29A is referenced interchangeably with the R-2600-35.<ref>Template:Cite report</ref>
R-2600-31<ref name="USAF_Parts"></ref> - 1,700 hp (1,268 kW); The Lockheed B-34 Ventura, originally powered by the R-2800, was chosen to be converted into a large, armed reconnaissance and observation aircraft, designated as the "O-56." This was later changed to "RB-34B," then to "B-37," and finally to "RB-37." 500 RB-37s were ordered, but the contract was cancelled after 18 were delivered. As the RB-37 was not expected to carry bomb loads, it was felt a lower-powered engine would suffice; The 2,000 hp (1,491 kW) R-2800 was replaced by either the 1,700 hp (1,268 kW) R-2600-31 or, with early models, the R-2600-13
R-2600-33 - 1,700 hp (1,268 kW)<ref>Template:Cite report</ref>
R-2600-34 - 2,100 hp (1,566 kW); Two R-2600-34s served as the powerplants of the early versions of the PBM-5 Mariner, before the switch-over to the R-2800<ref>Template:Cite book</ref>
R-2600-35 - 1,700 hp (1,268 kW),<ref>Template:Cite report</ref> 1,850 hp (1,380 kW);<ref>Template:Cite book</ref><ref>Template:Cite book</ref> An R-2600-29 or R-2600-29A modified with a Bendix Stromberg PR48A4 carburetor. The -29, -29A, and -35 may have been considered interchangeable to a degree.<ref>Template:Cite report</ref>
GR-2600-A71 - 1,350 hp (1,007 kW); May have been a simplified name of the GR-2600-A71-3<ref name="A71">Template:Cite book</ref>
GR-2600-A71-3 - 1,600 hp (1,193 kW); Early R-2600 model, developed in late 1938 or very early 1939. Powered the North American NA-40B, a twin-engine medium bomber of which only one was built. The NA-40 would lead the to B-25 Mitchell. May also be referred to as the GR-2600-A71<ref name="A71"></ref>
GR-2600-C14 - 1,750 hp (1,304 kW)