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.
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 1,600hp (1,200kW; 1,600PS) 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 2,000hp (1,500kW; 2,000PS)Pratt & Whitney R-2800 Double Wasp in the R-2600's place for both designs.
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 2,600cuin (43L), 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 2,600cuin (43L), 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 – 1,600hp (1,194kW)
R-2600-2 – 1,500hp (1,118kW); Prototype variant; Few were made.[2]
R-2600-5 (GR-2600-A79) – 1,600hp (1,194kW); Few made, possibly three or less. Utilizied a three-speed supercharger.[4]
R-2600-6 – 1,600hp (1,194kW)
R-2600-8[5] – 1,700hp (1,268kW); 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 1,700hp (1,268kW) at 2400rpm for limited periods at take-off power. With water injection, testing was able to achieve 1,943hp (1,449kW) (maintaining the standard 2400rpm), a 14.3% increase in power, with a fuel efficiency increase of 5%. By increasing to 2600rpm, testing was able to achieve 2,060hp (1,536kW), 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[6]
R-2600-9 – 1,700hp (1,268kW); 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[8]
R-2600-10 (GR-2600-B676) – 1,700hp (1,268kW); 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.[9][10] The R-2600-10 powered Grumman's
XR-2600-10 – 1,900hp (1,420kW); Experimental version of the R-2600-10 uprated to 1,900hp (1,420kW), a 12% increase over the 1,700hp (1,268kW) 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-2600-14 – 1,700hp (1,268kW); 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 2,100hp (1,566kW) R-2800-22, ultimately trading superior high-altitude performance for the R-2800-22's significantly improved low- and medium-altitude performance.[18]
R-2600-15 – 1,800hp (1,342kW); 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.[19]
R-2600-16 – 1,700hp (1,268kW); 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.[20] 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.[21]
R-2600-17 – 1,700hp (1,268kW); 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[22]
R-2600-21 (GR-2600-A5B) – 1,500hp (1,118kW), 1,600hp (1,194kW), 1,700hp (1,268kW); 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-2600-23 (GR-2600-A5B-0) - 1,600hp (1,194kW), 1,675hp (1,250kW); The R-2600-23 required 91 octane fuel (other R-2600 models accepted higher-octane fuel).[30] The -23 was normally rated at 1,600hp (1,194kW) at sea level while at take-off power, but could be "uprated" to 1,675hp (1,250kW). These "uprated" -23s were utilized in the Douglas A-20G Havoc, the most-produced (2,850 built) A-20 model[31]
R-2600-28 – No known information; Occasionally the 2,100hp (1,566kW) R-2600-22 is referred to as the R-2600-28
R-2600-29[5] – 1,700hp (1,268kW),[34][35] 1,850hp (1,380kW);[36][37] 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)[38] 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.[39]
R-2600-31[5] – 1,700hp (1,268kW); 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 2,000hp (1,491kW) R-2800 was replaced by either the 1,700hp (1,268kW) R-2600-31 or, with early models, the R-2600-13
R-2600-34 – 2,100hp (1,566kW); 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[41]
R-2600-35 – 1,700hp (1,268kW),[42] 1,850hp (1,380kW);[43][44] 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.[45]
GR-2600-A71 – 1,350hp (1,007kW); May have been a simplified name of the GR-2600-A71-3[46]
GR-2600-A71-3 – 1,600hp (1,193kW); 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[46]
↑ "Teesside Aviation News"(PDF) (Press release). Teesside, UK: Teesside Aviation Society. 1982-11-01. Retrieved 2021-04-06. ...for the RAF, 19 were experimentally fitted with R-2600-4-53 Cyclones... engines of 1650 hp.
↑ Bingham, Victor (1998). Major Piston Aero-engines of World War II. United Kingdom: Airlife. p.147. ISBN9781840370126. Archived from the original on 15 August 2025. Retrieved 15 August 2025. [...] the R-2600-5 (or -A79) is of interest as it introduced a three-speed supercharger.
1 2 3 4 5 6 7 8 Parts Catalog; Models R-2600-8, 8A, 12, 13, 20, 22, 29, 31; T.O. 2R-R2600-4 (Formerly AN 02A-35H-4) (Report). Marion, Indiana, USA: Secretary of the Air Force and the Chief of the Bureau of Aeronautics via Central Press, Inc. 1951-09-13.
↑ Mary F. Loughlin, Samuel Loring Morison, Robert J. Devlin, Everett Gordon Bowen-Hassell, John M. Patton, James L. Mooney, U.S. Naval Historical Center, United States Naval History Division (1970). Dictionary of American Naval Fighting Ships, Volume 5. Navy Department, Office of the Chief of Naval Operations, Naval History Division. p.589. Archived from the original on 2025-05-29. ...Wright R-2600-13, 1700 h.p....{{cite book}}: CS1 maint: multiple names: authors list (link)
↑ "Wright Cyclone R-2600-13 (GR-2600-B655), 2-Row, Radial 14 Engine". National Air and Space Museum. Archived from the original on 2024-08-16. R-2600-13 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; Northrop A-35; Lockheed B-37; Short Brothers Stirling; Vega O-56; and Vultee A-31A, Vultee XA-35A, A-35A/B.
↑ Mary F. Loughlin, Samuel Loring Morison, Robert J. Devlin, Everett Gordon Bowen-Hassell, John M. Patton, James L. Mooney, U.S. Naval Historical Center, United States Naval History Division (1970). Dictionary of American Naval Fighting Ships, Volume 5. Navy Department, Office of the Chief of Naval Operations, Naval History Division. p.589. Archived from the original on 2025-05-29. Data For: PBJ-1D... Power Plant: Two Wright R-2600-13, 1700 h.p....{{cite book}}: CS1 maint: multiple names: authors list (link)
↑ "Wright Cyclone R-2600-13 (GR-2600-B655), 2-Row, Radial 14 Engine". National Air and Space Museum. Archived from the original on 2024-08-16. R-2600-13 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; Northrop A-35; Lockheed B-37; Short Brothers Stirling; Vega O-56; and Vultee A-31A, Vultee XA-35A, A-35A/B. A total of 13,494 R-2600-13 engines were built between April 1941 and January 1944... Power rating: 1,268 kW (1,700 hp) at 2,600 rpm...
↑ Hal Andrews (1998). "Naval Aircraft; F7F Tigercat"(PDF). Naval Aircraft. Archived from the original(PDF) on 2023-11-29. Both the Army and Navy planned to use Wright R-2600 engines with advanced supercharging... XF7F-1 engineering design began in late spring 1942, with mockup inspection in September. By summer 1943, production was being negotiated and a major engine change from Wright's R-2600 to the Pratt and Whitney R-2800 eliminated supporting an engine model unique to the F7F...
↑ White, Graham (2001). R-2800: Pratt & Whitney's Dependable Masterpiece. Warrendale, Pennsylvania, United States: Society of Automotive Engineers. p.508. ISBN9780768002720. Archived from the original on 2025-04-01. XF6F-2*... This designation was used twice... Intended to be powered by turbocharged version of Wright R-2600-16, instead re-engined with R-2800.
↑ The Illustrated Encyclopedia of Aviation. Vol.20. United States: Marshall Cavendish Corporation. 1979. p.2304. Archived from the original on 2025-04-01. ...clean design was maintained in the Vengeance, though the cranked wing panton made some observers think (wrongly) that the aircraft's centre of gravity had given problems. Power was provided by a 1,600hp Cyclone R-2600-9 or 1,700hp R-2600-17.
↑ Dorr, Robert F. (1997). "Variant Briefing: Martin Flying Boats: Mariner, Mars and Marlin". Wings of Fame. 7. London: Aerospace Publishing: 125. ISBN1-874023-97-2.
↑ Aircraft Listing: July 1, 1949 (Report). United States: U.S. Department of Commerce, Civil Aeronautics Administration. 1949-07-01. p.68. Archived from the original on 2025-03-30. R-2600-23... 91 Octane... Sea level... 1600 hp...
↑ Johnson, E.R. (2012). American Attack Aircraft Since 1926. United States: McFarland, Incorporated, Publishers. p.67. ISBN9780786471621. Archived from the original on 2025-03-30. The A-20G was the most widely produced version of the series, a total of 2,850 being built at Douglas's Santa Monica plant in 1943 and 1944. Influenced largely by Pacific-based A-20As and Cs, the G model introduced a solid nose equipped initially with four fixed 20-mm and two .50-caliber machine guns, along with R-2600-23 engines uprated to 1,675-hp.
↑ Griffiths, Harold (1944). Mathematics for Aircraft Engine Mechanics. United Kingdom: McGraw-Hill. p.317. R-2600-25 has a 100 per cent normal rated hp. of 1,350 at 2,300 r.p.m. with a manifold pressure of 37.0 "Hg at 5,800' altitude...
↑ Aircraft Engine Listing, May 15, 1950 (Report). United States: U.S. Department of Commerce, Civil Aeronautics Administration. 1950-05-15. p.42. R-2600-29... Take-off... HP... 1700...
↑ Wilson, Stewart (1998). Aircraft of WWII. United Kingdom: Aerospace Publications. p.116. ISBN9781875671359. PBM-5 — two 2100hp (1566kW) R-2600-34; four-bladed propellers.
↑ Aircraft Engine Listing, May 15, 1950 (Report). United States: U.S. Department of Commerce, Civil Aeronautics Administration. 1950-05-15. p.42. R-2600-29... Take-off... HP... 1700...
↑ Liss, Witold (1967). The Lavochkin La 5 & 7. Aircraft Profiles. Vol.149. Leatherhead, Surrey, UK: Profile Publications. p.3.
Bibliography
Andrade, John (1979). U.S.Military Aircraft Designations and Serials since 1909. Midland Counties Publications. ISBN0-904597-22-9.
Bridgman, Leonard, ed. (1998). Jane's Fighting Aircraft of World War II. London: Studio Editions Ltd. ISBN0-517-67964-7.
Gunston, Bill (2006). World Encyclopedia of Aero Engines: From the Pioneers to the Present Day (5thed.). Stroud, UK: Sutton. ISBN0-7509-4479-X.
Thruelsen, Richard (1976). The Grumman Story. New York: Praeger Publishers. ISBN0-275-54260-2.
White, Graham (1995). Allied Aircraft Piston Engines of World War II: History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States During World War II. Warrendale, Pennsylvania: SAE International. ISBN1-56091-655-9.
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