Wright R-2600 Twin Cyclone


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

History

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 R-2600-3 was originally intended for the C-46 Commando. It was also the original engine choice for the F6F Hellcat; a running change for the CW-20A, and one in late April 1942 for the second XF6F-1, led to the adoption of the 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.

Variants

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, 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 the "2600" indicating an engine displacement of, 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. Engines known only by their governmental designation will be listed at the bottom.R-2600-1 – 1,600 hp R-2600-2 – 1,500 hp ; Prototype variant; Few were made.R-2600-3 – 1,600 hp R-2600-4 – 1,650 hp R-2600-5 – 1,600 hp ; Few made, possibly three or less. Utilizied a three-speed supercharger.R-2600-6 – 1,600 hp
  • R-2600-7 — 1,700 hp ; Provisioned for a turbo-supercharger. Unknown use and unknown quantity produced.R-2600-8 – 1,700 hp ; Utilized, among other uses, by the National Advisory Committee for Aeronautics 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 at 2400 rpm for limited periods at take-off power. With water injection, testing was able to achieve 1,943 hp, 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, 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 enginesR-2600-8A – 1,700 hp ; 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. The USN provided them to the U.S. Marine Corps, 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)-531R-2600-9 – 1,700 hp ; Powered the initial production run of the B-25 Mitchell, the B-25, B-25A, and the B-25B. The B-25C would see the -9 replaced with the R-2600-13R-2600-10 – 1,700 hp ; 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. Very few were produced. The R-2600-10 powered Grumman'sXR-2600-10 – 1,900 hp ; Experimental version of the R-2600-10 uprated to 1,900 hp, a 12% increase over the 1,700 hp R-2600-10. The XR-2600-10 powered two examples of the Grumman TBF Avenger, the XTBF-2 and the TBM-2. Neither the XTBF-2, TBM-2, nor the XR-2600-10 would enter serial productionR-2600-11 – 1,600 hp ;R-2600-12 – 1,700 hp R-2600-13 – 1,700 hp ; 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. The -13 would also power a maritime patrol-bomber variant of the B-25, the PBJ-1D. 13,494 R-2600-13s were built between April 1941 and January 1944R-2600-14 – 1,700 hp ; Powered at least one of the prototypes of the Grumman F7F Tigercat, 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 R-2800-22, ultimately trading superior high-altitude performance for the R-2800-22's significantly improved low- and medium-altitude performance.R-2600-15 – 1,800 hp ; Planned to power the XB-33A, a prototype model of the B-33 Super Marauder. The project was cancelled, and neither the prototype XB-33A or production B-33A were ever built.R-2600-16 – 1,700 hp ; 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. 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.R-2600-17 – 1,700 hp ; May have powered a Vultee A-31 Vengeance variant. May have also powered one of the C-55 prototypes, a derivative of the C-46 CommandoR-2600-17A – 1,750 hp ; Uprated R-2600-17R-2600-19 – 1,600 hp, 1,660 hp R-2600-20 – 1,700 hp, 1,900 hp R-2600-21 – 1,500 hp, 1,600 hp, 1,700 hp ; 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 designationR-2600-22 – 2,100 hp ; Powerplant of the experimental XSB2C-6 Helldiver as well as the PBM-3D Mariner. Power is referenced as low as 1,900 hp and as high as 2,100 hp R-2600-23 - 1,600 hp, 1,675 hp ; The R-2600-23 required 91 octane fuel. The -23 was normally rated at 1,600 hp at sea level while at take-off power, but could be "uprated" to 1,675 hp. These "uprated" -23s were utilized in the Douglas A-20G Havoc, the most-produced A-20 modelR-2600-25 – 1,350 hp R-2600-27 – 2,000 hp R-2600-28 – No known information; Occasionally the 2,100 hp R-2600-22 is referred to as the R-2600-28R-2600-29 – 1,700 hp, 1,850 hp ; Likely the most-produced R-2600 variant, with at least 17,848 produced. The R-2600-29 powered the B-25C and -25D 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.R-2600-31 – 1,700 hp ; 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 R-2800 was replaced by either the 1,700 hp R-2600-31 or, with early models, the R-2600-13R-2600-33 – 1,700 hp R-2600-34 – 2,100 hp ; Two R-2600-34s served as the powerplants of the early versions of the PBM-5 Mariner, before the switch-over to the R-2800R-2600-35 – 1,700 hp, 1,850 hp ; 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.GR-2600-A71 – 1,350 hp ; May have been a simplified name of the GR-2600-A71-3GR-2600-A71-3 – 1,600 hp ; 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-A71GR-2600-C14 – 1,750 hp

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