| R-760 Whirlwind | |
|---|---|
 Female mechanic working on the R-760 engine of a U.S. Navy N3N trainer in October 1942 | |
| Type | Air-cooled 7-cylinderradial piston engine |
| National origin | United States |
| Manufacturer |
|
| Major applications |
|
| Manufactured | 1929–1945 |
| Number built | around 1400 |
TheWright R-760 Whirlwind was a series of seven-cylinder air-cooledradialaircraft engines built by theWright Aeronautical division ofCurtiss-Wright. These engines had adisplacement of 756 in³ (12.4 L) and power ratings of 225-350 hp (168-261 kW).[1]
Wright introduced the J-6 Whirlwind family in 1928 to replace the nine-cylinderR-790 series. The J-6 family included varieties with five, seven, and nine cylinders. The seven-cylinder version was originally known as theJ-6 Whirlwind Seven, orJ-6-7 for short. The U.S. government designated it as theR-760; Wright later adopted this and dropped the J-6 nomenclature.
Like all the members of the J-6 Whirlwind family, the R-760 had larger cylinders than the R-790. The pistonstroke of 5.5 in (14.0 cm) was unchanged, but the cylinderbore was expanded to 5.0 in (12.7 cm) from the R-790's bore of 4.5 in (11.4 cm). While the R-790 wasnaturally aspirated, the R-760, like the other J-6 engines, had a gear-drivensupercharger to boost its power output.
Over time, Wright refined the R-760, using suffix letters to indicate successive versions. The original R-760 (or J-6-7) was rated for 225 hp (168 kW),[2] while the R-760E of 1931 could do 250 hp (186 kW) thanks to an improvedcylinder head design.[3][4][5] Wright later added another suffix to show different power levels. The R-760E-1, introduced the same year as the R-760E, had a takeoff power rating of 300 hp (224 kW) thanks tohigher-compression pistons and a greaterRPM limit.[3][6][7] The even more powerful R-760E-2 of 1935 could reach 350 hp (261 kW) for takeoff due to increased supercharging and an even higher RPM limit.[3][8][9] On the other hand, the R-760E-T, designed for trainer aircraft, had the R-760E-1's high-compression pistons, but the supercharger was removed, thus giving just 235 hp (175 kW).[3][10][11]
The R-760 was a direct replacement for the R-790, with similar displacement and power. The U.S. Navy used it as the powerplant for several biplaneprimary trainers, including theConsolidated NY, theCurtiss N2C Fledgling, and theNaval Aircraft FactoryN3N Canary. The last of these was produced in large numbers, with most of the engines built under license by the Naval Aircraft Factory. Trainers usually had the unsupercharged R-760E-T engine.
A variety of civilutility aircraft also used the R-760, including models built byBeechcraft,Cessna,Curtiss-Wright,Howard DGA-8,Stearman,Stinson, andWaco. These aircraft generally used the various supercharged versions of the R-760.
Production of the R-760 continued until 1945, with about 1400 examples being built by Wright, and more under licence by foreign manufacturers such asFábrica Nacional de Motores inBrazil.[3][12]
Wright R-760 engines on display are uncommon, but there is an R-760E-2 exhibited at theEvergreen Aviation & Space Museum inMcMinnville, Oregon.[14][15]
Data fromFAAtype certificate data sheet for the R-760E-2;[9] dimensions from Curtiss-Wright (1983).
| Engine | Power, continuous | Power, takeoff | Compression ratio | Supercharger gear ratio | Octane rating | Dry weight |
|---|---|---|---|---|---|---|
| R-760E[5] | 250 hp (186 kW) at 2,000 RPM | 5.1:1 | 7.05:1 | 73 | 530 lb (240 kg) | |
| R-760E-1[7] | 285 hp (213 kW) at 2,100 RPM | 300 hp (224 kW) at 2,250 RPM | 6.1:1 | 7.05:1 | 73 | 565 lb (256 kg) |
| R-760E-2[9] | 320 hp (239 kW) at 2,200 RPM | 350 hp (261 kW) at 2,400 RPM | 6.3:1 | 9.17:1 | 80 | 570 lb (259 kg) |
| R-760E-T[11] | 235 hp (175 kW) at 2,000 RPM | 6.1:1 | none | 73 | 540 lb (245 kg) |
Related development
Comparable engines
Related lists
The followingFederal Aviation Administrationtype certificate data sheets, all available from the FAA'sRegulatory and Guidance LibraryArchived 2016-11-12 at theWayback Machine:
