Wright Whirlwind J-6-9 (R-975), Radial 9 Engine

Type: Reciprocating, 9 cylinders, radial, air-cooled

Power rating: 224 kW kW (300 hp) at 2,000 rpm

Displacement: 16 L (975 cu in.)

Bore and Stroke: 127 mm (5.0 in.) x 140 mm (5.5 in.)

Weight: 250 kg (550 lb)

Charles Lawrance designs for air-cooled engines began in 1915. In 1921, his own small company’s J-1 149 kW (200 hp) engine was designed for a Navy contract. Wanting a better, compact, lightweight engine not plagued with water leakage problems for use on aircraft carriers; the Navy encouraged the 1923 merger with the larger Wright Aeronautical Corporation. The Lawrance engine then progressed through the Wright Whirlwind J-3, J-4, J-5, and J-6 series, with the fully supercharged, high compression R-760-E2 certificated in December 1935. However, the most famous of these models was the J-5 which powered Lindbergh’s Spirit of St. Louis.

The R-975 was a nine-cylinder engine in the J-6 series. Versions of the R-975 ranged from 224 to 354 kW (300 to 475 shp), and powered aircraft such as the Consolidated BT6, Stearman BT3/YPT-9C, North American BT-9/A/B/C/D, Vultee BT-15, Lockheed 10, Beech D-17R and 18R, and Ford 4-AT-E. The R-975 also had autogiro, airship, and tank applications.