Wright R-790 Whirlwind

The Wright R-790 Whirlwind was a series of nine-cylinder air-cooled radial aircraft engines built by Wright Aeronautical Corporation, with a total displacement of about 790 cubic inches (12.9 L) and around 200 horsepower (150 kW). These engines were the earliest members of the Wright Whirlwind engine family.

Design and development

The R-790 Whirlwind began as the Lawrance J-1, a nine-cylinder air-cooled radial developed in 1921 by the Lawrance Aero Engine Company for the U.S. Navy. The Navy was very enthusiastic about air-cooled engines, which it considered better suited for naval use than liquid-cooled ones. Lawrance was a small company, though, and the Navy doubted it could produce enough engines for its needs. Despite urgings from the Navy, the major U.S. aircraft engine makers, Wright and Curtiss, were satisfied with their liquid-cooled engines and showed no interest in building air-cooled engines. Since the Navy was already a major buyer of Wright engines, it pressured Wright into purchasing Lawrance and building the J-1 itself, by informing the company that the Navy would buy no more of its existing engines or spare parts. To retain the Navy's business, Wright complied in 1923 and the Lawrance J-1 became the Wright J-1.

By the time Lawrance merged with Wright, it had already developed the more powerful J-2, a version of the J-1 with slightly enlarged bore and displacement. However, Lawrance decided the J-1 was large enough, and the J-2 never went into production; only two examples were built.