Rotary Engine

A rotary engine has a fixed crankshaft that is rigidly mounted to the fuselage of the airplane. Cylinders are arranged around the crankshaft. The propeller is bolted firmly to the engine. The cylinders, crankcase, and propeller rotate around the crankshaft as a unit. The rotary engine of the early twentieth century used castor oil for lubrication.

The Australian Lawrence Hargrave built, but did not fly, the first rotary engine--a three-cylinder engine--in 1889. The Gnome and Le Rhône are famous examples of rotary engines that were used extensively in the World War I period.