The French Le Rhône rotary aircraft engine is one of the most important engineering designs of early aviation and provided air power for the Allies during World War I. This air-cooled engine provided better power-to-weight ratio than in-line liquid-cooled engines.

Early aircraft engines suffered greatly from overheating. What makes the Le Rhône an engineering marvel is the entire engine block rotated along with the propeller around a fixed crankshaft. The rotating engine design for the most part solved the overheating issue. Of interest, the torque created by the rotating engine caused the aircraft to want to “roll” with the engine, making it difficult and dangerous to fly. Learn more.

During one hour of flight time, the Le Rhône engine sprayed over two gallons of castor oil into the air. With the engine rotating and open cockpits, pilots found themselves covered in oil and often sick from the laxative effects of castor oil.

Pilots wore goggles and a white scarf to protect their faces. The silk scarf kept their neck from chafing as they scanned the skies for enemy aircraft and served as a cloth to clean their goggles. Why white? White means clean, and they didn’t want to wipe their goggles and face with an oily scarf!

Many WWI aircraft utilized this type engine, including most Sopwith and Nieuport designs.

Produced in France by Gnome et Rhône, some 25,000 Le Rhône rotary aircraft engines served during WWI. This particular engine is dated around 1918 and on display in the Museum’s WWI Gallery. Overhead hangs a Sopwith Pup, one of the aircraft this type engine would power. Built with safety in mind, the Museum’s Sopwith Pup (replica) does not have a rotary engine as it would in its original configuration.