Note: This engine is located in the Research & Development Gallery on a controlled-access portion of Wright-Patterson Air Force Base. Click here for requirements to visit this gallery.
The four-cylinder Liberty was an experimental water-cooled engine of 102 hp, built during World War I by the Hudson Motor Co. and intended primarily for use in training airplanes. Only two were produced since other types of engines for trainers were perfected and placed in production, eliminating any requirement for the L-4. As far as is known, the L-4 was never test-flown in an airplane.