Liberty L-6

The Liberty L-6 was a six-cylinder, water-cooled, inline, aero-engine developed in the United States during World War I.

Design and development
The Liberty L-6, which developed 200-215 hp, was built by the Thomas-Morse Aircraft Corp. and Wright Aeronautical Corp. Since it was based on the same engine design as the more successful Liberty L-12 V12 liquid cooled aviation engine, the L-6's resemblance to the Mercedes D.III German aviation engine, the source for the Liberty V-12's own cylinder and valvetrain design, resulted in the American L-6 engine design bearing a close visual resemblance to the German straight-six aviation powerplant in a number of respects, with at least one L-6 even being mounted postwar into a captured Fokker D.VII fighter for testing in the USA.

Since the L-6 was too large for mail airplanes and other engines were available, the L-6 was canceled after only 52 had been built. In 1920 10 more L-6 engines were ordered, designated L-825, several of which were installed in the Curtiss PN-1, (only two built), and the Engineering Division TW-1, (only six built).