Fokker D.IX

The Fokker D.IX was a Dutch single-seat, single-engine fighter, the final and most powerful development of the Fokker D.VII of the First World War, and it first flew in 1921. Its Hispano-Suiza 8Fb water-cooled V-8 gave 224 kW, far more than the 120 kW of the D.VII's original Mercedes engine, and the airframe was a single-bay biplane with N-form interplane struts, a welded steel tube fuselage and an axle fairing enlarged to hold a fuel tank. The sole example was sold to the US Army Air Service in 1922 and tested at McCook Field as the PW-6 with a 238 kW Wright M-2 engine and two fixed machine guns; although it was about 20 percent faster than a standard D.VII and climbed twice as fast, the Americans judged it not worth further development.