The Fokker V.9 was part of a series of experimental aircraft which led up to the low-production D.VI fighter. The aircraft were very similar, varying in detail and power plants.
The V.9 was powered by a Oberursel U.O (later re-engined with a 110 hp Ur.II rotary) and first flew in December 1917; all others flew in 1918.
The V.12 was powered by an experimental , Steyr-Le Rhône engine.
The V.14. Like the V.12, the V.14 was powered by the Steyr-Le Rhone.
The V.16 was powered by the Oberursel Ur. II.
The V.33 was a development of the V.9. It was tested with both an Ur. II engine and then a Ur. III engine.