The Fokker D.IX
The D.IX was the last model to emerge from the D.VII concept.
The biggest change from the D.VII was the tail section of the D.IX and the choice of engine.
The D.IX could also be equipped with an additional fuel tank between the wheels of the landing gear.
It was a single-seat biplane with a 300 hp water-cooled Hispano-Suiza 8Fb V-8 engine.
The only example of the D.IX built made its first flight in 1921.
The D.IX was sold to the US Army Air Service in 1922 and shipped to the American research center at McCook Field.
At the USAAS the D.IX was designated PW-6, the sixth fighter aircraft in a series with a water-cooled engine,
Pursuit
Wwater-cooled.
Other engines were experimented with on the D.IX at McCook Field, including a US-licensed Hispano-Suiza Type 42 of 320 hp.
Minor changes were also made to the landing gear at McCook Field, as flights were conducted both with and without an additional fuel tank between the landing gear.
The D.IX could be fitted with synchronized armament, as with the D.VII, but for ammunition of a different caliber.
Despite its good climb performance, the aircraft was not further developed for the USAAS, and only one aircraft was built.
Click on the photo to enlarge the photo
America
During his visit to America in late 1920/early 1921, Anthony Fokker did not fail to notice that many captured D.VIIs were still flying there.
And also that experiments were being carried out there with other engines for the aircraft.
Noorduyn reported in late 1921 that the Army Air Service was interested in purchasing D.VIIs with the Wright (Hispano) H-2 engine.
This Wright H series was based on the Hispano-Suiza 8F and was available in large numbers. It was then decided in the Netherlands to adapt the D.VII for this purpose.
The Wright Aeronautical Corporation lent a new version of that engine (the H-3) to Fokker for this purpose. It was sent in early January 1922. The new aircraft was nevertheless slightly larger than the D.VII and had an extra fuel tank between the wheels of the undercarriage.
Fokker decided to send the D.IX together with the prototype of the C.IV to America at his own risk. But because it was requested that this be done on an Army transport ship via Antwerp and with a guarantee that no import duties would be levied, the shipment was delayed.
General Mitchell, who visited the factory at the time, could not arrange this either. Because Fokker wanted to fly the planes himself at McCook Field, he finally decided to go to America with the planes on the Nieuw Amsterdam.
On 28 May 1922 he arrived there and by mid-June the D.IX (but now without the extra tank) was ready for him. With McCook Field number P246 on the keel. Because the aircraft had not yet been purchased, the type designation PW-6 and the registration AS 68557 had not yet been applied.
In the meantime, the D.IX had been subjected to an intensive inspection. And again it was found that the aircraft deviated considerably from the regulations in the Handbook. The application of this would lead to considerable extra weight.
Taking this into account, the test program showed that the D.IX would not outperform comparable devices.
The D.IX was nevertheless purchased, because an improved version with a more powerful engine offered more prospects.
As AS 68575 it flew until early February 1923. The aircraft was not scrapped until 1926. For Fokker, the D.IX was nevertheless a small success: an order was received for three improved aircraft, but now equipped with the Curtiss D-12 engine (the later D.XII).
