Fokker D.VII – the lethal weapon

[3d by Marek Rys]

In the summer of 1918 German industry was going through serious material difficulties. There was a shortage of steel necessary for manufacture of tubes also used for the construction of the Fokker D.VII fuselage frames. Therefore, Idflieg ordered Fokker to design a variant with wooden, plywood covered frame. Two such fuselages were built by Lübeck-Travemünde factory taken over by Fokker. The constructed planes were approximately 20 kg heavier that those with steel tubing welded frames, which resulted in decreased performance. One of the “wooden” Fokker D.VII planes took part in the second fighter competition in Adlershof (May-June 1918), while the other was sent to Austria, which was interested in production of that variant.
Independently from the Fokker factory, a wooden fuselage was also designed in the Albatros factory. The 514/18 aircraft built there also took part in the aforementioned Adlershof competition.
The wooden fuselage Fokker D.VIIs were never mass-produced.
To improve the plane’s performance, a modified 134 kW (180 hp) Mercedes DIIIaü over-compressed engine was used. Since its weight and dimensions did not change, there was no need for fuselage modifications. In the end of the summer of 1918, the Machinenfabrik Augsburg-Nürnberg managed to design and launch the production of an inline, liquid-cooled, 136 kW (185 hp) Mana engine. By November 1918, 73 units were manufactured. The engine was installed in three Fokker D.VII machines, including 10348/18 (Wn 3660).
During production, the Fokker factory designed a number of experimental variants, which are briefly described below:
Fokker V.21, a plane with same fuselage as the V.11/II and tapered wings was powered by 147 kW (200 hp) Mercedes DIIIaü over-compressed engine. Ceiling and rate of climb were inferior to that of standard Fokker D.VII machines. Moreover, tapered wings were more expensive to manufacture than the standard D.VII ones. The plane took part in the second fighter plane competition on June 1-21, 1918.
Fokker V.22 (Wn 2342) powered by Mercedes DIIIaü engine was developed for Austria-Hungary. It featured a Jaray four-bladed propeller, designed by Władysław Toman, with blades set not at right angles, but at 60 and 120 degrees. Moreover, the upper wing had a slight dihedral. The plane was armed with two 8 mm Schwarzlose M.16 machine guns. It was test-flown in front Fliegerarsenal (Flars) officials by Stabsfeldwebel Franz Kunter. The plane’s performance turned out to be superior to that of a standard Fokker D.VII, especially in respect to manoeuvrability and rate of climb. Kunter also stressed the good visibility from the cockpit. Flars representatives were sceptical of Kunter’s report, bearing in mind his connection to the Fokker factory. After installation of 154 kW (210 hp) Austro-Daimler engine the plane’s performance was further increased, although the V.22 was heavier then the Austro-Hungarian Aviatik D.I and its load carrying capacity was lower (190 kg against the Aviatik’s 230 kg). The plane fitted with twin-bladed propeller was shipped to Matyasford on April 24, 1918, where it received designation 90.95. Flars changed its opinion under influence of the successes scored by the Fokker D.VII aircraft in combat on the Western Front. It was decided to start its production in order to replace the Albatros (Oef) D.III and the Aviatki D.I planes in the nearest future. Fokker V.24 (Wn 2612) was powered by 176 kW (240 hp) Benz Bz IVü engine. It had an excellent rate of climb, but much worse handling qualities. The plane entered the second fighter plane competition at Adlershof, but finally, it almost brought up the rear.
Fokker V.31 was equipped with a hook to tow the V.30 glider. Fokker V.34 was originally powered by 176 kW (240 hp) Benz Be IVü engine. It was fitted with rectangular rudder with no fin, as well as a new oval-shaped radiator. There was no cut-out in the central section of the upper wing and the fuselage was shortened. Due to problems, the Benz engine was replaced with 138 kW (185 hp) BMW IIIa unit.
Fokker V.35 was a conversion of the production series Fokker D.VII to a two-seater, powered by a BMW IIIa engine. The fuel tank was mounted inside the undercarriage axle fairing and the space thus created was used for another seat without changing the fuselage length. The observers position was in front of the pilot and to facilitate his manning the plane, the cut-out in the central section of the upper wing was enlarged. The plane was test-flown not only by Fokker himself, but also by Seekatz and Udet. After the Armistice the plane was used for liaison flights.
Fokker V.36 was a powered by the BMW IIIa engine and had the same radiator as the V.34, but the wings area was smaller. The fuel tank was installed inside the axle fairing. The reasons for its relocation were the overheating of ammunition, which led to its self-ignition, as well as an attempt to protect the pilot in case the tank was hit with incendiary rounds and caught fire. It was assumed that in the case of hard crash landing the undercarriage along with the tanks would be swept away by the impact and left behind the plane, thus reducing the risk of a fire. The same solution was applied to the Fokker C.I.
Between October 15 and 31, 1918, the V.36 took part in the third fighter plane competition, where it proved to be faster than the Fokker D.VIIF, but lost to the Rumpler D.I.