Fokker V.4 (Fokker D.VI) Triplane Fighter Prototype
The Fokker V.4 triplane fighter prototype failed to meet company expectations and was eventually delivered to the Austro-Hungarians for formal evaluations.
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The engineering path to the classic Fokker Dr.I Triplane of World War 1 fame went through several prototype fighters put forth by the company. The entire line was inspired by the arrival of the Sopwith Triplane in late-1916 / early-1917 which became an immediate success for the Allies, offering unparalleled maneuvering capabilities, a high operating ceiling, and excellent rate-of-climb against the slower, heavier-armed Fokker biplanes of the period.
Originally conceived of as a fighting biplane for the government of Austro-Hungary when ordered on May 13th, 1917, the appearance of the Sopwith Triplane saw Fokker revise the type as a fighting triplane complete with the triple-wing configuration (upper, middle, and lower sections being fitted) - thus was born the Fokker V.4.
The wings were set ahead of the cockpit in a staggered fashion and aft of the engine placement which was fitted at the nose. The aircraft's fuselage was slab-sided in its general shape and carried the usual qualities - a fixed, wheeled undercarriage set under the frontal mass of the aircraft, a pair of horizontal tailplanes, and a single (very-well-rounded) vertical tail fin. The engine drove a standard two-bladed wooden propeller at the nose and the pilot sat in an open air cockpit. Power to the aircraft came from a Le Rhone 9-cylinder rotary piston engine developing 120 horsepower.
Interestingly, the triple plane wing configuration relied on a cantilever installation as no interplane struts were fitted for additional support - this differed from the finalized Dr.I triplane fighter still to come. Additionally, the upper wing assembly was of a wider span than the two lower pieces, these being of equal span to one another.
The V.4 achieved its first-flight during May of 1917 which led to balanced ailerons and elevators being fitted for improved controlling. Wing flexing proved an issue during these early flights and "I-type" interplane struts were finally added to the wings. A second prototype V.4 was ordered on July 5th 1917.
As a fighter-minded development, the V.4 was intended to carry 2 x 7.92mm LMG 08/15 series machine guns synchronized to fire through the spinning propeller blades. These were founded ahead of the cockpit and fired over the nose of the aeroplane in the usual way.
As the V.4 suffered from high control forces it was not submitted for formal testing by the German Air Service - instead it was sent to Austrian-Hungarian authorities for review in late-August 1917 while Fokker concentrated on two other triplane designs - the V.5 and V.6 prototypes (the V.5 becoming the direct basis for the Dr.I).
Performance specifications on this page are pure estimates on the part of the author.