After the Tripes the Quads
If three wings were good perhaps even more wings would be better. Fredrick Koolhoven obviously thought so for in late 1916 he designed the Armstrong Whitworth FK 10 two seat quadruplane fighter. Small numbers were manufactured and supplied to both the RFC and the RNAS.
This has been described in an earlier post
The Wight Quadruplane single seat fighter (confusingly built by a firm called Wright founded by a mister White and based in the Isle of Wight) first appeared in August 1916 and was initially regarded as unsafe to fly and as a result was the subject of several redesigns and rebuilds before flight testing could be attempted This finally took place took place in February 1917.
Despite the rebuilds it was still remained a dangerous aircraft. The wings were very short and spaced in such a way as to make it necessary to have a very tall relatively narrow undercarriage which in turn resulted in the aircraft being at a very steep angle when taxiing and taking off. It would have been at risk of ground looping on landing. Its performance figures are not recorded but with only a 110 hp Le Clerget rotary as the power plant they are unlikely to have been spectacular and there were certainly fighters already in production that would have surpassed them. Because of the delays in getting an airframe that was considered as safe to fly, by the time the aircraft could be tested it was already obsolete. The RNAS, for whom it had originally been intended, showed little interest and never even allocated it an official serial number. The aircraft was returned to Wright’s in August 1917 and finally scrapped in February 1918.
In Germany the Euler Vierdecker appeared in December 1917using the fuselage from a Eurler copy of the Nieuport 17. Purists might argue that this was technically a triplane rather than a quadruplane as the top wing acted as two moveable control surfaces. Nevertheless the Euler Company, which had already produced several prototype triplanes, defined it as a quadruplane and it certainly looked like one.
Two prototypes were built and tested by the Germany military but pilots were not impressed with its performance that was well below other fighters that p were already available for service. Euler returned to producing triplanes (none of which reached production either).
In 1918 the small German aircraft manufacturer Naglo also tried its hand at producing a quadruplane. They took an existing Albatross DV fuselage and fitted it with four wings. It appears that it had originally been intended to produce a triplane but the designer added an extra wing on a spine under the fuselage at the last minute. Albatross had already tried fitting three wings to the DV with no improvement in performance over the standard biplane version and Naglo’s four winged variant was no more successful. It turned out that the designer was drawing a salary from Albatross whilst moonlighting for Naglo.