| D.XII | |
|---|---|
 | |
| Role | Single seat fighter aircraft |
| National origin | Netherlands |
| Manufacturer | Fokker-Flugzeugwerke |
| First flight | with Curtiss engine 21 August 1924 |
| Number built | 3 |
The Fokker D.XII was a Dutch single seat, single engine fighter aircraft designed to an American specification which called for the use of a Curtiss D-12 engine, designated PW-7. Despite considerable efforts to improve the airframe, Fokker failed to win the USAAS competition.
The D.XII owed its existence to the Fokker D.XI, even though they had no design overlap; the connection was that the earlier aircraft had some success when submitted to the USAAS's call for entrants in its PW-7 specification competition, an order for three resulting. The D.XII was intended from the start to meet this specification and was designed around the required Curtiss D-12 engine. [1]
Initially, the D.XII was, like the D.XI, a single bay sesquiplane but its wings were different in plan and construction. The upper wing was straight edged with some sweep on the leading edge, it had a thinner aerofoil section than that of its predecessor and was fabric rather than plywood covered. Overhung ailerons were used, their ends projecting outboard of the squared wing tips proper, acting as aerodynamic balances. The lower wing, which lacked ailerons, was both much shorter in span and smaller in chord. The early D.XII had a V-form interplane strut on each side; another strut leant out from each wing root to the upper rear spar, assisted ahead of it on each side by a short V-form pair linking the two spars to the upper fuselage longeron, acting as N-form cabane struts. [1] [2]
The fuselage of the D.XII was flat sided and deep from nose to tail. Initially it had the same 300 hp (224 kW) Hispano-Suiza 8F V-eight engine as its predecessor, but this was soon replaced by the USAAS-specified 440 hp (328 kW) V-twelve water-cooled Curtiss D-12. Both were enclosed by a metal cowlings, though of slightly different shapes, and drove a two blade propeller. The single, open cockpit was well to the rear, about midway down the fuselage. Its horizontal tail was braced and the fin was small, carrying a balanced rudder that extended down to the keel. The D.XII had a fixed conventional undercarriage of the single axle type, supported by V struts. There was a small tail skid. [2]
The first flight under Curtiss power was made on 21 August 1924. Flight testing followed, resulting in major modifications. The upper wing was given an unswept leading edge and hence had constant chord and the small lower wing was replaced by one with the same chord as the upper plane and a span almost its equal, mounted with marked stagger. No longer a sesquiplane, the splayed V interplane struts were replaced with more rigid N-form ones. Another bracing strut ran from the forward foot of the interplane strut to the top of the root to upper wing inner strut, to further improve torsional strength. At the rear, the little fin was remove and the rudder, still balanced, reshaped. [1] Two more aircraft with these modifications were built. [2]
Despite Fokker's efforts, the aircraft was still not to the liking of the USAAS who did not buy any of the three D.XIIs; further development was abandoned. [1]
Data from Green and Swanborough 1994 [1]
General characteristics
Performance
The Fokker V.1 was a small German sesquiplane experimental fighter prototype built in 1916 by the Fokker-Flugzeugwerke. Sporting a parasol wing, it was the first Fokker aircraft purportedly designed by Reinhold Platz—the respective roles played by Fokker himself, Platz, and possibly others in the conceptual design of Fokker airplanes are a matter of dispute among historians—and was an early experiment in cantilever wing construction, eliminating the bracing wires typical of aircraft design at the time, something that had already been achieved with metal materials in Hugo Junkers' own pioneering Junkers J 1 in 1915.
The Fokker D.IX was a Dutch single seat, single engine fighter aircraft, the final, more powerful evolution of the Fokker D.VII World War I success, flown in 1921. The sole example was purchased by the US Army Air Service but not developed further.
The Hanriot HD.6 was a French two-seat fighter aircraft prototype, built towards the end of World War I though not flown until after the armistice with Germany. A biplane with an unusually narrow gap between upper and lower wings, powered by a single water-cooled radial engine, it did not enter production.
The Meyers Midget was a one-off small, low-powered, sporting single-seat sesquiplane, designed and built in the United States in 1926, incorporating several innovative structural features.
The Kondor D 7 was a prototype German single seat biplane fighter built over the winter of 1917-18. It was not a success and its development was soon abandoned.
The Naglo D.II was a German single seat quadruplane fighter, flown late in World War I. It took part in one of the fighter competitions but did not reach production.
The Pfalz D.VII was a German biplane fighter aircraft from World War I. It was not put into production.
The Pfalz D.VI was a German sesquiplane fighter aircraft from World War I. It was not put into production.
The Weymann W-1 was a French single seat biplane fighter aircraft, built during World War I. It had a most unusual layout, with an engine buried in the fuselage driving a pusher configuration propeller behind a cruciform tail. It was not successful and soon abandoned.
The Letov Š-7 was a single-seat, single-engine biplane fighter aircraft designed and built in Czechoslovakia in the early 1920s. It was designed for a single-seat fighter competition but did not reach production.
The Letov Š-13 was a single-seat, single-engine fighter aircraft designed and built in Czechoslovakia in the early 1920s. A biplane, it had aerodynamically thick wings which were originally cantilever structures, though interplane struts were later added. Only one was produced.
The Hanriot H.26 was a French single seat fighter aircraft prototype completed in 1923. Only one was built.
The Levy Biche LB.2 was a single seat French sesquiplane fighter aircraft designed to be used from aircraft carriers. With a watertight fuselage, jettisonable wheeled undercarriage and small under-wing floats, it could survive emergency sea touchdowns; it could also be fitted with seaplane type floats.
The LFG Roland D.XV was a World War I German single seat fighter aircraft, ordered as a test-bed for engine comparisons. It was distinguished from earlier Roland biplane designs by the elimination of flying wires. Two later aircraft, also called LFG Roland D.XV, were completely different designs with slab sided fuselages.
The LFG Roland D.XVI, initially designated the LFG Roland E.I, was a single-seat, single-engine, parasol wing German fighter aircraft flown close to the end of World War I. Only two were built.
The Schütte-Lanz D.VII was a single engine, biplane fighter aircraft designed and built in Germany towards the end of World War I.
The Potez 26 was a single seat fighter aircraft designed and flown in France in the mid-1920s. It did not reach production.
The Caudron Type D was a French pre-World War I single seat, twin-boom tractor biplane, a close but slightly smaller relative of the two seat Caudron Type C. More than a dozen were completed, one exported to the United Kingdom, where they may also have been licence built, and three to China.
The Villiers V, Villiers 5 or Villiers 5CN2 was a French night fighter built in the mid-1920s. It did not go into production.
The Naglo D.I was a German single seat quadruplane fighter, flown late in World War I. It took part in one of the fighter competitions but did not reach production.
 | Wikimedia Commons has media related to Fokker D.XII . |