| D.XII | |
|---|---|
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| General information | |
| Type | Single seatfighter aircraft |
| National origin | Netherlands |
| Manufacturer | Fokker-Flugzeugwerke |
| Number built | 3 |
| History | |
| First flight | with Curtiss engine 21 August 1924 |
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TheFokker D.XII was a Dutch single seat, single enginefighter aircraft designed to anAmerican specification which called for the use of aCurtiss D-12 engine, designatedPW-7. Despite considerable efforts to improve the airframe, Fokker failed to win theUSAAS 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 theUSAAS'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 requiredCurtiss D-12 engine.[1]
Initially, the D.XII was, like the D.XI, asingle baysesquiplane but its wings were different in plan and construction. The upper wing was straight edged with some sweep on theleading edge, it had a thinneraerofoil section than that of its predecessor and wasfabric rather thanplywood covered. Overhungailerons were used, their ends projecting outboard of the squaredwing tips proper, acting as aerodynamic balances. The lower wing, which lacked ailerons, was both much shorter in span and smaller inchord. The early D.XII had a V-forminterplane strut on each side; another strut leant out from each wing root to the upper rearspar, assisted ahead of it on each side by a short V-form pair linking the two spars to the upperfuselagelongeron, acting as N-formcabane 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 8FV-eight engine as its predecessor, but this was soon replaced by the USAAS-specified 440 hp (328 kW)V-twelve water-cooledCurtiss D-12. Both were enclosed by a metalcowlings, though of slightly different shapes, and drove a two bladepropeller. The single, opencockpit was well to the rear, about midway down the fuselage. Its horizontal tail was braced and thefin was small, carrying abalanced rudder that extended down to the keel. The D.XII had a fixedconventional 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 markedstagger. 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]
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Data from Green and Swanborough 1994[1]
General characteristics
Performance
