Fokker D XII
|FIGHTER||Virtual Aircraft Museum / Holland / Fokker|
The evaluation of three modified D XI fighters by the US Army Air Service prompted the design of the D XII tailored specifically to the USAAS specification. Designed from the outset for the 440hp V-1150 (Curtiss D-12) water-cooled engine, it was flown for the first time on 21 August 1924 with an example of this power plant loaned by the US service to the manufacturer. The D XII had no design commonality with the preceding D XI, but was of similar mixed construction and, initially, retained the sesquiplane configuration of its predecessor, the upper wing having some degree of leading-edge sweepback and overhung ailerons. Unsatisfactory characteristics displayed during initial trials necessitated major re-design, the sweepback being eliminated from the upper wing and a longer-span lower wing being introduced. Greater torsional rigidity was achieved by replacing the splayed V-type interplane struts with N-type struts and attaching these by single large-section struts to the top of the cabane strut system. At the same time, the small fixed tailfin was eliminated. Despite these extensive modifications, the D XII still proved unacceptable to the USAAS and further development was abandoned.