|FIGHTER||Virtual Aircraft Museum / Japan / Mitsubishi|
The acceptance of the Ka-14 9-Shi fighter by the Imperial Navy and evaluation of a modified prototype of this aircraft as the Ki-18 by the Imperial Army encouraged the formulation by the latter service during 1935 of a requirement for what was termed an "advanced fighter". Kawasaki, Mitsubishi and Nakajima were each asked to produce prototypes of a fighter surpassing the performance of the Ki-18. Whereas both Kawasaki and Nakajima produced fighters of entirely new design to meet the requirement (as the Ki-28 and Ki-27 respectively), Mitsubishi, preoccupied with refining the Ka-14 for series production for the Navy, lacked sufficient design capacity to develop yet a further fighter. The Ki-18, with comparatively minor changes, was therefore resubmitted. As the Ki-33, the modified fighter was powered by a Nakajima Ha-l-Ko engine rated at 745hp at 3700m and enclosed by a broader-chord cowling. An aft-sliding part-canopy was added, the aft fuselage decking was raised and the vertical tail surfaces were modified. Completed during the early summer of 1936, the Ki-33 was submitted to comparative trials with the Ki-27 and Ki-28 from November 1936 until the spring of 1937. It was found to offer marginally superior max speeds between 2500m and 3500m over the 167kg lighter Ki-27, but the Ki-33 revealed an inferior turn rate and climb to those of the Nakajima contender which was selected for series production.