Nakajima Experimental Ki-12 Fighter

Nakajima Experimental Ki-12 Fighter.

No sooner had production begun in France of the advanced Dewoitine D.510 fighter in 1935, than Mitsubishi imported two for study by September of that year. The outstanding appeal of this aeroplane was its new engine-mounted 20mm cannon which fired through the propeller shaft. Taking into consideration this and other features of the Dewoitine, Nakajima designed a comparable fighter but went a major step further by adding a retractable undercarriage, the first to be built in Japan.

Heading this project were two French engineers, Roger Robert and Jean Beziaud who were hired by Nakajima, with Shigenobu Mori as the chief Japanese designer. Although the D.510 served as a reference aircraft in creating the new Nakajima fighter, a number of details were further refined. Using the same 690hp Hispano-Suiza 12Xcrs engine with its 20mm engine-mounted cannon which was imported separately for this project, an oval-shaped radiator was mounted in front of the nose instead of beneath as on the D.510. This reduced the frontal area of this aeroplane as with the similar D.513. The hydraulically-operated undercarriage retracted inwards into the elliptically shaped wing which also had split flaps. The tailwheel was fully retractable. The headrest behind the open cockpit was extended aft to become part of the fin. The result was perhaps one of the most refined fighter airframes in the world at that time.

The aeroplane was completed in October 1936 and moved immediately into the flight-test phase. It was tested against the Mitsubishi Ki-18 which had been completed fourteen months previously, as well as the Mitsubishi Ki-33, Kawasaki Ki-28 and the Nakajima Ki-27, the last of these being finished about this time. The Nakajima Ki-12 was found to be inferior to all in manoeuvrability, a quality which the Japanese Army placed above all others. Failing this most important test, the design was doomed because it was not thought that a licence manufacturing agreement for the Hispano-Suiza 12Xcrs would be granted, and Japan did not want to rely upon imported engines for its combat aircraft. Consequently, the Ki-12 programme ended with but one prototype, and Nakajima's Ki27 won the Army's approval to become its next standard fighter. On a trial basis, two Hispano-Suiza 12Xcrs were tested in the normally radial-engined Mitsubishi A5M3a, greatly enhancing its fighter-like lines and adding a little more speed.

Single-engine low-wing cantilever monoplane fighter with retractable undercarriage. All-metal monocoque fuselage, with all-metal multi-spar stressed skin wing. Pilot in open cockpit.
610-690hp Hispano-Suiza 12Xcrs twelve-cylinder vee liquid-cooled engine, driving a fixed-pitch three-bladed metal propeller.
One 20mm engine-mounted cannon firing through propeller shaft, two 7.7mm machine-guns mounted in the Wing.
Span 11 m (36ft 1in); length 8.30m (27ft 2 3/4in); height 3.30m (10ft 10in); wing area 17sq m (182. 992sq ft).
Empty weight 1,400kg (3,086Ib); loaded weight 1,900kg (4,188Ib); wing loading 111.9kg/sq m (22.9lb/sq ft); power loading 2.75kg/hp (6Ib/hp).
Maximum speed 260kt (229.2mph); cruising speed 200kt (230mph); landing speed 65kt (74.8mph); climb to 5,000m (16,404ft) in 6min 30sec; service ceiling 10,500m (34,448ft); range 433nm (498sm).
One built in October 1936.