However, Japanese authorities were not blind to advancements being made on the Allied side. Basic fighter designs were all being put through new paces and completed with evermore improved performance specifications themselves. To stay ahead of the curve, the IJAAF charged Mitsubishi with evolving the Ki-46-II into an improved form through the installation of more capable engines. Mitsubishi engineers also took to refining key aerodynamic features of the airframe including the nose - now sporting a smoother, all-glazed look. The modified version first took to the air in December of 1942 and proved faster than the first incarnation. The aircraft was adopted as the Ki-46-III and 613 examples were delivered.
By the end of the war in 1945, a desperate Japanese defensive campaign saw the ki-46 series converted into an ad hoc heavily-armed interceptor platform. The main threat to the Japanese mainland now came from the high-altitude Boeing B-29 Superfortress which could essentially act with its own level of impunity over Japanese defenses and out of reach of enemy interceptors. As a bomber interceptor, armament of the Ki-46 was upgraded to include 2 x 20mm cannons in the nose and 1 x 37mm cannon in an oblique firing position. The latter armament was intended to engage bombers from the rear and underneath - the most vulnerable area of an enemy bomber when in flight. These versions (Ki-46-III-KAI) proved adequate for the role conversion but were not as successful as anticipated. The airframe was simply not designed for the sustained firing of the large-caliber 37mm cannon, especially in its semi-vertical fitting, and the aircraft had trouble reaching its defined interception altitudes within time. Even when it did reach B-29 bombers, the aircraft lacked any armor protection or self-sealing fuel tanks and essentially made for target fodder against B-29 gunners. The Ki-46-III-KAI appeared in October of 1944 and was in operational service by the following month. When the American aircrews converted over the night operations, the tactical usefulness of the Ki-46-III interceptor was even less for they were never adapted to the night fighter role with radar or similar tracking facilities. The Ki-46-IIIb was a similar III-series mark though developed specifically for the ground attack role and produced sans the oblique-firing 37mm cannon. Several other experimental forms existed to test out engines but these came to naught while still others never materialized from the drawing boards.
The Ki-46 was officially retired in 1945 after the Japanese Empire fell to the Allies. Two were operated by the Chinese after the war for a short time after but their recorded use ended by the mid-1950s.
The formal name of the Ki-46 was "Type 100 Command Reconnaissance Aircraft" and she was known to Allied forces by the codename of "Dinah".
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