Sunday, January 18, 2015

Mitsubishi Ki-46-III bomber destroyer

Defense interceptor/night fighter version of the Ki-46. Equipped with two 20 mm cannons in the nose and one 37 mm (1.46 in) cannon in the "Schr├Ąge Musik"-style dorsal frontal position.

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.


  1. How many Ki-46-III's were built, and how many B-29's did they shoot down?

  2. From William Green & John Swanborough’s WWII Aircraft Fact Files, Japanese Army Fighters, Part 1, page’s 51-52

    ‘Conceived by Tomio Kubo and Joji Hattori, for the high-altitude long-range reconnaissance role, the Ki.46 lacked the climb rate and powers of maneuver that were desirable in a fighter and it had been these shortcomings that led, in the summer of 1943, to the shelving of a projected fighter adaptation of the Ki.46 that had been studied by the Army Aerotechnical Research Institute, or Rikugun Kokuchijutsu Kenkyoujo. However, in the summer of 1943, the debut of the B-29 over the home islands had not been imminent – a year later the situation had changed dramatically. While the climb rate and maneuverability of the Ki.46 left much to be desired in the context of an interceptor fighter, its high-altitude performance and endurance commended it as a potential B-29 interceptor, and thus in May 1944, the project was revived and in the following month, with the appearance of the B-26 over Japan, assigned high priority. …

    …The conversion consisted of the removal of photographic equipment and the fuselage fuel tank, and the replacement of the extensively glazed fuselage by an entirely new section with a stepped cockpit, this mounting two 20-mm Ho-5 cannon with 200 rpg. In the position previously occupied by the fuselage fuel tank a single 37-mm Ho-203 cannon was mounted obliquely to fire forward and upward, this being provided with eight 25-round magazines. …

    …Some 200 Ki.46 were reportedly converted for the intercept role in which they enjoyed only qualified success on operations. Apart from its poor rate of climb, its firepower was deficient as a B-29 interceptor and the obliquely mounted 37-mm weapon proved ineffective. Furthermore, its structure, which, admittedly, had not been designed for the intercept task, was insufficiently sturdy to absorb much punishment and a variant with supercharged Ha-112-II Ru engines, the Ki.46-IV-Otsu was abandoned. Nevertheless, conversions of the Ki.46-III for the fighter task were continued by the Army Air Arsenal until late March 1945.’

    B-29 kills? Perhaps a handful….

    Maj Hideo Ueda, commander of the 28th Sentai, whose `Dinahs' went up that day, stated that his unit's aerial-burst bombs were fairly effective against B-29s. As previously mentioned, the 28th's Ki-46s were remodelled reconnaissance machines armed with 20 mm cannon and phosphorous bombs for high-altitude interception. Despite now being classified as fighters, the `Dinahs'' pilots came from reconnaissance squadrons, and had minimal combat training. Ueda said he lost five `Dinahs' to Mustangs on 7 April - P-51 pilots from VIIth Fighter Command claimed exactly five twin-engined fighters over Tokyo. Because of the losses, the Ki-46s were reassigned to their reconnaissance role, and Maj Ueda returned to the `Nick'-equipped 53rd Sentai.