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Mitsubishi Ki-46 (Dinah) Reconnaissance / Heavy Fighter / Bomber Interceptor (1941)

Authored By Staff Writer | Last Updated: 3/2/2012

The Mitsubishi Ki-46 began as a reconnaissance aircraft and was later developed into a heavy fighter intended to intercept Allied bombers.

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Since May of 1937, the Empire of Japan - both the Imperial Japanese Army Air Force and the Imperial Japanese Navy Air Service branches - relied on the Mitsubishi Ki-15 aircraft for light bombing and reconnaissance sorties. The aircraft featured an enclosed cockpit for two, a low monoplane wing assembly and spatted main landing gear legs, the latter in a permanently fixed positions. About 500 of these aircraft stocked Japanese inventories and only a few developed variants existed. In December of 1937, a new requirement came down from the Japanese air force for a long-range, fast reconnaissance platform to succeed the outgoing Ki-15.

The Mitsubishi concern returned with an all-new design that held some basic similarities to the Ki-15 in that it used two crew and held low-set monoplane wings. The new aircraft sported a well rounded fuselage with each wing fitting a streamlined engine nacelle powering three-bladed propellers. The fuselage design tapered off into the empennage which was capped by a single - rather cropped - vertical tail fin with applicable tailplanes. The crewed would sit in two segregated cockpits - the pilot in a forward compartment and the observer/rear gunner in a rear compartment ahead of the tail. To fulfill the long-range requirement, fuel was stored in multiple locations about the design including a large storage tank fitted between the forward and aft cockpits. Mitsubishi-brand radial piston engines were fitted into specially-designed streamlined nacelles that complimented the aerodynamic qualities of the aircraft. Armament consisted of only a single self-defense Type 89 machine gun set in a rear-firing position to help protect the aircraft's vulnerable "six". Construction of a prototype ensued and produced the "Ki-46" designation.

First flight of the Ki-46 was recorded on November of 1939 which proved her engines lacked the required output power and overall speed envisioned by the IJAAF. Worked continued on the type and a new Mitsubishi powerplant (Ha.26-I radial of 900 horsepower) was fitted while the IJAAF - satisfied with the aircraft's short-term outlook - ordered serial production of the Ki-46. The newer Ki-46-I reconnaissance version was introduced in July of 1941 and immediately made its mark in service to the IJAAF. 34 examples of this type were completed before manufacture switched to the definitive Ki-46-II refined production form of which 1,093 examples were completed.

First combat operations for the Ki-46 saw her acting over both Manchukuo and China before branching out further into the Pacific. Within time, the aircraft proved a regular sight in the skies across other territories for, from the outset, the Ki-46 was an excellent performing aircraft highly suitable for the fast, high-level reconnaissance role originally envisioned. Its inherent speed made her virtually immune to ground-based fire and assault from enemy interceptors. Such dominance allowed a certain feeling of superiority for the IJAAF and this was used to a grand advantage for as long as this dominance lasted. The Ki-46 would go on to become one of the best reconnaissance aircraft of the war.

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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Specifications for the
Mitsubishi Ki-46 (Dinah)
Reconnaissance / Heavy Fighter / Bomber Interceptor


Focus Model: Mitsubishi Ki-46-III-KAI (Dinah)
Country of Origin: Imperial Japan
Manufacturer: Mitsubishi - Japan
Initial Year of Service: 1941
Production: 1,742


Crew: 2


Length: 37.66ft (11.48m)
Width: 48.23ft (14.70m)
Height: 12.73ft (3.88m)
Weight (Empty): 8,446lbs (3,831kg)
Weight (MTOW): 13,730lbs (6,228kg)


Powerplant: 2 x Mitsubishi Ha-112II piston engines developing 1,500hp.


Maximum Speed: 391mph (630kmh; 340kts)
Maximum Range: 1,243miles (2,000km)
Service Ceiling: 34,449ft (10,500m; 6.5miles)
Rate-of-Climb: 1,970 feet per minute (600m/min)


Hardpoints: 0
Armament Suite:
Original:
1 x .303 caliber Type 89 machine gun in rear cockpit.

Ki-46-III-KAI:
2 x 20mm cannons in nose
1 x 37mm oblique-angled cannon in upper central fuselage.

Ki-46-IIIb:
2 x 20mm cannons in nose


Variants:
Ki-46 - Prototype Model Designation


Ki-46 I Type 100 - Reconnaissance Version based on the Army Type 100, or Mark I.

Ki-46 II (Mark 2) - Initial Production Model Designation.

Ki-46 II KAI - Trainer Model; seating for three personnel; based on the Ki-46 II.

Ki-46 III - Prototype Model Designation for improved Ki-46 model series; also serves as designation for Reconnaissance Model based on the Army Type 100, also known as the Mark III.

Ki-46 III KAI - Heavy Fighter / Interceptor Model based on the Army Type 100 model; fitted with 2 x 20mm cannons and 1 x 37mm cannon.

Ki-46 III - Strike Fighter Variant based on Army Type 100 sans 37mm cannon.

Ki-36 IIIb - Dedicated Ground Attack Model

Ki-46 IIIc - Proposed Model; unfinished.

Ki-46 IV - Prototype Model; fitted with 2 x Mitsubishi Ha-112-II RU series engines of 1,500 horsepower; increased fuel capacity; turbocompressor optimized.

Ki-46 IVa/b - Unfinished Reconnaissance/Fighter Platforms.


Operators:
China; Imperial Japan