The Mitsubishi Ki-46 was a twin-engine reconnaissance aircraft used by the Imperial Japanese Army in World War II.
On 12 December 1937, the Imperial Japanese Army Air Force issued a specification to Mitsubishi for a long-range strategic reconnaissance aircraft to replace the Mitsubishi Ki-15.
The specification demanded an endurance of six hours and sufficient speed to evade interception by any fighter in existence or development, but otherwise did not constrain the design by a team led by Tomio Kubo whose aesthetics are very significantly infused to the aircraft.
The resulting design was a twin-engined, low-winged monoplane with a retractable tailwheel undercarriage.
It had a small diameter oval fuselage which accommodated a crew of two, with the pilot and observer situated in individual cockpits separated by a large fuel tank.
Further fuel tanks were situated in the thin wings both inboard and outboard of the engines, giving a total fuel capacity of 1,490 L (328 imperial gallons).
The engines, two Mitsubishi Ha-26s, were housed in close fitting cowlings developed by the Aeronautical Research Institute of the Tokyo Imperial University to reduce drag and improve pilot view.
The first prototype aircraft, with the designation Ki-46, flew in November 1939 from the Mitsubishi factory at Kakamigahara, Gifu, north of Nagoya.
Tests showed that the Ki-46 was underpowered, and slower than required, only reaching 540 km/h (336 mph) rather than the specified 600 km/h (373 mph).
Otherwise, the aircraft tests were successful.
As the type was still faster than the Army’s latest fighter, the Nakajima Ki-43, as well as the Navy’s new A6M2, an initial production batch was ordered as the Army Type 100 Command Reconnaissance Plane Model 1 (Ki-41-I).
To solve the performance problems, Mitsubishi fitted Ha-102 engines, which were Ha-26s fitted with a two-speed supercharger, while increasing fuel capacity and reducing empty weight.
This version, designated Ki-46-II, first flew in March 1941. It met the speed requirements of the original specification, and was ordered into full-scale production, with deliveries starting in July.
Although at first the Ki-46 proved almost immune from interception, the Imperial Japanese Army Air Force realised that improved Allied fighters such as the Supermarine Spitfire and P-38 Lightning could challenge this superiority, and in July 1942, it instructed Mitsubishi to produce a further improved version, the Ki-46-III.
This had more powerful, fuel-injected Mitsubishi Ha-112 engines, and a redesigned nose, with a fuel tank ahead of the pilot and a new canopy, smoothly faired from the extreme nose of the aircraft, eliminating the “step” of the earlier versions.
The single defensive machine gun of the earlier aircraft was also omitted.
The new version first flew in December 1942, demonstrating significantly higher speed (630 km/h (391 mph) at 6,000 m (19,700 ft)).
The performance of the Ki-46-III even proved superior to that of the aircraft intended to replace it (the Tachikawa Ki-70), which as a result did not enter production.
In an attempt to yet further improve the altitude performance of the Ki-46, two prototypes were fitted with exhaust driven turbosupercharger Ha-112-II-Ru engines.
This version first flew in February 1944, but only two prototypes were built.
Mitsubishi factories made a total of 1,742 examples of all versions (34 units Ki-46-I, 1093 units Ki-46-II, 613 units Ki-46-III, 4 units Ki-46-IV）during 1941–44.
Army Type 100 Command Reconnaissance Plane
The Shiki designation for the Ki-46 Command Reconnaissance Plane
Army Type 100 Air Defence Fighter
The Shiki designation for the Ki-46 Interceptor Fighter
Army Type 100 Assault Plane
The Shiki designation for the Ki-46 Assault Plane
Reconnaissance version of the Ki-46.
The first operational model of the series.
Ki-46 II KAI
Three-seat training version of the Ki-46.
Used for radio and navigation training, with a redesigned cabin, dorsal echelon extension.
Conversions of the Ki-46 II.
‘Traditional’ stepped windshield replaced with a smooth, curved, glazed panel extended over the pilot’s seat giving a more aerodynamic nose profile.
Engine power increased to 1,500 hp (Ha-112-II), extra fuel tank added in the nose.
Defence interceptor/night fighter version of the Ki-46.
Equipped with two 20 mm cannon in the nose and one 37 mm (1.46 in) cannon in the “Schräge Musik”-style upwards-aimed dorsal frontal position.
Land strike version of the Ki-46, without 37 mm (1.46 in) cannon armament.
Unbuilt design project.
Prototype, equipped with two turbocharged 1,119 kW (1,500 hp) Mitsubishi Ha-112-IIru engines, and more fuel capacity.
Series models of reconnaissance/fighter aircraft, unbuilt design projects.
11 m (36 ft 1 in)
14.7 m (48 ft 3 in)
3.88 m (12 ft 9 in)
32 m2 (340 sq ft)
3,263 kg (7,194 lb)
5,050 kg (11,133 lb)
Max take-off weight
5,800 kg (12,787 lb)
2 × Mitsubishi Ha-102 (Army Type 100 1,050hp Air Cooled Radial)
14-cylinder air-cooled radial piston engines,
810 kW (1,080 hp) each for take-off
787 kW (1,055 hp) at 2,800 m (9,186 ft)
3-bladed constant-speed metal propellers
604 km/h (375 mph, 326 kn) at 5,800 m (19,029 ft)
400 km/h (250 mph, 220 kn) at 4,000 m (13,123 ft)
2,474 km (1,537 mi, 1,336 nmi)
10,720 m (35,170 ft)
Time to altitude
8,000 m (26,247 ft) in 17 minutes 58 seconds
1× 7.7 mm (0.303 in) Type 89 machine gun flexibly mounted in the rear cockpit (not fitted to all models).