Warplanes of Japan: Mitsubishi Ki-46

Mitsubishi Ki-46

(IJAAF Photo)

Mitsubishi Ki-46-II Army Type 100 Air Defence Fighter (Serial No. 2846), codenamed "Dinah".

The Mitsubishi Ki-46 was a twin-enginereconnaissance aircraft that was used by the Imperial Japanese Army in theSecond World War. Its Army Shiki designation was Type 100 CommandReconnaissance Aircraft (一〇〇式司令部偵察機); theAllied brevity code name was "Dinah".

On 12 December 1937, the Imperial Japanese Army Air Force issued aspecification to Mitsubishi for a long-range strategic reconnaissance aircraftto replace the Mitsubishi Ki-15. The specification demanded an endurance of sixhours and sufficient speed to evade interception by any fighter in existence ordevelopment, but otherwise did not constrain the design by a team led by TomioKubo and Jojo Hattori.

The resulting design was a twin-engined, low-winged monoplane with aretractable tailwheel undercarriage. It had a small diameter oval fuselagewhich accommodated a crew of two, with the pilot and observer situated inindividual cockpits separated by a large fuel tank. Further fuel tanks weresituated in the thin wings both inboard and outboard of the engines, giving atotal fuel capacity of 1,490 L (328 imperial gallons). The engines, twoMitsubishi Ha-26s, were housed in close fitting cowlings developed by theAeronautical Research Institute of the Tokyo Imperial University to reduce dragand improve pilot view.

The first prototype aircraft, with the designation Ki-46, flew in November 1939from the Mitsubishi factory at Kakamigahara, Gifu, north of Nagoya. Testsshowed that the Ki-46 was underpowered, and slower than required, only reaching540 km/h (336 mph) rather than the specified 600 km/h (373 mph). Otherwise, theaircraft tests were successful. As the type was still faster than the Army'slatest fighter, the Nakajima Ki-43, as well as the Navy's new A6M2, an initialproduction batch was ordered as the Army Type 100 Command Reconnaissance PlaneModel 1 (Ki-41-I).

To solve the performance problems, Mitsubishi fitted Ha-102 engines, which wereHa-26s fitted with a two-speed supercharger, while increasing fuel capacity andreducing empty weight. This version, designated Ki-46-II, first flew in March1941. It met the speed requirements of the original specification, and wasordered into full-scale production, with deliveries starting in July.

Although at first the Ki-46 proved almost immune from interception, theImperial Japanese Army Air Force realised that improved Allied fighters such asthe Supermarine Spitfire and P-38 Lightning could challenge this superiority,and in July 1942, it instructed Mitsubishi to produce a further improvedversion, the Ki-46-III.[6] This had more powerful, fuel-injected MitsubishiHa-112 engines, and a redesigned nose, with a fuel tank ahead of the pilot anda new canopy, smoothly faired from the extreme nose of the aircraft, eliminatingthe "step" of the earlier versions. The single defensive machine gunof the earlier aircraft was omitted not long into the production run. The newversion first flew in December 1942, demonstrating significantly higher speed630 km/h (391 mph) at 6,000 m (19,700 ft).[7] The performance of the Ki-46-IIIeven proved superior to that of the aircraft intended to replace it (theTachikawa Ki-70), which as a result did not enter production.[8] Duringoperational testing in March 1944, it was discovered that replacing theengines' single exhaust collector ring with individual pipes provided extrathrust and an increase in top speed to 642 km/h (399 mph).

In an attempt to yet further improve the altitude performance of the Ki-46, twoprototypes were fitted with exhaust driven turbosupercharged Ha-112-II-Ruengines. This version first flew in February 1944, but only two prototypes werebuilt.

Mitsubishi factories made a total of 1,742 examples of all versions (34 xKi-46-I, 1093 x Ki-46-II, 613 x Ki-46-III, 4 x Ki-46-IV) from 1941 to 1944.

Buffalo pilots of No. 488 (New Zealand) Squadron based at Kallang display thetail fin of a Mitsubishi Ki-46 which they shot down over Johore, Malaya,January 1942

This aircraft was first used by the Japanese Army in Manchukuo and China, whereseven units were equipped with it, and also at times by the Japanese ImperialNavy in certain reconnaissance missions over the northern coasts of Australiaand New Guinea.

The Japanese Army used this aircraft for the same type of missions (which werenot authorized) over present-day Malaysia during the months before the PacificWar. Later, it was used for high altitude reconnaissance over Burma, Indochina,Thailand, and the Indian Ocean. The Ki-46 was regarded by the British RAF inBurma as a difficult aircraft to counter, only occasionally intercepting themsuccessfully. On September 25, 1944, Flying Officer Wittridge shot down aKi-46, using a personally modified Spitfire Mk VIII. Wittridge had removed twomachine guns and the seat armour, and also polished the wing leading edges togain extra speed.[12] The leading American fighter pilot Richard Bong, flying aP-38 Lightning, managed to shoot down a Ki-46 over the coast of Papua NewGuinea in late 1942.

An abandoned Mitsubishi Ki-46 II on Okinawa, June 1945.
In 1944–45, during the last days of the war, it was modified as a high-altitudeinterceptor, with two 20 mm cannons in the nose and one 37 mm (1.46 in) cannonin an "upwards-and-forwards" position – almost like the Luftwaffe'sSchräge Musik night fighter cannon emplacements – for fighting USAAF B-29Superfortresses over the metropolitan Japanese islands. It lacked stability forsustained shooting of the 37 mm (1.46 in) weapon, had only a thin layer ofarmour plating, lacked self-sealing fuel tanks, and was slow to climb.

The Ki-46 was also assigned to two whole Sentai (wings/groups), as well asindividual Chutaicho (junior operational commanders) in the Imperial JapaneseArmy Air Service, during the Pacific War.

The Allies captured some examples during the conflict, which were then repairedand flown for evaluation purposes. The Ki-46 III was the only Japanese aircrafttype sent to the NII VVS Soviet Air Force Test Institute, for evaluation during1946–7.[13]

Variants
(note:- The Shiki designations must be used in full, as written below, becausethe Type number only refers to the year of the designs inception.)

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
Ki-46
Prototype.
Ki-46 I
Reconnaissance version of the Ki-46.
Ki-46 II
The first operational model of the series.
Ki-46 II KAI
Three-seat training version of the Ki-46. Used for radio and navigationtraining, with a redesigned cabin, dorsal en echelon extension. Conversions ofthe Ki-46 II.
Ki-46 III
"Traditional" stepped windshield replaced with a smooth, curved,glazed panel extended over the pilot's seat giving a more aerodynamic noseprofile. Engine power increased to 1,500 hp (Ha-112-II), extra fuel tank addedin the nose.
Ki-46 III-KAI
Defense interceptor/night fighter version of the Ki-46. Equipped with two 20 mmcannon in the nose and one 37 mm (1.46 in) cannon in the "SchrägeMusik"-style upwards-aimed dorsal frontal position.
Ki-46 III
Land strike version of the Ki-46, without 37 mm (1.46 in) cannon armament.
Ki-46 IIIb
Ground-attack version.
Ki-46 IIIc
Unbuilt design project.
Ki-46 IV
Prototype, equipped with two turbocharged 1,119 kW (1,500 hp) MitsubishiHa-112-IIru engines, and more fuel capacity.
Ki-46 IVa/b
Series models of reconnaissance/fighter aircraft, unbuilt design projects.(Wikipedia)

(IJAAF Photos)

Mitsubishi Ki-46-II Army Type 100 Air Defence Fighter (Serial No. 2846), codenamed "Dinah".

Mitsubishi Ki-46-II Army Type 100 Air Defence Fighter (Serial No. 2846), codenamed "Dinah", green cross surrender markings.  (IJAAF Photos)

Mitsubishi Ki-46-III Army Type 100 Air Defence Fighter (Serial No. 2846), codenamed "Dinah".  (IJAAF Photos)

Mitsubishi Ki-46-II Army Type 100 Air Defence Fighter (Serial No. 2846), codenamed "Dinah".  This aircraft was captured at Hollandia in New Guinea is Sep 1944 and made airworthy by the 13th BS, 3rd BG whose "Grim Reaper" insignia was applied to the nose.   It was assigned code TAIC 10 and is shown here in USAAF markings before being shipped to USA.  It was test flown at Patuxtent, NAS Anacostia and Eglin AFB.  Five Dinahs were brought to the USA, including Ki-46-III, USAAF FE-4801 and FE-4802 both scrapped at Park Ridge ca. 1950, FE-4806 scrapped at Newark, FE-4807 scrapped at Middletown and Ki-46-IV, FE-4812 scrapped at Middletown.  (USAAF Photo)

Mitsubishi Ki-46-III Army Type 100 Air Defence Fighter, USAAF FE-4801, scrapped at Park Ridge ca. 1950.  (USAAF Photo)

 (G.F.Petrova Archive)

Mitsubishi Ki-46 Army Type 100, reconnaissance aircraft captured by the Soviet Union.

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