The almost uncatchable Mitsubishi Ki-46
Japan's ultra fast twin-engined beauty
Mitsubishi Ki-46
一〇〇式司令部偵察機, Ichi rei rei-shiki shirei-bu teisatsu-ki (Type 100 Command Reconnaissance Aircraft)
Reconnaissance aircraft seldom get the attention they deserve, performing totally essential work, usually alone and often unarmed. In the Ki-46 the Japanese possessed the world’s finest example of this type of aircraft. As a reconnaissance platform it was unmatched by any other machine until the appearance of the Mosquito and proved maddeningly difficult to intercept throughout the conflict. As late as September 1944, a Spitfire Mk VIII (itself no slouch) required the removal of armour and a pair of machine guns to achieve the performance necessary to effect an interception. According to an oft-repeated claim, the Germans were impressed enough that they attempted to obtain a manufacturing licence (without success), though a reliable original source for this tale remains elusive. If this is true however, it paints the Ki-46 in a remarkable light, for the race-obsessed Nazis to admit that a superior aircraft was built by an ‘inferior’ people was praise indeed. What is not in doubt, however, is the fact that the Ki-46 was the only Japanese aircraft deemed of sufficient interest to be sent to the Soviet Air Force Technical Institute in 1945 for further evaluation. Even the Japanese Navy, who detested the Japanese Army and everything to do with it, were forced to concede that the Ki-46 was superior to any aircraft they themselves possessed and used it for missions over New Guinea and Australia.
Curiously however, the Ki-46 programme started with the decidedly unimpressive Ki-46-I. Despite the Japanese aircraft industry being exceptionally good at streamlining radial engines (and the Ki-46 was possibly the finest exponent of this trend) the Ki 46-I handled poorly, failed to meet performance estimates and was used largely for evaluation and training. An engine change to the Mitsubishi Ha-102 featuring two-stage, two-speed supercharging transformed the aircraft and when the Ki-46-II entered service in July 1941, its performance rendered it immune from interception. Throughout 1942 and 43, the Ki-46 swanned about in near perfect safety, with only an occasional unlucky or careless example falling to Allied fighters. The Ki-46-II was built in the greatest numbers of any variant and remained in service until the end of the war by which time its performance advantage had diminished somewhat but was still potent enough to allow it a decent chance of survival in Allied-controlled airspace which was more than could be said for most Japanese aircraft from mid-1944 onwards.
The improved Ki-46-III was faster still due to a weight reduction programme, the adoption of more powerful Ha-102 engines with direct fuel injection, and a revised fuselage design resulting in near perfect streamlining. In this form it could achieve a maximum speed a shade over 400 mph. 654 examples of the Ki-46-III were built, a total that would have been higher but the combination of bombing and an earthquake at Mitsubishi’s Nagoya factory crippled production. The development of a replacement aircraft, the Tachikawa Ki-70, resulted in an aircraft with inferior performance and as a result the Ki-46 was improved further to become the turbo-supercharged Ki 46-IV. Although it never entered production due to the difficulty of manufacturing the turbochargers, its performance was incredible: in February 1945 two of the prototypes flew from Peking to Yokota in 3 hours 15 minutes, covering 1,430 miles at an average of 435 mph. By contrast, the cruising speed of the contemporary and much-vaunted Mosquito PR Mk XVI was 318 mph and its absolute maximum was 407 mph. Loved by its crews and respected by its enemies, the Ki-46, designer Tumio Kubo’s masterpiece, was for most of the war in a class of its own.