19 April 2016

Nakajima's Demon: The Ki-44 Shoki

Throughout World War 2 the standard practice of all of the major powers both Allied and Axis in introducing a new combat aircraft into operational use was that use in combat followed an extensive flight test and pre-production development period. One of rare exceptions to this established practice came with the Nakajima Ki-44 which was christened "Shoki" (Demon) by its pilots. And it wasn't on account of its performance against Allied aircraft- the first pilots to fly the Shoki in combat gave it that name out of disdain for an aircraft that represented a new philosophy in fighter aircraft for the Imperial Japanese Army Air Force.

The Nakajima Ki-44 Shoki's Allied code name was "Tojo"
(San Diego Air and Space Museum Collection)
Until the Ki-44 Shoki (codenamed "Tojo" by the Allies) came along, the prevailing wisdom in Japanese fighter aircraft design was to put maneuverability as the prime design objective- all other considerations were secondary, which to quite an extent explained the relative lack of significant armor protection for fighter pilots, as that would have added weight to the aircraft and adversely impacted maneuverability.

Nakajima had been exploring the ideas of trading off maneuverability for increased speed as far back as the mid-1930s after the experience of the brief border war with the Soviets in which the Polikarpov I-16 savaged the IJAAF by using its superior speed and diving abilities to avoid close combat with the more maneuverable Japanese fighters and conduct hit-and-run attacks. Based on the experience, Nakajima's engineers contracted the services of two French engineers from the Dewointine aircraft company to develop the Ki-12 experimental fighter that in 1935 was more modern and faster than anything else the IJAAF was fielding but it remained experimental as it was deemed too radical for the established fighter design philosophy of the day.

The lead engineer at Nakajima just prior to the outbreak of the Second World War was Professor Hideo Itokawa (who later would become the father of the post-war Japanese space program and have an asteroid named for him in honor of his contributions to space science) revisited the ideas behind the Ki-12 experimental fighter by using a short-span wing which would make for a faster fighter that if highly-loaded, could also be a stable gun platform at high speed. His work is what resulted in the Ki-44 Shoki- a powerful radial engine but a comparatively stubby wing with much higher wing loading that other Japanese fighters.

By 1940 there was a greater willingness in the IJAAF for new ideas and it was decided by the Japanese High Command that the Ki-44 Shoki prototypes would be combat tested before going into production. On 15 September 1941 the IJAAF created an evaluation squadron called the 47th Dokuritsu Hiko Chutai (Independent Air Squadron) equipped with the seven prototype Shoki fighters that were quite literally handbuilt by Nakajima. The initial plans were to combat test the Shoki prototypes in China, but with Japan's declaration of war in December on the Allies, the so-called "Kingfisher" Chutai and its seven prototypes were sent to Malaya for use against the British. The Shokis ranged across the peninsula as the invading Japanese forces pushed the British southward to Singapore, scoring victory after victory on hapless British fighters.

By early 1942, Nakajima began work on 40 pre-production Shokis which had improved armament and other modifications such as a combat flap that was a modified Fowler flap that could be extended rearward with little deflection to improve the lift from the Shoki's stubby wings. As production kinks were being worked out, the Doolittle Raid in May 1942 laid bare the vulnerability to the home islands to Allied air attack and the 47th Chutai was recalled from Malaya for home defense duties where its speed and rate of climb made it a natural bomber interceptor. The last pre-production Ki-44 Shoki was delivered in October 1942 and by the end of 1942, the Imperial Japanese Army Air Force formally accepted the Shoki for operational use- after the prototypes had been in combat for nearly a year!

The Shoki's performance led it to be used primarily in the defense of the Home Islands
In the fall of 1944 the last of the 1,225 Ki-44 Shoki fighters was delivered to a home defense unit. By that point in the war, the Shoki was used primarily with reasonable success against the B-29 Superfortresses that were ranging all across the home islands. After the war, the Nationalist Chinese operated the Shoki against the Communists, who themselves had their own Shoki squadrons which were flown by Japanese mercenary pilots. The last Shokis used by the People's Liberation Army Air Force were retired in the early 1950s. No Shokis survived to this day, but a college in Xian, China, has a wing center section. 

Further reading:

Source: Air Enthusiast, Volume 3, Number 1 (July 1972), "Nakajima Demonology: The Story of the Shoki" by William Green, managing editor, Gordon Swanborough, editor. Pilot Press Ltd, 1972, p17-25.

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