The alliance between Germany and Japan has been the subject of much debate since the end of World War II. Theoretically, neither nation should have considered the other a viable ally because of their own similar concepts of their own racial superiority that considered the other inferior. However, given the geographical distances between them their own immediate interests were unlikely to clash at least for the foreseeable future. One thing they both had in common was the possibility of clashing with the British Empire; Germany on mainland Europe against Britain herself while Japan against her Eastern possessions. Despite this it was actually the threat from the Soviet Union to both parties that laid the groundwork for the formalising of an alliance in the shape of the Anti-Comintern Pact. When Italy signed on to the treaty the Axis powers were created.
When the Axis powers finally found themselves thrust in to war with Britain, the USA and the Soviet Union they effectively fought two separate conflicts. There was very little coordination between them in the same way that there was between the Allied nations but both sides of the Axis compass knew of the importance of keeping the other’s fight alive because the defeat of one would only see the Allies relocate the resources fighting the defeated nation brought to bare on them and this is exactly what happened after Germany and Italy fell in 1945. To that end there was a lot of technology exchange between them with Nazi Germany going to great lengths to get scientists and technology to Japan hoping they could put them to good use to perhaps ease the pressure in Europe. This was especially true in military aviation and in turn led to the development of the Kawasaki Ki-61 Hien – a fighter that would not look out of place over the skies of Europe.
The story of the Ki-61 can be traced back to the appointment of German engineer Dr. Richard Vogt to the position of chief designer at the Kawasaki Aircraft Engineering Company between 1923 and 1933. During his time at the company he impressed many Western design philosophies on the aircraft he worked on and this left a great impression on his Japanese successor Takeo Dai. One of Vogt’s biggest influences on Takeo Dai and Kawasaki was the belief in liquid-cooled inline engines as opposed to the air-cooed radial designs that prevailed in Japan at that time. This relatively radical approach produced the Ki-10 biplane fighter powered by a license built BMW inline engine but these aircraft remained the exception.
Advances in Europe with such engines couldn’t be ignored forever and in 1935 the British flew the prototype for what would become the Hawker Hurricane for the first time while Germany flew the Messerschmitt Bf109 prototype a year later. Both of these aircraft were fitted with inline engines which gave them performance far in advance of the many radial-engined aircraft then in Japanese service. This resulted in Japanese interest in the Bf109 and plans for an acquisition reached an advanced stage before being cancelled. While they were impressed with the Messerschmitt design they disliked the short range of the aircraft which didn’t meet their requirements for an offensive fighter. They were however impressed with the aircraft’s Daimler-Benz DB 601A engine and so plans were made for a license produced version to be built in Japan and fitted to a Japanese designed aircraft that could meet the Imperial Japanese Army’s requirement for an offensive fighter.
In 1939 the Japanese aviation bureau, the Koku Hombu, issued a requirement for two aircraft to be built around the new engine. The first was to be a high altitude interceptor while the second was to be a general purpose offensive fighter. Takeo Dai went about designing the Ki-60 and Ki-61 respective to these requirements but ultimately the Ki-60 was dropped. Development of the Ki-61 continued but the first flight didn’t take place until December 1941 by which time the engine was falling behind its competitors in the West.
Even before the aircraft flew Britain’s Royal Air Force began receiving the latest Spitfire, the Mark V, which was designed to address some of the shortcomings of the earlier Spitfires such as Mark I/II. Unfortunately the Mark V will always be remembered as being too little too late for its arrival coincided with the arrival of the “Butcher Bird” – the mighty Focke-Wulf Fw190 over Europe. While it was a poor match for the Fw190 it was still a good aircraft comparable to nearly all other fighters in the European and North African theatres including the Messerschmitt Bf109E and Macchi C.202 (see comparison here) both of which used the DB 601 engine. The similarity of the Ki-61 to the C.202 was such that Allied pilots actually initially mistook it for the Italian fighter and this in turn resulted in it receiving the Allied codename of “Tony” based on the Italian name “Antonio”.
Early combat experience with the Ki-61 revealed that it was still underdeveloped despite being an improvement over previous Japanese designs that it was replacing. This was especially true in terms of its armament and the designers at Kawasaki went back to the drawing board producing a slightly longer variant with a heavier punch. This “new” aircraft was designated as the Ki-61-I KAIc.
In a fight between the Supermarine Spitfire V and the Kawasaki Ki-61-I KAIc which aircraft had more going for it?
The Spitfire V was powered by a Rolls-Royce Merlin 45, a variant of the Merlin XX and came fitted with a single-stage, single-speed supercharger. The engine still lacked the direct fuel injection system of the German engines but improvements to the carburettor did allowed the Spitfire V to undertake negative-G manoeuvres without major disruption to the flow of fuel as had been the case in earlier variants. First production Merlin 45s were delivered in January 1941 and churned out around 1,450hp at 9,000ft, an advance over the Spitfire II/Merlin XII combination of some 275hp, which it translated it in to forward motion via a three bladed propeller.
Despite these advances the Merlin 45 proved problematic in the Pacific theatre. The Royal Australian Air Force found quite quickly that the Spitfire V was a logistical headache in the extreme since the parts for it were built half way around the world. The dust and heat of the outback of Northern Australia was particularly hostile to the Merlin where it went from extreme heat on the ground to extreme cold at high altitude causing numerous breakdowns and leakages thus further straining the logistical chain supporting it.
It would be more accurate to say that the Kawasaki Ha-40 engine was a development of the DB 601A rather than a direct license produced version as was the case with the Macchi C.202’s RA.1000 R.C.41-I Monsone version. While the engine had the same layout and configuration as the DB 601 it was tweaked slightly to better meet Japan’s requirements. Consequently the Ha-40 offered more power at take-off than the DB 601A and was actually marginally lighter. The engine was delayed briefly which meant that the first three Ki-61 prototypes flew with DB 601A engines provided by Germany before the first Ha-40s became available.
Even before the constraints of war with America the engine suffered chronic reliability problems compared to the more reliable DB 601A as a result of infrequent manufacturing practices at the Akashi plant where it was built. The situation was only exacerbated by the intervention of the US Navy’s submarine blockade of the Japanese home islands meaning that production of later Ha-40 engines was often undertaken with sub-par materials sourced in Japan rather than the high quality materials imported from the Asian continent. When functioning properly the Ha-40 produced 1,159hp which turned a three bladed propeller.
The Merlin 45 pulled the Spitfire Vb along at a comfortable top speed of 375mph at 20,000ft. The dust encountered at lower levels such as during take off or straffing enemy formations required the fitting of a large Vokes air filter that not only ruined the Spitfire’s elegant lines but also incurred a 7-9mph speed penalty. The aircraft had an initial climb rate of 2,600ft/min which increased to over 3,100ft/min above 14,000ft once clear of the thicker air lower down leading on to a service ceiling of 36,500ft. The Spitfire Vb had a respectable wing loading of 27.35 lb/ft2 and had a maximum of 639hp to share for every ton in weight while with a full fuel and weapon loadout this figure fell to 490hp per ton.
The Ki-61 topped out it’s air speed indicator at 367mph at 16,400ft which was still a good figure for the period given that more powerful engines were available by the time the Ki-61 was entering service after its protracted development. It was capable of reaching a service ceiling of just over 38,000ft and had an initial rate of climb of 2,983ft/min which increased around 16,000ft before dropping off again. The Ki-61 had a higher wing loading than most of the contemporary Japanese designs again betraying its Western influence being in the region of 35.5 lb/ft² which was even higher than the Spitfire Vb. With the Ha-40 installation the Ki-61 had a maximum power to weight ratio of 440hp for every ton. When flying under a full load however this ratio dropped to just 330hp per ton.
It’s name may have been “Spitfire” but in the early marks, Supermarine’s legendary fighter was barely an adequate gun platform. It’s eight .303 machine guns were spaced out across the wing making it difficult to train them to a point ahead of the aircraft where their collective firepower could inflict heavy enough damage on an enemy aircraft equipped with self sealing fuel tanks and armour. This was why the Hawker Hurricane, with its eight .303 machine guns coupled closely together, was the superior gun platform in the Battle of Britain.
Efforts were therefore made to up-gun the Spitfire by fitting 20mm cannons but early trials were abysmal with the Hispano 20mm cannon proving extremely unreliable and prone to jamming after just a few shots. Nevertheless the RAF persisted and after the bugs had been ironed out cannon armament became the standard on all later Spitfires. The Spitfire Vb was therefore armed with a pair of 20mm cannon each with 60 rounds and these had a muzzle velocity of 2800ft/sec. The .303s were still there however and the Spitfire Vb carried four of them spaced along the wings. There were alternative wing configurations available and some variants of the Mark V were armed with four 20mm cannon mainly in the light attack mission but this didn’t become standard for fighter variants until the last two years of the war.
The early Ki-61s too suffered from light armament. The early production versions were armed with two 7.7mm (0.303in) Type 89 machine guns in the wings and two synchronized 12.7 mm (0.50 in) Ho-103 machine guns in the upper engine cowling in a similar arrangement to the Messerschmitt Bf109 and Macchi C.202/205. This proved inadequate against the sturdy American bombers such as the B-17 Flying Fortress and so the Japanese began a series of efforts to up-gun the aircraft including at one point the fitting of German Mauser MG 151/20 cannons brought to Japan by U-Boat.
By the time the Ki-61-I-KAIc appeared the Japanese had settled on having two Ho-5 20mm canon mounted in the forward fuselage position synchronised to fire through the propeller. The Ho-5 was developed from the Ho-103 machine gun which was itself developed from the American Model 1921 Browning aircraft machine gun and as such used belt-fed ammunition that utilised Browning-style steel disintegrating links between the rounds. Each gun was given 120 rounds and these could be discharged at 2,460 ft/s with a rate of fire of 950rds/min.
The wings featured a pair of 12.7 (.50cal) Ho-103 machine guns that each was given a generous 250 rounds each. The weapon could fire put these rounds on to a target at 2,600 ft/s with a rate of fire being 900rds/min. As the war progressed some aircraft saw these weapons replaced by another pair of Ho.5s finally giving the Ki-61 the heavy punch it always needed.
The Spitfire pilot sat sandwiched between two fuel tanks; one ahead of the cockpit behind the Merlin engine and an auxiliary tank behind the cockpit. This meant that should his aircraft be hit in either of these areas he was likely to suffer horrendous burns if he didn’t get out quick enough. To that end Martin-Baker, the company that would eventually become synonymous with ejection seat technology, developed a quick release system that allowed the Spitfire pilot get the canopy off in one quick movement and allow him to exit. The fuel tanks featured a rubber self-sealing system that expanded over single small calibre bullet holes but was rendered ineffective if there was a number of impacts.
He was not entirely without protection as he had armour plates behind his seat and head as well as a bullet-resistant windscreen. While the Spitfire was often cited as a delight to fly it was a notoriously bad aircraft to handle on the ground thanks to its narrow undercarriage that raised from the centre fuselage towards the wingtips as opposed to the opposite which was much more common and much more stable on semi-prepared airstrips as was often the case in the Pacific and the China-Burma-India theatres.
The pilot of the Ki-61 sat ahead of the fuselage fuel tank while ahead of him was the ammunition feed and storage tank for the cowling mounted weapons. This provided some additional level of protection to the pilot from an attack from the forward hemisphere such as when facing defensive guns on a bomber. This was because there was a lot of objects to get in the way of the bullet reducing how far it could travel through the aircraft. The Ki-61 was one of the first Japanese aircraft to feature self-sealing fuel tanks making it more resilient than many other Japanese aircraft of the period.
The aircraft was more robust than the Spitfire being of solid construction and having a wider set landing gear making it far more stable on the ground. It also made it far more likely for the pilot to walk away from a hard landing such as when occurs after taking heavy damage. The narrower wing positioned more centrally to the pilot as opposed to the Spitfire meant that he did enjoy a greater field of downward view fore and aft although both aircraft had poor rearward vision.
Both of these aircraft enjoyed very brief periods of superiority over their contemporaries before new models rendered them obsolete. Compared to one another they are quite well matched in many respects but each have their own strengths and weaknesses. The Ki-61-I-KAIc pilot enjoyed a certain degree of superiority in performance at lower levels where his aircraft had a speed and climb advantage. Between 15,000 and 20,000ft the two aircraft become more evenly matched while above these altitudes the Spitfire V began to enjoy a greater degree of performance thanks mainly to its larger wing area that produced more lift and the fact the Rolls Royce Merlin was tailored for this flight regime. This is despite the fact that the Ki-61-I-KAIc enjoyed a very slight advantage in terms of service ceiling.
In terms of agility the larger wing area of the Spitfire meant that the aircraft’s rate of roll, especially lower down in the denser air, was behind that of Ki-61-I-KAIc. It did however aid in the aircraft achieving a very high rate of continuous turn and with a higher power-to-weight ratio the Spitfire was therefore more agile in the horizontal plane than the Ki-61-I-KAIc. If attacked the Spitfire pilot’s best defence would be to try to keep turning ahead of the Ki-61 pilot’s arc of fire.
Regarding firepower, even though the Spitfire technically had more guns, the larger calibre of the wing mounted machine guns in the Ki-61-I-KAIc helped negate this advantage somewhat which means that in terms of damaging an enemy aircraft the two aircraft’s effectiveness was broadly the same although with more bullets flying the Spitfire at least had a higher chance of hitting something.
In this instance there is no clear winner as the altitude at which the combat would take place would have a major impact on the aircraft. As always we also have to take in to consideration pilot capability and in this respect the quality of Japanese pilots diminished as the war went on and their situation became more desperate. Another important factor to consider is that the Spitfire Vb was never considered ideally suited for operations against the Japanese given the environment they were expected to operate in that played havoc with it. The Spitfire VIII however was a far superior aircraft and enjoyed far more success against the Japanese although The Spitfire Vs did soldier on until the end of the war in an increasingly diminishing capacity.