How good was the Ki-84?

by Andrew Johnson

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To assist those wishing to assess the qualities of the Ki-84 against its possible allied opponents I have compiled the following information:

The Aircraft

The Ki-84 has a lower unladen weight compared to its Allied opponents with the exception of the Spitfire.

When operating well, the Nakajima ‘Homare’ engine was reasonably competitive to its Allied opponents. However, its single stage supercharger proved inadequate when close to the 30,000 feet mark. This would put it at a disadvantage against all of its allied opponents since the P-38 and P-47 were turbo-supercharged and F4U, F6F, P-51 and Spitfire VIII had two stage supercharging.

With five separate fuel tanks holding 154 imp. gallons the Ki-84 had excellent range, an important attribute in the Pacific theatre. Japanese fighters often had to fly long crossings over the Pacific ocean to reinforce struggling garrisons. The most similar aircraft to the Ki-84 in terms of all round performance and hitting power in this survey is the Spitfire. However, in the range department the Spitfire is well beaten by the Ki-84, and the RAF as a whole failed to develop a long range single engined fighter.

From the data tables the Ki-84 could outpace the F6F but would lag behind the other Allied fighters. However, 390 mph made the Ki-84 the fastest Japanese fighter of the war. Apparently a captured example run on high octane petrol, not available to the Japanese, was able to outpace both the Mustang and Thunderbolt.

This has been determined from unladen weight, but puts the Ki-84 as the design with the best amount of power for its weight available. This would mean it could it could theoretically out accelerate the allied fighters from a low to medium starting speed.

The favourable power to weight ratio has helped to give the Ki-84 the best climbing performance in the survey.

The light weight of the Ki-84 coupled with its fairly generous wing area has given it the best wing loading of all the fighters present bar the Spitfire. Thus, it could enter a turning fight with any American fighter with some confidence. The F6F would have the best turning performance of the American fighters and would be fairly close to the Ki-84 in the turn.

In this analysis the rounds per minute, projectile weight and muzzle velocity of all weapons have been multiplied to give an impact factor with arbitrary units. The Ki-84 with its combination of two 12.7 mm Ho-103 and two 20 mm Ho-3 guns gives a creditable performance.

No Japanese fighter aircraft had a better all-round performance than the Ki-84. As far as protection goes, the Ki-84 had seat back and head armour of 12 mm steel, and self-sealing fuel tanks. The self-sealing tanks were not considered as efficient as those fitted to American aircraft at the time.

The Ki-84 was not clearly superior to any of the Allied fighter aircraft opposing it. In perfect running order it was perhaps the equal of any allied fighter at 20,000 feet or below. A good pilot would be able to take advantage of its excellent turning, climbing and acceleration characteristics to at least give an allied opponent a hard fight.

However, good pilots and Ki-84 in excellent running order where in short supply for Japan between 1944 and 1945.
 
 

Review, Tables and Image Copyright © 2002 by Andrew Johnson
Page Created 30 August, 2002
Last updated 30 August, 2002

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