As you may know… all variants of Ki-43-I were powered by Ha-25 engine.
As soon as the power plant was upgraded to Ha-115 it became the Ki-43-II and its variants.
Finally the last and best powerplant that was put into the Oscar Fighter was Ha-115-II engine from which the Ki-43-III was born from. The Oscar 3 came in 2 variants. The Ko version was the mass produced version with the standard 2x 12.7mm Ho-103 armament. Then there was the Otsu version which didn't go beyond the prototype stage since the project was eventually abandoned. Arguably the biggest flaw of the Oscar fighters was their weak firepower, having only 2x .50 cal guns with only 270 rounds per gun. The Otsu version was a project to up-gun the Oscar 3 to be armed with 2x 20mm Ho-5 cannons. However the cannons didn't fit. The Japanese had to create buldges on the nose along with other changes to get the guns to fit in the nose area. This increased weight and drag of the plane. Other things had to be adjusted to fix the centre of gravity, further adding weight to the plane. Obviously the bigger guns and heavier ammunition also added more weight. As you can imagine, the performance deteriorated compared to the Ko version. In the end the Japanese deemed the Otsu project a pointless hassle which in the end wasn't worth the time to pursue.
However at some point in time someone published that the Ki-43-III Otsu had Ha-112 engine which is incorrect (Probably Francillion at fault) and it has been copied over and over into the other sources to this day. If it had the Ha-112 engine, it would of became the Ki-43-IV. The Ko and Otsu were still Oscar 3's using the same engine. If the Otsu did have a better Ha-112 engine, it would be illogical statement that the Otsu had worse performance than the Ko, resulting in the abandonment of the project. Furthermore from the images in the post you can see the engine is definitely not a Ha-112, because if it was the nose would look a lot different from the Ki-43-III Ko which had the Ha-115-II engine.
However… I cannot find the loaded weight of this prototype Oscar 3 fighter and it's performance. Maybe someone has sources on this?
Source of image:
Bunrindo - Famous Airplanes of the World No.65 - Army Type 1 Fighter "Hayabusa" Page 33
As soon as the power plant was upgraded to Ha-115 it became the Ki-43-II and its variants.
Finally the last and best powerplant that was put into the Oscar Fighter was Ha-115-II engine from which the Ki-43-III was born from. The Oscar 3 came in 2 variants. The Ko version was the mass produced version with the standard 2x 12.7mm Ho-103 armament. Then there was the Otsu version which didn't go beyond the prototype stage since the project was eventually abandoned. Arguably the biggest flaw of the Oscar fighters was their weak firepower, having only 2x .50 cal guns with only 270 rounds per gun. The Otsu version was a project to up-gun the Oscar 3 to be armed with 2x 20mm Ho-5 cannons. However the cannons didn't fit. The Japanese had to create buldges on the nose along with other changes to get the guns to fit in the nose area. This increased weight and drag of the plane. Other things had to be adjusted to fix the centre of gravity, further adding weight to the plane. Obviously the bigger guns and heavier ammunition also added more weight. As you can imagine, the performance deteriorated compared to the Ko version. In the end the Japanese deemed the Otsu project a pointless hassle which in the end wasn't worth the time to pursue.
However at some point in time someone published that the Ki-43-III Otsu had Ha-112 engine which is incorrect (Probably Francillion at fault) and it has been copied over and over into the other sources to this day. If it had the Ha-112 engine, it would of became the Ki-43-IV. The Ko and Otsu were still Oscar 3's using the same engine. If the Otsu did have a better Ha-112 engine, it would be illogical statement that the Otsu had worse performance than the Ko, resulting in the abandonment of the project. Furthermore from the images in the post you can see the engine is definitely not a Ha-112, because if it was the nose would look a lot different from the Ki-43-III Ko which had the Ha-115-II engine.
However… I cannot find the loaded weight of this prototype Oscar 3 fighter and it's performance. Maybe someone has sources on this?
Source of image:
Bunrindo - Famous Airplanes of the World No.65 - Army Type 1 Fighter "Hayabusa" Page 33
